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Strut
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# Posted: 29 Apr 2012 02:05am
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Wow, this is such an awesome web-site....just found it tonight. I start building my 16x24 cabin next month and had originally wanted to put in a loft. After researching roof ridge vents, gable vents, soffit vents, etc... it seems a little complicated to vent a roof like this. I will have a combination A/C & heat window unit and a wood-stove (or one of those new little heat pumps that you can install yourself). Is it really necessary to vent the roof of such a small cabin? (I live in the DEEP south....very hot). I will probably just forgo the loft & have trusses with a flat ceiling and use a gable vent on each end of the cabin. Any feedback would be welcomed. Again, thanks for everyone's input on this great site!
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MtnDon
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# Posted: 29 Apr 2012 11:44am
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Cathedral ceiling roof. It needs venting soffit to ridge if built in the conventional manner with batt insulation. There are ways to construct a cathedral ceiling roof and not vent.
A flat ceiling is easier to insulate to higher R values than a cathedral ceiling. Best venting would be soffit vents combined with a ridge vent.
Being in the deep south, hot 'n' humid, and using A/C watch be careful of your techniques and materials. Google "Building Science" and use their website search for building techniques appropriate the the deep south.
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Sustainusfarm
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# Posted: 29 Apr 2012 03:35pm
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I built alreay exactly what you described...I have cathedral ceilings with a loft...I used 2x10 rafters and insulated with fiberglass, had a continuous roof vent on the peak and vents under the soffits. I will tell you that after 10 years I will be pulling out the fiberglass and getting rid of the roof and soffit vents for good! Even with all the caulking and sealing up of the smallest holes and cracks I have bugs in the insulation...I will be spraying foam insulation in the roof cavity instead and then you do not need any venting in the roof! The product I am going to use is Icynene. You can get more info here http://www.icynene.com/
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MtnDon
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# Posted: 29 Apr 2012 03:57pm - Edited by: MtnDon
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I know people who are very happy with their icynene ceiling/roof insulation. Works well. Another solution for roofs that have not been built yet or roofs that will be reshingled is to use rigid XPS foam sheets on top of the roof sheathing. After that a second layer of sheathing is applied using special long screws. Then shingles or whatever over that. That can totally take the place of any cavity insulation or can be an adjunct to batts in the rafter bays. No venting required. Thickness of foam varies with climate and has to be thick enough for colder climates when used in conjunction with batts.
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Sustainusfarm
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# Posted: 29 Apr 2012 04:11pm
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Interesting concept MtnDon....I will have to ponder that one! I have not yet removed my fiberglass and since there is not any drywall on any surface yet I am guessing it may take a few years for me to get the ambition up to do the work it has been 10yrs since I put in the insulation!...LOL
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Strut
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# Posted: 1 May 2012 07:03pm
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Thanks for all the replies.......this info is very helpful. For simplicity, I am going with the flat ceiling and trusses. Hoping to "break ground" this week!
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BigDuke6
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# Posted: 9 Dec 2012 11:17pm
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I have been researching all day on this same topic. Looks like the biggest thing to remember is that there is some airflow space between the soffit vents and the ridge vent, making sure the insulation does not block either.
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