rigid foam ins as vibration isolation?

dymaxian · Post by **dymaxian** » Fri May 21, 2004 12:39 am

Hey guys! This one is more for Knightfly and Rod I guess...

When using concrete block as an outer envelope wall, heat transfer is going to be a concern of mine. Even tho I'll have fiberglass blanket and plenty of 703 on the inside of the rooms for acoustic treatment, I'd like to have an insulation layer around the envelope of the building.

The easiest thing to do would be to put an inch or 2 of extruded foam insulation on the inside of the concrete blocks. No acoustic value, but good for heat loss. My question is how to relate the remaining construction inside to this foam. At first I left a 2" gap between this foam and the interior floated floors and stud walls, but I'm wondering if that gap is necessary.

The foam won't structurally couple the inside walls to the block, so that's not an issue- and since it has zero acoustic value, I'm wondering if I could just count the insulation as filling a 2" gap between the inside and outside walls.

Is that a bad idea? Will it change the walls into a single-leaf system? (I'm using inside-out wall design, so the drywall would be pressed up to the rigid foam) Or will the foam not allow the air gap between the 2 leaves to act as the spring it's supposed to?

Thanks in advance

Kase
www.minemusic.net

knightfly · Post by **knightfly** » Fri May 21, 2004 3:02 am

That type of foam will couple sound pretty effectively, so should NOT be considered "air space" - it will likely have a speed of sound propagation of around 1500-2000 feet per second, and almost no damping whatever. If you're planning on a layer of that inside blocks, I would still leave a real air/absorbent gap, ESPECIALLY if you're doing "inside out" walls - the wider this gap, the higher the isolation, all other things being equal... Steve

rod gervais · Post by **rod gervais** » Fri May 21, 2004 4:15 am

as always - Steve hit the nail right on the head.

You want the air space for sure......

Rod

dymaxian · Post by **dymaxian** » Fri May 21, 2004 5:38 am

Thanks guys!

... chances are I'll be trying to get the ICF stuff Steve posted about back in the day. Nobody seems to know what it is around here tho, so I'm looking for backup plans...

Kase
www.minemusic.net

knightfly · Post by **knightfly** » Fri May 21, 2004 6:55 am

Kase, are you in Colorado? don't remember, and the one thing you musta forgot to read was my plea to include a location in your profiles - I'm trying to figure out where you are that ICF isn't being done by at least a few brave souls - from what little I know about it so far, I don't think you want to be the first guy your contractor does this for... Steve

rod gervais · Post by **rod gervais** » Sat May 22, 2004 12:11 am

manufacturer's of IFC products will always provide you with a list of trained installers in your area..........

In the entire state of CT there are only a few (think less than 5) companies that the manufacturer's will reccomend -

So if you want to find them - this is the best (safest) way to proceed......

Rod

dymaxian · Post by **dymaxian** » Sat May 22, 2004 12:24 am

Aha, there it is. I had thought I'd put the location up there, but it didn't take.

The board won't log me in automatically the way it used to either. Oh, well, if it's gone again tomorrow, I'll whine to John about it.

He doesn't have anything else to do, right?