Conference Program ADVANCED BUILDING SKINS 2015€¦ · Advanced Fenestration Technology Chair: Urs...

8:30 - 10:00

8:30 Opening: Andreas Hempel, International Academy of Architects; former President Association of German Architects BDAWalter Steinlin, President, Commission for Technology and Innovation, Bern, SwitzerlandDaniel Schafer, CEO, ewb - Energie Wasser Bern, Switzerland

9:15 Keynote: Justin Hall-Tipping, Chief Executive Officer, Nanoholdings, Rowayton, CT, USA

10:00 - 10:45 Coffee break

A1 - Room 2 B1 - Room 3 C1 - Room 4 D1 - Room 1 E1 - Room 6 F1 - Room 7

10:45 - 12:30

BIPV 1 - Energy Performance of Façades with Photovoltaics Chair: Heiko Schwarzburger, Editor-in-chief, photovoltaik, Berlin, Germany

Enhanced Energy Performance and Daylighting of Building Envelopes for HospitalsChair: Marilyne Andersen, Ecole Polytechnique Fédérale de Lausanne, Switzerland

Eco Materials for the Building SkinChair: Bruce Dvorak, Texas A&M University, USA

Advanced Building Skin DesignChair: Andreas Hempel, International Academy of Architects; former President Association of German Architects BDA

Advanced Fenestration Technology Chair: Urs Buehlmann, Bern University of Applied Sciences, Switzerland

Nachhaltigkeit von HochhausfassadenModerator: Marvin King, Technik & Architektur Hochschule Luzern, Schweiz

Envelope performance analyses for low energy buildings with BIPVAlejandro Stochetti, Adrian Smith + Gordon Gill Architecture, Chicago, USA

Benefits of translucent building envelope made of DSC-integrated glassblocksLuisa Pastore, Università degli Studi di Palermo, Italy

Holistic evaluation system for BIPV façadesMaria Roos, Fraunhofer IWES, Kassel, Germany

Glazed photovoltaic-thermal component for building envelope structureTomas Matuska, Czech Technical University, Prague, Czech Republic

Energy, daylight and thermal analysis of a geodesic dome with a photovoltaic envelopeMarco Lovati, EURAC Research, Bolzano, Italy

Brief Presentations:Solar-driven form finding - Functionality and aesthetics of a solar integrated building envelope Walter Klasz, University of Innsbruck, Austria Designing energy generating building envelopes Daniel Mateus, University of Lisbon, Portugal Building skins for the i-Generation: Vision - Design - Product Stefano de Angelis, deltaZERO, Lugano-Paradiso, Switzerland The importance of the basic material research for the development of innovative BIPV Michele Pellegrino, CR ENEA Portici, Italy Technical challenges for the cell interconnection in a customized BIPV module Wendelin Sprenger, Fraunhofer Institute for Solar Energy Systems, Freiburg, Germany

Impacts of building envelope options on hospital energy performanceHeather Burpee, University of Washington, USA A double skin to stimulate the healing environment of a new state-of-the-art hospitalMichel Van der Beken, VS-A Architectes - Ingénierie de l’Enveloppe, Lille, France Reducing the length of stay in hospitals with daylight optimizationHelmut Köster, Köster Tageslichtplanung, Frankfurt, Germany Daylight quality in healthcare designSahar Diab, University of Jordan, Amman, Jordan

Conserving energy with biodiverse building skinsBruce Dvorak, Texas A&M University, USA Passivhaus envelope with modular straw panelsBjørn Kierulf, Createrra, Senec, Slovakia Environmental implications of cork as thermal insulation in façade retrofitsJorge Sierra-Pérez, Universitat Autònoma de Barcelona, Spain The potential application of agro-based polymers in building façadesMahjoub Elnimeiri, Illinois Institute of Technology, Chicago, USA Brief Presentation: Materials for Sustainable Building Skins Innovative pre-coated steels for aesthetical, durable and sustainable building skins Jérôme Guth, ArcelorMittal - Global R&D, Luxembourg

London Sky GardenBernhard Rudolf, Head of Engineering, Josef Gartner GmbH, Germany Unitised façade assemblies for high rise residential buildingsRon Fitch, Trimo UK Ltd. The dynamic response of the semi-closed cavity skin to changing of load conditionFumihiko Chiba, University of Technology, Toyohashi, Japan Brief presentations:Innovative block on housing in the Mediterranean climateCalogero Montalbano, Politecnico di Bari, Italy Acceptance by durability: Quality assurance and insurance favour the use of innovative façades Iris M. Reuther, Technische Universität Graz, Austria Including traditional architectural elements to optimize building skin Joan Ramon Dacosta Díaz, Generalitat de Catalunya, Barcelona, Spain Optimum solutions to satisfy preference façades and energy consumption of an office building Ali Alajmi, College of Technological Studies, Mishref, Kuwait Evolution of building envelopes through creating living characteristics Elaheh Najafi, Iran University of Science and Technology, Iran

Discomfort glare with complex fenestration systems and the impact on energy use when using daylighting controlSabine Hoffmann, University of Kaiserslautern, Germany Structural sealant glazing: reinventing the wooden windowMarc Donzé, Bern University of Applied Sciences, Switzerland

Thermal properties of door and window access systemsWolfgang Rädle, Bern University of Applied Sciences, Switzerland New material for an ecological solution for wooden window frame enlargementsUrs Uehlinger, Bern University of Applied Sciences, Switzerland Brief Presentations:Modelling complex fenestration systems in TRNSYS – a comparison between a simplified and a detailed thermal model Giuseppe De Michele, EURAC Research, Bolzano, Italy Building Elements Smart Technology (BEST) - Analysis of thermal behaviour of windows in old buildings Pierfrancesco Prosperini, University of Camerino, Ascoli Piceno, Italy Measuring condensation water in the interspace of coupled windows Max Bauer, Sapa Building Systems GmbH, Ulm, Germany

Ein Beurteilungs- und Entscheidungsinstrument zur Erstellung nachhaltiger Fassaden mehrgeschossiger GebäudeChristian Hönger, Giuliani Hönger Architekten, Zürich, Schweiz Aus- und Wechselwirkungen von Fassadenentscheiden in frühen Konzept- und PlanungsphasenPatrick Ernst, brücker+ernst gmbh, Schweiz Energie- und Ökobilanzen von HochhäusernGianrico Settembrini, Technik & Architektur Hochschule Luzern, Schweiz Qualitative Wegweiser in der FassadenplanungThomas Wüest, Technik & Architektur Hochschule Luzern, Schweiz Planung und Entwicklung von Gebäudehüllen hoher HäuserReto Gloor, gkp Fassadentechnik AG, Schweiz Gesamtheitliche Betrachtungen der Nachhaltigkeit von HochhausfassadenMarvin King, Technik & Architektur Hochschule Luzern, Schweiz

12:30 - 14:00 Lunch


14:00 - 15:30

Lessons learned from the Solar Decathlon Competitions 2014 and 2015Chair: Hans-Martin Henning, Fraunhofer Institute for Solar Technologies, Germany

Façade Design for Optimized Daylighting Chair: Helmut Köster, Köster Tageslichtplanung, Frankfurt, Germany

Integration and Performance of Phase Change Materials (PCM) in the Building Envelope Craig Farnham, College of Human Life Science, Osaka City University, Japan

New Developments in Concrete for Smart and Energy-Efficient Building EnvelopesChair: Oliver Kinnane, Queen’s University, Belfast, United Kingdom

Adaptive and Dynamic Building Skin DesignChair: Maria Eftychi, University of Cyprus, Nicosia, Cyprus

BIPV 2 - Integration von Photovoltaik in die GebäudehülleModerator: Christian Renken, CRenergie, Schweiz

Photovoltaic technologies used in the prototypes of the Solar Decathlon Europe 2014Núria Sánchez-Pantoja, University Jaume I, Castelló, Spain

The Ekihouse: an energy self-sufficient house based on passive design strategiesRufino Hernéndez, University of the Basque Country, San Sebastian, Spain NexusHaus: prototype for a green alley flatPetra Liedl, School of Architecture, University of Texas at Austin, USA

RhOME for denCity - Inertial mass for lightweight drystone stratigraphyChiara Tonelli, University of Roma TRE, Rome, Italy The Solar Decathlon knowledge for new urban development strategiesIlaria Montella, University of Roma TRE, Rome, Italy A critical review of the Solar Decathlon: origins, evolution, and futureJamie Russell, EPFL, Lausanne, Switzerland

A parametrical study for the optimization of daylighting in advanced façadesNelly Moenssens, University of Leuven, Ghent, Belgium Control strategies and user acceptance of innovative daylighting and shading conceptsMichaela Reim, Bavarian Center for Applied Energy Research, Germany Building envelope design for enhanced daylight distributionErika Figueiredo, Universidade Presbiteriana Mackenzie, São Paulo, Brazil Light and outside vision at restaurantsUrtza Uriarte, Universitat Politècnica de Catalunya, Barcelona Tech, Spain

Brief Presentations:Parans solar lighting system Rawan Allouzi, Ministry of Public Works and Housing, Amman, Jordan Daylight performance analysis for building skin improvement and energy demand reduction Norbert Harmati, University of Novi Sad, Serbia

Thermal performance of lightweight walls with phase change materials (PCM)Efraín Moreles, National Autonomous University of Mexico, Morelos, México Difficulties of heat transfer from PCM type board to ambient roomMartin Zálešák, Tomas Bata University, Zlin, Czech Republic Simulation of the thermal performance of translucent phase change materials and whole-building energy implicationsPhilipp Kräuchi, Lucerne University of Applied Science and Arts, Switzerland Application of PCM panels of different solidus temperatures on inner wall surfaces to reduce seasonal heating/cooling loadsCraig Farnham, College of Human Life Science, Osaka City University, Japan A comprehensive approach to Passive House envelope designJuan F. Rodríguez, University of Castilla, La Mancha, Spain Ultramarine blue pigment with thermal storage for buildingsMaría Isabel Arriortua, Universidad del País Vasco, Bizkaia, Spain

Shrinkage and temperature effects in glass-concrete composite panelsPietro Crespi, Politecnico di Milano, Italy Light transmitting concreteKarsten Heller, LUCEM GmbH, Germany Improvement of indoor air quality using photocatalytic cement-based mortarsChiara Giosuè, Università Politecnica delle Marche, Ancona, Italy Functional lightweight and air purifying concreteJos Brouwers, Eindhoven University of Technology, Netherlands Infra-lightweight concrete in multi-story residential buildingsClaudia Lösch, Technische Universität Berlin, Germany Experimental investigation of thermal mass in hemp-lime concrete wallsOliver Kinnane, Queen’s University, Belfast, United Kingdom

