24mm Double glazing...

House_Hunter

Hi all,

What are peoples thoughts of 24mm double glazing units? I believe the current standard is 28mm no?

What are the possible impacts with regards to thermal and acoustic insulation?

The reason I am considering is as a replacement for sash windows and so can't take a too wide unit...

Any help appreciated.

Cheers.

McAzrael

24mm and 28mm are both perfectly normal. They can be made narrower while maintaining thermal efficiency if they are argon filled. They can be made really narrow and maintain their thermal efficiency if they are krypton filled and made with low iron glass, and warm-edge spacers, and even lower-e glass - there are endless options. With regards to accoustic insulation then narrow units will not perform so will, but the difference is minor. If you want to improve accoustic insulation without shelling out for the fanciest glass or ugly secondary glazing then have the units made with different thickness panes of glass (say 4mm/14mm spacer/6mm for a 24mm unit), or with different materials (have one of the panes made with laminated glass, say) or both. Whoever is supplying your windows should be able to advise you. The glass manufacturers will have figures for typical make-ups on their websites.

SatanicHare

My understanding of document L is that 16mm is considered the optimum air gap, i may be wrong, have a read at this it might help
http://www.theworldofwindows.com/documentl.html

sashman

house hunter, ditto everything McAzrael said.

No such thing as standard, as in British standard. 4.20.4 (28) often quoted as best for air filled units. 4.16.4 is however very common.

Gas has an optimium of 8/10mm thats why our premiere sash windows now has 4.10.4 units to achieve A ratings, AND it looks more tradtional.

The smaller the sealed units the larger the bar and beads are (just like original sash windows) so you can expect others to follow suit.

To increase the sound reduction use different glass thicknesses.

sashman

leveller2911

I also currently use 4-10-4 Argon gas filled,Pilkington K glass units which gives a U value of around 2.0, come October I think we will need to go to a 4-12-4 unit to comply ,which will give a rating of 1.8 or 1.9.....Now for my gripe, having been making Joinery for nearly 25 yrs why are we worrying about U values so much?.I agree we should make energy efficient windows but its getting to be a bit like the Petrol combustion engine in that its about as efficient now as its ever going to get and we really can't squeeze any more out of it.

Increasing the space between the 2 panes of glass from say 12 mm to 18mm will only bring the U value down by 0.1 is it really worth it??? Not in my opinion .

McAzrael

You could stop using Pilkington K - there's much better glass out there and it can be cheaper. Come October, if all goes to plan, you're going to be needing to get a window u-value of less than 1.6 (for domestic replacements), so the glass is going to even lower. You can comply by producing a WER class C window and in this case K glass may help because the WER method takes into account g-values. There's the third option of 1.2 centre pane u-value where you're matching some existing windows.

sashman

1.6 or WER C is fine for October 2010, but government want 25% reduction in 2013 AND a further 25% in 2016, thats 1.2 in 3 years time and 0.9 in 2016!!