Attic Insulation: Batt vs. Loose Fill
luddite20
| Posted in Energy, Heating & Insulation on
Hi Everyone-
I’m about to install insulation in our Bay area CA home. Our home is old, and has knob and tube wiring, which I will update prior to insulation. My question is this, given that I’ll probably want access to the attic from time to time to update new circuits and potentially add on to our house or add skylights, should I use Batt insulation? Everything I’ve read and everyone I’ve talked to speaks to the potential to poorly install batt insulation, and that loose fill is much more effective. This makes sense, but if I plan on adding circuits or accessing this space a few times a year, wouldn’t batt, properly installed, make more sense?
Thoughts? Declarations? Rants?
Chad
Replies
Proper installation would be the key to either. Fiberglass itself doesn't insulate, it's the air that is trapped in it that does the work. If there are any gaps or compression, the insulation value is compromised. Here in Maine, batts are the choice in new construction. If an older home has uneven or oddly spaced joists, that can make for a lot of extra work and any slight misfit will lower the insulating value. You want the batts to fill the cavity and be able to expand completely. R38 is the minimum here and that means 12", usually double batts installed perpendicular to each other. Adding a third layer starts to add weight which can compress the first layers. When higher R values are wanted, either or both layers can be thicker than the standard 6" or blown is used on top of a double layer of batts.
Loose blown was used around here on top of batts for a short time during the 90's. It quickly fell out of favor. Completely blown loose isn't something I've seen or lived with. Someone else would have to address whether it gives the same values batts do. If I were doing my own place, I'd choose the new, white, no itch, formaldehyde free batts. If they fit your situation they would be easier to remove and replace when needed and still maintain consistent loft and density.
Agreed
Install cellulose, move it out of the way when you need to add stuff in the attic.
Loose fill always provides better coverage to fill odd areas and such ... leaving no voids. Batts simply cannot do that well unless the install is meticulous ... which it will not likely be.
Worst case for loose fill ... get a blower and reverse it and suck out what you need to do work.
I've heard some talk about nob and tube wiring and code issues w/ insulation in contact with it. ... Don't know if there is anything to that. I've done my own old house w/ cellulose and seen others done (doesn't mean it met code, though). A quick call to the BO would answer that question, maybe.