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03/11/2016
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LABC
Barry Turner – Director of Technical Policy [email protected]
Thermal Performance: detailing considerations
• Why does it matter?
• Important construction points
• Thermal bridging values and help available
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The Performance Gap!
The Performance Gap• What is it?
• Research and testing of buildings has highlighted a big difference between the intended energy performance predicted by the designer, and the actual energy performance when the building is handed over and in use.
• This difference is known as the Performance Gap.
• How it’s built and occupied falls short of expectations, and does not meet the designed energy standards (Part L).
Does it do what it says on the tin?
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Thermal energy overviewLosses
• Gains become losses and these need to be managed.
• It is important that thermal losses are reduced in winter…
• …and controlled in the summer.
Thermal energy overviewLosses
• Gains become losses and these need to be managed.
• It is important that thermal losses are reduced in winter…
• …and controlled in the summer.
To close the performance gap we must reduce the unintended or unexpected losses to a minimum
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Wall to roof
Intermediate floor to wall
Ground floor to wall
Ridges/verges
Openings
Service penetrations
Wall to wall
Think about the junctions
In more detail…
Windows and doors
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At a practical level
Why is it important?
Condensation damage
As we move toward a lower energy building stock, performance failures can lead to fairly catastrophic building failures.
Moisture management in airtight buildings is of paramount importance.
This needs to be controlled by correct fabric design, matched with correct installation and ventilation provision.
Photo: Ian Mawditt, Four Walls
Photo shows condensation in a new flat roof on a section where insulation had been missed – not a new problem…
…but in a low energy/airtight building any moistureinside the building will find the weakest point – so the effect is concentrated (not distributed). This leads to quicker, localised failures.
Thermal bridges – some effects
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Technical details
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Getting them right
Pay particular attention to the details for:
Continuous insulation
Good airtightness
Minimal thermal bridging
Avoiding thermal bypass
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Continuous insulation1
Insulation properties
• Conduction causes the most heat loss throughthe elements of a building.
• Insulation can significantly reduce these conduction losses to the outside (or unheated areas) and help to increase the surface temperatures of the thermal elements.
• If insulation is not continuous, heat loss will increase at the edges of the insulation layer.
Thermal image shows additional heat loss at a ceiling perimeter where loft (cold roof) insulation does not join the wall insulation
Photos: Ian Mawditt, Four Walls
Good Practice
X Common Practice
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Better homes through Registered Construction Details
© Presentations and their content are the copyright of LABC
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11%
10%
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SAP 2012 Appendix K
SAP 2012 Appendix K
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LABC Registered Construction Detail
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•Appendix K•DER 20.43 TER 20.22•FEE 54.13•Y = 0.077
•LABC Registered•DER 19.55 TER 20.22•FEE 50.51•Y = 0.053
Example small dwellingAppendix K ‘Approved’ Using LABC Registered Values
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Better homes through Registered Construction Details
© Presentations and their content are the copyright of LABC
These details are available to download now from the LABC website
Easy to use details including:
• CAD drawings
• Hints and tips
• Construction checklist
Better homes through Registered Construction Details
© Presentations and their content are the copyright of LABC
For more information please go to the
LABC Website
www.labc.co.uk/registeredconstructiondetails
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