How can architects integrate shading to combat overheating?

Our homes are overheating. This isn't a problem that starts with a future warming climate. It is happening now and needs to be addressed to prevent further environmental, economic and social distress.

The obvious solution is found in southern Europe, where architectural shading design is second nature. Yet despite some notable exceptions, shading design hasn’t yet become mainstream in the UK. Approved Document Part O (2022) requires developments to address overheating but prioritises smaller windows and increased ventilation over external shading. Any increase in ventilation and cooling demand leads to an increasingly unacceptable position for energy bills, grid resilience and carbon emissions. So, what can we do? 

In the first instance, architects can consult Shading for Housing: Design Guide for a Changing Climate, which we at Pollard Thomas Edwards have produced for the Good Homes Alliance and the British Blind and Shutter Association (BBSA). This expands on the cooling hierarchy (see figure 1 below) and promotes a complementary ‘shading hierarchy’, showing where you should start in thinking about effective shading. It can be used on all developments whether new-build or retrofit.

The guide’s purpose is to forge a new design culture in which shading is central to UK housing design, and built-in from the start. It is anchored by a detailed study of the best design-led shading products that architects can specify today, showcasing a wealth of potential strategies (figure 2 below) presented in detail and evaluated for environmental and cost performance. The guide also provides a short history of shading design, explores UK-specific design challenges, and wraps up with best practice advice with appendices covering product performance and other useful resources.

Central to our remit was understanding why the default position for design teams and clients is to downplay the issue, value-engineer the shading out, and leave it to mechanical ventilation and cooling to solve. This is why we consulted industry stakeholders in two focus group sessions.

We found that barriers to good shading design practice span economic, cultural, technical and legislative sectors. Clients often see shading products purely as a maintenance cost, while specifiers, despite the dangerously hot summers of recent years, often adopt a ‘cold climate’ outlook and consider shading products superfluous.

For many, upfront cost is still a significant barrier, despite the mechanical ventilation and cooling savings that early shading design integration can bring. Furthermore, open-ended legislation fails to propose external shading products to deal with overheating. Health and safety guidance also stymies the use of shading products, especially on high-rise buildings.

Regarding cost and maintenance in the expanding build-to-rent market, for example, clients tend to prioritise active cooling solutions because they can sell them as a benefit to prospective tenants, driving up rental costs in the process.

Similarly, cultural attitudes have worked against the adoption of even the most traditional shading products. Our focus group reported that, in some cases, planners refuse proposals on the basis of townscape policies that do not consider shading to be ‘vernacular’. A particular incident was cited where external shutters were pushed back by conservation officers for this very reason.

Technical matters and health and safety concerns are another barrier to the uptake of shading design. One focus group member told us: ‘Clients will not accept a four-storey-high façade of moving parts’. Another cited logistical issues: maintenance and cleaning of protruding products on high-rise facades mean clients prefer simpler solutions – regardless of the carbon cost.

And while solar shading can assist with glare and daylight control, the frequency of overcast weather in the UK means that reducing the amount of daylight entering a building is not always an affirmative act. In this respect, careful consideration must be given, calculating the daylight required, for example, to ensure the right shading device is specified.

We need to refocus priorities while engendering a positive design culture to using shading products to minimise a building’s carbon profile. The guide spotlights 19 different shading products, setting out specification advice and performance evaluations to help architects properly address their building’s shading needs. Each product page features a brief description, a table detailing its functionality, an in-situ product photograph, and a ‘performance web’ visualising a product’s strengths and weaknesses covering daylight, overheating and cost. Where relevant, we also include the architect’s comment on a product’s added value.

There are five top tips for architects seeking to integrate shading into their design process:

Ultimately, this guide calls for a new design culture in the UK. A design culture in which the everyday specification of shading products on new and existing domestic buildings – or the designing for shading from the start – is second nature among developers, housebuilders, architects and consultants. The public too, buyers and tenants alike, should be well-versed in the benefits that shading products bring, in terms of reduced running costs, improved comfort and general wellbeing. This guide goes part of the way by presenting good practice and case studies, clearly showing the range of shading types available.

To download the guide, visit: https://kb.goodhomes.org.uk/guidance/shading-for-housing/

Tom Dollard is a partner at Pollard Thomas Edwards, leading on sustainability and innovation​