A new approved document has been proposed to tackle overheating in residential buildings.

Overheating in homes is becoming an increasingly important issue, with homes becoming more insulated, and glazing systems achieving much higher thermal performance ratings, residential dwellings can run the risk of overheating and creating uncomfortable living temperatures.

The aim of this document will be to reduce the occurrence of overheating to protect the health and welfare of the building’s occupants.

Approved Document [X], yet to be officially named, will apply to residential dwellings including houses, flats, institutional residential buildings such as home or schools and residential colleges, halls of residence.

Overheating prevention can be done through the ‘Simplified Method’ which focuses on the glazing area vs the floor area. This method includes taking precautions to limit solar gain during warmer months and providing adequate ventilation or means to remove excess heat from the internal living spaces.

Alternatively, there is a dynamic thermal analysis method that can be used to ensure these dwellings comply with the new document. This method will be useful for those seeking a more flexible approach to building design.

For homeowners who desire a highly glazed home, large glazing elevations can still be incorporated as long as certain requirements are met.

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tables showing how to minimise solar gain for groups in the new approved document proposed to tackle overheating

Minimising Solar Gain

The location of the building and the type of residential dwelling will affect which guidance should be followed to limit solar gain in warmer months.

Buildings are categorised into either ‘Group A’ or ‘Group B’ depending on how many fabric elements they have and where the openings are located, as cross-ventilation can play a significant part in reducing overheating.

For the location, England has been broadly split into two locations: England excluding Greater London and Greater London. To the left are tables that show how to minimise solar gains using the simplified method.

Where shading is required, this can be provided using external shutters with adequate ventilation, glazing with a maximum g-value of 0.4 and light transmittance of 0.7, or overhangs with a 50° altitude on south-facing facades.


Removing Excess Heat

Group and location also affect which guidance should be followed for removing excess heat. The proposed document outlines what means will be considered appropriate for this.

The document outlines requirements for the minimum geometric open area of a ventilator, known as a free area. The new document also states that opening elements should open to a minimum of 60 degrees.

Extra care should also be taken when designing corridors that have pipes for heating or hot water as they can create more excess heat that needs to be removed.

Dynamic Thermal Analysis

This method for preventing overheating is suitable for all residential buildings and can offer additional flexibility in design over the solutions outlined in the ‘simplified method’.

Using an adapted version of the CIBSE’s TM56 methodology, this analysis predicts the risk of overheating and offers a wider range of acceptable strategies for reducing the risk.

Strategies mentioned in the document include certain glazing designs, the shade of adjacent permanent buildings or structures and mechanical or louvred ventilation systems.

With around 2,000 heat-related deaths a year in England and Wales this is not something that should be taken lightly. Temperatures are predicted to continue rising, making it vital that we take action to ensure the welfare of a home’s occupants.

The proposed document is not yet in effect but if you are worried about the impact these new rules will have on your proposed design the team at Sieger are happy to talk to you.

Get in touch with the team today.

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