garage ceiling insulation

get the 24 ni. bats and let it squeeze in two inches on each side.....

Do NOT do this. Insulation works because it traps air in between all the "stuff" that does the insulating, not the insulation medium itself. Compressed insulation is worthless.

Buy 24" batts and use a 2x4 or some other long straight edge to cut 4" of fiberglass out.

What about doing blown, the depot will basically give you the machine if you buy enough bags. All you need is someone below to feed the machine. Might even be cheaper.

I have never heard of 20 inch on center framing especially in a ceiling. You measured center to center or edge to far edge ,,,right?

I vote cellulose blown in. PJ

It's probably actually 19 1/4", which is a moderately rare but acceptable spacing, that works out to 5 joists per 8' panel. (at least, there's a column for that on my joist-load tables.) Squeezing 24" batts into the spaces will work, but not as well as insulation that fits properly. For a garage, I wouldn't bother trimming bats. For a finished attic space, I might.

On the other hand, I wouldn't normally be insulating a garage, anyway.

--Goedjn

Makes sense if it's an attached garage with living space overhead. Like at my house. Floors get REALLY COLD in the winter... socks and slippers are cheaper but don't help the resale value. For my situation, sounds like blown-in is easier (no new drywall for ceiling)?

Dr. M

remember to put a big plastic tarp for air infiltration and vapor barrier. Put it on the "warm" side. if the garrage is heated, then put the barrier down then the insulation... if not.. the other way around...

you can get plastic sheeting at most home improvement places.

I say blow the insulation in too, most places will lend you a blower if you buy enough insulation. I did my garage in Minnesota, it worked well. It's nice to be able to work in a heated garage when it's cold out. I can easily heat it when the outside temp is zero or above, below that, it gets to difficult, but it can be done. I have a 45k gas heater. 20x22 garage.

You say 20" apart. That would mean 24" centers. You buy insulation made for 24" centers. It is cut to allow for the wood.