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Old 01-06-2010, 10:04 AM   #1
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Attic Insulation


Ok so I did some searching and didn't find an answer that matched my situation exact enough. I am in N.E. Pa and have a ranch built in the early 1960's. Currently I have a problem with condesation in the attic in part due to a lack of proper insulation and in part inadequate ventilation. My question is about insulation, as I will fix the ventilation when the new roof is put on. There is currently 1-3 inches of material lying between the rafters that resembles a cellulose but could actually be the wool that others have posted about, I would have to go back up to confirm. What are my options to best insulate my attic? Do I remove the cellulose and roll out fiberglass? Can I roll over what is there? Should I just add to what is there?

Part two of the question is how far from the soffit should I keep back the insulation to promote proper ventilation? What is there now is at least a foot back from where the outside wall meets the rafters. This has over time discolored the interior of the ceiling leaving a gray scalloped look to the edge of the ceiling. I would like to prevent that from happening again as I have painted all my ceilings but I would also like to keep the attic vented properly.

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Old 01-06-2010, 10:33 AM   #2
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Attic Insulation


If there is nothing wrong with the cellulose you can just leave it. You could add more cellulose instead of batts or go with batts. Cellulose is a better insulation. It handles moisture better and if memory serves, stops air flow better.

How far back from the soffits? Obviously you need to keep them open. If you put some thing there to keep the batts from encroaching into the soffits you can get pretty close. If you search I think you will see some different ideas.

I would search this site using terms like "soffit flow insulation attic". I believe this topic has been covered and remember seeing some pretty good and detailed discussions.

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Old 01-06-2010, 08:33 PM   #3
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Attic Insulation


Well, you are really looking at the visible symptoms of a 'leaky' house; don't worry, we all have them to a greater or lesser extent - that's they way they were built back then. The problem comes down to the fact that you are letting warm moist air into the attic space where it is condensing on the colder surfaces up there. Could eventually lead to mould...

This air used to get blown out by the natural ventilation of the roof - but nowadays we try to save on energy costs - by insulating for example. Trouble is that insulation on its own just slows down the process, doesn't stop it and it opens up another problem: vapour diffusion.

Right now you have a loose-fill type of insulation, probably cellulose - but it only comes up to about halfway up the rafters, either because that's all they put up there, or because it has compressed over time. If you are going to add any insulation at all that empty space must be filled completely - with new cellulose preferably. Once that cavity is fillled to the height of the rafters, then you can add batt fibreglass if you want.

Theoretically, you should go through the whole exercise of establishing what sort of vapour retarder you have on the ceiling below and that comes down probably to painted drywall, that's all. Well, that'll have to do unless you want to tear it down. But that combo (drywall+paint) will slow down the transmission of vapour through the ciling and into your attic.

But what you can do is seal up the places where pipes and cable comes throught the ceiling into the attic, like venting pipes etc. And make sure your shower fan (if you have one) is venting outside the house, not into the attic space.
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Old 01-06-2010, 09:17 PM   #4
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Attic Insulation


Quote:
Originally Posted by covelle View Post
Ok so I did some searching and didn't find an answer that matched my situation exact enough. I am in N.E. Pa and have a ranch built in the early 1960's. Currently I have a problem with condesation in the attic in part due to a lack of proper insulation and in part inadequate ventilation. My question is about insulation, as I will fix the ventilation when the new roof is put on. There is currently 1-3 inches of material lying between the rafters that resembles a cellulose but could actually be the wool that others have posted about, I would have to go back up to confirm. What are my options to best insulate my attic? Do I remove the cellulose and roll out fiberglass? Can I roll over what is there? Should I just add to what is there?

Part two of the question is how far from the soffit should I keep back the insulation to promote proper ventilation? What is there now is at least a foot back from where the outside wall meets the rafters. This has over time discolored the interior of the ceiling leaving a gray scalloped look to the edge of the ceiling. I would like to prevent that from happening again as I have painted all my ceilings but I would also like to keep the attic vented properly.
I have a ranch from the 60's. Here's what I did. All the existing insulation was removed. The attic floor between the floor joists (which is the backside of the ceiling below) got vacuumed with my shop vac. I removed the soffit on the exterior of the house, so I could install vent baffles and blocking. The blocking allows insulation to be placed directly over the wall while air flows above through the baffles. This is critical to prevent ice dams.

