[Toxarch]

Alright, my theater is going in a 600 square foot room over the garage. Part of the walls of the theater are the underside of the theater. I'm not that worried about sound going out of the house since I live on a 10 acre lot. If the neighbors can hear the movie, then I am already deaf in the theater and won't be able to hear them complain.


When I was buying all my materials at HD, the pro desk guy said I should use those styrofoam Durovent vents on the underside of the roof decking. It is to allow any heat created from sunlight on the roof to either move up into the attic or down to the vents in the soffits on the bottom edge of the roof. I've put some up and covered it in insulation and compared it to a section without the vents. I can tell it does help by touch, but I did not measure anything like temp difference. I am wondering if I NEED to put a fire stop in there somewhere. I am assuming that I don't have to put firestops in since it is the underside of the roof but I thought I better ask now before I finish it all. The Durovent vents I am adding work better if they can draw cooler air from the soffits and vent the hot air into the attic. A definite plus in Texas summers.


BTW, the rest of the rooms upstairs do not have any of these vents in their walls. The house was built in 1987 if that matters.

 

[bwolff]

The vents will add years to your shingles. If you insulated right up to the roof decking it would over heat the roofing. The desk guy is right on the money there. As for the fire stop, in my area at least. As long as you do not have more then a 9-foot cavity you are ok. A good example is if there is no top plate on the walls below and the fire could roll right up the garage wall and into the attic. I am not a pro I just play one on TV.

 

[Toxarch]

Well then, I am not going to put any firestops in. The side walls already have top and bottom plates so those are fine. Good thing I don't have to add the firestops since I would have to do something about all those wires I already ran.

 

[settopguy]

I am not sure what you mean by fire stop.


To reduce the chance of fire you could use fire rated cement around all places wires pass through a hole in a joist or other structural member. Or at least do that around the first hole entering/leaving a room.


Also you should have gypsum board or other fire resistant materials as one of the layers in your walls, and ceilings.

 

[Toxarch]

On the underside of your roof, there is no top and bottom plates (firestops). The joists go from the soffits under the bottom edge of the roof up to the peak (think of a roof with a single ridge i.e. gabled roof). My theater is going on the second floor above the oversized 3 car garage. So, I have (roughly) 7 foot side walls, then 7 foot sloped walls, then a ceiling that is 9 feet across and reverse going down the other side. It's the sloped walls I was wondering about. There really shouldn't be any firestops in there since the heat from the roof needs to be vented. I just wanted to make sure that I wasn't supposed to add any.


Actually, I am covering up about a 16 foot cavity (since there are closets on the sides too), but the vents are supposed to run top to bottom to vent all the way through. Here is what I am putting in the 2x6 24 inch on center cavities from roof decking inward:

Roof decking, Durovent vents, R-30 faced insulation, soundboard, sheetrock.


The picture of the room shape is in the following link to an older thread. The wall I am talking about is the one labeled "B". On each side, not shown, are triangle shaped closets. Hence the 16 foot total length I am filling.

http://www.avsforum.com/avs-vb/showt...hreadid=133110


Maybe I will stop by the pro desk at HD to make sure I don't need to add a firestop in the middle or something.