Aluminium foil under roofs shown to reduce summer heat gain in buildings

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Aluminium foil is gaining attention as a potential passive cooling solution after research found that a reflective layer installed beneath roofs can significantly reduce the amount of heat entering buildings during summer.

As temperatures rise, roofs absorb large amounts of solar radiation, increasing indoor temperatures and placing greater demand on air conditioning systems. Researchers have found that installing a thin reflective aluminium layer beneath the roof can help reflect a substantial portion of this radiant heat before it reaches living spaces.

A study by Stefano Fantucci and Valentina Serra, published in the journal Energy and Buildings in 2019, found that aluminium foil used as a radiant barrier reduced summer heat gain by 10 per cent to 53 per cent, depending on the material's reflectivity and the installation method.

The researchers explained that aluminium foil functions as a radiant barrier by reflecting solar radiation rather than absorbing it, reducing the amount of heat transferred through the roof into the building.

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The study also highlighted that installation plays a key role in performance. The reflective surface should face an open air gap, as placing the foil directly against another material reduces its ability to reflect heat effectively. The researchers noted that the 53 per cent reduction was achieved under optimal test conditions and may vary depending on roof design and installation quality.

The findings suggest that reducing heat entering a building can lessen the workload on air conditioning systems, potentially lowering cooling costs.

Supporting this, separate tests conducted by the Florida Solar Energy Center found that roof-mounted radiant barriers reduced ceiling heat flow by 30 per cent to 50 per cent and lowered annual cooling electricity consumption by around 7 per cent to 12 per cent in the homes studied.

Although the research focused on pitched roofs, the findings add to growing evidence that passive cooling solutions, including reflective aluminium barriers, can improve indoor comfort and reduce energy use during hot weather.

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