Batts with No Hard Surface Covering
My church is renovating the oldest movie theater in Arkansas to use as our new facility. The walls are two-foot thick sandstone. The plan for the upper half of the sanctuary walls is to frame with 2×6’s and use batts (with the paper side out), and then cover this with a burlap material, stretched tight and stapled to the studs. This will be covered with “drapes” to mimic the look and feel of the original theater. This design was suggested by the sound consultants to “soften” the upper walls accoustically. For that purpose, it seems to make sense.
However, from an insulation standpoint, my gut feeling is that not having a hard surface over the batts is going to severely compromise the R-value, that there will be significant air movement through the “soft-faced” bays thus created. The draperies will be loose at the bottom and top which to me will create a chimney effect as well.
Spraying on closed cell foam has been suggested but the sound folks think this will be too reflective. I suggested maybe open-cell foam would be better, but I wonder if that would stick to the walls tightly enough (I was hoping we could eliminate the studs on the upper portion since the walls are around 30 ft. high)
Our architect is about as old as the building, and is not at all current in best practices. For acoustics we are using a dropped ceiling (but still pretty high) and we need to insulate the roof to prevent the sprinkler system from freezing. He is resistant to the idea of spraying foam on the roof deck (plywood over wood trusses) – thinks it will eventually start falling off.
Personally, I have serious doubts about the effectiveness of 6″ batts against 2′ thick stone walls, especially in the winter. But cost is a concern for us (large building, expensive project).
Would be interested in your thoughts on these matters.
Replies
You might consider covering the batts inside with housewrap, with all seams taped, and also sealed well to the top and bottom plates to prevent entrance and exit of air currents. If the walls are 30 ft tall, it might also be good to break up the cavities horizontally every 10 feet. I think you may have to do that anyway for firestopping reasons, but I'm not sure on that.
Edit: I'm wondering if you need to sheetrock the lower 8 feet anyway, to prevent damage when folks lean up or stumble and fall against the wall.
Edited 7/19/2009 10:52 am ET by DickRussell
Another edit: if you apply spray foam, you'll have to cover that with sheetrock anyway for fire protection reasons. Someone ought to do a heat load calculation for any proposed solution, to see what an appropriate level of insulation is for that size building and its intended frequency of use.
Edited 7/19/2009 10:55 am ET by DickRussell
You've got issues to go to your BO with. Exposed insulation must meet fire safety codes ... paper or poly. Foam insulation will not likely meet code w/out e.g. sheetrock "in substantial contact" with it. Paper or poly may not meet it either. You need sound control ... why not sheetrock under your wall covering? It won't be the best, but not the worst, either.
As far as energy - the batts [installed properly!!!] would be fine, but sheet finish materials (sheetrock) does help w/ air flow issues.
Don't focus on energy ... get the fire code right. It's a theatre ... deserves to be done right to protect the occupants. Maybe the sprinkler syste buys you some latitude. Not sure.
They are trying to solve two problems at once. i.e. tuning the thermal insulation for acoustic properties. Good luck.
I would insulate, then apply acoustic treatment. Do each task properly.
Sorry I didn't give more details. The lower 10 ft (or so) will have drywall. The upper portion will have the curtains. They don't want to use drywall on the upper portion because it creates a reflecting plane (echoes); thus the drapes over the "soft" wall. Not sure they have thought about the fire code. I'll ask about that. My concern was mostly about the loss of R-value, but the fire code is probably a bigger concern. Thanks for thinking of that.