Energy Frames - A new technology for intelligent glazed façadesFrederik V. Winther, Rambøll, Copenhagen, Denmark Biomimetic principles for thermally adaptive façades: thermal adaptability in nature and engineeringSusanne Gosztonyi, Lund University, Sweden Analysis of potential biomimetic applications of skin and shell analogies on the building envelopeLeopoldo Saavedra, Technical University Munich, Germany Adaptive architectural envelopes for temperature, humidity and CO2 controlMarlén López, University of Oviedo, Gijon, Spain

Lightweight modular structure for an energy-efficient adaptive building envelopeMaria Eftychi, University of Cyprus, Nicosia, Cyprus

Die Zukunft der Energiefassade – Von der Gebäudehülle zum EnergiesystemFlorian Fey, Bosch Solar CISTech GmbH, Deutschland Photovoltaik - ein Baustoff mit Charme Patrick Hofer-Noser, Geschäftsführer, Meyer Burger Energy Systems, Schweiz

Von „Building integrated“ zu „Building oriented“ PhotovoltaikUrs Muntwyler, Leiter, Labor für Photovoltaik, Berner Fachhochschule, Schweiz

Gebäudeintegrierte dynamische PhotovoltaiksystemeUlrich Köhl, Vertriebsleiter Solar Shading Europe, Colt International, Berlin, Deutschland Hybrides, stromproduzierendes und transluzentes FassadensystemReto Giovanelli, GWJ ARCHITEKTUR, Bern, Schweiz


A3- Room 7 B3 - Room 3 C3 - Room 4 D3 - Room 6 E3- Room 1 F3 - Room 2

16:15 - 17:45

BIPV 3: Architectural Integration of Photovoltaics into the Building SkinChair: Dieter Moor, ertex solartechnik, Austria

Modeling and Simulation for Enhanced Daylight PerformanceChair: Mitsuhiro Udagawa, Prof. emer. Kogakuin University, Tokyo, Japan

Applications of PCMs in Buildings for Energy Savings and Control of Thermal LoadsChair: Jan Kosny, Building Enclosure Program Lead, Fraunhofer USA, Boston, MA, USA

Wood-cement Compounds for Building Skins – Structure, Building-physics and Sustainability Chairs: Daia Zwicky, University of Applied Sciences, Fribourg, Switzerland, and Alireza Fadai, Vienna University of Technology, Austria

Future Adaptive Building EnvelopesChair: Andreas Luible, Lucerne University of Applied Science and Arts, Switzerland

Textile Membranen für die Gebäudehülle der ZukunftModerator: Robert Roithmayr, TensileEvolution, Österreich

Integration of photovoltaics in a load-bearing timber-glass façadeVitalija Rosliakova, Vienna University of Technology, Austria Building integrated PV applicationsDominik Müller, Solvatec AG, Switzerland Photovoltaics in architecture: separating facts from fictionDieter Moor, ertex solartechnik, Austria

Baukulturelle Potentiale von Solaraktivtechnik in der energetischen SanierungRoland Krippner, Technische Hochschule Nürnberg, Deutschland

Optimised solar shading control systems for passive houses in cold climatesSøren Gedsø, Erichsen & Horgen, Oslo, Norway Measurement method for solar heat gain coefficient of high-performance façades using small solar spectroradiometersTakefumi Yokota, Nikken Sekkei Ltd, Tokyo, Japan Geometric focalization of sun rays in residential building applicationsAlexandra Saranti, Technical University of Crete, Polytechneioupolis, Greece Comparing the efficiency of solar shading devices in reducing building cooling needsOlivier Dartevelle, Architecture et Climat, Université Catholique de Louvain, Belgium Modelling of an anidolique daylight systemDaich Safa, University of Mohamed Khider, Biskra, Algeria

Year-round comfortable environment in a multi-storey building by melting and solidification of PCMVadim Dubovsky, Ben-Gurion University of the Negev, Beer-Sheva, Israel Optimization of PCMs installed on walls and ceilings for light-weight residential buildingsPaulo Tabares, University of Denver, Colorado, USA Aerogel insulation enhanced with phase change material for energy conservation in structuresGeorge Gould, Aspen Aerogels, USA Implementation and application of a PCM model in a hygro-thermal building simulation softwareMatthias Winkler, Fraunhofer Institute for Building Physics, Germany Measuring thermal storage properties of PCMsDavid W. Yarbrough, R&D Services, Cookeville, Tennessee, USA

Application of phase-change materials in buildingsRami Alsayed, Saudi Aramco, Saudi Arabia

Mechanical properties of wood-cement compounds Daia Zwicky, University of Applied Sciences, Fribourg, Switzerland Wood-cement compound-based load-bearing wall elementsNiccolò Macchi, University of Applied Sciences, Fribourg, Switzerland Thermal and acoustic insulation properties of Wood-cement compoundsAlireza Fadai, Vienna University of Technology, Austria Numerical simulations of the overall building-physical performance of wood-cement compound-based building skinsJoachim Nathanael Nackler, Vienna University of Technology, Austria Combustibility of wood-cement compoundsDaia Zwicky, University of Applied Sciences, Fribourg, Switzerland Economic and ecological performance of wood-cement compound-based wall elementsWolfgang Winter, Vienna University of Technology, Austria

Adaptive façades NetworkAndreas Luible, Lucerne University of Applied Science and Arts, Switzerland Monitoring energy and comfort performance of transparent adaptive façadesValentina Serra, Politecnico di Torino, Italy Experimental facilities for adaptive façades characterizationFrancesco Goia, Norwegian University of Science and Technology, Trondheim, Norway Adaptive façade systems – A review of performance requirements, design approaches, use cases and market needsChristian Struck, Saxion University of Applied Sciences, Enschede, Netherlands Adaptive façades System Assessment Shady Attia, University of Liège, Belgium Design for façade adaptability – Towards a unified and systematic characterization Roel Loonen, Eindhoven University of Technology, Netherlands

Textile Architektur: Entwurf bis RealisierungRobert Roithmayr, TensileEvolution, Österreich Textile Architektur: Materialgerecht bauen und EnergieübertragungRainer Blum, Stuttgart, Deutschland Die Haut des PterosauriersHorst Dürr, TensileEvolution, Konstanz, Deutschland Konzepte für mechanisch vorgespannte Membran- und Folien-Konstruktionen in Verbindung mit standardisierten FassadensystemenMarcel Ebert, Bauhaus-Universität Weimar, Deutschland

Conference Program ADVANCED BUILDING SKINS 2015


8:30 - 10:00

BIPV 4 - Architectural Integration of Solar Technologies into the Building SkinChair: Cinzia Abbate, AeV Architetti, Rome, Italy

Energy-Efficient Building RefurbishmentAlex Terzich, HGA Architects & Engineers, Minneapolis, USA

Improving the Envelope Performance with MaterialsChair: Andreas Hempel, International Academy of Architects; former President Association of German Architects BDA

Sustainable Cities: New Developments and Practical OperationChair: Leo W.M. Lau, Green Energy Technology R&D Center, Chengdu, China

Digital Fabrication and Material Systems of the Building EnvelopeChair: Chris Knapp, Bond University, Queensland, Australia

Optimierung des Gebäude-Designs mit Simulationen des GebäudeenergieverbrauchsModeratorin: Monika Hall, Institut Energie am Bau, Fachhochschule Nordwestschweiz, Muttenz, Schweiz

A size-flexible, shade robust photovoltaic system for integration in roofs and façadesJosco Kester, ECN Solar Energy, Netherlands Design of a photovoltaic sliding shutter for a historic mansionStephen Wittkopf, Lucerne School of Engineering and Architecture, Horw, Switzerland Symbiosis between solar technologies in the building envelopeChiara Tonelli, Università degli Studi Roma Tre, Rome, Italy Simple models for architecture with BIPVT or BISTChristoph Maurer, Fraunhofer Institute for Solar Energy Systems, Freiburg, Germany Transformation of a historical coal bunker into a solar power station using multi-colored BIPVKerstin Müller, baubüro in situ ag, Basel, Switzerland

Holistic RefurbishmentStefan Oehler, Werner Sobek, Frankfurt, Germany Differential rates of change as an opportunity in façade replacementAlex Terzich, HGA Architects & Engineers, Minneapolis, USA Smart façades for existing, non-residential buildings: An assessmentKonstantinos Panopoulos, International Hellenic University, Thermi, Greece Energy performance of existent external walls in IstanbulÖzlem Karagöz, Istanbul Technical University, Turkey Timber passive solar façade – an adapative façade for the refurbishment of existing buildingsAntonio Spinelli, Politecnico di Torino, Italy Integrating structural glass systems in historic building facadesMeltem Nevzat, International University, Haspolat, Cyprus

Light-weight panel for buildings: an integrated optimization processFabio Manzone, Politecnico di Torino, Italy Comparing the energy saving of timber frame cladding with PUR foam insulationZdeněk Fránek, Technical University Liberec, Czech Republic A new stucco coating based on pearlescent pigments for improving wall thermal insulationAlessandro Premier, Iuav University of Venice, Italy

Lime carbonation, environmental footprint and Life-Cycle Cost Analysis in mortar applicationsShtiza Aurela, European Lime Association, Brussels, Belgium Soil as skin: ancient rammed earth and passive solar technologies in the modern ageMartin Knap, Atlin, British Columbia, Canada

Design of a zero-carbon town-subdivision in Dongxiang in ChinaJun Mei, Green Energy Technology R&D Center, Chengdu, China Low and zero energy buildings - towards green cities in AustraliaA.B. Sproul, University of New South Wales, Sydney, Australia Sustainable town development - the case of Sino-Singapore Tianjin Eco-city in the perspective of materials and building engineeringQuan Jiang, China Building Material Test & Certification Group Co., Ltd., Beijing, China Zero-energy urban quarter: experiences and results from a university teaching courseUdo Dietrich and Lena Knoop, HafenCity University Hamburg, Germany

Satu Kankaala, Aalto University Properties Ltd., Espoo, Finland

Prototyping of composite structural envelopes through CNC and robotic fabricationChris Knapp, Bond University, Queensland, Australia Advanced ceramic environmental screensRosa Urbano Gutierrez, University of Liverpool and Amanda Wanner, Leeds Beckett University, UK Metal mesh shading devices optimization by parametric approach designAndrea Zani, Politecnico di Milano, Italy Advanced BIM tools for building planning, collaboration and analysisKai Oberste-Ufer, DORMA, Germany

