For next winter I’d like to improve the insulation situation in my Cape Cod style house. The unfinished parts of the second floor have plank flooring and kraft-faced fiberglass batts in the rafters and on the gable walls. But the insulation is from 1970 and if you even look at it wrong the paper rips, ends hanging down, stained black from all the passed air, etc.
I was thinking of taking it out and getting the rafter bays filled with closed cell foam. But will I have to have all the ceilings removed or can it be done with more surgical openings in the ceiling?
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Bump. Anyone?
If you fill out your profile, or amend your post to let people know where you live, you'll get some answers.
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Northern NJ. I don't see what that has to do with removing celings to spray the rafter bays, but please enlighten me!
Its important to enter your information in your profile, not just the post. Chances are you'll have another question here.
Why is profile information about where you live/build important? Because a house built in New England is built VERY differently from a house built in Florida, which is built VERY differently from a house built in Souther California, which is built VERY differently from a house that is built in Nebraska.
What is different? Where you put the vapor barrier. How much shear resistance is needed in the outer shell. How breathable the walls and roof need to be.
All of these relate to the question you asked. Please add your information that you just posted into your actual profile - it makes it easier for the pros here to help you!
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
Please add your information that you just posted into your actual profile
Done. Thanks for your interest.
You could pump this stuff into ceilings 'surgically' but it probably does not have as high an R value as closed cell foam.
http://www.retrofoam.com/
Interesting. But I think by code it's gotta be closed cell to go against the underside of the roof so it acts as a vapor barrier.
I guess by implication from your answer I'd have to lose the whole ceiling to do it right.
open cell poly foam has been approved in some areas, and some say it is preferred because is allows some moisture escape, although air movement is all but stopped. But depending on the rafter depth, you might not get much insulation value with open cell.However, to do spray foam right with either product, opening the ceiling would be preferred. Cross strapping to create thermal breaks would be beneficial, too, which could be done if you remove the ceiling.---mike...Madison Renovations
Cambridge, Mass.
Thanks. My understanding is that open cell under the roof sheathing would only be ok if there was enough impermeable insulation above the roof sheathing to keep it above the dew point.
I'm thinking that opening all the ceilings for closed cell application is going to cost a lot less than redoing the whole roof to add sheet insulation outside and open cell foam inside.
How old is your current roof, and what is it made of?
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
The underside of the roof looks original (around 1930). 10 or 12" planks. The shingles are about 7 years old. I don't know what kind of underlayment is under the shingles.
I'm guessing the house got a new roof just before you moved in. You'll probably get another 10 years out of it.
Rats! It would be easier to say "Jest tear it off" if it was an older roof!
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
Yeah, about 6 years before I moved in actually. The shingles are in good shape.
Even if it was a good time to rip the shingles up and add sheet insulation, I would still need to replace the decrepit fiberglass in the rafter bays. Would this all cost less than closed cell and new ceilings?
Closed cell is the most expensive, but it's also carries the most advantages. Water resistant, high R, air tight, increases wall strength. You get alot for a buck, but you pay alot of those bucks!
If you tore off the existing roof, you could blow in cellulose into the bays, recover with your existing roof planks, cover that with a few inches of ridgid foam board, strap with 2x, cover with sheeting and synthetic underlayment and reshingle. You would need to redetail the roof line edges as it would add a few inches of height.
EDIT: For what you have, and what you want to do, closed cell foam is probably where you want to go. You can combine 2" of spray foam with cellulose to really up the R value, especially if you give yourself a little extra depth by strapping the ceilings and walls.
Drywall is easy to replace.
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
Edited 1/22/2009 1:31 pm by xxPaulCPxx
The other guys (TOH) like open cell filling the rafter bays. With my 2x6 rafters, I wouldn't have the R-value I wanted. Closed cell was the way to go. I don't know for sure, but at least in New England, I think the energy savings will pay for itself then be paying me in relatively short order, both in the winter and summer. I cool the attic with a ceiling fan and the backyard trees. Even before it was done, the workers didn't complain on the 90 degree days when the fan was running.---mike...Madison Renovations
Cambridge, Mass.
We're buying a house that had that process done.Home inspection today: the inspector had a thermal imager (very cool), and didn't see any voids.Awesome.
I have a cape cod style home and what i did was removed all the fiberglass from the vaulted portion of the ceiling. I used 2" rigid foam as a baffle for roof venting.leaving a 1" piece of foam up against the roof sheathing in each bay.I sealed the bottom of the bay with closed cell spray foam you can buy in a kit (foampower.com).I went up into the attic where i attached a 5ft length of3/8 soft copper tubing to the nozzle of the gun and filled each bay to the top with the foam. it was the best option for the fixed 2x6 space. It has a higher r value per inch. I used the rigid foam because i felt the commercially available baffles would have been crushed by the expanding foam.
I'm going for an unvented roof, so no baffles for me. I don't have any ridge vents to deal with. There is a gable vent I might be able to use for controlled whole house ventilation.
I had an idea that by removing just the angled portions of the ceiling and cutting a manhole-sized strip in the horizontal portion one could access and spray the entire underside of the roof without taking all the drywall down. The attached sketch shows what I'm talking about.