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Old 18th September 2020 | Show parent
Lives for gear
Kyle P. Gushue's Avatar
Originally Posted by C247 View Post
Thanks Kyle. The maximum air gap I can achieve is about 125mm. Any idea how I'd calculate the density of glass needed? Most of the secondary glazing units I've seen are around 7-12mm which I realise isn't particularly thick.

Basically wondering if I'm better off leaving double glazing as is or is there a marginal gain from adding secondary glazing. Obviously don't want to do it if it's going to be detrimental.

Just for info, the rest of the room is constructed as below:

Walls: Double layer of 15mm Acoustic plasterboard with Green Glue between on isolated wooden studs with 100mm insulation between the studs. There's then an air gap of about 50mm and then brick outer walls (9" thick). The ceiling is the same construction (2 layers of 15mm board+ GG, hanging from their own joists)
Its density, not thickness that's key. Different types of glass ie float vs laminate, have different density, despite the same thickness. Its about mass.

Youve got a nice amount of mass and decoupling in your assembly, and the windows need to match or exceed that level of performance, to not be a weak link. There is an equation i can dig up to calculate less massive sections of a wall if you need it.

Ive never had to calculate a 3 leaf assembly, but the wyle report (attached) does show how if your inclined to do so. Otherwise it should be pretty short work for a full time acoustician.

Ill assume you want to keep the window, so i wont delve into window plugs ect, which are an option.

You have to make sure that the window assembly is completely air tight. is well liked, and might be able to help you.

This thread might help.

Exterior Windows - Prefab ?
Attached Files
File Type: pdf Wyle WR 73-5R.pdf (11.69 MB, 13 views)