Combating Urban Heat - why the colour of our buildings matters

We all know the psychological impact of colours - from their ability to cheer us up, or their ability to inspire us, or their ability to simply make us feel different things depending on how they are used. Want to brighten up a room and your mood? It would be hard to go wrong with a sunny yellow for a room. Looking to create a chilled, relaxing space - steer clear of neon and opt for a soothing, light blue or pastel colour.

The impact of colours

Colours mean something, and their ability to affect our mood and emotional wellbeing has been recognized for centuries. We use colours to decorate rooms and buildings for a myriad of different reasons. We also use colours to represent a way we are feeling, or to describe an emotion, or to tell a story we need to tell. When we really start to delve into what colours mean, we realize that the worlds we inhabit, from the natural to the manmade, are not only filled with colour but that colour has the potential and the power to influence the quality of our lives too. 

But the idea that colour plays a key role in how we design and construct buildings (regardless of their intended use) for a more sustainable future is only just now gaining traction amongst urban planners and architects alike. In the process, this realization, is also prompting some very interesting and important discussions around the impact of colour, not only in promoting our mental and emotional wellbeing, but in helping contribute to our physical health as well, and in helping us live more sustainable lifestyles. 

The Urban Heat Effect

It is common knowledge that darker colours absorb more heat, they attract heat if you will. This means darker surfaces are hotter - and this phenomenon is one of the reasons cities experience what is known as the Urban Heat Effect. Cities filled with dark coloured roads, pavements and buildings are more likely to be hotter and create islands of heat that set urban temperatures soaring. 

Fred Pearce from Yale Environment 360 says, ‘Fresh asphalt reflects only 4% of sunlight compared to as much as 25% for natural grassland and up to 90% for a white surface such as fresh snow.’ 

This in turn not only causes increased discomfort for urban residents but can place vulnerable inhabitants (the very old and the very young) at risk. Add to these rising temperatures worldwide, and our cities are set to become epicentres of rising temperatures and the subsequent heat they bring. 

In some cases this might seem like a short term positive - take the example of the UK and more consistent summers (and less rain!) but what even temporary or passing heatwaves teach us is that often our infrastructure is not designed to handle even a few degrees rise in temperature. Hand in hand with heat waves comes some real concerns for the health of the vulnerable members of our communities. 

What does this mean for how we build and redevelop our cities?

It means we need to remember that colours matter - not just from an aesthetic viewpoint, but from a mental and physical health perspective as well. Some European countries are aware of these concerns already and have adopted maximum sun reflectance requirements for the exteriors of buildings and new developments. In France the maximum reflectance requirement is 30%, and 20% in Germany. 

In other examples, simply opting for white reflective coating, such as those applied to roofs in New York City under the NYC CoolRoofs Initiative have helped reduce temperatures by 5 degrees Celsius as a start. What this then does is to reduce the need for air conditioning (our increased use of which is not sustainable long term in terms of electricity and energy usage) and has also pushed the city closer to achieving its goal of cutting carbon emissions by 80% before 2050. 

Better building design, in order to combat the Urban Heat effect, is not necessarily as solvable as painting everything white - although this is a tactic to exterior decoration that has been adopted in Southern Europe for centuries - but also involves an in-depth understanding of not only reflectance but the ability of a building to handle moisture, and other weather and temperature related conditions as well. 

Prioritising the Natural

Crucial also to the prioritizing of sustainable development is the need to pay attention to the colours that make up our natural environments. Many cities include green and blue spaces which are naturally cooler spaces, and their natural hues are a great example to those designing and constructing new buildings. Taking our inspiration and cue from our natural environment not only provides a nod to the natural beauty all around us (even in our cities), but also reminds us that sometimes nature does it best and opting for natural cooler colours, both in the interior and exterior of our buildings, can help cool our spaces and at the same time help us reconnect with the natural world. Taking our cue from nature is a win-win. 

Hand in hand with this comes the need to protect, maintain and increase the number of green and blue spaces within our cities. They are naturally cooler environments and reducing or limiting their number only serves to make urban centres hotter. Building more green spaces, reinstates more natural colours in our urban habitats and provides a natural cooling effect. This does not necessarily need to always be something grand - simply planting more trees along city streets and pavements has been proven to be effective in keeping urban environments cooler, naturally. 

This, combined with prioritizing our use of colour in building design, specifically exterior design, will help us combat rising temperatures and the knock on impact of these climate changes on urban life. 

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