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I am renovating an A-Frame (circa 1970) and would appreciate input on insulating and venting the roof/walls. The trusses are 2″x6″ on 24″ centers. I will finish the interior walls with cedar or pine tounge and groove for a rustic look. Should I plan on building up the 2″x6″‘s with 2″x2″‘s in order to provide more room to vent and insulate? What type of insulation is recommended? Is a 2″ vent space on the inside of the roof sheathing required? Thanks in advance. Location: northern Indiana
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I fyou want to use tongue and groove, then I would strongly recomend using spray foam. It is expensive, but eliminates the need for venting, furring down rafters, and drywalling (or sheeting with foam)under the tongue and groove boards.
You would need to drywall or install foam under the boards to maintain a continuous air barrier. Without this continuous air barrier, the air leaks through all of those several hundred feet of T&G joints and overwhelms the venting and rots the roof anyways.
Just spray the foam and your done, then cover it up.
*Joe,A cheaper option would be dense-packed cellulose. Put up 2" of ridged foam over the tops of the stud/rafters, tape joints, and blow cells to 3.5 lbs cu/ft.Put your t&g over the whole shebang.Steve
*as steve said.. you can fasten a 3 inch iso-panel with OSB bonded to it to the outside of the 2x6.. this will give you.. about R14-15and then 5.5 inch of Cellulose will give a (net) of about another R18.. so this would be a relatively cost effective way to get R32...the panels come in vented or nonvented varieties...the last overlay job we did with this material the 4x8 panels cost $52 each... then our roofing was applied right to that.. with extended rake and eave boards...
*Mike, I'm glad to hear your using the Nail Base Insulation. I love the product, and thought for a while that I was the only person on the planet that put it on houses. Lstiburek does too, so we are in good company.-Rob
*So wait a sec here, you mean the roof rafters are 2x6? And you have a vaulted ceiling? R-28 attic insulation (fg batts) are 6" thick. So, if you fur your 2x6's out another 1-1/2 you'll have an extra say 1-1/4 for ventilation. BTW if you want to save some $ to fur your place out, and have a bench saw, just by 2x4's and rip them in half. Just make sure to always put the cut edge to the side, so as to always have the same thickness of furring strip when you go fur down your rafters. Buy a sheet or two of Styrofoam 1-1/2" thick, and cut strips off it about an inch or two wide. Put a couple of strips in each rafter space to make sure the fg batts don't block the ventilation path. Or you could use RaftRMates going all the way up the cavity but this costs more, and I hate paying a couple of bucks for something worth a couple of cents. I don't understand what Rob is saying when he says you have to drywall under the t&g to get a ctnuous air barrier. Isn't that what the 6mil poly vapor barrier does? I'd suggest that after you fur out and insulate, just install the v.b. over it as usual and put up your t&g. Sounds simple, unless I'm missing something!
*Marko- With this being an A-frame, the 2"x6" roof rafters are also the walls (one and the same). Yes, the ceiling/walls will be vaulted. I have heard a lot of good input, but I welcome more. I will start the insulation adventure in approx. a month. Any A-Framers out there?
*I agree with Steve but believe he meant to attach polyiso to interior side of farming, seal joits with foam or tape, blow cells solid beteen foam and existing sheathing, and then cover with t&g. It's a super approach, simple, and easy to see that you get a good quality air barrier.
*Well, my house has a vaulted ceiling throughout the second floor, so I guess you could call it an A-frame. You can insulate it same as a regular wall, and if you believe what the experts say, the profile of r-28 on a 40 degree angle gives it about the same insulating value as R-44, since heat rises. I thnk that's a bit of a stretch, but anyway, you insulate it just the same as you would a wall. If you want to go code then up here it's R-40 in a flat roof and R-22 in a wall, so that's why my inspector required R-28. Just fur the rafters down and you'll have plenty of room for vent gap and insulation. I'm just letting you know what worked for me. BTW is your roof strapped or sheathed?
*MikeWhen u said, "fasten a 3 inch iso-panel with OSB bonded ....will give you.. about R14-15", did u mean PolyIsoCyanurate board? PIC board is supposed to have an R-factor of 7.2/inch. This should yield R21.6 for just the PIC and then some additional R-factor for the OSB, right? Unless of course you meant something different.... or the 3 inches includes the OSB "sandwhich" on both sides of the PIC?For those who don't know, PIC board over rafters is supposed to be a very supperior insulation method. Acts as a thermal block on the rafters. Stuff the cavity with cellulose and use a couple of light bulbs for your heating needs.Phil
*patchogue....whatever the mfr says is good enough for me...in my head i usually carry eps at 4... styro at 5 and polyiso at 7...i got confused because i've stopped using polyiso.. and switched to eps...it's more cost effective in most of my situations..even the r4 thermal break is so fantastic compared to a regular stud wall and i pay about $3.50 for a 4x8...and i can get it treated with borate for termites (Performguard)..if i need a stronger board. i can spec 1.5 lb. / CF or even 2 lb/ CF...this is after thumbing my nose at eps for 25 years...b but hey , whadda i no..marko.. what do you do to keep the wolves from the door ?
*Wolves? Door? Huh? I don't get it. But hey, what do I know....
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I am renovating an A-Frame (circa 1970) and would appreciate input on insulating and venting the roof/walls. The trusses are 2"x6" on 24" centers. I will finish the interior walls with cedar or pine tounge and groove for a rustic look. Should I plan on building up the 2"x6"'s with 2"x2"'s in order to provide more room to vent and insulate? What type of insulation is recommended? Is a 2" vent space on the inside of the roof sheathing required? Thanks in advance. Location: northern Indiana