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OLD BUILDINGS, NEW CITIES:

Energy renovation strategies for the historic residential stock of Brussels.

Abstract: This papers aims to provide a vision of integrating the possibilities of Renewable

energy in today´s society with respect to the cultural and architectural aspects of the

buildings.It stresses the role of renovation and implementation of renewable energy strategies

in historic residential buildings in Brussels as the main element to achieve energy efficiency

targets. In addition, it will elaborate on the need to develop a methodology to assure success

during the renovation of historical residential buildings from design phase.A new vision of

Brussels Capital Region is offered where buildings are conceived as a stock rather than individual

entities. This approach seeks to contextualize the heritage value and to achieve important

improvements of the energy performance in order to highlight the importance and relevance of

retrofitting the old residential building sector.Resulting from the respect for the historical

elements of the buildings, this paper will be divided into the exterior and interior changes of

the building.

Keywords: Building stock, building energy retrofit, energy integration strategies,

renovation, renewable energy, pre-assessment methodology.

Introduction

Buildings are at the core of sustainable energy policy as long as the sector keeps

accounting for 40% of the EU´s energy demand. The EC Action Plan for Energy Efficiency

identifies energy efficiency in the building sector as top priority as the largest cost-efective

savings potential lies in the residential (households) and commertial buildings sector (tertiary

sector).The building sector faces the inevitable challenge of producing more efficient

buildings whilst at the same time responding to even more demanding occupants in terms of

confort.

1. Existing buildings

There are a huge number of historic buildings in Europe and many of them are wasting

large amounts of energy. This architectural heritage deserves very particular attention within a

sustainable architectural approach, with regard to sustainable energy development and historic

buildings protection.

Replacing an existing building with a new one requires a considerable investment of

embodied energy in materials, transport and construction. In global environmental terms, the

balance of advantage strongly favours the retentionof existing building stock, particularly

when performance in terms of energy consumption in use can be improved. Retaining existing

elements of construction in old buildings and seeking to enhance their thermal performance,

rather than replacing them, is a heritage conservation principle in line with sustainable

development.

Even if the actual buildings regulation exempts most of the listed buildings from energy

performance improvements, these buildings can and should accommodate some

improvements.

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In Brussels we have a beautiful example of historic renovation in the 140 year-old

Renewable Energy House (REH) refurbished so as to minimize energy consumption and to

explore different methods for integrating renewable energy technologies, making it a 100%

renewable energy building.

Figure 1: Front and back fachade of the REH, Brussels, before refurbishment. http://www.new4old.eu

Figure 2: Front and back fachade of the REH, Brussels, after refurbishment. http://www.new4old.eu

2. Historic buildings

Preservation of the architectural heritage is considered a fundamental issue in the life

of modern societies. This heritage contributes significantly to the value of the city by

branding the city´s character.

The need of preserving historical constructions is thus not only a cultural requirement,

but also an economical and developmental demand.

Architectural conservation deals with issues of prolonging the life of architectural character

and integrity, such as form and style, and/or its constituent materials, such as stone, brick,

glass, metal and wood.

Historic buildings vary greatly in the extent to which they can accommodate change

without loss of special interest. These considerations will influence the extent of change that

is appropriate to improve energy efficiency. Before any work is carried on, it is important to

understand how the building works and to check if the foreseen alterations are compatible

with this system.

When alterations for energy conservation are proposed, regard should be given to:

Ensuring that the building is well understood

Minimizing disturbance to existing fabric

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Reversing the changes easily without damaging the existing fabric

Introducing modern materials: new materials and techniques designed for new

construction should be treated with caution.

Part I: The outside of the building

In historic and protected buildings energy efficiency measures can only be provided if

they do not alter the unique character of the building or increase the risk of long-term

deterioration to fabric or fittings. According to Straube [1] the envelope can be described in

terms of performance and function. The main expectable non-structural functions of the

building envelope can be summarized in the following aspects:

Energy conservation: Resist thermal transfer through radiation, convection and

conduction

Air: Resist excessive air filtration and ensure sufficient ventilation

Sound: Attenuate sound transmission

Water: Resist water penetration and enable humidity discharge

Energy losses through the building´s exterior walls, floors, roof, windows and doors account

for 10 to 25% of the energy used by most buildings, depending on the outdoor conditions and

construction of the building elements [2]

Energy losses are governed by two main parameters:

Temperature difference between the indoor and outdoor environment

The ability of the envelope to resist heating transfer due to conduction, convection,

infiltration and absorption of solar radiation.

