Attic insulation basics

Old 01-12-17, 02:53 PM
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Attic insulation basics

I have a walk up attic in a colonial, roughly 28' x 38', the floor is boarded with insulation under it but the roof is not. To make the area more usable I am considering insulation as a first step and later doing more finishing.

From what I understand there are several considerations, no doubt the choice of material but also in terms of ventilation. There are what I believe are soffit vents along the edges (I see daylight!) and while I cannot see it I assume there is a ridge vent. As I am currently looking at the plywood roof I have several questions:

1. Do I need to run a vent channel from the soffit to the ridge to allow airflow behind the insulation?
2. Does the need for #1 vary by insulation type?
3. What are the pros and cons of sprayed insulation, XPS, fiberglass etc?
4. Assuming I will drywall later would I put a vapor barrier over the insulation (between the drywall and insulation) or does the need depend on the type of insulation?
5. If I'm later going to add a ceiling, closing off the "peak" would/should I insulate up to the ridge or just go as far up as I need then insulate the ceiling, leaving the upper area bare?

Living in NH and only being in the house for a few months I am curious to see how insulation changes the "livability" of the attic, as it stands in winter it is too cold and in summer it is too hot - there is no Heat or AC up there (yet).

Thanks in advance for any help, I got tremendous guidance on basement tips!

Old 01-12-17, 04:09 PM
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So you say you have insulation and a floor?

Are you attempting to make this into a living area by insulating the roof or just adding more insulation to what exits?
Old 01-12-17, 04:34 PM
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There is a lot involved in converting an attic to living space and insulation is only one step.
Atart by talking to your code office to see what permits are required and what current level of codes thay are following. For the insulation requirements here is a link to the 2009 energy codes but some municipalities have moved on to 2012 or 2015 and I'm unfamiliar with those changes.

New Hampshire has 2 climate zones north and south. South, from the link above needs r-38 while north needs r-49. How you achieve your requirement depends upon how thick your rafters are.

Heat and electric and possibly an egress window need to be part of the plan and the permits.

It can be a problem installing just the insulation without the drywall (the air barrier) in a 2 step approach. Covering with plastic doesn't keep the air out resulting in condensation.

That will get you started/

Old 01-14-17, 08:33 PM
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Cape Cod- Gap between roof sheathing and fascia board.

I have a cape cod with no overhangs or soffits ( Never again will I buy a cape cod...arghh!) Anyway there is a cavity above the top plate where stuff from the gutters blows in, seed pods, probably water and there were some things I found in there when I demoed our bathroom.

I Kept getting things blowing in there so I spray foamed it due to a lack of a better idea. That has worked, but I want to do it right and am not sure how to proceed.

I could put roxul insulation up against it, but i am fairly certain water was blowing up in there during a driving rain, which caused part of the top plate to rot out and a floor joist to get damaged. I fixedthis and don't want further issues. I can see where the roof decking has gotten water damaged.Name:  20170114_204632.jpg
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I thought about adding a block such as this and caulking it
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I am unsure how to proceed, any suggestions are appreciated.

Old 01-14-17, 09:01 PM
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Leaks are best addressed from the outside, not the inside.
Old 01-15-17, 05:18 AM
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Could a Mod move the second poster to its own thread?


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