Insulation problem!

Hello everybody! In the attachment you will find Base.skp, looking at it while reading my post should clear things up. First of all, the wall. The wall is a 10cm brick, then 2cm air gap and another 10cm brick. Does this count as a leaf? How could I further insulate this? Since there will be acoustic drums in the room, I need as little noise outside as possible! How much insulation would this 2 wall system be? Second of all, also seen in the attachment, I thought of 2 different ways, one is 18CM rockwool with 2,5cm plaster on top of that. On the other side is 9cm rockwool, then 1,2CM plaster and another 9CM + 1,2cm. Is this a good way of insulating the room? Or would I be better off trying something else? Also, not related to the insulation topic; The walls on the outside are tilted towards the middle to form the roof, do I also need to put these in an angle so they do not face eachother, or is this not a neccessity because they aren't really facing eachother? All input appreciated!

Hey all, Had a quick talk with my dad, he's building the garage this summer. He told me he could simply fill the 2cm gap with concrete or cement (cement is the dutch word, though after googling it seems its also english, correct me if Im wrong though). Would this be better? Since then I'd have a 22cm thick wall, without airgap and I could build another leaf against it.. or 22cm concrete may just be enough to fill my need.. Looking forward for advice! Cheers, Rene

Updated version of the sketchup in the first post, since I got some new info on how the build will be. I didn't edit the walls to be 22cm thick, because thats open for discussion right now.

Does this count as a leaf?

Hard to say, for sure. If the two brick "leaves" are tied together internally, such as with metal ties, brick or mortar, then they will probably act more like one single mass than two separate ones. If they are fully decoupled, then they'd probably act more like two leaves than one. That said, two layers of brick is a lot of mass, so you should already be getting fairly decent isolation from that. The density of brick is somewhere around 1800 to 2800 kg/m3, depending on the type of brick. Guessing around 2000. According to mass law, 20 cm of that density should be giving you around 45 dB of isolation above 100 Hz. Hard to say below that. That's pretty good. Adding a third leaf of drywall on studs, fully decoupled, should be an option here, if you need a little more isolation. However, I suspect that your major isolation problem is not going to be the walls, but rather the roof and floor. How are those built?

He told me he could simply fill the 2cm gap with concrete or cement

That would not make much difference. The density of concrete is only a bit higher than that of brick, so you'd only be increasing your mass by about 10%. Mass law says you have to DOUBLE the mass to get a 6 dB increase in isolation, so increasing it by 10% is going to have an insignificant effect. Building a proper 2-leaf room-in-a-room would help much more, at much less expense and complexity. But once again, the issue is probably not the walls: the issue is the roof and floor, windows, doors, HVAC and electrical system. Those are going to be your weak points.

Updated version of the sketchup in the first post,

You show the roof as a 3cm wood deck, a 16cm air gap (insulation filled) and a single layer of 1.9cm drywall, all on the same joists/rafters. That will give you maybe 35 dB of isolation, with luck (it is a fully coupled 2-leaf system) But on the other side of the roof, you show a 3cm wood deck, an 8cm gap, a 1cm layer of drywall, another 8cm gap, and a final layer of 1cm drywall. That is a three-leaf system, so the isolation there will be somewhat LOWER than for the other side: I'd guess at around 30 dB, maybe. I didn't have time to actually do the math, but that side of the roof (the 3-leaf side) is going to be your weak point. So right now it looks like your overall isolation is going to be somewhere in the region of 30-35 decibels, maximum. But we still need to know about the floor, windows, doors, HVAC and electrical system, to see if any of those are even weaker points. - Stuart -

Soundman2020 wrote:

Does this count as a leaf?

Hard to say, for sure. If the two brick "leaves" are tied together internally, such as with metal ties, brick or mortar, then they will probably act more like one single mass than two separate ones. If they are fully decoupled, then they'd probably act more like two leaves than one.

Okay, since the walls will be touching due to, as you said, metal wires etc. I might just as well let them fill up entirely, its not much more of a cost.

Building a proper 2-leaf room-in-a-room would help much more, at much less expense and complexity.

So if I were to build a frame completely decoupled from the outer wall with 2 leaves that would be the best option at this point? Or do I see this wrong?

But once again, the issue is probably not the walls: the issue is the roof and floor, windows, doors, HVAC and electrical system. Those are going to be your weak points.

There are no windows on the top floor. HVAC I haven't thought about yet, dumb. Ill have to look into that. For the doors I was thinking to build 2 after eachother for the entreance. Electrical system? How should I interpret this? The way I get my 220v's upstairs? About the floor; Its a simple wood underlayment floor, like this; Its going to be 18mm. I guess there will be my weak spot, how could I insulate this as good as possible?

You show the roof as a 3cm wood deck, a 16cm air gap (insulation filled) and a single layer of 1.9cm drywall, all on the same joists/rafters. That will give you maybe 35 dB of isolation, with luck (it is a fully coupled 2-leaf system) But on the other side of the roof, you show a 3cm wood deck, an 8cm gap, a 1cm layer of drywall, another 8cm gap, and a final layer of 1cm drywall. That is a three-leaf system, so the isolation there will be somewhat LOWER than for the other side: I'd guess at around 30 dB, maybe. I didn't have time to actually do the math, but that side of the roof (the 3-leaf side) is going to be your weak point.

Well I made the 2 sides different, in order for you all to tell me which would work better. Looks like neither works, haha. What would you suggest to increase the insulation?

So right now it looks like your overall isolation is going to be somewhere in the region of 30-35 decibels, maximum.

Thanks for the thorough reply. What do you think my maximum insulation would be? ------------------------ EDIT; Added a sketchup file of a inner wall, you can show it under the layers tab. Is this a start of whats ment with the "room-inside-a-room" idea? After uploading I noticed the room in a room construction is touching the roof beams, that shouldnt happen, right?

Well I made the 2 sides different, in order for you all to tell me which would work better. Looks like neither works, haha. What would you suggest to increase the insulation?

There are a couple of options, but your "room in a room" model is the best way to do it.

Thanks for the thorough reply. What do you think my maximum insulation would be?

That depends on many factors: the best idea is to measure it yourself, with a sound level meter: measure how loud you normally work in your current location, and also measure how quiet you need to be. The difference is how much isolation you need.

Is this a start of whats ment with the "room-inside-a-room" idea?

Exactly, yes. You show it with "inside-out" construction, meaning that the studs are facing the room, and you can also do it the other way around, with the studs facing the cavity and the drywall facing the room. There are advantages and disadvantages for both methods.

After uploading I noticed the room in a room construction is touching the roof beams, that shouldnt happen, right?

Right! That should not happen. The inner "room" should not touch the existing walls or ceiling anywhere. Just the floor. - Stuart -

Een tukker, leuk! :D To get an idea about the amount of isolation you need, you have te tell where the people are situated that might get bothered by your music. So what kind of music do you intend to generate and where are the neighbours situated? With that information we can think of what you gonna need.