Blow in cellulose insulation?

[mrbigstuff]

when renovating a roof, it's a fairly straightforward process to leave a gap between the rafters and the sheathing, with an air pass from the eaves. not saying I"m going to do the work personally, but I've discussed it with contractors.

[davester]

Blown in cellulose is excellent insulation. Before it goes in, have them attach sticks adjacent to the pipes that will stick up above the insulation and show you where the pipes are. Also take photographs of the pipes before the insulation job.

As mentioned above, it is critical to make sure all attic vents are protected before installation. Also, it is critical to have the contractor seal all plumbing and electrical lines that pass through the attic floor using impermeable material (i.e. aerosol foam, NOT stuffed in insulation). This will make the insulation job much more effective. Make them pull up your old insulation to check all the lines. Lazy contractors won't do these things because they will be hidden after the insulation is installed.

One more thing...since you live in Texas, you probably have the issue of too much heat in the summer, right? Insulation will be only marginally effective against that. Have them install radiant barrier between the rafters above the insulation. That will keep a lot of the heat out. Also, have them check to be sure your attic is adequately vented. Poor venting makes all of that insulation virtually useless during the summer.

[cbelt3]

Ah.. Texas ! Whew... Hmm.... pinkoos... ever think about just putting a nice big 'ol loop of steel pipe up there to act as a hot water reservoir in the summer ? Betcha you won't need to use your hot water heater much ! Of course you'd need to bypass that sucker in the winter...

[pdq]

I did this for my son's house. "Rented" a blower at Lowe's for the day (which I think was actually free if you bought the insulation there). As I recall, it was maybe $500 total (DIY) to add ~8" of insulation depth in a ~24x60 ft attic.

Will second (or third, or fourth) the comments re ventilation; I put formed styrofoam baffles between the rafters of the roof down low toward the eaves to leave a path for air to rise up through the eaves and over the insulation, and out through end or roof vents (assuming you have eave vents- if you don't, put them in). Make sure you have a vapor barrier below the insulation. Good idea to mark the pipes. I also nailed down two 2x12's laid on end across the ceiling rafters, next to the ceiling access panel, to serve as a support for a 4x8 foot plywood sheet that went _over_ the insulation when it was all done, to make for a small attic storage spot. And you may need to build a box out of 1x12's around your access panel to hold back the insulation.

Then blast away, for a few messy, dusty hours. Start at the farthest end from the access panel, working your way back toward said panel. Then, wash off in a long hot shower, and start to enjoy a quieter, warmer home with lower heating bills.

[OWC Jamie]

My house had it blown in in the late sixties , early seventies.
Attic and walls.


Diminishing returns with increased depths, but cellulose is a rather old and time proven product.

It can be topped over whatever you have now as long as what you have now is not defective.

Absolutely air-seal first.

Maybe your state has an energy program in place where your house can be tested for leaks and the leaks identified ?

[pinkoos]

Thanks for the great and informative replies. Looks like its not as straightforward as I initially thought.