I am in the process of renovating a family room and I am insulating a cathedral ceiling. The ceiling joists are 2×6 with a 12′ span 16” oc. with 1×3 strapping. There is no ridge or soffit vents. I will be using R19 fibreglass insulation. Do I need to use those plastic spacer between the insulation and the roof sheathing, to give air movement?
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You will need to if you what to guarantee a clear flow of air above your insulation. I would use the air chutes, its cheap insurance. Make sure that you do a good air sealing job, in a small space like that you could have a lot of problems if not properly sealed.
Bay Shore Building & Design. Inc.
Residential Building & Computer Aided Design Services
http://bsbad.tripod.com
What the hell are the air chutes going to do if you have no vents? Those things allow for the flow of air between the soffit vent and a ridge vent, so what might they do for your situation?
Joe H
Joe,
That is what I don't understand. What is their purpose if there are no vents above or below. How do they get rid of the humidity issue? Is there a humidity issue? I remember doing insulation 30 years ago without these chutes and have heard of no problems.
Kevin, they don't or can't do anything in your application.
You're treading on the verge of Flame Wars here with any questions re venting, but my thoughts on your situation are 1. Spray the cavity with foam and forget it. Much better insulation and no further vapor barrier needed. Hard to get a small job done, maybe not even possible in your area. 2. Dense pack it with cellulose, no vapor barrier needed there either. R value is much higher than fiberglass although not as high as the foam, but much cheaper. Also available nationwide, can be bought at Lowes & HD, they also have the machines to install if you can't find someone to do it for you.
Was there any moisture problem with whatever insulation was in this roof before?
What climate are your in?
Joe H
What climate are your in?
Now we're in the riight track...
Kevin:
Your question is more appropreate for the Energy, Heating and Insulation section and you will probably get a better answer than I am about to give.
I assume that you are talking about just a 2x6 that is both the ceiling joist and rafter?...or are you talking about a sissior truss with a sloped bottom chord for the ceiling and a steeper top chord for the roof? Either way I think you need to vent the cold side of the insulation which would mean lots of venting at gable ends, freeze blocks and maybe dormer and ridge vents. Heck..what do I know I'm only a finish carpenery contractor?
Ross
The 2x6 are now both ceiling and roof rafters. I am in New England. The previous space was an attic with insulation on the ceiling. There was no moisture poblem before. There will be no gable area to vent.
Do you really NEED insulation in New England? Didn't know it got cold there. :)
I forgot to mention that I would definitely insulate the roof system also, from eave to ridge.
Bay Shore Building & Design. Inc.
Residential Building & Computer Aided Design Services
http://bsbad.tripod.com