Sonnenschutz und Behaglichkeit – Komfortgewinn durch Optimierung mittels GebäudesimulationEva-Maria Pape, Leiterin, Institut für Energieeffiziente Architektur, Fachhochschule Köln, Deutschland Einfluss der Wärmespeicherfähigkeit auf die energetische Flexibilität von GebäudenMonika Hall, Institut Energie am Bau, Fachhochschule Nordwestschweiz, Muttenz, Schweiz

Optimierung von Gebäude-Design mit Simulationen des GebäudeenergieverbrauchsEmil Grüniger, Soltherm AG, Altendorf, Schweiz Simulation des Eigenverbrauchs für gebäudeintegrierte Photovoltaik (BIPV)Samuel Summermatter, Leiter Ingenieur-Abteilung, BE Netz AG, Schweiz



10:45 - 12:30

BIPV 5 - Innovative Business Models and Financing Mechanisms for PV DeploymentChair: Zeger Vroon, PVPS Task 15, International Energy Agency, Paris, France

Performance-based Retrofit of the Building EnvelopeChair: Matteo D‘Antoni, Eurac Research, Bolzano, Italy

New Materials for Energy-efficient Building EnvelopesRoberto Garay Martinez, Tecnalia, Spain

Sustainable Cities: New Developments and Practical OperationChair: Leo W.M. Lau, Green Energy Technology R&D Center, Chengdu, China

Parametric Design and Simulation of the Building EnvelopeMate Thitisawat, Florida Atlantic University, Fort Lauderdale, USA

Materialien für Ökologische und Energieeffiziente GebäudehüllenModerator: Andreas Hempel, International Academy of Architects; former President Association of German Architects BDA

Transition towards sound business models for BIPVZeger Vroon, Zuyd University of Applied Sciences, Netherlands; International Energy Agency, PVPS Task 15 Integration of photovoltaics in office and commercial buildings: economical and energy optimization Valérick Cassagne, TOTAL - New Energies, Paris La Défense, France

Unlocking the BIPV marketGaëtan Masson, Director, Becquerel Institute, Belgium; International Energy Agency, PVPS Task

Fostering BIPV in the Mediterranean areaGiuseppe Desogus, University of Cagliari, Italy Strategies to increase the deployment of PV in façadesChristian Renken, CR Energie Sarl, Collombey, Switzerland

Performance based retrofitting of façades for nearly zero-energy buildingsSheikh Zuhaib, National University of Ireland, Galway, Ireland Towards user-oriented plug & play façades - Upgrading the energy performance of row housesMieke Oostra, Hanze University of Applied Sciences, Groningen, Netherlands The use of BIM in the restoration of the Teatro LiricoLidia Pinti, Politecnico di Milano, Italy End effectors for an automated and robotic façade componentKepa Iturralde, Chair for Building Realization and Robotics, TU Munich, Germany Retrofitting building envelopes in warm regionsCarolina Caballero Roig, Universitat Jaume I, Castellón de la Plana, Spain

Performance assessment of advanced materials in architectural envelopesRoberto Garay Martinez, Tecnalia, Spain Investigations on vacuum insulation panels based on medium sized powdersRoland Caps, VA-q-Tec, Germany Aerogel: a sustainable manufacture for building applicationFrancisco Ruiz, KEEY Aerogel, France Hygro-thermal performance assessment of prefabricated hemp-concrete wallsTimea Bejat, CEA-Ines, France Making thermal insulation adaptiveNikolaus Nestle, BASF SE Advanced Materials and Systems, Ludwigshafen, Germany Aerogel insulation in refurbishmentMichal Ganobjak, Slovak University of Technology, Bratislava, Slovakia

Review and analysis of exemplary cases of sustainable town developments in the worldLeo W.M. Lau, Green Energy Technology R&D Center, Chengdu, China Energy self-sucient Otaniemi campus

Zoning ordinances as tools for energy self-sufficiencyAnders Nereim, School of the Art Institute of Chicago, USA APEC Low-Carbon Model Town Project: Progress and ProspectKazutomo Irie, Asia Pacific Energy Research Centre, Tokyo, Japan

Exchanges between physical computing and performative parametric modelsMate Thitisawat, Florida Atlantic University, Fort Lauderdale, USA Application of interactive 3D visualization and computation for energy appraisal: enhancing BIM practices in small companiesVladeta Stojanovic, Abertray University, Dundee, United Kingdom Lighting performance simulation and adaptive control of an advanced building skin based on human behavior inputsKristis Alexandrou, University of Cyprus, Nicosia, Cyprus Climate-based control strategies of adaptable ventilated double skin façades to reduce energy consumptionAdrienn Gelesz, ABUD Ltd, Budapest, Hungary

Polypyrrol: Zusätzliche Funktionen für Fassaden aus Biomaterialen Michael Sailer, Unit Innovative Technology in Construction, Saxion University of Applied Science, Enschede, Niederlande Biologisch-abbaubare Gebäudehüllen der ZukunftDaniel Friedrich, Technik & Architektur, Hochschule Luzern, Schweiz Ökologische und energetische Aspekte von Fassadenelementen aus umgeformtem TextilbetonKevin Pidun, Lehrstuhl für Plastik, RWTH Aachen, Deutschland Phasenwechselmaterialien für die Klimatisierung eines WohngebäudesNadège Vetterli, Zentrum für Integrale Gebäudetechnik, Technik & Architektur, Hochschule Luzern, Schweiz Building Information Modeling bei der Ökobilanzierung der GebäudeherstellungGeorg Reitschmidt, Fachgebiet Bauinformatik und Nachhaltiges Bauen, Technische Hochschule Mittelhessen, Giessen, Deutschland Wirkung von dampfdurchlässigen und strahlungsreflektierenden Materialen auf Feuchtigkeitshaushalt, Wärmeübertragung und Dauerhaftigkeit von FassadenHeinrich Thielmann, HTC, Grenoble, Frankreich

12:30 - 14:00 Lunch

A6 - Room 1 B6 - Room 3 C6 - Room 4 D6 - Room 3 E6 - Room 7

14:00 - 15:30

BIPV 6 - From Design Concepts to Real Buildings: How Stakeholders Envision BIPVChairs: Francesco Frontini, SUPSI, Switzerland; Alessandra Scognamiglio, ENEA, Italy

Envelope Performance Simulation and ModelingChair: Valentina Puglisi, Politecnico di Milano, Italy

Super Insulating Materials in Building Components and Systems Daniel Quenard, Centre Scientifique et Technique du Bâtiment CSTB, France

Strategies and Policies to Improve the Energy Performance of BuildingsChair: Renato D’Alençon Castrillón, Universidad Católica de Chile, Santiago, Chile

Membranes for High Performance Building Skins Chair: Kayhan Nadji, Nadji Architects Ltd., Canada

Building-integrated photovoltaics (BIPV) and Building Information Modelling (BIM) from the perspective of a general contractorRobert Hecker, Züblin AG, Stuttgart, Germany PV interpreted and recognized as a façade materialTom Minderhoud, UN Studio, Amsterdam, Netherlands Building Integrated Photovoltaic as a multifunctional façade system: experiences from research and laboratory testsTilmann Kuhn, Fraunhofer Institute for Solar Energy Systems, Freiburg, Germany

New design possibilities with HJT solar cellsChristof Erban, Meyer Burger Energy Systems, Thun, Schwitzerland Making the building skin active: the experience of the construction industryOliver Schwarz, Strabag, Switzerland

Resilience of Swiss offices to climate change: A comparison of four buildings with different façade typologiesDominic Jurt, Lucerne University of Applied Science and Arts, Switzerland Building envelope: assessment and certification of its performanceValentina Puglisi, Politecnico di Milano, Italy

Comparing the eneregy efficiency of a timber curtain wall with an aluminium systemNebojša Buljan, Permasteelisa Group, Rijeka, Croatia Optimal characteristics and dimensions of glazing components in building skinsDavid Kammer, Bern University of Applied Sciences, Switzerland Simulation-based optimization of vertical static shading for improved thermal performanceMouza Mohammed Al Kaabi, Masdar Institute of Science and Technology, Abu Dhabi, United Arab Emirates

Brief Presentations:A new approach for advanced building skin design and testing: the BUILDING FUTURE lab Corrado Trombetta, Università Mediterranea di Reggio Calabria, Italy Design choices and thermal simulations of a test cell facility - Performance tests and building envelope components Giulio Cattarin, Politecnico di Milano, Italy Condensation within building skins: temperature-gradient calculation, modelling and finite-elements simulation Amir Hassan, WSP, Alberta, Canada Simulations with reflective and absorbent materials for a better acoustic quality of the building skin Stefania Masseroni, Politecnico di Milano, Italy The effects of pavement albedo changes on conditioning energy use in buildings as a function of building skin properties Pablo Rosado, Heat Island Group, Lawrence Berkeley National Laboratory, USA

VIP in building applicationsSteffen Knoll, Porextherm GmbH, Germany Advanced Aerogel composite insulation systemsBrice Fiorentino, Enersens, France Benefits Silica technology in building applicationsGabriele Gärtner, Evonik Industries AG, Germany Evaluation of architectural VIP in JapanAtsushi Iwamae, Kindai University, Osaka, Japan Application of Vacuum Insulation Panels in Canada’s NorthDoug MacLean, Energy Solutions Centre, Whitehorse, Canada

The efficacy of policy instruments to reduce the energy use of privately owned dwellingsBram Entrop, University of Twente, Enschede, Netherlands Polices to reduce market barriers for building performanceIrene Boles, Christchurch Polytechnic Institute of Technology, New Zealand Energy performance of buildings in Santiago, Chile: results of unregulated and high solar radiation contextClaudio Vásquez Zaldívar, Universidad Católica de Chile, Santiago, Chile The user‘s benefit as financial reference for building refurbishmentsCarmen Alonso, Spanish National Research Council, Madrid, Spain The influence of end user perception on the economic feasibility of sustainable building skin renovationsBob Bogers, University of Technology, Delft, Netherlands Optimized refurbishment strategies for building envelopes of post‐war office buildingsÖzlem Duran, Centre for Doctoral Research in Energy Demand, London, United Kingdom

Performance analyses of tensile membrane façadesEve S. Lin, Tensile Evolution, Irvine, CA, USA A lightweight plug-in adaptive envelope to reduce the energy consumption of existing buildingsStyliana Gregoriou, University of Cyprus, Nicosia, Cyprus

Architectural membrane for insulation of the building envelopeKayhan Nadji, Nadji Architects Ltd., Canada

