Insulation installers have been warned that it is vital to bring wall junction performance up to overall insulation standards or risk condensation build-up and mould growth.
The stark warning, from Sustainable Building Solutions, part of the Travis Perkins Group, is the result of increased concerns that improved insulation in the UK’s housing stock will result in thermal bridging issues at junctions.
The concerns have led to Sustainable Building Solutions, which is actively supporting the Green Deal in its attempts to improve the insulation of the UK’s housing stock, to develop its own technical solution involving improving the thermal performance of the junction in line with the rest of the wall.
Thermal bridging occurs at junctions between elements, such as PVC windows and at interruptions in insulation. When warm internal air bridges the gap with cold external walls there is often a build-up in condensation which can ultimately lead to mould growth.
Lee Jackson, an expert in thermal bridging issues at Sustainable Building Solutions, explains. “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.”
He continues: “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,” says Mr Jackson.
“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, which includes addressing thermal bridging issues around junctions, and not just cherry-pick the quick wins.”