An On the wire story
Loughborough University research has revealed how outside shading systems can keep homes cooler by up to six degrees.
In experiments led by PhD student Niloo Todeh Kharman, the university used two identical semi-detached houses to compare the effect of external shading on internal temperatures.
In the study, one home was left untreated and the other fitted with external shading, heat sensors and so-called heat boxes that mimic the warmth produced by people living inside.
Dr Ben Roberts, a senior lecturer in healthy buildings at Loughborough University, said the findings so far suggest that outside shading can make a meaningful difference. He believes housing developers may need to build this kind of protection into new homes, particularly as heatwaves become more frequent. The university says around one in five UK homes is already prone to overheating, underlining the scale of the problem.
The results from the test houses have been striking. Roberts told the BBC that the shaded property has stayed up to six degrees cooler than those in the unshaded one, with temperatures in the untreated house climbing above 33°C while the shaded home remained nearer 29°C.
The research has also shown that during heatwaves, keeping windows closed in the daytime can help prevent hot air from pouring inside, even if that advice feels counter-intuitive during heatwaves.
The broader case for external shading is supported by building specialists, who say systems such as louvres, canopies and other outside-mounted screens work by stopping solar heat before it reaches the glass. In practice, that can be especially useful in homes with large windows, glazed extensions or other features that admit strong sunlight.
Roberts also warned that widespread reliance on air conditioning would place fresh strain on the electricity Grid, which he said is not currently equipped to handle a major jump in demand.
Todeh Kharman, who presented her initial findings and methodology at the 2025 CIBSE Symposium1, and has recently published her first journal paper on the subject2.
In a research project supported by CIBSE, she is also looking at how external blinds impact natural ventilation rates when deployed, which will help inform future developments in TM59/TM52 (see below).
2025 – 2029 | Loughborough University and the British Blind and Shutter Association The next step in this research is to develop a predictive model to estimate internal operative temperatures – with and without shading – under future climate scenarios. To support this, Todeh Kharman is using CIBSE 2025 weather files.Evaluation of external shading devices to mitigate overheating in naturally ventilated UK dwellings
The project carries out testing in two twin domestic houses and makes use of modelling tools to better understand and evaluate the impact differing external shading systems have on UK homes and the occupants within them. The project aims to inform overheating risk assessments and support the development of practical, occupant-centred design guidance for residential buildings.
For more on the research, see September’s issue of CIBSE Journal.
References
1 Todeh Kharman, H., Roberts, B.M., Beizaee, A. and De Grussa, Z. (2025) ‘Developing a method to measure the effects of external shading devices on summertime indoor temperatures in naturally ventilated dwellings’, CIBSE Technical Symposium, London, UK, 24–25 April 2025
2 Todeh Kharman, H., Roberts, B.M., Beizaee, A. and De Grussa, Z. (2026) ‘Overheating adaptation in temperate European dwellings: a systematic review of evidence on shading devices’, Building and Environment
Sources
Main source BBC News: [1]
Sources by paragraph:
– Paragraph 1: [2], [6]
– Paragraph 2: [2], [3]
– Paragraph 3: [1], [3]
– Paragraph 4: [4], [5], [7], [2]
• This On the wire article was created using Noahwire AI and reviewed by CIBSE Journal’s editorial team