Coated textiles: smart wraps for old and new buildingsKatja Bernert, Mehler Texnologies GmbH, Germany Performace analyses of the Ducati superbike pavilionMariangela De Vita, Università degli Studi dell‘Aquila, Italy


A7 - Room 1 B7 - Room 3 C7 - Room 4 D7 - Room 3 E7 - Room 7

16:15 - 17:45

Architectural Integration of Solar Thermal Technologies into the Building SkinChair: Stephen Wittkopf, Lucerne School of Engineering and Architecture, Switzerland

Building Energy Performance Simulation and ModelingChair: Umberto Alibrandi, Nanyang Technological University, Singapore

Aerogel-based Solutions and Adaptive Insulation of the Building Envelope Chair: Samuel Brunner, Empa, Switzerland

Balancing Performance, Cost, and Maintenance: Designing Building Envelopes for Affordable HousingChair: Gianpiero Evola, University of Catania, Italy

Natural and Mixed Ventilation for Increased Comfort and Energy SavingChair: Mario Grosso, Polytechnic University of Turin, Italy

Performance analysis of solar air heating systems for the refurbishment of commercial buildingsBenoit Sicre, Lucerne University of Applied Sciences and Arts, Switzerland Venetian blinds as a solar thermal collector in a mechanically ventilated transparent façadeAlfredo Guardo Zabaleta, Polytechnic University of Catalonia, Barcelona, Spain

Integrating solar vacuum tubes in a high rise building façadeWalid el Baba, Webco sarl, Beirut, Lebanon Architectural integration of solar collectors made with ceramic materialsJordi Roviras Miñana, Universitat Internacional de Catalunya, Barcelona, Spain Thermal analysis of a flat evacuated glass enclosure for building integrated solar applicationsTrevor Hyde, Center for Sustainable Technologies, University of Ulster, UK

Thermal bridging assessment and its impact on the building energy performanceKaterina Tsikaloudaki, Aristotle University of Thessaloniki, Greece

Commissioning and optimization of a new office buildingNiels Radisch, Ramboll, Copenhagen, Denmark Impact of infiltrations in energy demand of a dwelling: Sensitivity to infiltrations for Mediterranean climateSilvia Guillén-Lambea, University of Zaragoza, Spain Lessons of bioclimatic passive design in the Herbert Jacobs II house by Frank Lloyd WrightJuan Sebastián Rivera Soriano, Universidad de la Salle, Bogotá, Colombia Bayesian Networks for uncertainty analysis in building performance simulationUmberto Alibrandi, Nanyang Technological University, Singapore Validation of the PHPP program calculations in Mediterranean climatesBeatriz Rodríguez Soria, Centro Universitario de la Defensa, Zaragoza, Spain

Aerogel – a superinsulation materialWim Malfait, Empa, Switzerland

Aerogel based solution for energy efficiency on the building envelopeSamuel Brunner, Empa, Switzerland Aerogel based plaster for retrofitting façades with historical/cultural valueSeverin Hartmeier, Fixit, Switzerland Application of aerogel technology in curtain wall façadesDavid Appelfeld, Dow Corning Belgium Innovative high performance façades in high-density buildingsRobert Lüder, Glassx AG, Zurich, Switzerland

Optimization through life cycle costs analysis - Social housing retrofitting in ItalyAngela Poletti, Politecnico di Milano, Italy Retrofitting for social housing: A sustainable solution towards zero energy buildingsGianpiero Evola, University of Catania, Italy A cost approach to evaluate sustainable building design for a social housing complexAntonio Talarico, Politecnico di Torino, Italy

Industrialised renovation strategies and prefabrication – Cost optimisation and added values in focusSonja Geier, Lucerne University of Applied Science and Arts, Switzerland

Climate-dependent wind-driven passive ventilative cooling potential in Central and Southern EuropeMario Grosso, Polytechnic University of Turin, Italy

Controlled natural and hybrid ventilation of school gymnasiumsFlourentzos Flourentzou, Estia SA, Switzerland

Natural ventilation in existing buildings by hybrid draft guardJan de Wit, Saxion University of Applied Sciences, Enschede, Netherlands Advanced control of natural ventilation with solar and noise protectionShuqing Cui, Mines Paris Tech, France

Brief Presentation: Performance of the traditional building envelope in Malta Antonio Mollicone, University of Malta, Iklin, Malta

Die grün markierten Sessions werden englisch-deutsch simultan übersetzt

Sessions day 2

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Optimal characteristics and dimensions of glazing components in building skins

Marc Donzé1, David S. Kammer2, Urs Uehlinger2 1 Research and Development; Architecture, Wood, and Civil Engineering;

Bern University of Applied Sciences, Biel, Switzerland

[email protected] 2 Research and Development; Architecture, Wood, and Civil Engineering;

Bern University of Applied Sciences, Switzerland

Abstract

The overall shape and the details of construction projects typically are determined by planning zones, laws, and norms, as well as by economics and by energy requirements and the incidence of light. However, this approach often leads to sub-optimal solutions in respect of thermal efficiency when operating buildings, as the passive solar energy available may not be used optimally inside the building. To achieve a better use of this important source of renewable energy, planers need to be able to assess the influence of their decisions on capturing passive solar energy through the building skin early in the planning process with a simple, yet accurate, software tool.

The impact of glazing on the energy balance of a building depends on factors like the geographic location, surrounding topography and buildings, orientation and the shape and size of the building, building insulation, thermal capacity of the building, transmission losses, light transmission, summer heat protection, heating and cooling energy requirements, energy needs for lighting, and the sources of energy used. Since the glazing of a building’s skin also determines the aesthetics and the uses of said buildings, the software tool needs to allow for an easy, quick assessment of different solutions at the earliest stage of a project.

Keywords: Glazing, building skin, energy assessment, software development

1. Introduction

In recent years, glazed components in the building skin have gained more and more importance in modern architectural design. Buildings with large windows or completely glazed facades are quite common in today's built environment. Increased demand for large glazed components with low thermoconductive properties has led to important research efforts and to modern windows with improved structural and thermal performances.

At the same time, our society faces new challenges with an energy turnaround that aims at reducing the consumption of fossil fuels and of nuclear energy. Given that the energy consumption for heating constitutes a major part of the total energy consumption in many developed countries – heating represents more than 30% of the total energy consumption in Switzerland [1] – new research efforts are needed to help reduce the energy need of contemporary buildings. It is, therefore, important to consider not only the technical aspects of a façade's components, as for instance the windows, but also the building skin as in its entirety. In addition to other energy-saving strategies, the improvement of the facade design of new buildings from an energetic point of view is a promising approach to contribute to the energy turnaround. Well-designed building skins with strategically located glazed elements promise to improve the solar energy gained and thus reduce the needed heating energy.

In this work, we present a case study showing the influence of various building skin components on the thermal performance of a reference building. The main objective is the illustration of the possible energy savings due to an energetically improved design of the building. Further, we present an optimization strategy that allows finding an optimal facade design with respect to the energy consumption for heating. Integrated

512 | Conference Proceedings of the 10th ENERGY FORUM

into a software tool, this approach provides engineers the possibility of finding a better building skin design in the planning stage of a project.

2. Thermal performance of buildings: a case study

2.1 Basics of energy balance of buildings

The energy consumption for heating of a building depends on various factors such as the geographic location, surrounding topography and buildings, orientation, shape, and size of the building, building insulation, thermal capacity of the building, transmission losses, light transmission, summer heat protection, heating and cooling energy requirements, energy needs for lighting, and the sources of energy used. The energy needed for heating is generally computed by determining the energy balance of the building including energy losses and gains, which is given by Equation (1).

(1)

where is the required annual energy for heating, is the energy loss by transmission, the energy loss by ventilation, the energy conversion efficiency, the internal energy gain, and the solar energy gain.

The various losses and gains have multiple causes. For instance, the wall, the windows and the roof contribute to the loss by transmission, and various household appliances, the lighting and the room occupation add to the internal energy gain. The energy losses and gains of this case study are computed following the guidelines of the SIA 380/1 norm [2].

2.2 Case study description

The potential of an improved building skin for decreasing the heating energy consumption of residential houses is illustrated in this case study. The reference building is a typical single-family home with a first floor build in masonry and a second floor with a wooden structure. It is located in Lajoux in Switzerland at an altitude of 1020m above sea level. The principal properties are summarized in the following table.

Properties Value

Living area (reference area) [m2] 225.6

Area of building skin [m2] 451.2

Area of vertical facade [m2] 214

Area of glazed elements [m2] 31.8

Area of south-oriented facade [m2] 70

Area of glazed elements in south-oriented facade [m2] 20

Shade coefficient of south-oriented facade 0.77

Table 1: Properties of reference building.

It can be expected that the type of window and glasses, the insulating property of the walls, and the share of the glazed area in the south-oriented facade are some of the most influential factors for the energy balance of the building. In addition, the location of the building is of great importance for the heating energy consumption as well as for the energy-saving potential of smart building skin designs. The influence of these main factors is analyzed by computing the energy balance for the reference building with two different window types, two different glazing elements, two different areas of glazed elements in the south-oriented facade, two different types of wall insulation, and at two different locations. In total, this results in 32 different cases, which are then compared in respect to the heating energy requirements.

The two different types of windows used in this case study are summarized in the following table:

ADVANCE BUILDING SKINS | 513

Description Conductance of frame [W/m2K]

Area of glass (share)

PVC window 1.45 0.79

Wood/Aluminum window 1.46 0.88

Table 2: Properties of windows used in the case study.

Description Conductance

[W/m2K] Psi value

[W/mK] Energetic

transmission Insulated double-glazed 1.1 0.05 0.6

Insulated triple-glazed 0.6 0.04 0.5

Table 3: Properties of window glasses used in the case study.

Furthermore, the share of glazed elements in the south-oriented facade is modified from 28%, which corresponds to a facade of a typical family home, to 45%, where the entire top floor is equipped with glazed elements. The two different types of wall insulations present conductance of 0.14 W/m2K and 0.06 W/m2K, respectively. The energy balance is computed for the reference building at two locations. The first location, Lajoux, is a mountainous region at an altitude of 1020m above sea level, whereas the second location, Neuchatel, is at a much lower altitude (480m).

2.3 Results and discussion

The results of the energy balance computation of the reference building at Lajoux are shown in Figure 1.

Figure 1: Required annual heating energy for reference building at Lajoux.

As expected, the wood/aluminum windows (in this particular case) and the triple-glazed windows result, compared to their counterparts, in slightly lower energy needs for heating. This is due to lower conductance values and lower share of the frame area, which lead both to lower energy losses through the windows. However, the effect of both factors, the window type and the glass type, is considerably smaller than the energy saving achieved with better insulated (thicker) walls and larger shares of the south-oriented glazed area.

