What type of glass is in my windows?
If you’re wondering whether the glass in your windows still provides sufficient insulation, you first need to know the type of glazing and its age. Only then can you decide whether it needs to be replaced. This article explains how to figure this out.
Generally speaking, there are six types of glazing. We have listed them below in the order of their insulation value, with single glazing providing the poorest insulation and triple glazing providing the best insulation.
Single glazing (Ug = 5.8 W/(m2K))
- One glass pane
Standard double glazing (Ug = 2.8 W/(m2K))
- Two glass panes
- With an aluminium spacer bar and ordinary air in between the panes
High-efficiency glazing HR (Ug = 2.0 W/(m2K))
- Two glass panes
- With an aluminium spacer bar
- With single insulating coating
This type of glazing has been on the market since 1985 and is mainly found in homes built or refurbished before the year 2000.
High-efficiency glazing HR+ (Ug = 1.4 W/(m2K))
- Two glass panes
- With an aluminium spacer bar and inert gas in between the panes
- With single insulating coating
This type of glazing has been on the market since 1990 and is mainly found in homes built or refurbished after the year 2000.
High-efficiency glazing HR++ (Ug = 1.2)
- Two glass panes
- With an aluminium spacer bar and inert gas in between the panes
- With improved single insulating coating
HR++ glazing is currently a good choice.
Triple glazing (HR+++, Ug = 0.7 W/(m2K))
- Three glass panes
- With aluminium spacer bars and inert gas in between the panes
- With two improved insulating coatings
To find out the difference between double glazing and high-efficiency glazing:
- Check the documents and invoices related to your home.
- Check the information on the aluminium spacer bar between the glass panes
- Pay attention to the letters.
If you see the letters ‘HR’ – which stand for ‘Hoog Rendement’ – you are dealing with high-efficiency glazing. If you see no letters, or you see letters other than ‘HR’, you are most likely dealing with double glazing. - Identify the Ug value (the thermal conductivity of glass: the amount of heat (in watts) conducted through a square metre of glass relative to the difference between the indoor and outdoor temperatures).
- Pay attention to the letters.
- Perform a test using a lighter or a match.
Carefully keep a lighter or a match five to ten centimetres away from the window. If you look at the window from an angle, you should see four little flames reflected in the glass. If all the flames have the same colour, you have standard double glazing. If the second or third flame has a slightly different colour, you have high-efficiency glazing.
You may also be able to identify the type of high-efficiency glass in your windows based on the documents and invoices related to your home and the code and U value on the aluminium spacer bar.
If you are not the first owner of the home, be sure to check the type of glass in all your windows. Previous owners may have replaced some glass panes in the past.
If you want to know how old your double or high-efficiency glazing is, you should be able to find this information in your documents and invoices. You can also check the information on the aluminium spacer bar between the glass panes, which often states the date of production. It may also be worthwhile to check the age of all your windows, as the previous owners may have replaced some of them.
This article was published on 12-10-2023. Unless expressly provided otherwise, all information you consult or obtain here is entirely without obligation and for information purposes only. The information applies exclusively to the Brussels Capital-Region.