What U-Value Should your Timber Windows Have?

Looking to save money and be energy efficient? Your U-Value rating matters!

Window U-Values can have a big impact on multiple points within your property and the financials surrounding it, including how well your property would sell if put to market, and your energy bills. If you already have timber windows installed, then both of these points are already positively reflected in your property and finances, but your U-Value can make all the difference.

What is a U-Value?

A U-Value is the measurement used to assess how well heat is transferred by the entire window/ door, including the frame, sash and glass. The lower the U-Value is, the better the window or door will keep heat inside a building on a cold day.

What is the best U-Value for your windows?

When looking at properties as a whole and windows, you want the lowest U-Value possible. Building regulations now state that new timber windows must have a u-Value below 1.4 W/m2k, meaning that they will be energy efficient and will maintain the desired temperature within the building. 

New buildings will require U-values for all components within the building envelope. These values will work towards the Standard Assessment Procedure (SAP) calculation that will form the calculation used to provide homeowners with an Energy Performance Certificate (EPC) rating once the building is completed.

How do you find U-Value?

When it comes to windows, U-Value is measured in a few different ways to determine the overall value.

Ug Value = Which measures the thermal performance of the glass.

Uf Value = Indicates the thermal performance of the window frame.

PSIG = Which indicates the thermal performance of the frame spacers.

U-Value for Timber Windows

Taking into account that timber is already an insulating material, your overall U-Value rating should be reasonably low, so this will mainly just depend on the thermal performance of the glass that your windows are provided with, or that you have chosen. At Dale Joinery, we chose to use thermally enhanced insulating glass, creating glazing units almost twice as effective as normal, which helps with the overall U-Value rating. 

Generally speaking, a double glazed window gives a U-Value rating of 1.1 W/m2K, and at Dale Joinery our timber casement and sash windows rate at exactly this, making our timber windows some of the most thermally efficient around.

The regulations have just changed in June 2022. Timber windows actually have until next year to reach 1.4Wm2K which is the new base rate.

About Dale Joinery

​​At Dale Joinery, we pride ourselves on creating the ultimate timber window and door for you. We carefully source all parts of our frame and only use the best materials to guarantee product security, quality and longevity. If you’re interested in our sustainable timber windows and doors for your project, please get in touch or call us 0800 030 2222. Download our digital brochure or request your physical brochure online for more inspiration.