Can Reflective Roofs Offer Relief For Hot Cities?
Can Reflective Roofs Offer Relief For Hot Cities?
Here in Britain we openly acknowledge we are slightly weather obsessed. We watch the weather, we talk about the weather, we even on occasion get to enjoy the weather on those rare sunny days!
This national past-time comes about due to our slightly erratic weather patterns, and the fact we can never guarantee exactly what we will get from one day to the next.
But can you imagine living in constant heat? How would you cope?
The Urban Heat Island Effect
Have you ever noticed when you visit a city, they always seem hotter than the surrounding countryside? This is known as the Urban Heat Island Effect and is caused by human activities. In particular, changing how we use land, as well as waste heat created by energy usage and pollution are common contributors to this phenomenon.
Cities in hot countries therefore feel stifling and oppressive; not only are they coping with all the natural heat, but the man-made heat exacerbates the problem. Over time, it can make us hot and grouchy, demanding better cooling systems; at worst, it can lead to an increased death rate.
Roofs That Absorb The Radiation
What happens to all this circulating heat? City roofs absorb between 20% and 95%of the solar radiation that hits them, although this variation depends on the colour of the roof; the lighter it is the more reflective it becomes. During the day city roofs absorb more solar energy than the countryside, and during the night this heat is then radiated back into the atmosphere.
Using Cooling Roofs
Luckily, there is something we can do to improve matters, by using cool roofs (lighter or reflective roofs), which help to reduce the Urban Heat Island effect. They work by reducing the daytime temperature of the roofs, and hence cool the air immediately above the rooftops.
Research has also discovered that the impact of cooling roofs also goes into the lower atmosphere. This has a knock-on effect on the regional weather patterns, reducing convection – the process of warm air rising.
Green spaces and green roofs also help tackle the effects of Urban Heat island, but some studies believe light roofs are a more effective method at combating the problem. Painting roofs white is a quick solution, whereas developing green areas and roofs is longer term outlook. It also takes a lot of trees to make an impact.
Typical buildings to be subjected to white or reflective roofs include flat roofs, outbuildings and warehouses. Residential properties in countries with distinctive seasons need to be heated during the winter season; therefore homes with white roofs tend to have to work harder in the winter to increase their core temperature, which can negate the positive summer effect.
White asphalt is an ideal choice of material for city warehouses, and domestic flat roofs, such as this one. Not only is easy to apply and cost effective, it has the added bonus of reflecting the heat during the day, which, as we’ve seen, has a positive effect on Urban Heat Island effect.
There’s still a long way to go to combat the long-term effect of city heat, but we have a lot to learn from the Greeks, who have been painting their roof tops white for centuries. Head to any hot Mediterranean town or city and you will be surround by light buildings, all designed to reflect the heat.
Maybe London one day will be a city of white – watch this space!
If you need some advice, or to arrange a free, no obligation site visit please get in touch with our expert team today.