From 15th June 2022, changes to ‘Conservation of fuel and power: Approved Document Part L Building Regulations’ come into effect as part of the Government’s progress towards its goal of delivering zero carbon ready homes by 2025. As part of the updated regulations, all new homes must produce 31% less CO₂ emissions than that stated in the current 2013 version of Part L. This is viewed as a stepping-stone toward the new Future Homes and Buildings Standard to be introduced in 2025, stating that new homes built from this date will produce 75-80% less carbon emissions than homes delivered under current regulations.

Thermal bridging

A key issue to address in the construction of Zero Carbon homes is thermal bridging. A thermal bridge is a disruption in the thermal envelope of a building, most commonly in the form of a gap in insulation, which can generate heat loss and condensation. This has the potential for the building to underperform in terms of energy efficiency, increasing the CO₂  emission rate. To combat this problem, Fabric Energy Efficiency Standards (FEES) have been tightened, and as a result, thermal bridges must now be independently assessed following the removal of Accredited Construction Details (ACDs).

ACDs are a standardised set of building practices that many smaller housebuilders across the UK worked to, and techniques detailing how to reduce heat loss through thermal bridges were a part of the practices laid out in the manual. However, these practices were drawn up over two decades ago, and building best practices have moved on significantly since, therefore when the Approved Document Part L changes come into effect in June, the ACD calculations will be removed.

Airtightness

Formerly, developers were able to test the airtightness of one dwelling within the development and apply the results to the whole scheme, but under the new changes, each individual home within the development must be tested independently. Airtightness is a crucial aspect to consider as it promotes lower running costs through a reduced heart loss and therefore few carbon emissions, along with comfort improvements and fewer defects.

Transitional Arrangements

The transitional arrangements have been reduced, as previously developers would be allowed to build to the standards that were in place at the time planning approval was granted, they now will have just 12 months to transition to the new standards to remain compliant, and local planning authorities can add their own requirements on top of the national Building Regulations. This does place much more pressure on staying in line with regulations to the letter, as a much keener eye will be kept on the specificities of construction.

Carbon Emissions

There are many aspects to be addressed to meet all of these new standards in a very short space of time, and it is important to note that these standards will change again in 2025 when the Future Homes and Buildings Standard comes into effect. A tried and tested solution that can help to meet these challenges is building with lightweight structural timber. The Climate Change Committee noted in a publication that using wood in construction to displace high-carbon materials such as steel and cement is one of the most effective ways to use limited biomass resources to mitigate climate change. Felled trees store carbon and timber has the lowest embodied carbon of any mainstream building material, making it the perfect material to meet the new standards.

The STA’s mission is to enhance the quality of construction across the industry through technical guidance and research, underpinned by a members’ quality standard assessment – STA Assure. The STA Assure scheme provides assurances that our members are working in accordance with legislative compliance and to the best possible quality, and with so many changes occurring in a short space of time, enlisting the help of an STA member is invaluable.

The STA has developed design solutions to meet the heat loss standards required by the new Approved Document Part L and Section 6 of the new Scottish Building Standards which are also fire tested. These design solutions allow developers to achieve the required U Value of 0.18W/m2K and can be found in the guidance document ‘Structural timber buildings fire safety in use guidance Volume 1 – Pattern book systems’ in our library, available to download here.

For more information on how vital timber is to helping the UK achieve Net Zero status by 2050, download the STA’s whitepaper ‘Increased Use of Timber’ here.

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