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A bonus room will exist over a garage by using trusses that allow for the bonus room to be about 12 x 24. The roof has a 9/12 pitch that puts the batt insulation up against the roof of the slopping ceiling. Also the walls have dead spaces where heat builds up. I did this in another house and the room gets exceptionally hot in the summer and do not want to recreate the same problem. Any suggestions on how to ventilate and insulate the bonus room? Also, is there any fix for my previous completed house that has the bonus room that has the existing high temperature problem? Thanks.
Rockie
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Rockie, you haven't gotten any responses, so this has probably been treated in the archives. Do a search, or just read some of the threads that are obviously related.
But since I've got the same situation, I'll tell you what I intend to do. First I am not a builder, GC, etc. I am a mechanical engineer with a lot of exposure to thermal topics, though not as a contractor.
We have continuous ridge vents installed and will install continuous soffit vents as well. Will not use gable vents as this can create cross currents which might interrupt the flow of air through the rafter bays. Vent/NoVent is often debated here, but it our case (attic trusses) I think you have to. Where you have just a rafter, I would fir down to increase the depth. You can buy styrofoam vent channel thingeys (what ARE they called) that you just staple to the roof sheathing that will have the "channels" built in. This is easiest and probably cheapest. I have a supply of cheap, foil- faced foam, and I intend to put firring strips up against the sheating and then insert panels, cut to width, to create an air gap next to the sheathing. Besides the insulation, this should provide somewhat of a radiant barrier. I will then have wet cellulose sprayed in the remaining cavity, or possibly even foam. I plan to also use the foil-faced foam on the outside of the knee walls, and with cellulose sprayed in. If you have not built it already, specify 2x6's for the knee walls -- it will cost very little extra and will make a big difference.
To recap, MY thinking is, make sure everything that can be vented is, provide some sort of radiant barrier, put in all the insulation you reasonably can.
*Another method is to create a thermal break across the sloped ceiling (the roof rafters) and the flat ceiling joists if it has hardly any attic space above by attaching 2" polyisocyanurate (PIC) board to the rafters/joists inside the room (R-factor of 7.2 to 8.0 per inch). Then attach furring strips perpendicular to the rafters. Next attach your drywall to the furstrips. Inside the rafter bays, put in your vent chutes and insulation (blown-in cellulose done from above down the ridge vent opening or from below up thru soffit area). A stiffer vent chute will be needed if packing in the cellulose tight. The foam furing strip method is good, just put a third one down the middle for extra support against the cellulose pressure.The PIC board is expensive, but the payback in cooler rooms with less airconditioning is worth it.
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A bonus room will exist over a garage by using trusses that allow for the bonus room to be about 12 x 24. The roof has a 9/12 pitch that puts the batt insulation up against the roof of the slopping ceiling. Also the walls have dead spaces where heat builds up. I did this in another house and the room gets exceptionally hot in the summer and do not want to recreate the same problem. Any suggestions on how to ventilate and insulate the bonus room? Also, is there any fix for my previous completed house that has the bonus room that has the existing high temperature problem? Thanks.
Rockie