Thermal bridges are junctions between building elements and insulating materials which create a ‘weak link’, thus having a negative effect on the thermal performance of the building.
HIBEC Ltd are suitably qualified to undertake 2D and 3D construction Thermal Bridging calculations using accredited HEAT software.
The Part L SAP and SBEM calculations incorporate thermal bridge values for a number of building junctions to establish the Building Emission Rate.
In nearly all buildings, these values are defaulted, with detrimental impact on the overall result.
For example, by using Accredited Construction Details in a SAP calculation on a detached house, the buildings overall Building Thermal Bridge Coefficient (Y value) reduces from 0.15 (the default value) to 0.08 (accredited construction value).
This can equate to a 6-8% reduction in the Building Emission Rate.
The question is: what would your buildings actual Y value be using your standard constructions?
We believe that it is probably better than the default value, with a potential advantage to be gained in the SAP/SBEM calculations whenever you use those construction details, therefore reducing your dependence on expensive renewable systems to pass Part L.
However, for house builders there is another significant reason why establishing your thermal bridges and U Values could be of benefit.
In the Code for Sustainable Homes, item Ene 2 Fabric Energy Efficiency (FEE) has a number of credits available.
The Y value of the property, along with the U value and building air tightness, affect the FEE. The better the FEE the more credits are available, which means other code credits can be ignored saving you money.
With Part L changing in 2014 the FEE will be a second mandatory target on the SAP, so this is an aspect of construction that can no longer be ignored.
With the expected tightening of the emission rate as well, undertaking proper U value and thermal bridging calculations may become a necessity.