Some points of attention need to be taken into account when we are facing the renovation of

the envelope of an historic building:

Opaque elements: Insulation of the external opaque elements or the use of additional

insulation to the fachades and the roof is one of the simplest and also very efficient

measures to consider. Proper location of insulation may increase the thermal inertia of

the building and buildings with condensation problems on surfaces will experience a

reduction or even an elimination of this kind of problem.

Transparent elements: Actions to improve or replace transparent components should

enhance penetration of solar radiation during the heating period and minimize it

during the cooling period, decrease heat flow through the opening, improve day

lighting, and permit a more efficient airflow during the summer season.

Infiltration: Air leaks through the building enclosure can take one of several forms: 1.

Orifice flow, Diffuse flow and Channel flow. The latter is probably the most common

and serious of all types of air leaks. The air entry point and exit point are distant from

each other, giving the air enough time to cool below its dew point and deposit

moisture in the building enclosure.

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Airtightness: A high degree of airtightness will provide insufficient air through

infiltration and thus necessitates a designed ventilation system. Furthermore, if the

building is completely sealed then moisture migration is prevented what can suppose a

serious problem especially for historical buildings. Thus, some infiltration is needed to

avoid condensation problems.

Moisture problems: Sometimes an important effect of filtration through the building

envelope can be the condensation of moisture from the exfiltration air that takes place

in northern climates. Moisture problems are especially important for historical

buildings. Air pressure differences between the indoor and outdoor environment can

transport significant amounts of water vapour through air leaks in the building

envelope. In order to avoid this kind of problems in northern climates a vapor barrier

is added facing in.

Some rules of thumb to follow in the building envelope related to the afformention points in

order to solve the problems highlighted before are:

Insulation material can be added either to the inside or the outside of the exterior walls

or fachade, or by filling the cavities within the wall structure. Use of additional

insulation decreases the rate of heat loss, may improve the air tightness of the wall and

reduce condensation problems on surfaces, while it generally increases indoor thermal

confort.

Opening windows is the basis of natural ventilation design since they allow a

controllable fow of air, which can satisfy the needs to carry way surplus heat in

summer and provide pollution free environment.

Balanced mechanical ventilation systems require low infiltration rates. The rate of air

entering the building must equal the air leaving the building. If the rate of the exhaust

air is higher than the rate of air introduced in to the building, then infiltration might

occur.

Creating an atrium or a light well to provide natural light, assuring the preservation of

the structural system as well as character-defining interior spaces, features, and

finishes is recommended.

Vestibules may be very useful since they create a secondary air space at a doorway to

reduce air infiltration occurring while the primary door is open. Adding a vestibule

should be considered in very cold climates, or where door use is very high.

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Table 1: External adaptations and possibilities of the envelope and outdoor equipment

Part II: The inside of the building

In historic buildings energy efficiency measures should only be provided if they do not alter

the unique character of the building or increase the risk of log-term deteriorationto fabric or

fittings. However, this doesn´t mean that there aren´t ways of creating a better comfort and a

lower yearly primary energy consummation while not changing the appearance of the

building.

The internal adaptations and possibilities of historic buildings are being summarized in the

table below. This includes internal isolation on walls and roofs, internal sun screens, etc, so

every change does not affect a unique or protected part of the building.

In future steps, the disadvantages/advantages, possible problems, limitations, options or

changes of the envelope will be discussed with the goal to optimize or change parts of the

building´s interior that aren´t protected.

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Table 2: Internal adaptations

Case Study: Extension East of Brussels

This research focuses on the study of new tools for the refurbishment of historic

residential buildings in the Extension East of Brussels. The revitalization of old cities would

imply the increase of dwelling availability in areas where greater social diversity is needed

and higher population density can be beneficial. The older the construction, the more delicate

and necessary the upgrading process is and the more specialised knowledge is required.

This paper focuses on the study of the context and the identification of the main

characteristics that are common to the listed historical housing in the East Extension, linked to

their environmental performance.

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Figure 3. Location of the case study area on the map of Brussels.

Autor: http://www.skyscrapercity.com/ and Aránzazu Galán González

The Extension East of Brussels is a predominantly residential area, where the

following types of buildings are represented:

Figure 4. Building typologies of the Extension East of Brussels compared with the total of the Region

Source: Cadastral matrix of Brussels Capital Region and Urbis map

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In addition to the strict building regulations, socio-economic homogeneity of the

neighbourhood gives it a rare unit. The majority of the houses are built for well off middle

class family with almost invariably the same plane-type three rooms in a row, along with attic

reserved for domesticity. The facade has usually two or three equal spans, decorated with a

balcony or loggia. The homes of the middle class respond to the same pattern, in however

modest proportions.

In contrast, this program can be found amplified in mansions for the upper class.

