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Old 12-08-2009, 05:25 PM   #1
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Insulating walkin attic


I have a attic im going to convert to a home theater room. The rafters are exposed so its un finished. When i insulate can i put the insulation right up againist the roofing boards or do i have to leave a gap. Was thinking of just putting up that pick foam sheets right on the rafters . Then just put the drywall right over that instaed of roll insulation just because its probably easier and faster to do hte foam.

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Old 12-08-2009, 06:27 PM   #2
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Insulating walkin attic


I always use rafter vents, even when soffit vents are not present
Soffit vents can be installed after
Keeps the roof deck cooler


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Old 12-08-2009, 09:33 PM   #3
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Yes, you could put Styrofoam right up against the sheathing. I am guessing this will not give you enough R-value for your area though. You never mentioned what size joists you have so I have no idea what to recommend to get your R-value up. Spray foam works great. You could also rip sheets of styrofoam and then rip 2 inch strips down and glue them to the larger rips to make chutes for allowing air to circulate and then add fiberglass underneath that. Having air circulation is not a necessity as long as you have adequate air being exchanged, a vapor barrier, and enough insulation. You may need to screw on extensions to make your joists deeper to allow for enough insulation.
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Old 12-09-2009, 07:11 AM   #4
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Hmmmm....that's quite an ambitious project - I think; are you saying that you now have a true "unfinished" attic space that is cold during the winter', has a vapour barrier somewhere, has insulation on the floor, has vents here and there and that you want to convert that into a liveable space?

Or is that space already warm in winter?

My concern is that if you see "rafters", why don't you see insulation? You're in a cold - if not a very cold - climate zone so something is missing in the picture. You get ice and snow don't you? What you seem to want to do is push the house heating envelope outwards to now contain the attic, whereas before it wasn't an area you heated at all...

Just putting insulation in between the rafters or onto the rafters, and either leaving a gap or not, have major consequences in terms of condensation/moulds/ice dams and a mess of other things that require careful consideration before you just throw up a few pink boards. You may end up with an uncomforatble space that's too cold or too humid to be good for you or your equipment, to say nothing of the damage it might do to your roofing system. You may pay x times the heating costs...

Tell us more about the insulation, vapour barriers, roof type etc before we go out on your limb and advise you what to do. You may be in essence turning a cold roof into a warm one and that could be a major and costly headache if not done right.
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Old 12-09-2009, 07:16 AM   #5
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Insulating walkin attic


It's just a unfinished attic space. The rafters are 2x4's. Real 2x4"s its a 105 year old house. It has no heat at all it's just used for storage right now. Was going to put electric base board heat in. Not sure if there is soffit vents will have to check tonight. If not is that a problem?

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Old 12-09-2009, 07:25 AM   #6
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Insulating walkin attic


Stepping back a bit:

1) Have you determined if the attic floor structure sufficient to support the additional load?

2) Are you planning to removed any structural members running from the floor of the attic to the rafters, or across the attic between the rafters?

3) What sort of access is currently present to the attic?
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Old 12-09-2009, 09:04 AM   #7
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It will hold the weight its pretty full of stuff right now. There's a door right in my bedroom open the door walk right in same level as bedroom .Will not be removing any strutcure. All it needs is insulation and drywall. And some more electric.
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Old 12-09-2009, 09:19 AM   #8
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Here we need R30 min in a ceiling, R38 is much better, R49 great
Due to Cathedral ceiling I will have R38, but on flat ceilings I have R49-57
I can't see you getting anywhere near that in 4"
Rigid in 4" would be R20 total
Spray foam is R7 per inch (?) = R28

Rigid in the cavities = R20, then add another 2" across the rafters would bring you to a total of R30
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Old 12-09-2009, 11:06 AM   #9
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is it a problem if there is no soffit vents.
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Old 12-09-2009, 12:04 PM   #10
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Can you spray it and make it air tight without the venting or does that cause moisture problems?
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Old 12-09-2009, 01:01 PM   #11
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Insulating walkin attic


Where do you find those foam baffle's at? I looked at lowes (our only store in the area) and they dont even cary them here! and how much do they usually cost? thanks!
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Old 12-09-2009, 01:11 PM   #12
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We got ours at a local lumber store and they are quite inexpensive I do not remember how much.
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Old 12-09-2009, 01:25 PM   #13
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Attic ventilation is a comparatively new concept; they didn't think much of attic insulation and venting back in the 1960s or before - but with the energy crisis and people trying to save their bucks (and not send them to Dubai to build yet another architectural extravagance), keeping heat in has become a national pastime. But controlling the heat flow has a lot to do with moisture levels - and the two are intricately connected.

We heat and cool our "living spaces"; attics aren't always part of that living space - but can be. It just depends on what area of your house you call 'living space' because that space is what we normally blanket to control moisture flow and heat loss. Don't have to insulate it - but since hot air rises and carries warm humid air from the house interior to the outside, the attic is where things happen: warm air drops it's moisture, that moisture sometimes freezes, mould can happen if there's too much humidity up there and not enough air flow to get rid of it. A bad scene all around...

Now you can spray-foam the underside of the attic sheathing and keep that area warm and liveable. You'd have to keep it really dry and ventilated for it to be cozy, but it's do-able. Not the best idea, but do-able...
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Old 12-09-2009, 04:17 PM   #14
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I just went and looked i have gable vent up there.
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Old 12-09-2009, 06:44 PM   #15
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...so what's the temperature up there then, tonight?

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