Underfloor Heating and overheating

According to The Zero Carbon Hub, the definition of overheating in residential properties is ‘The phenomenon of a person experiencing excessive or prolonged high temperatures within their home, resulting from internal and/or external heat gain which leads to adverse effects on their comfort, health or productivity.’ Overheating is something you should carefully consider during the design process of a new build or refurbishment project.


The effects of overheating

Overheating can have some negative health effects including adverse effects on sleep quality and a negative impact on professionals who work from home, affecting both their productivity and concentration by causing thermal discomfort. Thermal discomfort can have a detrimental effect on a person’s ability to concentrate on a given task, increasing the risk of errors. In extreme situations ‘excess’ heat exposure over prolonged periods can lead to more serious health impacts such as increased heart rate and blood vessel expansion, which can cause strain on the cardiovascular system and even lead to fatalities.

Overheating can also create ‘The Urban Heat Island Effect’. This describes the effect that cities and urban areas can have on air temperature. According to the 2015 ‘Impacts of Overheating’ report, cities can be around 5 to 9°C warmer than the surrounding countryside. The heat absorbed in materials during the day is released at night, which increases the temperature outside. All materials can absorb and reflect light with darker coloured objects absorbing more light and lighter coloured objects absorbing less. When an object absorbs light, it converts that light into thermal energy and emits it back out as heat.



Climate change is set to make overheating worse as it is expected to increase the frequency and the severity of extreme weather. This includes hotter and drier summers, longer and more frequent heat waves, and higher and more frequent maximum temperatures. Also due to an ageing population, a greater proportion of the population is likely to be vulnerable to the effects of overheating.

Overheating also negatively impacts the NHS by damaging residents’ health. A 2018 report by the Environmental Audit Committee on ‘Heatwaves: adapting to climate change’ predicts that higher temperatures that caused 2000 plus deaths in 2003 will be the summer norm by the 2040s as temperatures could regularly reach a sweltering 38.5°C.

This is in addition to increased social care costs, reduced economic activity through reduced productivity, and an adverse effect on infrastructure through increased risks of power cuts.

Homes are also becoming more efficient with insulation keeping heat inside the house to save energy and houses are being built closer together, all causing an increased risk of overheating.

Developers of new build homes currently do not account for all of this, therefore new legislation is being proposed by MPs where properties have to take overheating into account to help deal with the threat of more frequent and extreme heatwaves.


How to prevent overheating

The common response to overheating is to open a window. You will often see offices and homes with all the windows open during warm summer weather, however, opening a window when it’s hotter outside will only make the overheating problem worse because you are letting hot air in. You should keep windows in direct sunlight shut during the day and open them at night because it is much more likely that the room will be warmer than it is outside during the night, so when you open the window you’re letting in air that is cooler than the air in the room.

Electric fans are also ineffective against overheating when it is warmer outside as they do not cool the air, they draw in cool air from outside when it’s available.

There is not much evidence for the effect of air conditioning on overheating, however, studies in the US have found that the use of air conditioning decreased the risk of mortality significantly.


How wet underfloor heating prevents overheating

Radiators are inherently prone to overheating as they provide convected heat that draws cold air across the floor, heating it and then convecting it upwards towards the ceiling. This creates cold spots, which means the heating might get turned up to warm up the cold spots, creating overheating in other areas.



Wet underfloor heating works by circulating warm water through a series of continuous loops that are fitted underneath your floor, creating a large radiant surface that heats the room from the floor upwards. This radiant heat comfortably warms the entire room, leaving no cold spots and therefore less overheating.

Another benefit of wet underfloor heating is the ability to control each zone (room) separately. This gives homeowners the ability to create an efficient heating pattern for each room in the house, heating up only the room that needs it, rather than the whole house. Smart control solutions such as the Ambiente Neostat will assist in having a system that is easily controllable from your smartphone. You can learn more about underfloor heating thermostats in our installer’s guide to wet underfloor heating thermostat controls.

Another aspect to consider is thermal mass. According to Homebuilding & Renovating, thermal mass is the ability of a material to absorb and store heat. It takes a lot of heat to raise the temperature of a dense material like concrete, so this has a high thermal mass. For thermal mass to be effective it needs to absorb heat when it is available and store it until needed and release that heat when appropriate. Underfloor heating within a screed has excellent thermal mass, which helps to maintain comfortable, even temperatures as well as reduce energy usage and running costs.

Using different floor coverings with UFH shouldn’t have much of an impact on thermal mass and overheating, although the use of rugs could lead to overheating as heat can gather beneath the rug.


Do you have a new build or refurbishment project coming up or are you concerned about overheating due to UFH?

Get in touch with our team today to discuss your underfloor heating requirements. Simply call us on 01707 649 118 or email info@ambienteufh.co.uk

Did you find this article useful? Check out our guide to underfloor heating for new build properties and an installer’s guide to underfloor heating manifolds.

This article was written by Robert Tuffin.

Robert is the General Manager at Ambiente and has been working in the underfloor heating industry since 2012.