U-values BREAKING DOWN THE NUMBERS As Sunny Lotay, National Commercial Manager at PermaRoof Commercial, explains, U-values have recently undergone regulatory changes to enhance energy efficiency in new builds and renovations – but he says there is still some concern about how these are calculated and how best to ensure the right value is given. Below, he discusses what contractors need to understand about U-values for both commercial and domestic projects. U-values determine whether a building meets the required energy standards, helping drive forward more efficiency and bringing down carbon emissions. Thermal transmittance - the U-value - is measured in units of W/m²K, which stands for Watts/meter square Kelvin. This illustrates how effective a material is as a heat insulator by indicating how quickly it will lose heat. The lower the U-value, the more efficient the construction is at keeping heat flow through the structure to a minimum, for instance, a U-value of 0.5 will lose heat at double the rate of a 0.25 structure. If the U-value is not calculated correctly, the impact is a concerning loss of heat, which for homeowners and building managers means higher fuel bills. Not to mention the negative effect this has on sustainable housing and commercial properties. As experts in the industry of flat roofing, we know the difficulties contractors face in trying to meet tight budgets and deadlines – but we are also aware of the importance of building regulations and ensuring these are upheld for our clients and customers. Contractor compliance In 2022, the UK building regulations were updated to include revised, lower U-values for new builds and renovations – essentially requiring thicker insulation. These updates are designed to improve the energy efficiency of buildings and reduce the carbon footprint. Left: Sunny Lotay. The new regulations now state the walls, floor and the roof all need to meet minimum U-value requirements depending on the situation and materials used. Part L of the building regulations covers the requirements for roofing in particular, which specifies that all roofs to rooms (except those in unheated buildings) must be thermally insulated to a maximum U-value of 0.15 W/m²K for new build and 0.18 W/m²K for refurbishment. These changes to Part L for England and Wales have been implemented to cut carbon as part of the Government’s move towards its target of Zero Carbon Ready Homes by 2025. The aim is to ensure building practices reflect this shift by helping to reduce carbon output for new homes by 30%, and for other buildings by 27%, when compared to the standards in 2013. This is because heating and powering buildings in the UK accounts for 40% of our total energy usage. As a result, increasing the thermal performance of all properties is essential for reducing the demand for energy, the need for heat and power in homes, and for reducing energy bills too. Calculation and installation When calculating the U-value of a flat roof, contractors need to consider all areas that contribute to thermal performance such as screeds, timber, air spaces, and plasterboard. Many insulation manufacturers have useful U-value calculators for an approximate figure. But in practice, this can only be backed up through correct installation. If insulation is fitted poorly, with gaps and cold bridges, then the U-value can be considerably higher than desired, no matter how good the individual products are. When installing a flat roof, suitable insulation is required to minimise heat losses in the winter and control excessive solar gains in the summer. This will help to conserve energy and ensure thermal comfort is maintained within the building. Without appropriate flat roof insulation, the project will not pass building regulations. Furthermore, speaking to the right people and utilising expertise when needed will ensure the installation achieves the best results. Whether you are a contractor, homeowner or commercial property owner, it is crucial to get the right advice from reputable suppliers to avoid being mis-sold or misinformed. PermaRoof has a team of registered installers nationwide to provide guidance to contractors on projects. Contact PermaRoof www.permaroof.co.uk PermaGroup 50 TC DECEMBER <strong>2023</strong>
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