INSULATION 61
leads to architectural features which are not common in the UK.
Reducing the g-value of glass (a measure of how much solar heat is allowed through) makes a difference, but this alone will not be enough in many UK locations. Reducing glazing also make a difference, but where an open window can be used to remove excess heat, the window openings need to be sufficiently sized to allow the necessary air flow. Increasing the proportion of floor area of a room compared to glazed area, or recessing windows, also reduces heat gain a little, but there are obvious limitations to how far this can be taken. The regulation permits the use of adjacent buildings to provide shading, but it does not allow modellers to account for external foliage or internal blinds, as either could be removed and result in non-compliance. After these measures have been exhausted, the next effective step is to consider external shading. This is the most controversial element, as (outside of London) our residential buildings do not have any deliberate shading elements and introducing them changes the appearance significantly. Balconies on apartments are a
good way to shade the windows below and where they have solid upstands and provide noise reduction, but more commonly we are likely to need to consider elements such as brise soleil, awnings, external venetian blinds or shutters to provide reduced solar heat gains.
Another unfavourable feature if the objective is to avoid mechanical systems, is to use an acoustic louvre when needing to avoid an open window. However, the size of the louvres needed without a mechanical system (and sometimes the appearance) mean that this option is often not chosen. This points us towards more mechanical systems to ensure a usable overheating strategy. While on the face of it this sounds bad, when you consider that if a design is done correctly, and that these systems are operated infrequently (in the current climate), this is perhaps not as bad as it might seem. Nevertheless, the goal should be to naturally cool a building wherever possible – and therefore we will need to improve our outdoor environments in the places we build.
James Healey is director of overheating & acoustics at the Institute of Acoustics
The Building Regulation stipulates that where the prescribed noise or air quality conditions are exceeded, an alternative method other than opening windows is required
ADF DECEMBER 2022
WWW.ARCHITECTSDATAFILE.CO.UK
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