So, what exactly is Approved Document L? In the United Kingdom, this document provides guidance on the conservation of fuel and power in buildings. It covers various aspects of building performance, including energy efficiency, insulation, and ventilation. The document is periodically updated to reflect changes in building regulations and energy efficiency requirements. Approved Document L used to be made up of four parts, but as of the 15th of June 2022 has been compressed into two volumes. There’s Volume 1: Dwellings, and Volume 2: Buildings other than Dwellings. When the changes were announced on this date, they were given a year’s grace period, so since the 15th of June 2023, the new version of the document is now in full effect. And buildings which haven’t started construction will need to comply with the new values.
The change to the document which affects smoke ventilators is based around U Values. So, let’s start off by explaining what a U Value is. In the context of building construction and energy efficiency, a U-value (also known as thermal transmittance or heat transfer coefficient) is a measure of how well a material or an assembly of materials can conduct heat. It quantifies the rate of heat transfer through a structure, such as a wall, roof, window, or door.
The U-value is expressed in units of watts per square metre per Kelvin, and it represents the amount of heat that passes through one square metre of a structure for every degree Kelvin of temperature difference between the interior and exterior environments.
A lower U-value indicates better insulation properties and lower heat transfer. Materials or building components with low U-values are more effective at preventing heat loss or gain, resulting in reduced energy consumption for heating or cooling a building. The U-value is influenced by factors such as the type and thickness of materials, air gaps, and the overall construction of the building element.
U-values are important in building design and energy efficiency assessments, as they help determine the thermal performance of a building and inform decisions about insulation materials, glazing options, and overall energy efficiency strategies.
Basically, the required U Value for smoke ventilators has dropped to 3.0 Watts per square metre per Kelvin in the new version of this document, from a previous 3.5. And the lower the number, the stronger the product’s thermal properties. This may seem like a minor change, but it’s important to stay on top of the correct documentation to make sure products remain compliant. If this change to Approved Document L concerns you, rest assured that Sertus have a wide range of smoke ventilation products which comply with these changes. Please find our product page here.
Thanks for reading and as always, if there's anything we can help with please do Contact Us.