Then I bought two 602 polyurethane spray foam kits and sprayed 1" of foam on the attic floor between the joists. I also sprayed two inches of foam on the blocking. All protrusions through the attic floor were covered with foam, including the backsides of electrical boxes. Then I blew cellulose insulation into the attic over the top 16" deep, which should settle to about 13".

Keep in mind, I'm in zone 6 which is a considered cold. My roof is a 4/12 pitch, so the attic was otherwise unusable. With all that insulation, I cannot use it for anything other than ventilation space.

I have a continuous ridge vent and eve vents between every rafter.

The foam provides air sealing and about R7. The cellulose provides the bulk of the R value at R48 after settling. The total R value is about 55, insulation alone.

Sounds like you could do something like this for your home.

I would definitely recommend finding a way to air seal first. After I air sealed and before blowing in the cellulose, my house was warmer than when I had fiberglass with kraft paper facing.

Hope this helps.

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Old 01-06-2010, 09:19 PM   #5
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"how far from the soffit should I keep back the insulation to promote proper ventilation? What is there now is at least a foot back from where the outside wall meets the rafters." ----- You need insulation over the wall and to the opposite "over the wall." You need baffles to keep the air flow clear: http://www.bergerbuildingproducts.co...sAccuvent.html Remember to gap them as instructed. Yes, I read you will do the ventilation after, with the new roof but then the cart would be before the horse. Now you can walk on the ceiling joists before they are covered completely. You might also install some lumber for an elevated catwalk at this time for future access.

You may need R-49 for your area, depends on your zip code:http://www.ornl.gov/sci/roofs+walls/...on/ins_16.html

With cellulose, doing it yourself, at 2#, figuring r-3.7 per inch, you need 13-1/4”.http://hes.lbl.gov/hes/makingithappe...omparison.html Of course check the bags and machine settings.


Leave what is there to offset the settling involved.(3-1/2" of rock wool = R-11) I wouldn’t use fiberglass due to it’s convective heat loss.



Figure out you venting requirements before the roofer comes: http://www.fureyco.com/content/image...ng_The_Air.pdf
Be sure to get a baffled ridge vent, if needed: http://www.oikos.com/esb/30/atticvent.html


Be safe, Gary
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Old 01-06-2010, 09:31 PM   #6
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Thanks for the help........ between the answers here and the ones on the other threads I found since posting i think I am figuring this thing out. Will post again with any more Q's
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Old 01-08-2010, 01:10 AM   #7
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Attic Insulation


Don't hurt to use some ice shield for cheap insurance with a new roof also.

Where I'm at ( in northern Il. ) code says you can run your bath fans to the eaves with no termination caps. Don't do it.

Its a joke IMO the moisture gets drawn right back into the roof.

I see alot of baffle and then batt , every other one is a batt to the rafters

around here on new construction , I would think its a thermal short .

Any good reason for it?
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Old 01-08-2010, 07:02 PM   #8
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Possibly because a vapor retarder is required in that Zone 6, so when figuring the State's requirements for attic venting they use 1/300, which would use every other bay to get the required amount of NFVA. Start a good read on page 606: http://books.google.com/books?id=Z8a...20NFVA&f=false

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Old 01-08-2010, 10:45 PM   #9
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Attic Insulation


Good read thanks , 1/300 yeah just wondered If the batt couldn't possibly

contribute to an ice dam .

Always wondered why the odd baffle couldn't be just stapled tight at the top. so open baffle then closed baffle.. open then closed.


I had a ridge vent put in my old place , made a big difference ( dutch colonial, no eaves, just gables).

I have Ridge and eave vents now ( ranch) best ventilated attic yet.

Pretty typical around here to have 60's homes with moisture trouble from lack of venting.

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Last edited by High Gear; 01-09-2010 at 06:00 PM.
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