best value, best product for attic insulation

[Don Meinke]

Looked at the store yesterday at different insulation products.  No calculator in hand but seemed shake and rake(I call it shake and bake) was double or triple cost of blow in regular stuff.

From there it was hard to see IF roll stuff or blow in would be better.  Also thinking maybe roll type might be better IF repairs or access is required down the road.  Could move the roll type over and moved back.  Just wished they made wider longer rolls.

Has anyone actually analyzed what is cheapest,,,best,,,most efficient? Fliberglass? Cellulose? or that new denim product?

thanks, don

[Nicholas B.]

I agree with @Michael Paris and add that sometimes the best price/value may be a product that happens to be on sale. It also depends on if you're doing the work yourself. I know if I was paying an installer, it would be to spray foam. Fiberglass and cellulose are usually about the same price in my area.

If you have access to the attic, you can move blown in out of the way temporarily. If you don't you're probably hanging batts from below anyway.

Batts don't always work well if you have a complicated structure with angles or varying spacing. They're also difficult to install if the roof is a low pitch - and if there's "shiners" (nails poking through the roof), wear a hard hat because you'll probably give yourself a scalp piercing without one. 

Don't forget that with batts, you'll need to install both inside the ceiling joists and lay a 2nd layer on top. Fiberglass insulation absolutely has to go in tight with no gaps, meaning cuts around electrical boxes, wiring, ducting, etc. That's where blown in shines, as it's much easier to fill in everything.

I'll install batts on any angled ceilings (like cathedral or vaulted) and walls because cellulose compresses so much that it eventually leaves a big gap at the top.  If I'm adding a 2nd layer to a very simple ceiling, I may use batts if they're on sale, but otherwise, I'll blow in cellulose myself.

Vapor barriers/retarders are important, both that they are where you need them and that you don't put a 2nd one where you don't need it. You don't want to use a kraft faced batt as a 2nd layer when there's already a vapor barrier installed.