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Del_Gue
join:2001-10-03
Lancaster, OH

Del_Gue

Member

Insulation compression

I am planning to add some insulation in my twin single to bring it to R49 or better as my electric bill has doubled in the last couple of years. Sadly it is an area that I neglected for many years and just never accessed. On one side, the previous owner has blown in 6" of cellulose and topped it off with pink fiberglass that looks like R19. That Owens Corning stuff looks pretty compacted in most places as I believe the previous guy has used plywood to access the attic for running wires and other projects and just let them lay.

I know the fiberglass comes compacted and then expands, but will it expand after it has been allowed to age and it also has accumulated a little dirt and roofing shingle debris in places. Will compression affect R value?

jack b
Gone Fishing
MVM
join:2000-09-08
Cape Cod

jack b

MVM

said by Del_Gue:

Will compression affect R value?

Absolutely. Insulation "works" by trapping air within it's structure. Compressing it displaces that trapped air reducing it's R value.

You can fluff it back up and restore it's effectiveness.

alkizmo
join:2007-06-25
Pierrefonds, QC

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said by Del_Gue:

I know the fiberglass comes compacted and then expands, but will it expand after it has been allowed to age and it also has accumulated a little dirt and roofing shingle debris in places. Will compression affect R value?

They are vacuum packed when they are shipped.

Poke a hole in those bags and you'll see air whooshing in, and the plastic bag suddenly fighting for its life!

They probably won't fluff back to their original designed thickness, but it can't hurt to uncompress them. The debris won't do anything, they're too light.
AVonGauss
Premium Member
join:2007-11-01
Boynton Beach, FL

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Isn't dust / dirt, the real enemy of fiberglass insulation?
iknow
Premium Member
join:2012-03-25

iknow

Premium Member

said by AVonGauss:

Isn't dust / dirt, the real enemy of fiberglass insulation?

yes, if it fills up the air gaps, it defeats the insulation properties. high amounts of moisture can do that too.
kherr
Premium Member
join:2000-09-04
Collinsville, IL

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It's been near 20 years since I was in my attic. Originally I had cross layered 6" batts. In one half of the attic, the f/g looks just like it was when installed. In the other half 70% of it is gone .... I mean gone. And what's left is all shredded and mauled ..... How do you file a police report on that ??? I had a squirrel/mice problem for a short while, but how can they make off with that much ....
iknow
Premium Member
join:2012-03-25

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OP, it seems like you need to get away from very expensive electric heat, and switch to natural gas, or at least a heat pump..