Double Glazed Windows and Doors Energy Ratings Explained
A simple guide to UK Double Glazed Windows and Doors Energy Ratings
It is important to know that your replacement windows or doors are energy efficient. These days this information will be displayed on the unit in the form of an Energy Rating Label (WER).
The widest known of these ratings are provided by British Fenestration Rating Council (BFRC), British Standards Institute (BSI) and CERTASS (UKAS approved certification scheme).
The energy efficiency performance of the whole installation can be identified by this label. It does not apply just to the glazed elements only.
Double Glazed Windows and Doors Energy ratings cover the performance of these main points:
- U- Value: how much heat is lost (thermal conductivity)
- Solar Gain: how much heat is allowed to enter (G-Value)
- Air integrity: how much air is allowed to leak or enter (L-factor)
So in summary, the WER will help you identify how good the product is at reducing energy wastage – the ratings currently run from A++ to G and are colour coded much like a rainbow.
Understanding your Double Glazed Windows and Doors Energy Ratings Label
If you break the label down into 4 parts, therefore you will be able to relate information to each section.
Section 1) Heading
If we use the BFRC label as our example, at the very top you will find the details of the certified company, a product description and a product / reference number.
Section 2) Colour Coding
Once Again with the BFRC label as our example, just below the heading you will see a colour chart with an alphabetical rating for that particular colour.
As a result, the overall rating of your product will be easily identifiable from here. Currently, A++ is the highest rating on the BFRC label.
UK building regulations require, that for new & replacement windows, at least C-rated windows fitted. However, there are a few exceptions for certain specialised properties.
Section 3) Energy Index
This section differs slightly from provider to provider, but will give the energy index together with the U-value, G-value and L-factor.
The energy index is a number that is arrived at by using a formula based basically on gains minus losses (U-value Vs G-value & L factors).
You can find positive or negative numbers here. In general, the higher the number the lower the heat loss. A negative number indicates the unit loses more heat than it gains.
Section 4) Footer
This section includes information related to the rating itself. For BFRC labels, it will tell you when the rating was given to the product. You should also find a link to a site where you can verify the rating.
As mentioned briefly beforehand, there are variations on the style of labels, but the above should enable you to easily understand what you are looking at.
Are A++ rated windows worth installing?
As it’s likely to cost more to buy A++ rated double glazed windows than any other rating. Consequently, it’s reasonable to ask the question “are A-rated windows worth the extra cost?”.
To give you some sort of idea, we looked at the time it would take for the cost of your replacement windows to be recouped in money saved due to the added energy efficiency.
It’s estimated that the average cost of double glazing for a 3-bedroom house is between £3,000 – £5,500. (UPVC Windows double glazed with 28mm sealed units – house heated with electricity)
- A++ rated windows costing £3,500: Savings of around £200 per year & 15 years to recoup
- C rated windows costing £3,000: Savings of around £140 per year & 20 years to recoup.
Of course these are hypothetical installation costs, but there seems to be a distinct advantage to fit the most energy efficient windows that you can afford.
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