Similar results are observed for the energy balance of the reference building located in Neuchatel, as shown in Figure 2. In both cases, the energy savings with more insulated walls and larger south-oriented windows are essential and can reach values up to 50% of the total heating energy consumption of a household.


Figure 2: Required annual heating energy for reference building at Neuchatel.

This case study illustrates the importance of glazed elements in the building skin and the large potential to decrease energy consumption through an increase in solar energy gains. However, several aspects make the problem of finding an optimal building skin design for minimal energy consumption, tricky. These have been neglected so far. First of all, the presented energy balance computations are based on a monthly estimated of energy losses and gains. In reality, however, large temperature variations occur within the duration of a month. The interaction of these variations and the thermal inertia of the building make the problem nonlinear and the computation of the annual energy consumption more challenging.

Moreover, one could think that a building with a fully glazed south-oriented facade and without any windows in the north-oriented facade is the optimal solution. This approach, however, would most probably lead to overheated buildings during the summer months, which then would require another energy-consuming technology: air-conditioning. It is therefore likely that the optimal building skin design with respect to minimizing heating/cooling energy needs is not an extreme case (e.g., fully glazed facade). Finding such a (near-) optimal design is not a trivial problem considering its nonlinear nature and needs well-adapted methods. One such strategy is presented in the following section.

It is also worth noting that an optimal building skin design resulting in minimal energy consumption might not necessarily be “the” optimal solution if other aspects, such as living comfort, structural feasibility, and construction cost are considered.

3. Optimization strategy

The case study has shown that the energy-saving potential of well-designed building skins with respect to the glazed elements is important. It is therefore desirable to have an optimization strategy which allows for a quick detection of an optimal building skin during the design phase of a construction project. However, given that this search for an optimal solution involves a complex nonlinear problem, which requires considerable computational time for each annual energy balance determination, it is important to choose a well-adapted optimization strategy.

An important first step is the definition of a sampling plan (also known as experimental design) providing a set of parameter combinations for which the energy balance of the analyzed building is computed. The various parameter combinations should be distributed in the parameter space such that the sampling density is as uniform (homogeneous) as possible. One type of sampling plan, which is well adapted for this problem, is the Latin hypercube, where each parameter dimension is separated into N slices and N sampling points are distributed such that no slice has two points. An example of a two dimensional Latin hypercube is shown in Figure 3.


Figure 3: Two-dimensional Latin hypercube with 10 sample points.

Multiple Latin hypercubes of different space-filling character exist for a given multi-dimensional parameter space. Finding the most space-filling one is an optimization problem itself. Forrester et al. [3] proposed an optimization procedure based on an evolutionary process. Increasing population size and number of generations lead to better space-filling properties, but also to longer computational time. The improvement of the space-filling character of a Latin hypercube with increasing generations and population size is here analyzed at the example of a 20-dimensional parameter space with 30 sampling points. The results are shown in Figure 4.

Figure 4: (left) Space-filling property of Latin hypercube depending on the number of iterations (generations) and the population size (right) Computational cost (in seconds) to compute the Latin hypercube depending on the number of iterations and the population size. All results are averaged over 12 measurements.

These results show that the evolutionary process increases well the space-filling character of the Latin hypercube. Initially, the improvement is fast for each additional generation or population member. With increasing number of generations and population size, the increase in the space-filling property slows down, but the computational cost is growing even faster.

The values of this analysis cannot be generalized to problems of different dimension or number of sampling points. It shows, however, that the improvement in the space-filling property is comparable for increasing generations and populations with similar associated computational cost. The result is therefore “strategy- independent” and is mostly determined by the used computational time.

Starting from the sampling plan, various strategies can be pursued to find the optimum. If the studied building


is large and involves many facades, the computational time for the determination of a single energy balance (i.e., for one sample point) is high and the optimization procedure needs a surrogate model [3,4]. If, however, the building is small and the computational cost for an energy balance calculation is low, another strategy is more efficient in finding the optimal building skin design. In this case, a local search (e.g., steepest-descent, or Quasi-Newton methods), which uses full energy balance computations, can be started at each sampling point. This should lead to several local minima, which then can be compared to determine the best solution.

4. Conclusion

In this work, we have shown that glazed elements in the building skin have an essential effect on the energy balance of the building. It was illustrated that windows in the south-oriented facade can contribute favorably to the objective of decreasing energy consumption for heating by gaining additional solar energy. To be able to benefit from the solar energy, the building skin has to be considered as an entity and its design should be optimized during the planning phase of a construction project. We further highlighted that fully glazed facades are not necessarily the optimal solution from an energetic point of view as it could lead to overheating during the warm season and cause increased energy consumption due to air-conditioning. We finally proposed to start the optimization procedure with sampling plans of the type of Latin hypercubes and analyzed the potential improvement of their space-filling character with an evolutionary process.

5. References

[1] TEP Energy GmbH, Prognos AG, Basel, Infras AG, Bern, “Analyse des schweizerischen Energieverbrauchs 2000 - 2013 nach Verwendungszwecken”, 2014.

[2] SIA, Schweizerischer Ingenieur- und Architektenverein, “SIA 380/1 – Thermische Energie im Hochbau”, 2009.

[3] Alexander Forrester, Andras Sobester, and Andy Keane, “Engineering Design via Surrogate Modelling: A Practical Guide”, Wiley, 2008.

[4] B. Ladevie et al., “Analyses multicritères et méthode inverse en simulation énergétique du bâtiment”, 2012.


Structural Sealant Glazing (SSG) – reinventing the wooden window

Marc Donzé1, Urs Uehlinger1, Christoph Rellstab1, Urs Buehlmann4

1 Research and Development; Architecture, Wood, and Civil Engineering

Bern University of Applied Sciences, Biel, Switzerland

[email protected] 4 Department of Sustainable Biomaterials, Virginia Polytechnic Institute, USA

Abstract

To facilitate the manufacturing of wooden windows and to use the structural capabilities of glass, structural sealant glazing (SSG) technology, widely used in other industries such as car manufacturing, has been incorporated into the traditional windows design. Indeed, gluing the glass into the window frame facilitates the windows manufacturing process, which thus helps make windows less expensive and helps wooden windows, which generally are more expensive than plastic or metal windows, to be more cost-competitive. Also, the new system offers additional benefits, such as narrower frame widths or reduced exposure of the wood frame to the elements.

However, gluing glass onto other materials, such as wood, is a challenge. The bond of such a connection has to safely withstand stresses from daily operation, from UV exposure, as well as from external forces over the product’s lifetime. Thus, researchers at Bern University of Applied Sciences researched the benefits of using such structural sealant glazing (SGG) technology by reinforcing insulated glass elements with a steel profile that is being glued onto the glass edge, thereby making the glazing a structural element of the windows system. Tests found that such reinforced systems can increase a window's rigidity by as much as 13 times while the deformation due to the temperature difference between the two faces increases from L/540 to L/740 between the most rigid and the least rigid system. These positive results form the basis for further research to create a windows system that is fully functional and easy to manufacture.

Keywords: Structural Sealant Glazing (SSG), wood windows manufacturing, stiffness of glazing

1. Introduction

The wood window, the dominant window construction in Europe for centuries, has seen its dominance wither with the introduction of metal and PVC windows after WWII. The windows market in Western Europe (all countries belonging to the West prior to the fall of the wall in 1989) is estimated at 57 million units (turnover of 22 billion Dollars) annually with approximately 34% of the market residing in the German speaking part of Europe (Austria, Germany, and Switzerland, e.g., the DACH region). In Germany, almost 60% of the windows sold are PVC windows, followed by metal, wood, and wood-metal windows, all of which own less than 20% of the market (Anonymous 2015a), a distribution that is similar to the one found in Austria (Anonymous 2015b. In Switzerland, maybe due to more innovation by the wood windows manufacturers, PVC windows have less than 50% market share, while wood windows and wood-aluminum windows share more than 20% each, with metal making up the rest (Anonymous 2015c).


2. Background

In the DACH region (Austria, Germany, Switzerland) the wood window, which also includes wood windows with aluminum cladding, faces two major disadvantages against its competitors using PVC and/or metal:

- initial purchase price

- maintenance frequency and costs

The high cost of purchase stems to a large part from the rather labor-intensive assembly that traditional wooden windows require. In particular, the fixation of the glass into the windows frame with wooden battens requires considerable efforts by human labor and is difficult to automate. Figure 1 shows such a traditional wooden window.

Figure 1: Example of traditional wooden window with glass fixed into frame by wooden battens (Source: test report BFH).

However, in the public mind, wooden windows are perceived as requiring more maintenance than PVC windows due to the need to repaint the wooden surfaces every 5 to 10 years. Since such windows also cost up to twice as much as PVC windows, customers often prefer to go with the cheaper alternative. However, wooden windows are perceived as much more ecologically preferable than PVC-based windows. Thus, the future success of wooden windows systems will be largely determined by:

- cost (production and operation)

- ecological properties (raw material, production, and operation)

Furthermore, today's modern window systems need to be capable to accommodate the design preferences of modern architecture, which is often dominated by large openings for light and warmth. Thus, modern windows systems need to be mechanically strong to allow for freedom of design, yet have to meet safety and energy regulations while assuring proper operation and desired aesthetic. For the manufacturer, they also have to be profitable and carry little or no liability.


3. Results

3.1 Originally developed solution

In the late 1990s, researchers at Bern University of Applied Sciences together with industry collaborators investigated potential solutions to make wood windows more appealing for planners, builders, and owners. The goal was to develop a better system (strength, energy efficiency, maintenance) that is aesthetically pleasing, provides architects and designers with freedom to design based on their preferences, while reducing manufacturing costs. The researchers' attention was soon caught by structural sealant glazing (SSG) technology, widely used in the car industry and by the construction industry to build glass facades. Figure 2 shows the idea developed.

Figure 2: Schematic drawing of window-cross section of the newly developed wood window system (the adhesive bond is highlighted in red).

The appealing fact of the SSG technology is that the glass overtakes mechanical functions within the window and is not merely a burden to the windows frame. Figure 3a shows a traditional European wood window, where the glass is carried by the frame using glass packers. Glass packers transfer the forces from the glass to the frame. Figure 3b shows a frame with an adhesively bonded glass, where the forces are transferred continuously over the entire length of the bond making the frame much stiffer.

Figure 3a: Traditional wood window construction using glass packers and unevenly distributed forces.

