Thermal Bridge Details
When carrying out a house design then to make it much easier for a SAP Calculation, it is really important to consider the Thermal Bridge Details. The default accredited details are now already incorporated into Part L 2013 so you really need to consider enhancements.
The U value for a wall, roof and floor is the heat loss per m2 for every 1 degree temperature difference. The ‘Y’ value for the thermal bridge is then added to the overall area weighted U value.
So if you have a floor, wall and roof with an average U value of 0.18 W/m2.K, but use non-accredited details, then you add 0.15 W/m2.K to that figure. The overall is then 0.18 + 0.15 = 0.33 W/m2.K
Using accredited details, this is predicted to reduce heat loss through thermal bridging to 0.08 so would reduce the overall heat loss from 0.33 W/m2.K to 0.26 W/m2.K Significant, but this only meets the minimum standards under Building Regulations.
Here are some recommended guides and websites to obtain enhanced details:
- Knauf Insulation when used with aircrete blockwork (lamda <0.19 W/mK) or timber frame construction.
- Aircrete blockwork – for full fill and partial fill solutions.
- Concrete Block Association – For blockwork of all density values for partial and full fill insulation.
- Plasmor Blockwork – Specific details and values for use with Plasmor blocks.
- LABC Details – Check out these by LABC
- Xtratherm Insulation – lots of details including a handy calculator.
- Besblock – They have lots of details, scroll to the bottom of the page and this handy summary is also very useful.
- Celotex – Steel frame and masonry solution using their insulation. You need to login to access.
Need a bespoke calculation?
Low Carbon Box will research the best available option. If the detail is not currently available and we believe we can improve on this, then we can provide a bespoke thermal bridge detail.