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Could Part L increase overheating risk?

18 Nov 2019


In this series of articles, we aim to answer some of your questions about the upcoming changes to Approved Documents L and F, SAP methodology and the Future Homes Standard.

Current proposals suggest these regulations will be coming into force in England from October 2020. Contact us with your own questions about the regulation changes, or to discuss our training seminars and workshops.


Could changes to AD L increase overheating risk?

The proposed changes call for more insulation and lower air tests which could increase internal temperatures, but there are also plans to create a new building regulation to target overheating risk.

In recent years we’ve had some impressive summer temperatures. Unfortunately, a drawback of highly insulated, air tight buildings means our homes are more likely to overheat in these conditions, causing uncomfortable living conditions which can have a knock-on impact to our health.

Under England’s current Building Regulations there is little to target or reduce the risk of our homes from overheating in summer months.

AD L looks to limit the effects of heat gain by using the SAP model to provide a basic check of internal temperatures, but this is nowhere near detailed or reliable enough to use as the basis for a brand new regulation.

For those buildings considered to be high-risk (usually high-rise developments in urban areas) it falls to local planning authorities to condition developers to ensure their design allows for decent air movement during our hottest days by commissioning detailed thermal modelling analysis.

If you consider what is being proposed within the new AD L, you could argue homes will be more air tight and have more insulation which will make the problem of overheating even worse.

However, the Government is also looking to make changes to AD F (which covers ventilation and air quality) and to also introduce a new regulation which will ‘stop buildings being built which are prone to overheating’.

The latter follows an inquiry last year from the Environment Audit Committee into how heatwaves impact life in the UK.

Further details about this new section of building regulations haven’t yet been announced. One potential approach could require a standardised calculation to be completed on specific building types which are known to be high risk. Alternatively, the new regulation could work alongside AD L and use SAP’s basic check as an indicator to trigger a more detailed review.

We were hoping to receive more information about the new overheating regulation by the end of the year, but the snap election almost certainly means the details won’t be released until the new year.

If you have overheating concerns on a current development, we can complete detailed thermal analysis for you.

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