Tackling the climate crisis with a more sustainable building envelope

Umendra Singh from Soprema UK discusses how the right insulation can prevent overheating in new and existing homes, preventing the need for energy guzzling cooling in the summer months

The blink-and-you’ll-miss it nature of British summers has always been a punchline for any discussions about keeping homes cool during the warmer months. As Part L Building Regulations have become stricter to prevent thermal loss, save energy and reduce carbon emissions, considerations of cooling seem to have been absent from the drive for sustainability.

The reality is, however, that cooling systems often take more energy than heating, and average UK temperatures are creeping up. There is an urgent need for specifiers to consider the impacts of climate change on both new and existing properties and to find solutions that will prevent both heat loss in the winter and heat gain in the summer.

Why has cooling become a problem for UK homes?

Heat waves have always come and gone, and the jet stream protects the UK from most weather extremes, so why has cooling become such an issue? In fact, it’s not just climate change that is affecting the potential for homes to overheat. However, climate change is a key reason to do something about it and avoid the need for energy-hungry cooling systems.

There are lifestyle factors that impact on the amount of heat in our homes. With an increasing reliance on electrical appliances and devices, and steam generated by showers, we are generating more heat in our homes all year round. And with conventional approaches to insulation, this can become trapped within the building.

The building envelope of contemporary properties is also an integral part of the problem. With south-facing double-glazed windows and lightweight wall build-ups that do not prevent heat gain, heat penetrates the building envelope and becomes trapped inside. Good ventilation can help to reduce this issue, but it cannot tackle high levels of sustained heat gain.

Building design is also a factor. The trend towards maximising the footprint of the plot by building living accommodation into the roof space means that there is no buffer of unoccupied space. The low mass structure of the roof means there is a low decrement delay in the roof space, resulting in rapid overheating during warmer weather, particularly in cities where the impact of heat gain is exacerbated by the urban heat island effect.

Finding suitable solutions for ambient comfort

While newer homes built to higher standards of thermal performance and air tightness often overheat during warmer weather, older stone and solid brick wall structures do not. This may make them inefficient in the winter, but it demonstrates that the key to cooler homes in the summer is a wall and roof build-up with higher thermal mass.

Today’s lightweight building structures have lower environmental impact and there is no suggestion that we should return to more traditional brick and stone structures. However, there is a need to consider the density of the insulation being used.

Isolair, from Soprema’s Pavatex range, is a high density woodfibre insulation suitable for use on lightweight structures. It delivers a circular approach to sustainability by providing an effective defence from both heat loss and heat gain, using a material that is renewable and delivers carbon lock-up.

Used to encapsulate the building envelope like a blanket, with tongue and groove connections between panels, Isolair is fixed to the external surfaces of the walls and roof, in thicknesses between 60mm and 200mm, depending on the design, orientation and location of the property, giving a high thermal mass to the structure. During periods of warm weather, Isolair provides a decrement delay of 8-9 hours, ensuring the peak outdoor temperatures only reach the interior accommodation during the cooler night-time hours.

Isolair’s natural fibres act like a sponge for the heat, absorbing it and releasing it gradually, rather than allowing it to pass quickly to the inside of the building, as low-density insulation systems do. However, the material is lightweight, making it suitable for lightweight structures, and it delivers excellent thermal performance to meet the required U-values, along with good acoustic properties.

Comfort and an evolving climate

We can no longer rely on lack lustre summers and thick brick walls to keep homes cool in the summer; the issue of overheating needs to be addressed across new build and refurbishment projects. In a climate where hot summer days are usually tempered by cooler evenings, extended decrement delay must be a key criterion for insulation specification, and Isolair delivers on this goal.