This project investigates the thermal performance of the insulation in cold-pitched roofs of standard construction using site surveys and in-situ monitoring. Measured heat flux and temperature data from a pilot study investigation have been used to estimate in-situ point U-values at a range of locations and the results are compared with estimated design U-values based on standard assumptions.

Variability in the condition and coverage of the loft insulation is observed, particularly around storage and access installations however, the investigation found that the installed insulation has a better in-situ thermal performance than expected. This disparity between design and in-situ U-value estimates evidences a ‘performance difference’ where the predicted energy savings associated with installing loft insulation are not realised in practice. The results also suggest that the effects of solar gains and ventilation on the heat flow mechanism through the loft cavity are significant and could contribute to an overall performance difference across the wider UK residential stock.

A cold spot underneath the loft hatch demonstrating heat loss from the home through the ceiling