Lee Jackson, from Sustainable Building Solutions, explains the risks of ignoring thermal bridges when enhancing a property’s insulation.
When a householder insulates a wall, a nice warm house is created, but the junction is still performing at a much lower level, which in turn creates the risk of surface condensation.
The paradox is that, in a poorly insulated dwelling, thermal bridging is minimal, but actions to improve the insulation of the dwelling, which the Green Deal is likely to accelerate, increase the potential for thermal bridging with consequential implications for condensation build-up.
The Sustainable Building Solutions remedy is to improve the thermal performance of the junction in line the rest of the wall. Our modelling demonstrates that the installation of a small section of high performance insulation directly below the window sill can bring the junction up to the standards of the rest of the wall.
The window sill has to be removed anyway as part of the insulation process. With our modelling, it is clearly demonstrated that this simple process can bring the ψ value of a junction down to 0.012. In turn, this brings the temperature factor up to 0.927 which means there is negligible risk of condensation.
We are not criticising the Green Deal in any way. There is clearly a need for improved levels of insulation in the UK’s ageing housing stock, but it is vital that installers bring all aspects of a property’s insulation up to the highest possible standards. This includes addressing thermal bridging issues around junctions and not just cherry-picking the quick wins.
