Like electrical items, which are rated on how little energy they use, windows are also rated on energy efficiency. When looking to replace your windows, it is important to check the energy ratings of the replacement windows.
A window’s rating measures how efficiently the whole window (the frame and the glass) keeps heat in the property and the air infiltration through the window’s seals. Window Energy Ratings evaluate both the solar gain and heat loss aspects of the window.
When rating a window, a standard size and configuration is used to help keep the rating standard. The value is then rated on a scale of A – G, with A-rated windows being the most efficient.
What Are U-Values?
The U-value is a measurement of how quickly the heat from the inside passes through to the outside. Windows with lower U-values have better insulation. U-values are taken into account as part of the window’s energy rating.
As such, unlike energy ratings, U-values can be improved by draught proofing a window.
What is the U-Value of Timber Windows?
As the U-Value is affected by the design of the window, the type of glazing and the window frame. This means that there is no standard U-Value for all timber windows, as the U-Value will vary depending on the type of glass and timber used, alongside the design of the window.
Why Do Window Energy Ratings Matter?
With up to 25% of the heat in most homes escaping through the windows (source), energy efficient replacement windows can make a major difference to your home, along with saving money from heating costs.
Depending on the style and type of window you are looking to install, windows manufactured by The Sash Window Workshop have U-values ranging from 1.4 to 1.7 and energy ratings between A and C.