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Advice on plan for attic insulation

JamesNJ's Avatar

Join Date: Aug 2009
Posts: 104

10-22-09, 10:40 AM   #1  
Advice on plan for attic insulation

Looking for some feedback on upgrading my attic insulation.

I have a standard 60s bi-level, so the whole attic is pretty much a clear 28 x 40 space. Joists are 2x7, and existing insulation is about 4. The old insulation is dirty, nasty, packed-down, probably the original stuff when the house was built. I think I only have gable vents; no real soffit venting is visible. My exterior wall insulation is not so good (about 2 I believe) and Im replacing it as I renovate. But right now I have the chance to upgrade the attic.

Im not against throwing the old stuff out its dirty and packed down, and Ill have to pull it up anyway to find air leaks to plug up. Big question is what is best. I want to stick with fiberglass bats mainly because Im constantly trying to improve things, and what to have some kind of reasonable access to this area for running wires, new fixtures, etc.

Heres what Im thinking:
- remove the nasty old 4 insulation
- Foam or caulk any visible air leak, fixture, etc.
- insulate in between the joists with approx 7 craft paper backed fiberglass stapled to the top of the joist
- Run a 1x6 down the center of the attic for me to walk on when needed.
- Lay 12 fiber bats perpendicular to the joists

There is a chimney that I plan on stuffing with fiber fill and walling over with some scrap cement board and fire block caulk I have left over. I also have a whole house fan that just vents into the attic that I may try to caulk and wrap in insulation. I probably have massive air leaking around the attic hatch that Ill try to cover up, and some bathroom vents venting into the attic that Ill pipe over to the soffit. Ill have some challenge around the hatch as I have some makeshift flooring there for extra storage; perhaps Ill build a simple raised floor or shelving unit to accommodate that.

Thats the general plan any thoughts or suggestions?

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Bud9051's Avatar

Join Date: Oct 2008
Posts: 9,771

10-22-09, 05:24 PM   #2  
Hi NJ,
A couple of comments for you. No kraft on the insulation between the joists. The kraft would need to go next to the sheetrock, but not possible to seal in place not so just omit. If a vapor barrier were needed, a coat of oil base paint would do the job.

Make sure you maintain a space for air flow from the soffit area and check the amount of venting required in the soffit and gables.

With a whole house fan you need a LOT of venting so it doesn't just force hot air back into the house.

Check any recessed lights to be sure they are air sealed and IC (insulation contact) rated.

Venting the bath and kitchen fans to the gables is better than the soffits as some of the moist air can be drawn back into the attic.

Good luck

JamesNJ's Avatar

Join Date: Aug 2009
Posts: 104

10-22-09, 08:54 PM   #3  
Bud, thanks!
I thought the vapor barrier would help, but Ill just omit it actually it will be less trouble. I dont know if the original insulation is stapled from the ceiling side if it is, would it be better to overlay the old 4 with new 3 bat followed by my 12 perpendicular to the joist? Or is it just better to remove it all?

So as far as soffit space, is the space made between the rafters and roof down to the soffit enough?

Im not sure about venting of the house fan. In the summer if I open the windows, there seems to be quite a good breeze in when the fan is on. Ill probably disable it during winter.

As for the vents, that would make 3 (2 bath 1 kit). 3 separate vents to the nearest gable would be very visible and probably look bad; and the soffit is closer. Can a soffit vent be installed to reduce back draft? Wouldnt be better anyway, since everything vents directly into the attic right now?
Thanks for the help!

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