Having been around and involved in windows for many decades, if there’s a company that should know about U-values, it’s us!
We’d like to share our knowledge of U-values with you so that when you come across them whilst searching for new replacement windows, you have a firm understanding of what they mean.
Let’s make you an authority on the subject, just like we are.
Windows and U-values – What’s the Relationship?
All replacement windows have a designated U-value and it indicates how a window fares for thermal insulation.
You ideally want windows with the lowest available U-values as they are designs that will initiate home thermal efficiency and generate a consistently pleasant internal temperature.
Windows that have a high thermal transmittance (another word for U-value) insulate a lot less effectively and tend to do a poor job of keeping heat trapped inside.

How the U-values of Different Windows Compare
Pitted against double glazing and triple glazing, single glazed windows come last for thermal transmittance, which is no great surprise.
It can be as high as 6.0 W/m²K, a stark contrast to the average rate of 1.2 to 3.7 W/m²K for a double glazed window (1.4 W/m²K is the minimum requirement, as specified in UK building regulations). A triple glazed unit u-value figure is the best of the lot and it’s not unheard of for it to be as low as 1.0 W/m²K.

The Role of Energy Efficient Glazing in Window U-values
A window can only perform to the highest level of insulation when it contains energy-efficient glazing.
Glass deemed as energy efficient earns its name as it is purposely made to minimise heat loss and maximise thermal insulation. Low-E glass is a vital constituent of it and it possesses an invisible coating for heat reflection.
Incorporated into double or triple glazed windows, it will promote warmth in the home in winter and stop a buildup of excess solar gain in summer, relieving the pressure on your boiler and saving you money on energy bills.
When selecting any energy-efficient glazing, scrutinise U-values and don’t forget to also consider security, privacy and sound insulation too.

Permaframe makes a point of ensuring that each window we sell comes with energy-efficient glazing as standard so that our customers are assured of top-class insulation and can hopefully cut your energy costs.
Make contact with us if you’d like to be brought up-to-speed on any other window terminology commonly advertised in the product specifications of new replacement windows.
LOOKING TO REPLACE YOUR WINDOWS?
We have a fantastic range to choose from so whether it’s a modern style or traditional timber effect windows – we are confident that we will have windows to improve any home to give it the finished look with elegance.
LOOKING TO REPLACE YOUR WINDOWS?
We have a fantastic range to choose from so whether it’s a modern style or traditional timber effect windows – we are confident that we will have windows to improve any home to give it the finished look with elegance.
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