Figure 3b: Adhesively bonded glass in wood window frame with evenly distributed forces.

3.2 Improved solution concept

The improved wood window shown above (Figure 2) has some shortcomings of its own. While the structural sealant glazing (SSG) technology reduces manufacturing and maintenance costs and improves the static properties of the window, there are two main issues that need improvement:


• Broken windows: when the window glass is broken, the entire window frame has to be exchanged with a new one, thus creating large repair costs.

• Manufacturing: While SSG windows allow the automation of the insertion and the fixation (gluing) of the glass into the window frame, the investment costs are significant.

These two main disadvantages of SSG wood windows with glued glazing slow the adaptation of the technology considerably. Researchers at the University of Applied Sciences Bern (BFH) with support from the Swiss Commission for Technology and Innovation (CTI) started a search for solutions to these two main drawbacks. The project's goals were listed as follows:

• Favorable mechanical properties to allow for the largest design freedom possible,

• Good insulation properties, at least as good as current systems,

• No or little additional investments required for manufacturing such windows,

• Repairing a broken window without the need to replace the entire frame.

3.2.1 Solution

The solution developed by BFH researchers calls for gluing the glass onto a batten that is being fixed on the outside of the window frame. For this purpose, a special plastic profile was developed that is being mechanically fixed to the window frame (e.g., with screws), as shown in Figure 4.

a) b) c)

Figure 4: Semantic representation of the new SSG system for wooden windows, a) positioning of glass and plastic profile on the window frame, b) gluing of the glass to the plastic profile, mechanical fixation of plastic profile to the wooden window frame, c) overview of newly developed window system.

3.2.2 Adhesion

The gluing of the glass on the window's outside requires close attention in respect to the longevity of the glue, as such a bond has to withstand the climate (moisture and temperature) as well as the UV rays from the sun. The UV rays in particular are known to be able to render bonds useless within short periods of time. It was thus decided to test the most common adhesive used by the window and glass industry for SSG applications. The products tested were, in particular:

• One-component silicon (Sikasil SG20)

• Two-component silicon (Sikasil IG 25 HM)

• Two-component acryl (SikaFast 5215 NT)

• Two-component polyurethan (SikaForce 7888 L10)

• Acryl methylmethacrylat (Araldite 2047)

Adhesives from the silicon group (e.g., Sikasil SG20, Sikasil IG 25 HM) have good elastic properties, which makes them, however, less than perfect for creating a stiff bond. Yet, silicon-based adhesives typically have


excellent weathering and UV-resistance properties, which makes them of interest for this application. The three other adhesives tested (e.g., two-component acryl (SikaFast 5215 NT), two-component polyurethan (SikaForce 7888 L10), and acryl methylmethacrylat (Araldite 2047)) are more favorable to create stiff adhesion bonds but are inferior to silicon-based products in terms of weathering and UV resistance.

0

1

2

3

4

Sikasil SG20

Sikasil IG 25 HM

SikaFast 5215 NTSikaForce 7888 L10

Araldite 2047

Estimation of weathering resistance

Moisture resistance Temperature resistance UV resistance

Excellent: 4

Good: 3

Moderate: 2

Poor: 1

Figure 4: Comparison of the capabilities (moisture, temperature, UV) of the adhesives tested based on third party reports.

3.2.3 Adhesion

Based on the information publicly available and on findings from preliminary testing, three adhesives (Sikasil IG 25 HM, SikaFast 5215 NT, and SikaForce 7888 L10) were chosen to conduct mechanical testing. In particular, the slip modulus (Kel) as well as the shear stress at failure (τu) was tested according to SN EN 14869-2 (SNV 2011). Results are shown in Table 1.

Adhesive Number of samples slip modulus Kel [N/mm]

Shear modulus G [N/mm2]

shear stress at failure τu [N/mm2]

Sikasil IG 25 HM 10 58 0.43 0.8

SikaFast 5215 NT 8 1304 11.2 2.1

SikaForce 7888 L10 10 2826 20.5 5.1

Table 1: Mechanical properties of adhesives tested (slip modulus (Kel), shear modulus (G), and shear stress at failure (τu)).

3.2.4 Geometry of the frame

To find optimal sizes for the frame in respect of their mechanical properties, iterative calculation methods and actual testing was employed. The mechanical properties of the window system were calculated using the "γ" method. The "γ" method allows the calculation of the bending stiffness (EIeff) of a construction assembled from different materials. After several rounds of theoretical calculations of potential solutions, a system consisting of beech wood with the swing frame (e.g., the part of the window that can be opened) with cross section dimensions of 55/55mm and the fixed frame (e.g., the part of the window that holds the swing frame and that is fixed to the wall) with cross section dimensions of 70/80 mm was found to be most advantageous (Figure 5). To fix the glass on the outside of the swing frame, a fiberglass plastic batten from "Fiberline Composite" was selected.


70/80

55/55

Figure 5: Crosscut of the newly developed windows system with exterior adhesion.

3.2.5 Evaluation

After the theoretical development of the new windows system, its mechanical properties were tested in the laboratory. In particular, 4 points bending tests of the swing frames were conducted. While this 4 points bending tests are not part of any recognized standard, it allows to assess the mechanical properties of the windows system and enables the review of the values calculated using the "γ" method. Figure 6 shows a visual representation of the test set-up.

Figure 6: Picture of the 4 points bending tests of the swing frames

The results of these 4 points bending tests of the swing frames (Figure 6) are dependent on the slip modulus (Kel) of the adhesive (Table 1). The most elastic adhesive (Sikasil IG 25 HM) achieves an Eleff of 2.7*10e10 Nmm2 in the windows system. This is 1.5 times better as the swing frame without fiberglass plastic batten and without adhesion. The window system achieves the best value (Eleff) when the least elastic adhesive (SikaForce 7888 L10) is being employed. With this adhesive, the swing frame obtains a stiffness that is 1.9 times better than obtained for the swing frame without fiberglass plastic batten and without adhesion. Figure 7 shows the results obtained for the 4 points bending tests conducted.


1.50E+10

1.70E+10

1.90E+10

2.10E+10

2.30E+10

2.50E+10

2.70E+10

2.90E+10

3.10E+10

3.30E+10

3.50E+10

0 500 1000 1500 2000 2500 3000

Eff

ect

ive

Sti

ffn

ess

EI e

ff[N

mm

2]

Slip modulus Kel [N/mm]

Effective Stiffness EIeff

Theoretical

Experimental

Only Wood

Sikasil IG 25 HM

SikaFast 5215 NT

SikaForce 7888 L10

Figure 7: Relationship of the slip modulus (Kel) and bending stiffness (EIeff) for the three adhesives (Sikasil IG 25 HM, SikaFast 5215 NT, and SikaForce 7888 L10) and the wood swing frame alone.

The bending stiffness (Eleff) of a wood/metal windows systems with crosscut measurements of 65/65 mm achieves bending stiffness values of approximately EIeff = 1.9*10e10 Nmm2. Compared to these values, a window system with exterior adhesion of the glass using a fiberglass plastic batten with an elastic adhesive (Sikasil IG 25 HM) achieves approximately 40% higher values. The system with the least elastic adhesive tested (SikaForce 7888 L10), achieves values that are 75% higher. Figure 7 also demonstrates the relative accuracy of the theoretical calculations using the "γ" method. The deformation of this newly developed windows system tested in bending was found to be approximately linear up to failure. Failure then occurs in the insulation glass system between 12 and 17 kN.

4. Conclusions and next steps

This project developed and tested a new window system with exterior adhesion of the glass batten. For this purpose, theoretical calculations helped find the best geometry of the system and samples in the scale of 1:1 were then tested for their mechanical properties. Those tests showed the soundness of the new system and also demonstrated the relative accuracy of the theoretical calculations using the "γ" method. However, more research and development is necessary to bring the system to market, among them, the following challenges need to be addressed:

• At this time, no adhesive exists that provides an optimal combination of stiffness and weather and UV durability.

• The only adhesives that provide the necessary durability are based on silicon. However, despites the silicon-based adhesives elasticity, such adhesive increase the stiffness of the construction considerably.

• The manufacturing of the prototype windows went without problems. However, some details need to be investigated, still. Examples include assuring the tightness of the fiberglass plastic batten – wood frame connection, or the best type of fixation of the batten onto the wooden frame (in the prototypes used in this test, screws were employed).

• The application of the adhesives onto the glass and the fiberglass plastic batten, done manually for the prototypes manufactured, needs to be investigated and optimized. The manual application of the


adhesive does not require large investments on equipment and thus supports smaller shops with limited capacity to invest. Another scenario could be that the insulation glass manufacturer glues the fiberglass plastic batten onto the glass at the factory.

• The cross-section of the swing frame was designed rather large (55mm/55mm) to allow for the easy fixation of the hardware. This size could possibly be reduced when the hardware is being fixed onto the fiberglass plastic battens.

The tests conducted have shown that the concept developed is valid and achieves the main objectives of the project. Most importantly, broken glasses now can be replaced without replacing the entire swing frame. More work is needed to bring the system to market, but this research has proven the idea.

5. Acknowldedgements

The Swiss Commission for Technology and Innovation (CTI) supported this project, whose contribution is gratefully acknowledged.

6. Literature Cited

Anonymous. 2015a. Fenster- und Türenbranche rechnet mit gutem Jahr 2014. Bundesverband Flachglas. url: http://www.bundesverband-flachglas.de/presse/pressemitteilungen/2014/pm_03_2014_2.html. Accessed June 15, 2015.

Anonymous. 2015b. Die Fensterindustrie. Plattform Fenster und Fensterfassaden. url: http://kunststoffe.fcio.at/Default.aspx?site=fensterundfassaden.at&menu=Die_Fensterindustrie. Accessed June 15, 2015.

Anonymous. 2015c. Westeuropas Fenstermärkte vor Trendwende. Schweizer Holzzeitung. url: http://www.holz-portal.ch/westeuropas-fenstermaerkte-vor-trendwend/150/89/233935. Accessed June 15, 2015.

SNV. 2011. Strukturklebstoffe - Bestimmung des Scherverhaltens struktureller Klebungen - Teil 2: Scherprüfung für dicke Fügeteile (ISO 11003-2:2001, modifiziert). Schweizer Normen Vereinigung. Ausgabe: 2011-08.


