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Back to results Air movement and thermal performance report: an investigation into the effect of air movement on the thermal performance of domestic pitched roof constructions

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Air movement and thermal performance report: an investigation into the effect of air movement on the thermal performance of domestic pitched roof constructions (RR7)

Overview

This work, supported by the NHBC Foundation, was part of a programme of work (led by the Zero Carbon Hub) to understand the factors contributing to the gap between design and actual energy performance of homes. It played a part in understanding the effect of airflow through roof construction on U values.

Summary of content

Air movement and thermal performance report: an investigation into the effect of air movement on the thermal performance of domestic pitched roof constructions comprises:

Key observations

Testing indicated that U values can increase by up to 80%, when wind speeds are increased to typical levels achieved on windy days. The effect was variable however, depending on the type of roof construction.

The flow of air over the surface of insulation, wind-washing, was considered to be one likely mechanism that could account for higher than expected heat loss from buildings.

Insight and recommendations

The report highlights the common air flow paths that might be significant and suggests a number of ways of taking account of, or minimising, air flow through pitched roof construction.