question about attic insulation

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lincolnmania
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Post by lincolnmania » Wed. Jun. 15, 2022 7:42 pm

my dad insulated the attic in the 70's with vermiculite (yes the zonolite lol) then he put 3/4" plywood on the attic floor all but 4' or so on each side. the plywood is nailed down hardcore dad style with ring shank nails. everything dad did was overkill.
couple yrs ago i moved half the attic contents and put 2" foam over the plywood i think i installed 10 sheets.

since energy prices are at an all time high i would like to insulate it more but the 2" foam is now 50 bucks a sheet! and even in the areas with the vermiculite and the foam it's r26 at best.

the only thing that we can afford this summer is blow in cellulose.
I'm trying to make room in the outbuildings for 50 yrs worth of stuff
will it be ok to blow the insulation in over the plywood floor? would be nice to have that r49 like the garage

 
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Sunny Boy
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Post by Sunny Boy » Wed. Jun. 15, 2022 7:55 pm

My first house - a 1500 sqf. American Four square - had blown-in insulation in between the attic floor joists, which being a 1922 house those joists were only 2 x 4.

We wanted to put down plywood flooring and use the attic for storage, so I opted for adding R-19 foil-faced fiberglass in the 2 x 6 roof beams. And then added a 1 inch thick foam insulation board to the pull-down stairs board in the upstairs hallway. That along cut my yearly fuel oil from about 1200 gallons a year to about 900.

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grumpy
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Post by grumpy » Wed. Jun. 15, 2022 9:20 pm

I have cellulose , just FYI don't plan to up there without some heavy duty mask, or you will not breath....

 
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Rob R.
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Post by Rob R. » Wed. Jun. 15, 2022 10:00 pm

lincolnmania wrote:
Wed. Jun. 15, 2022 7:42 pm
my dad insulated the attic in the 70's with vermiculite (yes the zonolite lol) then he put 3/4" plywood on the attic floor all but 4' or so on each side. the plywood is nailed down hardcore dad style with ring shank nails. everything dad did was overkill.
couple yrs ago i moved half the attic contents and put 2" foam over the plywood i think i installed 10 sheets.

since energy prices are at an all time high i would like to insulate it more but the 2" foam is now 50 bucks a sheet! and even in the areas with the vermiculite and the foam it's r26 at best.

the only thing that we can afford this summer is blow in cellulose.
I'm trying to make room in the outbuildings for 50 yrs worth of stuff
will it be ok to blow the insulation in over the plywood floor? would be nice to have that r49 like the garage
I was in a similar situation and my contractor recommended pulling up the plywood. His reasoning was there was an air gap under the plywood, and I would not get the same air sealing benefit with the plywood. I cleaned out the attic, removed the plywood, and had another foot of cellulose blown in. It has made a huge difference, well worth the effort. The best part is I recovered most of the cost by selling the plywood.

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