Good day folks, we are going to insulate our attic here in hot southern California. Does anyone have any experience with this, and what type would be best for hot summer climates and mild winters? We are going to have it professionally done.

My experiences with attic insulation is only with fiberglass batting. 
When I worked for a builder, and it got too hot to put on shingles or bail hay, he’d send us into attics to add insulation 

Up north, we used blown in cellulose. If you use the A/C, and we did even up there, it helped keep the conditioned air from going into the attic. Down here, we used R12 Batts. Your pro might have a better plan for your climate.

Edited February 11, 20233 yr by Gene Howe

Around here the recommended insulation is foam. A bit more expensive but works  great.

Edited February 11, 20233 yr by Al B

My choice would be blown in insulation. I've had fiberglass batts, blown in fiberglass, and blown in cellulose. If you check the R values, under Federal Law they have to be correct. By "correct", they have to be the long term expectation. So, for instance, cellulose will compress over time....quite a bit in some cases. The R value stated by the manufacture will be for X" deep at time of installation adjusted for the compression that will occur. Blown in fiberglass (I'm told) will not compress nearly as much over time. For colder climates I like the cellulose, and that's what I had put in my current shop...but I paid to have it done (the other times I did it myself, never again). The other times I did it myself and it's a job for younger men......and other people as far as I'm concerned. The thing about blown in insulation in the attic is that it will cover all the areas, over the rafters or bottom chords, around the web runners (or whatever the vertical parts are called), etc. Batts pretty much just cover the space between the trusses/rafters, which will allow heat migration through that 1 1/2" wide space the rafter/chord occupies.

I have blown in the cellulose insulation in two different homes.  As stated, it will compress over time.  It is best that you have someone in the attic and someone on the ground.  Before you start, staple painted gauge markers to the trusses so that you can gauge  how much you are blowing in.  Without the gauge markers you will have highs and lows depths.  It is a messy job.  I was lucky both times that my attic access was from the attic and not from within a closet.  Both times the blower unit's remote switch did not work.  My wife was on the ground dumping in the insulation into the hopper in small amounts so that the hose would not clog.  Fun, Fun, NOT.  Danl

Rock wool is a denser product and doesn't condense as much over time as the fiberglass and the blown in makes such a mess I wouldn't .

Thanks for the information gents, appreciate greatly!

John, you're handy enough where you can do it yourself and save a lot of $.

 

I'll be doing the ceilings in our garages with Attic Cat blown in.  Around here, about 600 sf, 12" thick will cost about $500 with military discount at the blue box. Blower is free with 10 bags. 

 

Owens Corning has a pretty good video showing how to do it...