In a new report to government, the Climate Change Committee has said that 570,000 new-build homes constructed since its last assessment in 2017 will need to be retrofitted to ensure they can stay cool.
In each of the four years preceding the first report, a sub-committee of the Climate Change Committee, ASC, recommended that more should be done to address the risk of overheating in homes and other buildings.
Heatwaves in the UK are expected to occur at least once every other year until 2050 and there is a serious risk of death to inhabitants of buildings, as a result of overheating. The Met Office predicts temperatures in excess of 40 degrees during these heatwaves. Intensified ‘urban heat island’ microclimates will result in night time temperatures in major cities that could be compared to the tropics, due to factors including heat reflection and the daytime heat absorbed by buildings being released into the atmosphere at night.
The Climate Change Committee estimates there could be an increase in annual heat-related deaths, of which there were 2,500 in 2020, the most since records began in 2003. On average 2,000 people die from heat-related problems and it is estimated this may rise to 7,000 a year by 2050. Overheating can be the cause of health issues and reduced productivity and wellbeing, rising to major economic and social concerns.
The first UK Climate Change Risk Assessment in 2012 estimated that the economic cost as a result of overheated buildings and heat-related death due to climate change would increase annually from £10-50 million to £25-150 million. By 2080 the figure could be £40-350 million.
Many of the 300,000 new build homes scheduled to be built each year could become uninhabitable, unless building regulations are changed in relation to overheating. At this rate, at least 1.5 million more homes will be built across the UK in the next five years with the same problems.
A rise in home working, from 5% pre-pandemic to 30% today, has increased the urgency of dealing with the issue.
Cooling systems installed at the building stage cost on average £2,500. However, adding the system after the building is completed can increase the cost to over £9,000 per home.
The report says: “Out of the committee’s list of priorities, this risk is notable for being the one where policies still remain largely absent. There is still little preventative action being taken to address health risks from overheating in buildings, and in homes in particular”.
The government says it will set out proposals for reducing the risk of overheating in new residential buildings. However, the Future Buildings Standard lacks detail and the Heat and Buildings Strategy is still unpublished.
The Passivhaus Trust works to create buildings that observe the Passivhaus standard: homes that are comfortable to live in all year round, using very low amounts of energy for heating and cooling. Under its principles, outside shutters are used to shield windows from direct sunlight in the summer while still allowing light to enter the house during the winter when the sun is lower in the sky.
Glazing is a major source of heat within buildings, while very little heat is transmitted through the walls in comparison.
Poor design is often the reason for homes overheating, particularly in smaller homes and flats. It is sometimes impossible to create suitable ventilation within a property. For example, urban homes, in particular, face a single aspect – meaning heat is easily able to enter but it is hard to allow it to flow out.
New housing estates are increasingly located close to busy road and rail networks that can make it uncomfortable to open windows, even at night.
Hidden heat sources
There are heat sources within the home which you may not have though about, for instance fridges. They work by transferring the heat within the fridge to the outside, and can get quite hot – particularly larger models.
Uninsulated internal pipework, such as hot water pipes, can also increase indoor temperatures.