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-   -   Old Roof - Trying to ventilate and insulate (http://www.diychatroom.com/f19/old-roof-trying-ventilate-insulate-154394/)

Ilinizas 08-21-2012 03:56 PM

Old Roof - Trying to ventilate and insulate
 
I just bought my first house. It's about 80 years old, and there is absolutely no insulation in the attic. I'm replacing the rotten old fascia, and want a tight roof so I can insulate the hell out of it... 4500$ in oil is what I've spent since January! I live in PEI, east coast, Canada.

Anyway, my question is about a blockage between all the rafters right at the exterior wall. There seems to be a bunch of wood blocking any airflow from the soffits into the attic space. Here are pictures...

http://imgur.com/a/YmZ54#tfJQB

The close-ups show the inside of the soffit on the bottom, the roof on the top, and the blockage in the middle. What should I do? It's a hip roof, with a second floor apartment, and a bit of crawl space in the attic,... but mostly there is just a foot or so between the apartment ceiling, and shingles.

Last... Is this ok? I'm not replacing the pine soffit... just scraping, painting and venting it. And I'm using 1 x 6 pine boards with exterior acrylic for the fascia, and getting a company to put on the eaves.

A million thanks to anyone that can give me a little guidance.

hand drive 08-21-2012 08:50 PM

if you vent the soffit you need a ridge vent as well. Do you plan to put a ridge vent?

Ilinizas 08-21-2012 10:18 PM

I was planning on putting in a ridge vent. The problem though is that the space between the ceiling and roof is only about 6 inches wide, AND there's wood blocking air flow between all the rafters where they meet the exterior wall.

So how am I suppose to insulate well, and still ventilate that space?

What I'd really like to hear is that I don't have ventilate from the soffit to the ridge... I can just ventilate the open space in the attic above the insulation,in a way that doesn't intake a bunch of rain and snow. What do you think?

GBrackins 08-22-2012 05:06 PM

so if I understand your post and photos currently there are no soffit or ridge vents? Is your overhang the roof rafters with some type of siding (material) attached to the bottom of the rafters to create a soffit without any ventilation in the soffit?

Ilinizas 08-22-2012 07:03 PM

Thanks a lot for your interest.

Exactly, there are soffits, but they are not vented... because there has never been any insulation in the attic. I could vent them, but the slanted part of the roof I'd be venting them for is about 5 inches wide (vertical). It's small, and from the soffit, to accessible attic space is 9 feet... so I can't put in normal ventilation baffles through it. I can fill it with blown cellulose, but I'm told that will lead to problems if the underside of the shingles aren't ventilated.

Not only that, but some of the rafters lead up to the hip roof ridge, rather than open attic space. So they are basically boxes of dead air... that I'd like to insulate.

hand drive 08-22-2012 09:00 PM

Quote:

Originally Posted by Ilinizas (Post 994235)
Thanks a lot for your interest.

Exactly, there are soffits, but they are not vented... because there has never been any insulation in the attic. I could vent them, but the slanted part of the roof I'd be venting them for is about 5 inches wide (vertical). It's small, and from the soffit, to accessible attic space is 9 feet... so I can't put in normal ventilation baffles through it. I can fill it with blown cellulose, but I'm told that will lead to problems if the underside of the shingles aren't ventilated.

Not only that, but some of the rafters lead up to the hip roof ridge, rather than open attic space. So they are basically boxes of dead air... that I'd like to insulate.

That is certainly a problem. The way to get insulation into the 9' rafter bays would be to take down the drywall and use spray foam insulation and then put the drywall back up. Or, take down drywall and add 2x lumber to the underside of the rafters and then insulate with Batts and then put drywall back up.

Ilinizas 08-22-2012 10:10 PM

Thanks for that. I will definitely take a look at that option. It sounds promising.

GBrackins 08-22-2012 10:53 PM

1 Attachment(s)
check out the photo, you could install the blocking between the rafters from the outside, leave at least 1" clearance between the top of the blocking and the bottom of the roof sheathing for air flow.

install soffit vents (you could use the following https://ventmastersstore.com/shop/sm...ents-c-23.html) and install your ridge vent. install more soffit vent area than ridge vent area, should be around 1/150th of the square feet of the attic space

follow the photo for insulating the attic floor between the knee wall and outside wall (make sure not to install above top of blocking) with your cellulose.

install batt insulation from the knee wall towards the ridge vent.

hope this helps, just one way of doing it, but not the only way ....

for those that may want to know, photo is from "JLC Field Guide to Residential Construction, A Manual of Best Practice"

good luck! :thumbsup:

Gary in WA 08-23-2012 12:24 AM

Impossible to vent your full hip roof effectively. You see hip ceilings at the drywall, right? Go with a closed roof as Hand drive said, SPF or XPS against the sheathing. Furr out the rafters to get required R-value for location. Specify non-vented shingles at re-roof or lose 10% shingle life. Fig. 2: http://www.buildingscience.com/docum...rchterm=attic+

Gary


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