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Fiberglass vs Cellulose Loose Attic Insulation

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Haselmaier

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Ft. Collins, CO
Situation:
  • 25 yr old house
  • Colorado
  • Desired R-50
  • Currently has loose fiberglass insulation
  • No issues with moisture, animal infestation, etc.
I've gotten two bids to air seal the attic and bring the insulation up to R-50.

Company A will move the existing insulation around in order to get the air sealing done. Then they'll blow in additional fiberglass to get it up to R-50.

Company B completely removes all existing fiberglass insulation, air seals, and blows in all new insulation (cellulose I believe.......I need to confirm).

Their bids are within $100 of each other. :oops:

Does one method seem more effective over the other? Any key advantages or disadvantages of each insulation material that makes one company's bid more attractive than the other?

Thanks.

Jim
 

Snoonyb

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Welcome.
My 1st question would be; How much, in $, will you guarantee my cost savings will be, monthly, annually, that your CO will bond for?

The 2nd question will be; How many yrs. will it take for the cost savings to offset the present cost of the present system.

I'm old school, I'd have the ducts inspected and any air leakage fixed with duct tape and have unfaced batt insulation installed=lower cost, quicker cost recovery.

KISS principal.
 

Jeff Handy

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In my limited experience, blown cellulose is too easy to accidentally compact if you are ever working up there.
Like weak cotton candy.
And blown fiberglass gets airborne and irritating too easily, once again only a problem if you have to work up there afterward.

I am a fan of unfaced batts as Snoonyb said.

You can move them away to fix something, like a bath fan or ceiling fan box or adding a circuit.
Then move them right back.

Also, either type of blown in tends to clog up the soffit vents, unless they do a nice job installing those foam chutes to maintain airflow from the soffit vents.
 

Steve123

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A common opinion is that blown cellulose if preferred to blown fiberglass, in an attic, because the cellulose will have less convection loop losses.
 

tagal4

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I installed batts in my garage attic and had cellulose blown into my house attic, and the fiberglass batts are so much nicer than the cellulose. Cellulose insulation is a huge mess to deal with if you ever have to go up in your attic and do something: it will be all over you and you leave a trail of it after you exit your attic. Another concern I have about cellulose is its weight, especially if it takes on moisture (which it does easily since it is very porous) from humidity in th air in the summertime and the effects on weak ceilings of older houses (like mine). Then there's the health concern of cellulose from the chemicals used to treat it which become a big problem for some people who are sensitive to them, or if the installer mists the insulation while installing it to keep the dust down.

I regret having cellulose insulation installed in my house, regardless of the cost difference between that and other types. Saving a few dollars upfront on insulation by using cellulose I don't think is wise. Unfortunately I learned this after the fact.
 

kok328

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Situation:
  • 25 yr old house
  • Colorado
  • Desired R-50
  • Currently has loose fiberglass insulation
  • No issues with moisture, animal infestation, etc.
I've gotten two bids to air seal the attic and bring the insulation up to R-50.

Company A will move the existing insulation around in order to get the air sealing done. Then they'll blow in additional fiberglass to get it up to R-50.

Company B completely removes all existing fiberglass insulation, air seals, and blows in all new insulation (cellulose I believe.......I need to confirm).

Their bids are within $100 of each other. :oops:

Does one method seem more effective over the other? Any key advantages or disadvantages of each insulation material that makes one company's bid more attractive than the other?

Thanks.

Jim
I'd go with Company B if they will use fiberglass and am thinking they are the higher bid due to removal time and labor. Might ask them if they can use fiberglass for a small up charge. Either way, when blowing in, keep an eye on the soffit vents, these must be kept open.
 

ctviggen

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I think this is a very difficult decision. For one, trying to compare quotes in terms of what you might save over time is basically impossible. Even using estimates of R value, this is tough. There's no good way to ascertain how much difference you'll actually get.

If you know you won't be in the attic much for future repair/running wires, cellulose has benefits. One is increased air sealing. It's simply better at providing a higher amount of air sealing. And I know you're having air sealing done, but you'll still have areas where there will be air infiltration.

Also, wood has an R value of only 1 per inch. You really need to cover your joists to create a thermal break. While you can do that via fiberglass, cellulose does this better and will fill more gaps than will fiberglass. Just think about fiberglass between the joists and fiberglass on top of the joists, perpendicular to the joists. There will be an air channel between the fiberglass on top of the joists, the joists, and the fiberglass between the joists. That air channel won't exist with cellulose.

It's a difficult decision.

In my house, I have not insulated the attic (more than it already is), because I have multiple lights and switches that I want to put in. Once that's done, though, I might opt for cellulose.
 

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