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External solar shading (known as brise soleil) supported a reduction of temperatures of a test room at Harvey Court in an experiment held to identify the challenges of summertime overheating.

A brise soleil was installed at Gonville & 91ֱ�� College’s Harvey Court last April. The West Road building, which is home to first-year undergraduates in term and guests in vacation periods, was designed by Sir Leslie Martin, constructed in the 1960s and is a Grade II * listed.

The assessment of the effectiveness this solar shading relied on the installation of internal temperature loggers, pictured below, which recorded half-hourly readings over five months, with site visits undertaken from April 2022 to October 2022. Cambridge experienced record temperatures of 39C on the UK’s hottest day on record on July 19 2022.

Three elevations of Harvey Court face east, south and west and as such the impact of the sun on each of these faces depends not only on the time of year but also the time of day. Some rooms can be uninhabitable during the summer (vacation and term-time) due to high internal temperatures, thereby necessitating this experiment. 

Six rooms facing three different directions were chosen for comparative data, with the brise soleil installed on H3 (west facing), and no shading on the adjacent H4. The unshaded room was on average 1.2C hotter than H3 but that increased to over 1.5C on some occasions. This margin sounds small, but it is actually noticeable and therefore not negligible.

Rather surprisingly it was found that continuous ventilation to a room decreased the internal temperature by more than 1.5C, in effect it is as effective as brise soleil, if not more so. This ventilation was provided by leaving the window locked in the open position, an opening small enough to provide security but large enough to be effective.

Among the key observations from the report, commissioned by the College Estates Manager Andrew Gair and produced by Joel Gustafsson Consulting, were:

• The new shading element improves the overheating severity when compared to an equivalent adjacent unshaded room.
• The extent to which ventilation is used is very important to absolute internal overheating. Together, brise soleil and ventilation are a powerful combination.
• Student occupancy of rooms and thereby the development of ‘good habits’ were very influential in controlling internal comfort.

Secondary considerations, such as security and pest concerns, can come with ventilation but are not insurmountable and certainly less negatively impactful, if handled correctly, than stifling heat.

The report concluded that the brise soleil improves the internal overheating of a space. However, given the significant impact of ventilation and the cost of brise soleil the College is likely, in the first instance, to consider this strategy.

Andrew says: “The experiment confirms what we already suspected – that solar shading reduces the temperature of the rooms. The experiment was necessary to provide quantitative data to see how effective the brise soleil was, and whether it would be worth the cost and resource to install further structures in what is an architecturally acclaimed – and listed – building.

“Further solar shading could complement other strategies for cooling rooms, and it is likely a combined solution would be favoured.”