VIEWPOINT NET ZERO NEEDS THERMALLY
EFFICIENT SOLUTIONS Chris Cowley, Specification Manager at Keystone Lintels explores the use of thermally efficient lintels as a cost effective way to reduce carbon emissions and futureproof UK homes.
IN THE RACE TO net zero, achieving compliance with new updated building regulations will be crucial for housebuilders involved in the construction of new build homes. To meet the performance levels required and the challenge of enhanced energy efficiency within SAP, the specifier will need to address thermal bridging in all its forms
The latest changes to Building Regulations Part L are an all- important stepping stone to the Future Homes Standard (FHS) which comes into force in 2025. With all new homes needing to cut carbon emissions by 31% as an interim uplift, and by a further 75-80% in 2025, this will require fairly significant changes for housebuilders.
One of the most effective ways of reducing a home’s reliance on heating and cooling is by addressing the thermal performance of a building envelope through a fabric first approach. 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. 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 neither building consistently what we design, nor 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 instance. This can lead to a performance gap between as- designed and as-built building performance. It’s why these weak spots can significantly impact a building’s heat loss and have a detrimental affect on the overall fabric effiency of the external wall.
Thermal continuity Often overlooked when it comes to thermal efficiency due to a focus on insulation, windows and doors, traditional steel lintels can create a significant thermal bridge in homes. This is due to the high thermal conductivity
of steel and because they span over long lengths in a typical build. The other issue is that with many two-piece lintels, there is an issue with a lack of continuity of insulation. To ensure the insulation is continued all the way down to the cavity closer, it is necessary to cut a piece of insulation to fit beneath the DPC membrane. This detailing is difficult and cumbersome on site and quality control issues can occur. There are solutions to address this, for instance, the Hi-therm+ Lintel is prefabricated and fitted with PIR insulation, ensuring insulation continuity and eradicating poor detailing on site. 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 steel 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).
Better Buildability Unlike a two-part solution which can add costs and double installation time, the simplicity of a one-piece, structurally superior top hat design assists stablitiy between the internal and external leaves and creates stability throughout the building process.
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Furthermore, a split lintel does not have an angled profile, meaning the Damp Proof Course (DPC), if not installed correctly, can droop causing a build-up of water in the cavity. As stop ends are not generally installed, this build-up of water can then run down the side of the lintel and into the cavity. Due the top hat profile of Hi-therm+, water will naturally run off toward the external leaf and the weep vents. 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.
The current energy crisis is showing no signs of abating, which is why making homes more energy efficient through a fabric first approach will go some way to locking in savings for the lifetime of a building and achieving our climate change targets. Now is the time to start creating high performance building envelopes through the specification of materials and components which deliver where others cannot – as this can be the difference between a sustainable and an inefficient home. BMJ
www.buildersmerchantsjournal.net August 2022
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