An urban heat island (UHI) may sound like an exotic getaway but it’s becoming a real issue for some of our towns and cities. Especially given that up to 50% of people across the globe currently live in them and this is set to increase to as many as two thirds by 2050.

So why is the UHI effect such an issue and what can we do to combat it?

Firstly we need to consider what is causing the UHI effect before we can start to tackle the problem.

An urban heat island is identified as the effect of certain man made materials and human activities in towns and cities where temperatures become considerably higher than in more rural areas.

What are the main causes of the UHI effect?

1. Building materials used for roads and roofs

The type of material used such as tarmac coupled with its darker surface colour mean it absorbs more heat which is then stored rather than released back into the atmosphere. This results in an increase in temperature by up to 10 degrees according to a recent review in Building and Environment scientific journal as highlighted by Richard Lupo for Sustainable Homes.

2. Human factors such as higher energy use

This intense use of energy in towns and cities together with poorer ventilation than in the countryside also contributes to a rise in temperature. Thus leading to greater energy use from air conditioning and so the vicious cycle continues.

3. Denser building construction

Buildings are constructed in a tightly packed way in urban areas obstructing the natural wind flow which would normally help with cooling. Offices and homes are also being extended upwards which leads to greater heat loss through insulation.

Why is this a problem for urban areas?

The higher temperatures in towns and cities caused by UHI is predicted to worsen the already imminent effects of climate change. This is expected to result in a higher number of heat stress days from 7-15 per year to a staggering 45 by 2050, according to Building and Environment scientific journal.

A heatwave may sound like a good thing but these significant increases in temperature can cause disturbed sleep and even death, with death rates reported to rise by as much as 12% in a heatwave.

What can be done to counteract these effects?

1. Utilising reflective construction materials

Where possible reflective and light coloured materials should be used for surfaces such as roofs, pavements and roads to help reflect the sun and absorb less heat.

2. Building design

Buildings need to be designed to keep a constant temperature inside to help reduce unnecessary energy consumption from heating and air conditioning as well as heat radiating from the building itself.

3. Investing in green spaces

Housing developments should be designed to include as much green space as possible. Plants, trees and parks in particular help to reduce the effects of UHI by cooling the air temperature and absorbing CO2 in the air.

In conclusion, new housing developments should make use of reflective/light coloured materials during construction, be designed to maintain a constant indoor temperature and include as many trees and plants as possible.

By Anna Symington