U-Value for windows

What is a good U-Value for windows?

When looking for windows, there can be a lot of technical information, such as U-Values, which can be hard to understand for someone unfamiliar with this industry.

You may hear your installer or window manufacturer using the term U-Value, and this article will explain what they are, why they are important and what a good U-Value is.

Along with their appearance, one of the most important features of a window, and one which is high up on the list of priorities for buyers looking for replacement windows, is efficiency.

Having highly efficient windows helps keep your home at an optimum temperature by keeping the warm air in and the cold air out, which also leads to reduced heating bills.

Old windows, whether single or double-glazed, are often poorly insulated, resulting in high U-values and low thermal efficiency.

Old single-glazed windows can have U-values of around 5.8 W/m2K, and older double-glazed windows can be around 2.8. 

U-values are now much lower, and typically a good U-value for replacement windows is anything below 1.6 W/m2K.

What is a U-Value?

A U-value is the rate of heat loss over a surface or material measured in W/m2K. You will want windows that have a low rate of heat loss, so the lower the U-value, the more efficient the windows. 

Old windows, whether single or double-glazed, are often poorly insulated, resulting in high U-values and low thermal efficiency.

Old single-glazed windows can have U-values of around 5.8 W/m2K, and older double-glazed windows can be around 2.8. 

U-values are now much lower, and typically a good U-value for replacement windows is anything below 1.6 W/m2K.

What is the minimum U value for windows? 

In 2002, it was decided that windows had to comply with Building Regulations, meaning all replacement windows had to have a minimum U-value of 1.6 W/m2k or be rated C.

FINEO U-Value

FINEO is ultra-thin double glazing which boasts U-values which outperform standard double glazing and match that of triple-glazed windows while being 3 to 4 times thinner. 

For heritage-style windows, the frames have been typically built with single glazing, meaning standard double glazing won’t fit into the frame.

FINEO provides a thermally efficient solution to upgrade windows on heritage properties.

The experts at Scott James Sash Windows offer FINEO glazing as an upgrade to traditional sash windows, helping improve the efficiency of your home to save you money on your bills.