Let’s Talk Double-Glazing

Tue 27 Oct 2015

If you’ve never had double-glazing before, it can be hard to comprehend how much of an impact it will have upon your home. Not only can double-glazing make a house warmer, it can also reduce outside noise, drafts and condensation; noticeably decreasing your energy bills.

Will you make all your money back through lower energy bills straight away? Probably not for quite a stretch, however these figures and facts show double-glazing (or triple-glazing) is still certainly worth the investment:

1. Indicative u-values for a single-glazed sliding sash window are very poor, reaching around 5.4 W/m2K. However double-glazed windows are much lower at 1.4 W/m2K, triple-glazed windows only 1.0 W/m2K.

2. By investing in good quality, factory-finished timber windows you can add greater value to your home and they’ll last twice as long as UPVC windows. This is particularly worth knowing if you live in a period property.

3. Whilst window frames are less important than glazing, they are still worth thinking about. Softwood frames can be better for thermal insulation than other materials, reducing the risk of ‘cold-bridging’. The wood’s strength also makes it more suitable for triple-glazed windows.

4. The optimum glazing unit gap is 16mm which gives a total unit depth of 24mm with 4mm glass sheets. We recommend you consider low-emissivity glass as it can be over twice as energy-efficient as ordinary glass. For instance, Argon-filled units are around 5% more expensive but can improve a double-glazed unit’s energy-efficiency by as much as 30%. Krypton and Xenon are even more efficient but they will cost you more.

5. For most people, double-glazing offers the best value option. However, if you want to achieve U-values below 1.4, or if you’re building to Passivhaus standards, you’ll want to invest in triple-glazing. Just bear in mind that triple-glazing is likely to reduce solar gain.


Of course, no matter how energy-efficient your new windows are they won’t keep the cold out unless they’re installed properly. The window’s junction with the wall is crucial so it’s important you get your windows fitted by a professional.

Why not look at members of the Wood Window Alliance if you’re looking to get new double-glazed windows fitted? With all members meeting strict performance, quality and sustainability membership standards, you will know they’ve got in all under control. 


For more advice on windows for period homes or conservation areas, look here

For more advice on narrow cavity glazing units, look here

For details of members of the Wood Window Alliance, look here