Thermal properties of door and window access systems

Wolfgang Rädle1, Bernhard Letsch1, Peter Hans Kümmin1, Urs Uehlinger1, Urs Buehlmann2

1Research and Development; Architecture, Wood, and Civil Engineering; Bern University of Applied

Sciences, Biel, Switzerland 4Department of Sustainable Biomaterials, Virginia Tech

Abstract

Over the past decades, building skins have become much better insulated to minimize the operational energy requirements of buildings. One of the foci for increased insulation properties of building skins are doors and windows, as they have traditionally suffered from insufficient thermal properties. Today, systems exist that provide outstanding insulation properties, with the look being the weak spot. Water inside the access systems influences sensitive electronics controlling and operating the look and damages wood-based doors. Thus, research was conducted to evaluate existing looks’ performance regarding thermal insulation, air tightness, water tightness, and condensation. Based on these tests, prototypes of improved locks were then constructed and tested.

Researchers at Bern University of Applied Sciences investigated a door look system to address the shortcomings of existing looks in respect to thermal insulation and condensation. For the purpose of this research, a door look system comprises of door handle, lock cover, and the closing and locking mechanism. Such an access system that is available on the market was tested in respect to thermal insulation, air tightness, water tightness, and condensation on an actual building built according to the Minergie standard.

Results show that temperatures throughout the access system tested follow the respective temperatures on both sides of the system, indicating the existence of less than optimal thermal properties under the viewpoint of hands-friendly surface temperatures. Humidity inside the access system is also dependent on the outside conditions on both sides of the system. However, humidity inside the system is also dependent on the pressure differential between the two sides. While no damaging levels of humidity inside the access system were measured at any time during these tests, results indicate a need to design a better access system case to increase its surface temperatures and to reduce the existence of humidity inside the access system to better protect the electronic components of the system as well as the door itself.

Keywords: door lock, condensation, air tight, watertight, mechatronic

1. Introduction

As of today, no house access system (i.e., handle and look, Figure 1) specifically designed for energy efficient buildings are being offered on the market. However, as the building skins are becoming ever tighter in respect to heat, air, and water to meet today’s stringent energy requirement goals and to secure high comfort of living in those buildings, traditional access systems are still a weak spot. Systems sold today are often the source of high levels of humidity inside the element, due to potential leakage into the look of rain or snow or due to the occurrence of condensation from air flow. The humidity affects the reliability of the electronic access system and, longer term, causes damage due to corrosion. Also, further damage can be caused to the surrounding wood-based engineered materials, if the door in question is made of a hygroscopic material.


Figure 1: Example of traditional house door access system used (source: Glutz).

Also, today’s modern architecture, which exposes large parts of a building’s skin to the elements, it is possible that rain hits the door and it’s look directly during certain weather situations. However, todays access systems technology does not offer protection against such direct impact of the rain, thus allowing the water to penetrate into the system and cause damage to the surrounding area of the door as well as impacting the electronic access system negatively in terms of reliability and longevity.

These problems, long known to specialists in the field, but not being perceived as important and attractive enough to be addressed, have become more pronounced with the ongoing improvement of the building skin over time. In particular, the improved air tightness of the building skin and the increase in use of mechanical air conditioning systems have lead to increases of situations where there is a pressure difference between the inside and the outside of a building. These existing pressure differences combined with the increased air tightness of modern building skins create considerable volumes of air-flow through remaining leaks leading to an increased potential of building up humidity in such places. However, testing of the building skin most often does not reveal the weakness of the access system, as existing standards only apply to the entire door and not to individual components of the door. Thus, the access system, being just a relatively small part of the entire door system, does not invite scrutiny. Furthermore, even when a building is tested for air tightness, the entrance door is typically used to blow air into the building (blower door measurement), and thus the door and its access system is not part of the standard test.

Thus, little is known of the performance of standard access systems in actual situations. Empirical observations exist of damage caused by differences in air pressure combined with high volumes of air flows through the access system. However, no data is currently available as to the performance of such systems in terms of temperature and pressure gradients as well as in terms of absolute and relative humidity surrounding the system. Using an actual building, this study investigated the performance of one access system available on the market today.

2. Methods

To gather data on the performance of a standard access system in respect to temperature and pressure gradients as well as in terms of absolute and relative humidity surrounding the system in daily use in an actual situation, a commercially available access system made by Glutz, a leading Swiss manufacturer, was installed into an entrance door of a single family home in the suburbs of Solothurn, Switzerland build according to the Minergie Standards (Verein Minergie® 2014), yet not being certified . This entrance door in question faced west. Measurements including temperature on the inside and on the outside, differential pressure between the inside and the outside of the building and relative humidity inside and outside as well as inside the access system were taken. Figure 2 shows a cross cut of the access system and demonstrates the locations of the measurement points inside the system with red indicating surface temperature measurements and blue indicating measurements of relative humidity and air temperature.


Figure 2: Cross cut through Glutz access system used and measurement points. Inside the building is to the right (Drawing: Glutz and BFH).

Data was registered continuously over the length of the test. The test used measurement registration equipment from Ahlhorn (Almeno 2690 and 2890-9), pressure measurement devices (Alhorn DPS), thermo couples type K, humidity sensors from Sensirion (SHT 75), and a weather station. Figure 3 shows the actual door and pinpoints the locations for the outside pressure (“Messpunkt Luftdruck Aussen”) and for the ambient outside temperature and relative humidity (“Messpunkt Lufttemperatur und Luftfeuchte Aussen”).

Figure 3: Picture of door and measurement points for outside air pressure, temperature, and relative humidity.

The test was conducted from November 27, 2012 to April 16, 2013, with measurements analyzed from December 17 to December 24, 2012. Air temperature and relative air humidity as well as door access system temperature and humidity at the measurement points (Figure 2) were measured and recorded continuously over the time period of the tests.


3. Results

Figure 4 shows the temperatures measured at the measurement locations (Figures 2 and 3) the period from December 17 to December 24, 2012. Figure 5 shows the differential pressure between the inside and the outside of the building at the entrance door and the absolute humidity at the measurement points over the same period. Figure 6 displays the relative humidity inside and outside the building at the access system at the entrance door as well as inside the access system from December 17 to December 24, 2012.

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Figure 4: Temperature recorded at the measurement locations from December 17 to December 24, 2012


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Figure 5: Differential pressure between the inside and the outside of the building and absolute humidity at the measurement points from December 17 to December 24, 2012.

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Figure 6: Relative humidity inside and outside the building and inside the access system points from December 17 to December 24, 2012


4. Discussion

The temperature curve on Figure 4 shows that the temperatures throughout the access system follow the outside temperature. The peak outside temperatures on 21. 12. to 24. 12. 2012 show the influence of the evening sun shining on the door and its impact on the system’s temperature. The most pronounced effect of these sun-rays hitting the surface of the building component is at the location of the antenna for the access system. The antenna in this particular access system model (and thus the temperature and humidity sensor (Sensirion SHT 75) inserted at this location) are covered by a black plastic cover, heating up the location more than at other locations of measurement, where brighter colors (silver as from galvanized metal) were less impacted by the sun. However, the impact of the sun is visible throughout the access system’s surface, and can be seen even at the inside of the access system.

Figure 5 shows a permanent difference in air pressure between the outside and the inside with a range of ±5 Pa around zero. As the house used for this study has no mechanical air-conditioning system, the reason for this phenomena are natural (wind, temperature, user behavior). For example, the data shows when the kitchen stove air exhaust is running. Figure 5 also shows the absolute humidity inside the access system, where higher absolute humidity was measured at the inside face of the system. However, absolute humidity inside the access system cycles according to its cycles on the outside. Thus, absolute humidity inside the access system facing outside fluctuates in tandem while the absolute humidity inside the access system facing the inside of the building fluctuates in tandem with the absolute humidity on the inside of the building. The never-ending switching of the difference in air pressure from positive to negative around the access system supports the adjustment of the absolute humidity to the levels existing on the outside of the system.

Figure 6 supports the observation made on Figure 5. Figure 6 shows the levels of relative humidity measured outside and inside the access system as well as the temperature on the outside of the system. As with absolute humidity, relative humidity adapts to the existing conditions on the outside of the access system. However, during the duration of the tests, no damaging levels of humidity to the access system were measured at any time.

Modern access systems rely on electronic components to do their tasks. Thus, humidity matters much more than in the days when looks functioned purely mechanical. In the climate in question (Central Europe) and without air-conditioning being present, the potential for high humidity exists at all openings of a building where air-exchange between the inside and the outside occurs. When warm air with large amounts of humidity wander through the opening towards the colder side of the building, condensation may occur if the temperature differential is large enough. Access systems represent such an opening in the building skin and thus the levels of humidity occurring inside the system need to be understood and, in the final product, be controlled as possibly large amounts of humidity or liquid can accumulate. For example, given the situation as tested in this study, if the inside temperature of a building on a winter day is 20o Celsius with a relative humidity of 54 percent, while the outside temperature is 0o Celsius and the inside pressure is 4 Pa higher than the outside, as much as 0.9 g of water per hour can potentially accumulate inside the access system. To illustrate, this accumulation is equivalent to throwing the equivalent of an Espresso-sized glass of water into the access system casing every day.

This study has clearly demonstrated the importance of obtaining better understanding of and, ultimiately, better controlling the climatic events happening inside and surrounding modern access systems. Attention must be paid to the air penetration of such systems as well as to the thermal properties of such access systems. Additional challenges to be mastered exist in the form of protection against rain.

5. Conclusions

Research was conducted on a single-family home main entrance door access system (e.g., door look) available on the Swiss market. Focus was given on the temperature and the humidity throughout the system while in normal daily use at a single-family building in the suburbs of Solothurn, Switzerland with the door facing west. Measurements from December 17 to December 24, 2012 were analyzed.

Results include that current access systems such as the one tested perform less than optimally in terms of


heat transfer. Temperatures from both sides of the system were transferred through the system with relative ease, creating the potential for undesirable energy transfers. However, given the small area of building skin covered by such access systems, this effect is rather minor. More importantly is the humidity that traveled relatively easily through the system, with the pressure differential between the two sides of the system playing a critically important role in determining the levels of humidity existing at any given moment. However, during the duration of these tests, no potentially damaging levels of humidity were recorded.

6. Acknowledgements

The authors would like to thank Glutz AG, Swiss Access Systems, Solothurn, Switzerland for their cooperation and the provision of materials and knowledge. The financial support by the Swiss Commission for Technology and Innovation (CTI), which supported this project, is also gratefully acknowledged.

7. Literature

Verein Minergie®. 2014. Reglement und Nachweisverfahren zur Vergabe des MINERGIE®- Zertifikats für MINERGIE® - Modul Türen. ARGE Minergie® Türen. Bachenbülach, Schweiz. 31 pp.


