Quinn Building Products Thermal Bridging at Ecobuild 2016
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Transcript of Quinn Building Products Thermal Bridging at Ecobuild 2016
How to save on construction costs with effective thermal bridging solutions
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
Introduction
Jason MartinSpecification Manager
[email protected]@QuinnBPLtd_Jason
Part of the technical services team at Quinn Building Productsw : quinn-buildingproducts.come : [email protected] : +44 (0) 286774 8866
Andrew LundbergBuilding Fabric Consultant
• Structural Design• Project Management• Product Technical & Specification
• NSAI Accredited Thermal Modeller• Building Fabric Consultant• Lecturer in Thermal Bridging and Passive
house design in DIT
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
About Quinn Building Products
• Quinn Building Products manufactures a wide range of building materials.
• Providing multi-product systems and blended product logistics
• Supported by an in-house team of technical experts.
SectorsQuinn Therm High Performance PIR InsulationQuinn Lite-Pac Versatile & light weight EPSQuinn Lite Aircrete Thermal BlocksQuinn Rooftiles Concrete Roof and Ridge TilesQuinn Precast Pre-cast Concrete ProductsQuinn Cement Bulk and Bagged CementQuinn Quarries Concrete Products & Aggregates
Quinn Tarmac Blacktop tarmacadam products
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
The Objectives
• What is a thermal bridge?
• Different types of thermal bridges.
• Psi-values and y-values.
• Part L1a, SAP 2012 & how
compliance is achieved for the
building fabric
• Solutions to thermal bridging using
Quinn Lite.
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
U-Values
U-Value = 1 / Resistance= 1 / 4.928= 0.202= 0.20W/m2K
KEY POINT: • U-values can only measure heat flow in 1-dimension, that is they only
estimate heat loss which travels through the building envelope perpendicular
to the internal surfaces!
• As we rely on U-values to estimate building fabric heat loss, we are missing
heat loss in the 2nd and 3rd dimension (reality!).
• The vast majority of SAP assessments are done using default values for
thermal bridging, which in many cases grossly over-estimate heat loss
from thermal bridging!
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
Thermal Bridge
A thermal bridge occurs
anywhere in the building
envelope where the otherwise
uniform flow of heat is altered
or disturbed due to a change in
the building fabric, or due to an
increase in internal or external
areas due to the building form.
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Repeating vs. linear thermal bridges
Ceiling joists in cold pitched
roofs that are insulated at
ceiling level.
Ground floor joists in an
insulated suspended timber
ground floor.
INCLUDED IN THE U-VALUE!
INCLUDED IN THE U-VALUE!
INCLUDED IN THE PSI-VALUE!
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Linear Thermal Bridges
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Linear Thermal Bridges
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Measuring Linear Thermal Bridges
Psi VALUE (Ψ)• A measurement of the additional heat loss at a junction,
measured in Watts, for every linear metre of that junction and one degree temperature difference between inside and outside.
• Determined by the assembly of the junction and the thermal conductivities of the materials used to construct the junction, as well as the measurement convention (e.g. SAP) used on the building.
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
Thermal Bridging In Part L1a
Under Part L1a (new dwellings), accounting for thermal bridging can be done by any one, or combination of, the following methods:
• Assign a global y-factor of 0.15W/m2K to the entire dwelling.
• Use default individual values from table K.1 of the SAP document.
• Adopt the DCLG approved construction details (ACD’s), and assign psi-values from Table K.1 of the SAP document.
• Use psi-values that have been developed by a competent assessor
POOR VALUES NOT BASED ON ANY SPECIFIC CONSTRUCTION TYPE OR U-VALUE RANGE
LITERALLY TWICE AS BAD AS VALUES FROM THE ACD’S
IN ALMOST ALL CASES ARE GROSS OVER-ESTIMATION OF HEAT LOSS FROM THERMAL BRIDGING
THE ONLY ROUTE TO PROJECT-SPECIFIC LOW ENERGY DESIGN & CERTIFICATION
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Thermal Bridging In SAP
Compliance with Part L1a must be achieved by demonstrating that the building achieves a TER (Target Emission Rate) and TFEE (target fabric energy efficiency) at least as good as the reference dwelling of the same size. In terms of building fabric, what does this account for?
• U-values of opaque and transparent components, e.g. walls, floors, roof, windows, doors etc.
• Air permeability of the building fabric• Thermal mass• Exposed sides• Thermal bridging (y-factor)• Key point: Optimised efficient design involves the use of highly developed,
tested & certified junctions & their respective psi-values.
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
Measuring Linear Thermal Bridges
Y-factor: a single value which represents the sum of all linear thermal bridges in the building envelope as a function of the exposed thermal envelope
Y-Value = HTB / AHTB = transmission heat transfer coefficient from thermal bridging (W/K)A = Heat loss envelope area
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-0.141
-0.149-0.007
0.018 0.027
0.037
Quinn Lite certified values
SAP values
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Example 1
Average U-value of dwelling is 0.16 W/m2K
Envelope Area = 450 m2
No consideration for thermal bridges, therefore default Y-value = 0.15 W/m2K0.16 + 0.15 = 0.31 W/m2K
By using the default value, the SAP software estimates that 48% of total fabric heat loss is from thermal bridging!
The Impact Of The Y-value
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Example 2
Average U-value of dwelling is 0.16 W/m2K
Envelope Area = 450 m2
Accredited construction details & values from Table K.1 (SAP 2012)
Y-Value = 0.07 W/m2K0.16 + 0.07 = 0.23 W/m2K
By using the values from Table K.1 of the SAP document, it is estimated that 30% of total fabric heat loss is due to thermal bridging!
The Impact Of The Y-value
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What’s The Solution?
• Continuity of insulation
• Good junction design, detailing &
specification
• USE OF PROJECT-SPECIFIC PSI
VALUES
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What’s The Solution?
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
What’s The Solution?
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
What’s The Solution?
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What’s The Solution?
Example 3
Average U-value of dwelling is, say 0.16 W/m2K
Envelope Area = 450 m2
Bespoke Y-value calculated using ‘Quinn Lite Accredited Construction Details’
Y-value = 0.015 W/m2K0.16 + 0.015 = 0.175 W/m2K
By using Quinn Lite accredited details, fabric heat loss from thermal bridging is reduced to just 8.5%. This is optimal!
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Avoidance of mould growth & increased comfort
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Summary
• Using the default y-value of 0.15W/m2K will almost always have a significant &
detrimental impact on the heat loss of the proposed building and calculated FEE.
• Using the default y-value of 0.15 can involve the unnecessarily high specification of
other building fabric elements.
• Specifying and installing properly insulated junction designs will reduce the building’s y-
value, which will decrease capital and installation costs in other areas.
• By 2020, all buildings must be built to the nZEB standard. It will be extremely difficult to
achieve this standard using default psi values or y-values.
• We are mandated by Europe under the Energy Performance of Buildings Directive (EPBD
– 2010 recast) to deliver cost-optimal design solutions to our clients…there is no room
for guesswork and defaults in that!
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
• Visit us at stand 3039 to discuss your thermal bridging needs or use the Y-value calculator live!
• Check out the Y-value calculator at http://www.quinn-buildingproducts.com/resources/y-value-calculator/
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
Resources
Web : www.quinn-buildingproducts.com Twitter : @QuinnBPLtd
Technical ServicesContact our Technical Team : t : +44 (0) 286774 8866e : [email protected]
Visit Our Stand : 3039 (Beside BRE Stand)Virtual Reality DemoIPad Competition Mini Presentations
Or visit : quinn-buildingproducts.com/thermalbridging