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Joe (Joe)
Moderator
Username: Joe

Post Number: 831
Registered: 07-2006


Posted on Sunday, October 19, 2014 - 11:24 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Make sure you install a vapor barrier (i.e. sheet of heavy mill plastic) interior to the insulation. Standard fiberglass will work fine. A styrofoam baffle won't hurt. I have similar conditions in my own home and did not use the baffles (I did use fiberglass). It's been 30 years. The interior vapor retarder is important, otherwise you will get condensation on the interior of the roof deck.
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Old_school (Old_school)
Senior Member
Username: Old_school

Post Number: 1081
Registered: 01-2009
Posted on Saturday, October 18, 2014 - 07:34 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

With that situation, about the only way to cut down the heat bills would be to insulate directly to the bottom of the existing roof boards with urethane closed cell insulation and seal that sucker up. That would give you about an R:35 and you can see how it all works out. Not the best of scenarios but you have to deal with what you have to work with. Not too many options besides that.
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Marianweaver (Marianweaver)
New member
Username: Marianweaver

Post Number: 2
Registered: 10-2014
Posted on Friday, October 17, 2014 - 05:03 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Thanks for the responses.

Old School, I've attached a few more photos that hopefully give a better idea of my predicament. Cross-venting would be tough since the other side of the porch runs directly into what the former owners made into a kitchen - from yet another porch.

Kwhord I hear what you're saying about using the house be as it was built, however the former owners have modified this room in a way that the water/waste/steam rad lines all run through this room, so there's really no way to ignore it.


Also I've included a photo of what beam going lengthwise along the porch, and how it would necessitate having to make two separate venting systems as a result. Sorry if I'm not making sense, I'm just trying to make the best out of a crap situation and avoid $700 heating bills again this winter.

This is a better view of rear of house; both rooms were originally porches of some sort.


Here's a view of the "sleeping porch" looking into the kitchen.



And here's how that long beam interrupts the airflow along the rafter channels:

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Old_school (Old_school)
Senior Member
Username: Old_school

Post Number: 1080
Registered: 01-2009
Posted on Thursday, October 16, 2014 - 06:50 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

It has slate on it already!
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Kwhord (Kwhord)
Senior Member
Username: Kwhord

Post Number: 301
Registered: 10-2006


Posted on Thursday, October 16, 2014 - 03:25 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

you have no roof cavity to insulate right now because there is no finish material inside or out. if you had a ceiling on the interior you could vent through the blocking between each rafter. I guess the better question is why? this appears to be a sleeping porch and was designed to be "crossover" space between interior and exterior. the builder had an intent. insulation kills wood houses. put a sweater on and let the house function as it was designed. alternatively you could switch to an exterior insulation and standing seam roof on the shed dormer. this would keep it all original on the interior and move the dew point all the way outside. the pitch looks a little questionable for slate up there anyway.
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Old_school (Old_school)
Senior Member
Username: Old_school

Post Number: 1078
Registered: 01-2009
Posted on Sunday, October 12, 2014 - 08:37 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Could you make the ceiling a slightly less pitch and make a small "attic" that can be vented at both sides?(cross venting)?
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Marianweaver (Marianweaver)
New member
Username: Marianweaver

Post Number: 1
Registered: 10-2014
Posted on Friday, October 10, 2014 - 11:53 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Hi all,

I've been lurking around this board for quite some time, and am looking for reassurances as to my plan for slate roof insulation and ventilation of a poorly converted porch into sunroom.

The ceiling is currently just bare rafters and decking, and now that I've sorted out all the leak issues(badly neglected slate from previous owner)I'd really like to insulate it before winter gets here. Judging from what I've read on this forum, I don't thinking venting is going to be an option, as the windows come up so close to the roof that there's no place for soffit vents, and a half-ridge vent wouldn't be much help without soffit vents. If that weren't enough, there's a 6x6 beam about a third of the way up the ceiling that runs perpendicular to the rafters, and up in between them, so continuous ventilation wouldn't be possible without some significant structural renovations.

That being said, would the best option be to put in baffles for some natural breathing and then insulate with rigid foam? I'm working with 2x6 rafters so at best I'm looking at R18 or so.

Thanks for any advice you can give, and I'll get a photo of the inside when I get home this evening.
Outside roof

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