An ecological solution for wooden window frame enlargements

Urs Uehlinger1, Urs Buehlmann2, Peter Kümmin1 1 Research and Development; Architecture, Wood, and Civil Engineering; Bern University of

Applied Sciences, Biel, Switzerland

[email protected]

2 Department of Sustainable Biomaterials, Virginia Polytechnic Institute, USA

Abstract

Wooden window frame enlargements are often used to close the building skin around windows. However, windows, and their respective enlargements, are required to meet stringent demands concerning cost, element weight, and insulation against heat loss and noise, safety, and burglary protection, among other things. Currently, the most typical wood window frame enlargements are made of two particle-board panels with a polyurethane core, where the particle board often is laminated on the outside with a PVC skin for protection.

Today’s building processes often call for the installation of building components such as doors or windows at lower levels of the building before the building is protected from the elements above. Also, as windows and doors are installed before all the primary construction processes such as concrete pouring or brick layering are completed, chances are that high levels of humidity from such activities create a detrimental environment for wood-based materials.

This paper presents the development of an alternative material to make wooden window frame enlargements that are inert to humidity yet other properties are being maintained or exceeded. Research looking for such a material looked at different materials like wood (Balsa or Poplar), Cork, extruded rigid polystyrene (XPS), and polyethyleneterephthalate (PET). Tests revealed that only the solutions using XPS and PET were able to achieve U-values of less than 0.6 W/m2K at a thickness of 58mm. However, additional tests also revealed a better performance of PET-based panels in terms of being able to shape the panel and in terms of screw retention. Also, thanks to the use of recycled PET, an environmentally friendly, low-cost solution could be found that is inert to humidity.

Keywords: Window enlargement, building skin, product development

1. Introduction

The expectations of the performance of components used in building skins in respect to ease of maintenance, longevity, and insulation properties are ever increasing. This adage applies surely for smaller building skin components such elements behind blind casings or window frame enlargements. Focus on such components rests on their thermal insulation capabilities, but also on their tightness and on their sound insulation properties. Window frame enlargements, used to close the area around a window to the rest of the building skin, have been typically produced using engineered wood products in the past. However, mainly the producers of plastic windows are calling for solutions that do not involve hygroscopic materials (such as wood or wood-based products), so that the harsh conditions on today's construction site do not damage these components.

Today, in multi-floor buildings, windows are often installed on lower floors while the upper floors are still being constructed using concrete or gypsum, e.g., materials that cause a large amount of humidity to be residing in


the building and that have the potential to generate the flow of liquids onto lower floors. Figure 1 shows such a multi story building where the installation of windows was begun prior to the conclusion of all the construction work on the upper floors.

Figure 1: Constructing multistory buildings in the 21st century often involves the installation of the windows on the lower floors while the upper floors are still being constructed.

Thus, building components such as windows installed on the lower floors are in danger to be subjected to high humidity conditions while the upper floors are being constructed, creating the danger of moisture related damage, especially for hygroscopic biomaterials. To date, almost all insulating engineered composite materials panels used for facades involves the use of wood-based materials. Thus, high levels of humidity or the presence of liquids can damage these panels. Such damage is often found with window frame enlargements for windows, doors, or for parapet elements, showing the limits of these constructions.

2. Window frame enlargements

Window frame enlargements are used to close the space between the window and the building construction. Figure 2 shows a crosscut through a sample construction using window frame enlargement. Window frame enlargements typically are being screwed to the window frame and the building construction element. Critical points in this construction are mostly located at the joints where the window frame enlargement component is attached to the window frame or to the construction elements as well as in locations where window frame enlargement elements are joined together (if the required length of the final product exceeds the maximum length of the elements made). These points are critical because that is where the entire cross section of the window frame enlargement element is open, thus offering access to moisture and potentially creating problems due to the hygroscopic nature of bio-based materials.


Figure 2: Crosscut through a sample construction using window frame enlargements.

Figure 3 shows a schematic crosscut through a window frame enlargement element consisting of polyurethane hard foam insulation in the center followed by particle bard on each side and a cover consisting of PVC foil. The particle board can be covered by materials other than PVC, examples include but are not limited by high pressure laminates (HPL), aluminum, or veneers. In Figure 3, at the right hand end of the element, a solid wood edge is embedded for strength and protection. This solid wood edge also serves as a critical element to allow the screws used to fixed the window frame enlargement element to the window frame and to the building construction elements. However, such solid wood edges are expensive to insert into the construction (labor, processes) and they reduce the insulation capabilities of the element.

Figure 3: Crosscut through a window frame enlargement element.

PVC cover layer Particle board

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3. The Problem

As briefly indicated above, the hygroscopic nature of the biomaterials used is responsible for some unwelcome swelling when subjected to high humidity or liquid water. In particular, the particleboard used as the structural element on both sides of the insulation at the core of the element, swells quite considerably when subjected to humidity. This swelling leads to an opening of the joints, creating unpleasant aesthetics, reductions in the insulation capabilities of the element as well as negatively impacting the structural properties of the element, and giving even easier access to moisture and liquids to the particle boards, where the problem started in the first place. Figure 4 shows example pictures of the consequences of this undesired swelling of the particleboard inside such elements.

Figure 4: Example picture of damage due to the swelling of the underlying particle board

Thus, window enlargements made using particleboard as the structural component due to its hygroscopic nature are challenging to use in today's construction environment. For this reason, some producers have started replacing the particleboard with panels made from recycled polyurethane foam. Such PUR panels, however, lower the insulation properties of the window enlargement elements and thus are not fully replacing the original solution with better insulating particleboard panels.

4. Methods and Results

Given the facts described above, Bern University of Applied Sciences in Biel, in collaboration with Tavapan SA in Tavannes (a producer of window frame enlargements), with financial support from the Swiss Commission for Technology and Innovation (CTI), decided to develop a better product that would not suffer the shortcomings of the particleboard based or the recycled polyurethane foam solutions.

In a first phase, the team focused on finding promising materials (e.g., non-hygroscopic, good insulation properties) for replacing the particleboard and the recycled polyurethane foam. The search encompassed both, bio-based, sustainable materials like balsa wood or cork as well as oil-based materials. The goal was to develop a new composite panel system with the following properties:

- Non-hygroscopic

- Good insulation properties

- Shaping the edges without inserting edges

-- Good screw pull out resistance on edges without inserting edges

In addition to these must-meet criterion, the following secondary should-meet criterion were set:


- Variable thickness cover layers with free choice of material/finish (veneer, PVC, particle board, fiber board, OSB board, HPL, aluminum, paint foil, powder coating, others)

- Variable thickness of the element

- High noise protection values

- Low combustibility

After review of properties of potentially suitable materials, the following ones were selected for further tests: Balsa wood (longitudinal direction, e.g., the end grain forms the surface), cork, poplar LVL (laminated veneer lumber), extruded polystyrolhardfoam (XPS), and polyethylenterephthalat foam (PET). Figure 5 shows a picture of each of the materials infestigated and Table 1 summarizes the target values and values found in the literature.

a) b)

c) d)


e)

Figure 5: Pictures of sample materials investigated: balsa wood (a), cork (b), poplar LVL (c), extruded polystyrolhardfom (XPS, d), and polyethylenterephthalat foam (PET, e)

Technical data Unit Goal Balsa (a) Cork (b)

Poplar (c)

XPS (d) PET (e)

Density kg/m³ 153 110 450 > 30 80

Thermal conductivity W/mK 0.06 0.066 0.04 0.12 0.036 0.032

Swelling in thickness after immersion in water % <1 <1 ≈5

Heat resistance °C 80 163 up to 100

165 75 100

Compressive stress kPa 12900 110 30000 > 500

Surface finish quality very smooth

rather smooth

rather rough

smooth smooth rough

Edges shapeable Yes yes yes yes Yes yes

Costs (estimated) CHF/m² 25.00 64.70 16.75 31.50

Tabelle 1 – Properties for balsa wood (a), cork (b), poplar LVL (c), extruded polystyrene (XPS, d), and polyethylenterephthalat foam (PET, e)

The project's goal was to develop a window enlargement panel whose thermal conductivity is about or below 0.06 W/mK. However, only the XPS and the PET panels do achieve such a low value without problems. However, only PET fulfilled all the expectations in respect to screw withdrawal resistance and the ability to shape the edges without inserting edges. Environmental concerns due to the non-renewable character of the material as well as the high material costs were addressed by using, for the first time in such a product, recycled PET. Also, thanks to the favorable mechanical properties of extruded PET (structural strength, screw withdrawal, ability to shape edges), the window frame enlargement panels could be built as a one layer sandwich composite, e.g., only the cover layer is made of a different material.

5. Tavapet

The resulting material from this industry-driven applied research project has been patented and offers a recycled, environmentally friendly, water and frost proof, alkaline and fatigue resistant, and mechanically resilient material for all types of windows frame enlargements. The material also offers good thermal insulation values (U-value of 0.33 for thickness 84 mm) and decent sound insulation values (-28 DB) as well as a low unit weight (13.37 kg/m2). Also, the window frame enlargement does not require edge battens, resulting in a uniform U-value throughout the construction and to a lower total weight. The window enlargement panel's surface can be used untreated, painted, veneered, or with overlays such as PVC, CPL, or HPL. Standard thicknesses are available from 36 to 84 mm. Figure 6 shows a cross cut through a PVC window with a Tavapet window frame enlargement panel.


Figure 6: Cross cut through a standard PVC window with a Tavapet window frame enlargement panel screwed at the bottom

6. Conclusions

This publication presents findings from a search for an improved composite material for window frame enlargements that is inert to humidity yet achieves good properties in terms of environmental friendliness, water and frost proof, alkaline and fatigue resistance and has good structural properties. The edges of the material should be easy to shape and no additional edge battens should be required to be attached for shaping or structural strength. This study investigated a wide range of potential materials (balsa wood (longitudinal direction), cork, poplar LVL, extruded polystyrol foam (XPS), and polyethylenterephthalat foam (PET)).

PET was found to be the best fitting material for this application. Initial environmental concerns due to the non-renewable character of the material were addressed by using, for the first time in such a product, recycled PET. The material is structurally strong (relative to the competing materials), has good screw withdrawal properties, allows the edges to be shaped as desired, and is water and frost proof, alkaline and fatigue resistant, and mechanically resilient. The material also offers good thermal insulation values (U-value of 0.33 for thickness 84 mm) and decent sound insulation values (-28 DB) as well as a low unit weight (13.37 kg/m2).

7. Acknowledgements

The Swiss Commission for Technology and Innovation (CTI) supported this project, whose contribution is gratefully acknowledged.


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