ICF construction?

[floid]

on my day job right now we're building a house using a technique I'd never heard of before: ICF, or Insulated Concrete Forms. It's two 2.5" thick chunks of Styrofoam held apart by plastic webbing, that fit together like legos, and will have 6" of concrete poured between them. Obviously, a solid concrete wall is gonna have some considerable soundproofing ability, but I was wondering if anyone here has had experience with this stuff, if you have ideas for optimizing it for studio applications, etc.

[digitaldrummer]

it probably depends on what part of the country you live in (or even what country you live in...). 2x6 construction with appropriate insulation and multiple layers of sheetrock may be as good and cheaper. or not. another option is cinder blocks. I've heard in some areas they might be as cheap or cheaper than wood construction. I see others using steel construction (pole-barn like structures).

My builder had also told me about some pre-fab "walls" (I don't remember the details but supposedly popular with "green" builders). In the end I settled on 2x6 wood studs, a brick exterior and 2 layers of sheet rock. it was the least expensive and from what I can tell pretty darn effective.

Mike

[jhbrandt]

floid,

Yes, we do quite a bit of these type walls.

The mass of the concrete offers a great deal of sound-proofing via its mass. The Styrofoam, however offers nothing acoustically. - Great thermal insulation though.

Cheers,
John

[floid]

it probably depends on what part of the country you live in (or even what country you live in...). 2x6 construction with appropriate insulation and multiple layers of sheetrock may be as good and cheaper.

Yeah, my studio has offset 2x4s on 2x6 plates, more than enough isolation out here in the woods - and definitely cheaper, since this stuff requires enough lumber for bracing that you could frame up a whole 'nother building the same size.
But it's an interesting technique, and supposedly both sturdy and efficient as hell... I think I was probably expecting someone to chime in with a "what constitutes a leaf," and whether or not that even counts when one leaf is 6 inches of solid concrete.

[jhbrandt]

Yes, the Concrete wall IS ONE leaf. It definitely counts.

Are you saying that you built your interior walls 'staggered stud' construction? All you needed is a 2 X 4 wall with an air space of about 1" from the Styro to get you high isolation.

If you put drywall or sheeting between the concrete and the interior room shell, you will have compromised the isolation at low frequencies.. however, with the mass of the concrete, it wouldn't amount to much loss - it's just that is is unnecessary and a waste.

Are you currently BUILDING or are you already finished?

Cheers,
John

[floid]

yeah think i might have misspoken:
I have an open floor studio. it's done, finished, i'm happy with it. but i'm playing with the idea of adding a control room off the backend- and if I do one I want it dead nuts right, fuck the cost. i'm looking at ICF thinking, hmm, by the time you finish it out you've got exterior siding, stryofoam, concrete, Styrofoam... all that counts as one leaf?

[jhbrandt]

Exterior siding IS actually one leaf.. how much it will affect the iso is questionable. The Concrete is another leaf - which would matter greatly. The styro is simply thermal insulation - does nothing acoustically. For my calculations, I consider it as AIR.
But you don't want that stuff touching your decoupled interior partition.

so you basically have a double partition with that assembly, however NONE of it is decoupled. Add a decoupled, interior partition of at least 2 layers of 16 mm or 5/8" gypsum board with 2 x 6 or 38 mm x 140 mm studs, and you will obtain Isolation that will exceed STC-65. (min separation of 1" or 25 mm)

It is possible to build a studio within an ICF building without an interior decoupled partition. It depends on your isolation requirements.

Cheers,
John

[floid]

The styro is simply thermal insulation - does nothing acoustically. For my calculations, I consider it as AIR.
But you don't want that stuff touching your decoupled interior partition.

see, that's kind of the sticking point in my thinking - the Styrofoam's an acoustically useless layer that nonetheless couples. seems like it makes it impossible to arrive at a true two leaf system, but i'd think a board and batten siding wouldn't really count as a true leaf either...
yet I keep revolving back to SIX INCHES OF SOLID FRIGGIN CONCRETE