Glass thickness and Triple leaf Help!

How thick should my walls be, should I float my floors (and if so, how), why is two leaf mass-air-mass design important, etc.

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Creative24seven
Posts: 6
Joined: Sat May 25, 2019 4:53 am
Location: England

Glass thickness and Triple leaf Help!

Post by Creative24seven »

Hi.

I'm in the midst of a studio build and just thinking about the windows. The building has double glazing (4mm - 14mm gap - 6.8mm) and I was going to then add secondary glazing on the inner wall (so there would be roughly a 150mm gap between the original window and the secondary glazing) . Just a couple of questions.......

1) If I add the secondary glazing will I be creating a triple leaf and therefore making sound isolation worse than if I just had the standard double glazing window.
2) If it is still beneficial to add secondary glazing, what thickness should it be? They offer 4mm / 6mm or 6.8mm. Would 6mm be different enough from the 6.8mm in the existing window to negate any resonant frequency issues?

Any advice appreciated

Thanks!

Chris
Paulus87
Senior Member
Posts: 652
Joined: Sun Mar 02, 2014 8:42 am
Location: Wales, UK

Re: Glass thickness and Triple leaf Help!

Post by Paulus87 »

Creative24seven wrote:Hi.

I'm in the midst of a studio build and just thinking about the windows. The building has double glazing (4mm - 14mm gap - 6.8mm) and I was going to then add secondary glazing on the inner wall. Just a couple of questions.......

1) If I add the secondary glazing will I be creating a triple leaf and therefore making sound isolation worse than if I just had the standard double glazing window.
2) If it is still beneficial to add secondary glazing, what thickness should it be? They offer 4mm / 6mm or 6.8mm. Would 6mm be different enough from the 6.8mm in the existing window to negate any resonant frequency issues?

Any advice appreciated

Thanks!

Chris
Hi,

We need to know more detail - how is the rest of the building constructed?

In any case, double glazed units are not ideal for studios - they resonate, just tap them and you will hear it. The two panes are very thin and light and not decoupled from each other, and the air gap is tiny, therefore they act like a mid range resonator. This is not what you want when you're trying to reduce sound going through. Adding a secondary glazing over this will help in some ways and make it worse in others.

You need to treat the glass just like the rest of the wall(s), they need to have the same surface density. Find out the surface density of your walls and fill the hole in that wall with glass of the same surface density. Usually for a studio you would have a double leaf assembly for your walls and your ceiling/roof, all not touching and separated by an insulated air gap. Do you have this already?

Whatever you have and do, it all needs to be completely sealed air tight otherwise it's all in vain. People often forget to seal the gap between the frame and the jamb and therefore the windows/doors become very leaky and the weakest link in the system. Do it right and this doesn't need to be the case.

Paul
Paul
Creative24seven
Posts: 6
Joined: Sat May 25, 2019 4:53 am
Location: England

Re: Glass thickness and Triple leaf Help!

Post by Creative24seven »

Thanks Paul.

The rest of the room is 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) I can't replace the double glazed windows but just wondering if I'm better off keeping as is and sealing up to them (2 layers of board in the reveals) or adding another secondary glazing within the inner stud wall?

Thanks

Chris
Paulus87
Senior Member
Posts: 652
Joined: Sun Mar 02, 2014 8:42 am
Location: Wales, UK

Re: Glass thickness and Triple leaf Help!

Post by Paulus87 »

Creative24seven wrote:Thanks Paul.

The rest of the room is 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) I can't replace the double glazed windows but just wondering if I'm better off keeping as is and sealing up to them (2 layers of board in the reveals) or adding another secondary glazing within the inner stud wall?

Thanks

Chris
I would add secondary glazing in that case otherwise you'll end up shorting out the double leaf assembly by attaching them at the windows.

The double glazing will not match the surface density of the brick, but the good thing is it's on the outer leaf so work out the surface density of your inner leaf then make sure your new secondary glazing has at least that density. You can get glass with more surface density to try and compensate for the double glazing a little, and make sure you have the maximum distance possible between the inner and outer windows. Laminated or toughened glass is recommended.

Paul
Paul
Creative24seven
Posts: 6
Joined: Sat May 25, 2019 4:53 am
Location: England

Re: Glass thickness and Triple leaf Help!

Post by Creative24seven »

Hi Paul. Thanks for the help. I've found company who can do me a 16mm laminated pane so that looks like it might be a good option.

Can I just ask how I seal the between the two sets of windows? I've got a carpenter who's going to make me a frame / box that fits into the decoupled wall and the secondary window will sit within the box. I obviously don't want to attach the back of this box to the brick outer wall as that would bridge my two walls but am I right in thinking that the reveal between the two windows should be airtight?

What if I brought the window box to the brick wall but allowed a small gap (10mm?) I could then add backer rob into the gap and caulk the join. Would this be suitable? If not, any other ideas?

Many Thanks again

Chris
Paulus87
Senior Member
Posts: 652
Joined: Sun Mar 02, 2014 8:42 am
Location: Wales, UK

Re: Glass thickness and Triple leaf Help!

Post by Paulus87 »

Creative24seven wrote:Hi Paul. Thanks for the help. I've found company who can do me a 16mm laminated pane so that looks like it might be a good option.

Can I just ask how I seal the between the two sets of windows? I've got a carpenter who's going to make me a frame / box that fits into the decoupled wall and the secondary window will sit within the box. I obviously don't want to attach the back of this box to the brick outer wall as that would bridge my two walls but am I right in thinking that the reveal between the two windows should be airtight?

What if I brought the window box to the brick wall but allowed a small gap (10mm?) I could then add backer rob into the gap and caulk the join. Would this be suitable? If not, any other ideas?

Many Thanks again

Chris
Actually it doesn't need to be air tight since it is merely a continuation of your double leaf system. Imagine if the windows were not there you would have two walls with an air gap between them. Each of the windows and their corresponding walls need to be air tight independently, so make sure there are no gaps unfilled between the jamb and the wall for each.

You can cover the gap as you proposed, that would work fine. Or you can bridge the gap with some fabric covered rigid fibre. Or you can put a layer of rubber before you put the jambs between the two. Many ways to do it. Have a look at Rod Gervais's book, or a quick google image search for "recording studio window frame" etc.

Paul
Paul
Creative24seven
Posts: 6
Joined: Sat May 25, 2019 4:53 am
Location: England

Re: Glass thickness and Triple leaf Help!

Post by Creative24seven »

Thanks again. You've been really helpful!
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