CPD 15 2021: Residential overheat solutions

This Radiana sponsored CPD will look at how radiant cooling works and why it can be an efficient method for reducing overheat in a development without adding pressure to the climate


With the changes in Part L of the Building Regulations being introduced in June 2022 and the constant drive to increased building fabric standards, residential overheating issues are set to become more pressing.  

Such heating challenges have come under the spotlight following the government’s move to decarbonise not only the UK’s new-build housing stock but also existing homes, as part of its commitment to reduce carbon emissions to net zero by 2050, while the EU has a target to reduce non-CO2 greenhouse gas emissions by 60% between 2005 to 2050.  

A dwelling’s biggest energy outputs are heating and cooling. To reduce the emissions resulting from those outputs while also saving money, the industry must find a cooling solution that is both environmentally friendly and energy efficient. 

Why not air-conditioning? 

Globally, the amount of energy consumed by air-conditioning systems in buildings has doubled during the last decade and is set to increase by 90% from 2017 levels by 2050. It is estimated that cooling in air-conditioning systems may account for around 10% of total UK electricity consumption.  

Closer to home, in the UK our cities are becoming ever warmer. The urban heat island effect – where a metropolitan area is warmer than the surrounding area due to human activity – is not a new phenomenon, but countries like the UK are more exposed to the threats of extreme heat as summers get longer and hotter.  

Full air-conditioning will be demanded in more properties to control summer temperatures, and while air-conditioning obviously cools the interior of buildings, in so doing it heats up the external environment.  

This runs the risk of increasing the use and consumption of fossil fuels, and thereby carbon emissions. Refrigerants used in air-conditioning are much more potent greenhouse gases than carbon dioxide (by between 1,000 and 3,000 times). It has been reported that leakage from air-conditioning contributes significantly to the global warming impact of air-conditioning systems. 

Problems such as draughts and fluctuating temperatures associated with current systems cause dissatisfaction to homeowners, impacting the thermal environment in many dwellings.  

Looking at solutions 

Radiant ceiling cooling and heating systems can address these problems, improve wellbeing, offer energy savings and reduce a building’s carbon footprint.  

Such a system uses water as the basis of transferring heat, as water is much more efficient than air. Water can transport 3,500 times more heat than the same volume of air.  

Radiant ceiling cooling runs typically at 10 oC to 12oC, rather than the 7oC average of traditional air-conditioning systems. This means that radiant ceiling cooling can lead to an energy saving of between 30% and 40%. This results in lower costs, lower CO2 emissions – again by the same range of between 30% and 40% – and reduced contribution to the heat island effect. 

With a radiant ceiling system there is significantly less thermal mass than with radiant floor heating, with only 12.5mm of plasterboard covering a ceiling-based setup. The user will notice that it will be quicker to heat up, take less time to cool down, along with less temperature overheat in the zone and being able to run at lower flow temperatures in heating and warmer temperatures when in cooling mode.  

A study commissioned by the California Energy Commission and run by University College Berkley concluded that when radiant cooling is integrated as part of the overall design of the building, an energy reduction of between 31% and 33% could be realised.  

Another study found the average potential savings of a radiant cooling system with dehumidification or ventilation was assessed as being between 17% and 42%, depending on the climate, building age and design.  

Energy savings are generally dependent on the design of the building, its location, the local climate and what system it is being compared with.  

How radiant cooling works 

Radiant cooling reduces the temperature of a ceiling by passing cold water through the pipes which absorb the heat radiated from the rest of the room. Heat always travels to colder areas. Therefore, areas of the room that tend to be colder will attract the “rays” of heat.  

These hot “rays” travel from the radiant heat element until they reach a surface, such as a wall, floor or piece of furniture. There are no hot or cold spots in an environment heated or cooled from the ceiling because radiation expands equally in all directions.  

This is recognised by certification by the International WELL Building Institute. The Well v2 standard only gives credits to radiant systems. 

WELL standard 
WELL™ is the leading tool for advancing health and wellbeing in buildings globally. Originating in the US, it is being adopted in the UK for buildings where wellbeing is a real focus. The new standard gives specific credits to thermal comfort: 
Thermal zoning. Credit is given for multiple zones and individual control. 
Radiant thermal comfort. Credit is given to “hydronic radiant heating and/or cooling systems” if at least 50% of the project floor area is serviced by this system. 
Humidity control. Credit is given if the mechanical system has the capability of maintaining relative humidity between 30% and 60% at all times.  
It is important to note that traditional air-cooling systems are not eligible for credits for radiant thermal comfort. 
Utilising heat pump technology 
The huge benefit of a radiant ceiling system is that because it uses water to transfer energy and not air, this means it can link into the same heat pump that will run the heating and hot water – a total zero carbon solution. Further to this, such a system can also maximise the heat pump efficiency because it can run consistently at a higher temperature compared with air only systems. 

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