Improving insulation and sound

[ss]

Just recently got `free` cavity wall & loft insulation and would like to further improve the insulation and sound insulation in a couple of rooms. In one bedroom there are 2 windows which although double glazed have minimum spacing between the glass (approx cm) I also hear traffic noise through them. I was thinking of using some 10mm polycarbonate sheet in a frame to make a third `pane` . I am using this method as it is something I could do myself. Am I likely to gain much by way of heat loss and sound insulation or would it not be worth the effort?

thanks

[Martin Brown]

Why 10mm? Do you expect to need it to be bullet proof as well?

5mm polycarbonate sheet or perspex is pretty well behaved in frames. I secondary glazed the remaining single glazed windows with it. Really small windows you can get away with 3mm sheet. You have to think carefully about any opening windows depending on how you do it.

Good thick heavy curtains will prevent more heat loss than secondary glazing when they are closed. Hard to predict how well it will perform against traffic noise since it depends on what sort of noise and how it is coupling to the room. Wider spacing and having the inner pane damped rather than rigid and taught like a drum skin will help.

You will need a UV stabilised grade with the UV protection facing outwards. Glass stops some UV but not enough to avoid degradation of water clear plastics in windows.

[Dave Plowman (News)]

Normal double glazing isn't a very good sound insulator as the gap is too small. If you fit secondary glazing the thickness of the wall away from the original you'll get very good results. Glass will be better than plastic because it is denser - the thicker the better. And it needs a good air seal all round.

[Brian Gaff]

Also if there are drafts from the original windows, secondary glazed sliding panels can rattle annoying ly!

Brian

[Dave Plowman (News)]

To work correctly, sound wise, both need to be air sealed. Which means the secondary glazing should have runners similar to that used on cars which holds the glass firmly.