chris-cowley-keystone-lintelsNational Specification Team at Keystone Lintels


With the government’s commitment to bring all greenhouse gas emissions to net zero by 2050, it has become imperative to look at ways in which we can ensure our future homes are ‘zero carbon ready’. A critical first step is ensuring the fabric of our homes is well designed and by paying careful attention to detailing and thermal bridging, we can eliminate some of the issues that create poorly performing homes.


The new Part L requirements of the Building Regulations will be seen as an important stepping stone to the Future Homes Standard in 2025 but there needs to be a clear emphasis on the design of a building’s envelope without the need for further retrofitting work. The new interim Part L uplift to energy efficiency requirements will mean all new homes will be expected to produce 31% fewer carbon emissions through a combination of fabric improvements, low carbon heating technologies and PV panels. The 31% reduction is the first step but by 2025, new housing will be expected to produce 75-80% fewer carbon emissions compared to current standards. This is a potentially massive change for the industry and a real game changer.


Getting the fabric right

What will this mean for new homes and how will we meet these higher standards? One key area will be addressing the thermal performance of a building envelope through a fabric first approach to building design. If we get the fabric right and we build as designed, we will go a long way to meeting our targets. It’s an approach that will enable us to meet and even exceed regulatory performance criteria, whether it is for large scale social housing or a much smaller residential property.

Whilst a reduction in CO2 emissions is one consideration when designing thermally-efficient housing, an improvement in thermal comfort can also have a positive impact on occupants – adding to their thermal comfort, productivity and wellbeing.


Thermal bridging

A critical element of the fabric first approach will be addressing the issue of thermal bridging, which can be responsible for up to 30% of a home’s heat loss. Eliminating thermal bridging through good design and correct product specification will be essential if we are to ensure we meet these ambitious new regulations.

Whilst there are some design, measurement and calculation issues, the other concern in terms of thermal bridging is that we are not building consistently what we design, or we are not detailing the right products in the right places. There are also issues with site skills and workmanship; when you fail to build correctly it undermines the good work carried out in the first place. This can lead to a performance gap between as- designed and as-built building performance. It’s why these weak spots can have a significant impact on a building’s heat loss and have a detrimental affect on the overall fabric efficiency of the external wall.


High performance lintel

Often overlooked when it comes to thermal efficiency due to a focus on insulation, window and doors, traditional steel lintels can create a significant thermal bridge in homes due to the high thermal conductivity of steel and because they span over long lengths in a typical build. However, there are solutions to address this.

For instance, Hi-therm+ has set a new standard for thermal efficiency in steel lintels. It incorporates a thermal break and is up to five times more thermally efficient than a standard lintel. Hi-therm+ is a very cost-effective solution, particularly if we look beyond the unit price, as getting the fabric right will save energy throughout the entire life span of the house.

The Hi-therm+ lintel has made a significant impact on the thermal efficiency of homes and is specified on many housebuilder projects around the UK due to its low cost and improved performance in lowering carbon emissions within the Standard Assessment Procedure (SAP).

The importance of lintels should not be understated. The Hi-therm+ lintel has a positive impact on the SAP calculation due to its impressively low thermal conductivity performance, which contributes towards its Psi value of between 0.03 & 0.06 W/m.K. This makes it the ideal low cost and sustainable solution for specifiers aiming to achieve building regulations with the fabric first approach. When you consider the BRE has found that thermal bridging can account for up to 30% of heat loss from buildings, then paying close attention to the details and structural elements such as lintels can have a huge impact on the overall thermal performance of a building.

At a time of spiralling energy costs and the current gas crisis seeing no signs of abating, making homes more energy efficient through these welcome regulatory changes will go some way to achieving our climate change target. There will be challenges for housebuilders, but fabric first will be a key priority in locking in energy savings for the lifetime of a building.