When researching the purchase of new glazing for the home, understanding window and door U-Values helps you make a more informed buying decision. As well as U-Values, Window Energy Ratings is another term you’ll come across. This guide explains window and door U-Values, what they mean and why they’re important.
Why understanding window and door U-Values is important
U-Values is a measure of how any building material insulates your home. U-Values don’t just extend to windows and doors. Walls, cladding, aluminium panels, glass and insulation all have U-Value figures.
The higher the U-Value, the poorer the performance. The lower, the U-Value, the better the insulation properties. The measurement of U-Values is in Wm2K (Watts per metre square Kelvin). Another way of thinking about U-Values is thermal transmittance. In other words how effective they are in heat transfer or energy loss.
What about Window Energy Ratings?
Window Energy Ratings, or WER’s are a little different. These are measured in Ratings of A (being the best) down to G, being the worst. Furthermore, like U-Values WER’s measure the energy loss, but they also measure energy gain. And a WER even measures any air loss through the window frame .
Why do U-Values and WER’s matter?
Both U-Values and WER’s came into force ten years ago and they form part of the current Building Regulations. They’re covered by Part L1A for new build homes and L1B for existing dwelling. Here’s what you need to know on U-Values and WER minimum ratings for your home. Demonstrating how important these ratings are, they also form part of CE Marking. Here are the minimum requirements for doors and windows.
|Windows||1.6Wm2K or lower||Band C or better|
|Roof windows or rooflights||1.6Wm2K or lower||Band C or better|
|Doors (more than 60% glass)||1.8Wm2K or lower||Band E or better|
There are, of course, certain installations such as listed buildings or conservation area properties where it may not be possible to get the required ratings. Exemptions exist to cover these and your local authority or Building Control can provide more information.
What is the ‘centre-pane’ method?
In the early days of U-Values, compliance came by also using the centre pane method. Generally speaking this is a rating for the glass or panel only. In certain exceptions centre-pane method can be used such as listed buildings.
If your window company quotes centre-pane values for your new glazing, this is incorrect. Today, the performance figure you get must be for the entire window and door including the frame.
Do window and door U-Values and WER’s matter?
The good news is, most new doors and windows on the market meet at least the minimum requirement shown in our table. The great news is that many out-perform these figures. The better the U-Value or WER, the better performing your window. For you, this means greater energy efficiency and help in reducing your energy bills. For instance, our Origin OW-80 window fitted with Aerogel meets A++ window energy ratings.
Importantly these figures affect the heat loss from your home. But for balance, they won’t perform as well if your home is losing heat from other areas such as not having loft insulation.
Lower U-Values mean better interior temperatures, less heat loss, fewer draughts and cold spots. Also important is reduced electricity and gas bills and lower carbon emissions.
How we give you great U-values on windows and doors in pvcu, aluminium and timber.
First of all, is the glass. As standard all our PVCu, timber or aluminium products come with double glazed units of at least 24mm or 28mm depending on the product. As standard, you also get a soft-coat low-emissivity coating, warm edge spacer bars and argon gas fill. This glass specification is toughened safety glass in all doors regardless of location. It’s toughened too in low-level windows and screens.
PVCu frames provide thermal efficiency thanks to their multiple chambers within the frames. Aluminium frames come with a polyamide thermal break. Timber doors and windows need nothing more than the solid wood profile – it’s an excellent insulator.
For aluminium specifically, on it’s own, aluminium conducts heat. The thermal break, aerogel or another insulation type effectively separates the inside and outside profiles. This thermal break also prevents heat loss or transfer of cold.
What about large patio doors?
Our entire range of bifolding doors, comes in aluminium with an advanced, high performance thermal break. These meet and exceed the U-Values required. However, using glass upgrades, triple glazing, integral blinds even laminated glass, it’s possible to get even better thermal performance.
For large glass panels such as those in our slimline or standard sliding patio doors, the same applies. We use high performance toughened glass units, with additional glass options if you want even better performance.
Contact us for more information about energy-efficient doors and windows
At Aluhome our entire product range comes with the best in design, engineering and thermal performance. Whether you choose our aluminium, PVCu or timber windows and any of our aluminium doors. All promise you the latest glass and profile technology and designed for the best energy efficiency and window and door U-Values
Contact us today to find out more or visit our showroom.