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Roof insulation testing reveals strong contribution to performance gap

With just four years to go until the zero carbon homes policy comes fully into effect, the house-building industry is coming to terms with the challenges of addressing the CO2 performance gap between the designed performance of new homes and what they achieve in practice.  A report published by the NHBC Foundation earlier in 2012, Low and zero carbon homes – understanding the performance challenge, identified a number of potential causes of this gap, some of which are the ability of building materials and mechanical and electrical systems to perform as well in practice as laboratory testing predicts.

The BBA, together with NHBC Foundation, have recently published the results of an extensive research project using a large-scale rig specially constructed to replicate real life installation of a variety of roof insulation materials.  Supported by the insulation industry, testing was undertaken over a two-year period to establish the effect of air movement on the performance of roof insulation.  The findings of this research are outlined in the new report Air Movement and Thermal Performance.

Among the key findings of the research is that the thermal insulation performance is affected very significantly by air movement, with the U-value of the roof constructions tested increasing by up to 80% at higher wind speeds.

To download the report please visit

Low and zero carbon homes – understanding the performance challenge (NF41) can be downloaded from