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Old 01-28-2014, 10:25 PM   #1
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Unconditioned Attic Insulation Question


I have an uninsulated attic that currently only has Balsam-Wool Blanket insulation (1" silver foil encased blanket with balsam wool material on inside / non-permeable). I have installed the plastic vents to allow air from the vented soffit to enter the attic freely after I add blow-in fiberglass insulation to the proper depth to reach R60 status. My question is: " Can I blow in the new insulation on top of the existing balsam-wool blanket without producing a condensation problem with regards to the "first condensing surface and proper breathing??"

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Old 01-28-2014, 11:20 PM   #2
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Where is the home?

What side is the foil or which side is it facing?

Didn't hear anything about air sealing. I hope you included that as part of your retrofit.

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Old 01-28-2014, 11:44 PM   #3
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Unconditioned Attic Insulation Question


Adding your location to your profile is always a big help with questions like this.
Just go to quick links to edit.
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Old 01-29-2014, 09:34 AM   #4
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Where is the home?

What side is the foil or which side is it facing?

Didn't hear anything about air sealing. I hope you included that as part of your retrofit.
The home is in Charleston, West Virginia. The insulation is a blanket and has foil on all sides ------ the balsam wool is on the inside and it is encased in the non-permeable foil covering which is all 1" thick. As for air sealing, I installed the vents from the overhang into the attic and plan on using unfaced insulation to block the space on top of the walls (under the venting) before blowing in the new insulation.
Any and all suggestions are appreciated. Never have done this and I want to do it right and not create a second condensing surface to allow condensation and mold.
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Old 01-29-2014, 09:37 AM   #5
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Originally Posted by joecaption View Post
Adding your location to your profile is always a big help with questions like this.
Just go to quick links to edit.
The home is in Charleston, West Virginia. The insulation is a blanket and has foil on all sides ------ the balsam wool is on the inside and it is encased in the non-permeable foil covering which is all 1" thick. As for air sealing, I installed the vents from the overhang into the attic and plan on using unfaced insulation to block the space on top of the walls (under the venting) before blowing in the new insulation.
Any and all suggestions are appreciated. Never have done this and I want to do it right and not create a second condensing surface to allow condensation and mold.
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Old 01-29-2014, 09:38 AM   #6
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Unconditioned Attic Insulation Question


Quote:
Originally Posted by joecaption View Post
Adding your location to your profile is always a big help with questions like this.
Just go to quick links to edit.
The home is in Charleston, West Virginia. The insulation is a blanket and has foil on all sides ------ the balsam wool is on the inside and it is encased in the non-permeable foil covering which is all 1" thick. As for air sealing, I installed the vents from the overhang into the attic and plan on using unfaced insulation to block the space on top of the walls (under the venting) before blowing in the new insulation.
Any and all suggestions are appreciated. Never have done this and I want to do it right and not create a second condensing surface to allow condensation and mold.
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Old 01-29-2014, 02:52 PM   #7
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Unconditioned Attic Insulation Question


Dave,

You need to do some more searching on Air Sealing.

In terms of what you have there, as long as the floor is well air sealed, I don't that much of a problem with it if you didn't have condensation issues before as long as you are planning on covering it with a good R-50 insulation (fyi...cellulose is much better than fiberglass for the loose fill).

With all that being said, I would just remove it, air seal the floor, and then blow in new.
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Old 01-30-2014, 09:49 AM   #8
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I have never had condensation issues before --- I don't want to create them either! When you say "air seal the floor" do you mean using a sealing foam at the base of the floor joists where it contacts the ceiling below? I plan on using unfaced batt pieces to seal on top of the walls below my vents leading to the vented soffit area of the over hang.
Also, what is the difference between cellulose and fiberglass ---- basically why is cellulose better?
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Old 01-30-2014, 11:44 AM   #9
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Yes on the Air Sealing. You don't need to use foam though if you clear everything out (recommended here) as you can caulk the top plates for that matter.

Cellulose has a much higher density and doesn't suffer convection losses that fiberglass does.

http://www.advanced-fiber.com/EDU%20...Fiberglass.pdf
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Old 01-30-2014, 11:58 PM   #10
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Air sealing; http://www.google.com/url?sa=t&sourc...wWATQw&cad=rja

Air sealing will also help stop the "stack effect" robbing you of R-value and feeding the ridge exhaust with crawlspace air; http://www.wag-aic.org/1999/WAG_99_baker.pdf

You are in Zone; http://energycode.pnl.gov/EnergyCode...est%20Virginia Remove the old R-5-7 foil-faced and discard, you don't want/need that impermeable vapor barrier in the attic in either Zone 4 or 5; http://publicecodes.cyberregs.com/ic...2_8_sec006.htm
The old faced FG will stop/slow new cellulose from drying to the interior if any moisture from diffusion/roof leaks, or delay showing on the ceiling interior showing a leak. It could only dry one way- to attic.

WoW, the 20 year old test you sited does not pertain anymore, they stopped producing the "cubed" loose-fill FG soon after; https://docs.google.com/viewer?a=v&q...mAAqxY_9UrVORg

No caulk at the joists to drywall, caulk (or sealant) the joints of drywall to wood plate of the walls, then canned foam over all for a complete air seal/insulation- last example here; http://www.buildingscience.com/docum...sealing-guide/

Go in basement/crawl and air seal (canned foam/sealant) in all the holes through floor sheeting/plates, FB the rims (with canned foam) after caulking the joints at plate/sheeting to rim joist.

Use the foam/plastic vents (IMO, foam) as baffles at the soffits, add foamboard- stacked flat 12" wide-stair stepping to get your wall , if not ceiling, R-value per code (R-38) over the exterior wall perimeter. This way, no fibrous (cellulose, FG, etc.) insulation will be touching the baffle- in contact with colder roof sheeting to lose R-value there per conduction. With FB there, no worries.

Gary
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Old 01-31-2014, 09:12 AM   #11
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Originally Posted by Gary in WA View Post

WoW, the 20 year old test you sited does not pertain anymore, they stopped producing the "cubed" loose-fill FG soon after; https://docs.google.com/viewer?a=v&q...mAAqxY_9UrVORg

Gary
Good read.

I still much prefer cellulose based on density over loose fill FG. I see homes that have 13" of loose fill FG that don't show well on the IR camera.
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Old 01-31-2014, 08:42 PM   #12
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As you know, I'm not a big fan of FG. This is interesting- Table fig. 5; look at the various temperature differences in ceiling temp/attic temp using a "light "weight FG fill as they call it- aval. in US at 0.59#/ft3-- very thick .6m (24") FG insulation takes a bigger loss at the coldest temps than 16" (0.4m) does due to the convective loops; http://web.byv.kth.se/bphys/reykjavik/pdf/art_085.pdf Test done in 2005.... makes one think, lol. Oh, wait, Dave you are blowing FG in?

Gary

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