Moreover, their plots allow the development of additional parts such as lobbies or an office.

The facades are richly ornamented and with cubicles, with bow-windows or even turrets.

The obstruction of neighbouring houses and large building depth, due to urban density,

are very restrictive parameters in this architecture. Although these seem to be unalterable

characteristics, they may actually be modified without altering the appearance of the building.

The deep and narrow building form is very restrictive for a positive performance of the

dwellings.

Figure 5. Original plans of Square Marie Louise 62 (1894)

However, the potential of the roof and the courtyard for improvement is high. The patio can

be found in some houses, which is often small and partially occupied by the staircase, as a

space with large possibilities for raising daylight levels and ventilation rates. The increase of

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its surface might counterbalance the impact of the building depth.

Figure 5. Building typologies mapping (ArcGis)

The potential of the patio is both environmental and architectural. Enhancing its size

allows the increase of solar gains in the building and strengthens a semi-public space with

great possibilities. The patio shapes that occupy the longer side facade, with a surface-

oriented south, are proved to be effective, as they favour solar access in the long axis of the

building, increasing solar ray penetration into the dwellings.

The surface of the roof can represent around 50% of building’s envelope. It is also the

surface of the envelope that receives solar radiation the most. Thus, the rooftop house might

have greater opportunities or good environmental performance than the flat house. A

responsive design of the volume of the rooftop might increase the solar access of the lower

levels, improving the performance of the whole building.

On the other hand, as aforemention, natural ventilation is crucial in this climate, due to

high levels of humidity, and it is especially important in historic buildings, which use

evaporation and ventilation to reduce the moisture in the walls to an acceptable level. In a

deep building, the central area of the house may have little opportunities for ventilation,

which could cause damage to elements of historical value.

Common practice in the retrofitting of historic buildings is based on the improvement

of the envelope that it is generally un-insulated. The possibilities and its consequences has

been lited in the section above. When insulating during the retrofitting of the historic building,

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it is critically important to consider the constraint of the building itself as the uniqueness of

the building, the characteristics of its materials, the climate in which it resides, and the

specific building methods that were used in its construction. Adding insulation where it is not

needed, inappropriate, or ineffective can lead to irreparable damage in historic features.

Therefore, it must be considering whether or not to include insulation and if so, the fact that

this could be a reversible insulation that does not make drastic changes in the air flow that

could damage historic building fabric. It must be taken into account the importance of

preserving historic construction material that makes the isolation of the walls less

recommendable that the insulation of attic and basement.

Due to the form and the physical configuration of the area, the city blocks of this

Extension East work as a whole not only in terms of structure but also in terms of thermal

performance. It is because of this reason that the impact of refurbished houses on neighboring

buildings is remarkable. Improvements in some buildings can positively influence others, if

linking elements are provided, such as openings on the mediator walls.

Solar energy and wind power, geothermal and aero thermal energy might be

inadequate on this location from aesthetic reasons, archeological constraints and climatic

restrictions, respectively, although the third one might be appropriate for district heating

systems. Low temperature and condensing boilers might improve energy efficiency and

reduce energy bills but they would imply changes on the distribution systems. Biomass,

because it responds to the same principles as those of the traditional heating systems in

historic houses, might be a suitable option, easy to accept by the users and to install in the

buildings.

Conclusion

Sustainable refurbishment is significant problem in current buildings stock, taking

much of a scientists’ attention as well as European Commission initiatives. Sustainable

refurbishment is widely discussed in the literature and various models and decision making

tools proposed. This paper integrates sustainable development principles decision making

process and influencing factors into one unique conceptual sustainable refurbishment model.

Model involves macro and micro environment factors analysis, integrates participating

in refurbishment stakeholder’s decisions and needs. According to sustainable refurbishment

principles, refurbishment not only decreases energy consumption but also improves whole

condition of the building.

Much attention is paid on decision making process. In order to design and implement

buildings refurbishment basing on sustainable development principles it is necessary to follow

these principles from idea till implementation.

There is still the need of specialised knowledge to assist the design of holistic

refurbishment strategies in the early stages when decisions have bigger impact.

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This paper presents an integral approach to the energy upgrade refurbishment that

gives specific answers to key parameters of integrated refurbishment. It also determines how

improvements in the energy performance can be achieved. In this approach, different options

for each parameter are studied, calculated and designed in a level of construction detail,

providing a database of options and solutions. This systematic approach to the strategies,

divided into key aspects and different options, can be organised in the form of a matrix.

This approach recognises the diversity of each project as well as designer decision

freedom.

Acknowledgements

This research is funded by the Brussels Capital Region through the Innoviris Strategic

Research Platform 2012 - Brussels Retrofit XL.

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