Part L of the Building Regulations in the UK sets out the energy efficiency standards for new and altered buildings. This includes the requirements for windows, which play an important role in determining the overall thermal performance of a building.

When it comes to new aluminum windows, Part L requires that they meet certain thermal performance standards, including a specified U-value. The U-value is a measure of a window's ability to prevent heat loss and is expressed in W/m2K. The lower the U-value, the better the window is at retaining heat.

There are different U-value requirements for windows depending on various factors such as the type of building, location, and type of glazing. For example, in most cases, the maximum U-value allowed for new windows in the UK is 1.6 W/m2K for single glazed windows and 1.2 W/m2K for double glazed windows.

However, for buildings in more extreme climates, such as those in the Scottish Highlands, the requirements are more stringent, with a maximum U-value of 1.4 W/m2K for single glazed windows and 1.0 W/m2K for double glazed windows.

It's important to note that while aluminum is a popular material for windows due to its durability and low maintenance, it is not necessarily the most energy efficient material on its own. The U-value of aluminum windows can be improved by adding low-emissivity (Low-E) coatings, which reduce heat loss through the glazing, and by using gas-filled cavities between the panes of glass.

Another aspect of Part L that applies to new aluminum windows is the requirement for airtightness. The airtightness of a building is a measure of how much air can escape through gaps and cracks in the envelope.

Its all quite complicated but our Team at James Price can explain this for and work with your architect to make sure you new glazing makes your property as energy efficient as possible