Critical thermal gains

We talk to Thermoseal Group’s sales director, Mark Hickox, about how small gains can make a big difference.

A building’s fabric is still crucial to the energy efficiency of a building, even if the expected changes in the Future Homes and Buildings Standard – due to come into force in 2025 – appeared to favour energy source heat pumps over insulation, argues Thermoseal Group’s sales director, Mark Hickox.

“It was a bit of an own goal when the government unveiled the Future Homes and Buildings Standard consultation document in December 2023 and decided against lowering window U-values to 0.8W/m2K,” Mark says, “because our industry is capable of meeting those standards with triple glazing.

“Interestingly, though, we know there is an appetite for more energy efficient buildings, and the industry continues to make incremental improvements in the thermal performance of their products, despite hesitation at a regulatory level.”

Mark argues that the construction industry has taken its foot off the gas when it comes to thermal performance, ever since the government chose to reduce the ‘regulatory burden’ on developers rather than pursue ‘zero carbon homes’ from 2016 as set out in the consultation document ‘Building a Greener Future’, which was published in 2006.

“Today, though, developers are pursuing the green agenda because it is good for business,” Mark says.

“And the window industry is in a prime position to meet the key aims of that agenda.”

Mark points out that while triple glazing is not required to meet the U-values demanded by Building Regulations – in most instances – it provides a cost-effective and obvious statement of intent.

“Some see triple glazing as a cheaper way to lower SAP calculations (rather than upgrading the insulation, for example), and others recognise in the marketing value of triple glazing – an obvious energy efficiency statement,” he says.

“It also means that sealed unit manufacturers and window fabricators will need to pay close attention to the components they are using. Today, it is a lot more difficult to substitute one component for another while maintaining the overall thermal calculations of the window.”

Thermoflex, Thermoseal Group’s flexible silicone rubber spacer bar, achieves a thermal conductivity of 0.125W/(mK) for the UK’s preferred thickness of 4.8mm, which means it is the best performing flexible silicone rubber spacer bar in the world.

This is backed up by the latest test results from IFT Rosenheim and approved by BFRC in the UK.

In practice, if a window has had its thermal performance calculated on the basis that it is made with Thermoflex spacer bar, then no other foam spacer system can be used without putting the whole window through a recalculation.

Failure to do so will result in a non-compliant window.

Thermoflex, on the other hand, can substitute other flexible silicone rubber spacer bars without recalculation.

The rubber in Thermoflex in the UK is made with 100% silicone. According to Mark, other competitor products in the UK are generally a compounded blend containing EPDM rubber, which is a cheaper raw material than silicone, and is less thermally efficient.

“Interestingly, the Future Homes and Buildings Standard raises the possibility that each window manufactured will need its own bespoke U-value, which means the thermal performance of each component part is expected to be critical,” Mark says.

“By moving away from a ‘standard’ window when calculating U-values, window fabricators will have to produce a certificate for every window manufactured to prove that it complies with the revised regulations. And the fact that Thermoflex is higher performing than other similar spacer systems could easily make the difference between a window complying or failing.”

Mark concludes by saying that regulation in construction is coming under ever greater scrutiny, and window companies would be foolish to think that they could skirt round laws just to save a few pence on component parts.

“Now is the time to work closely with your suppliers, to develop quality products that are fit for purpose, compliant, and the most thermally efficient,” he says.