Our Jeans Keep Us Warm
A few years ago we insulated our home's attic which made a huge difference in our heating bills. At the time we didn't insulate above the garage because I thought it was unconditioned space. But, the walls between our kitchen/living room and laundry room are poorly insulated - allowing lots of heat transfer between the house and garage. That makes the garage "indirectly-conditioned space" and in dire need of insulation.
The attic is ventilated making it "unconditioned space", so it makes sense to insulate the ceiling above the garage. Instead of having cellulose insulation blown over the garage ceiling I used denim batt insulation. I chose the DIY-friendly batts as they are materially similar to cellulose, made of 80% recycled material, and avoid the potential sulfate issue of DIY-available cellulose insulation. The trade-off with denim batt insulation is cost - it is expensive compared to other batt insulation options.
I now have R-13 rated insulation covering the attic ceiling. The effective insulation value for the garage ceiling is closer to R-9, but that is a big improvement over R-0.5 of the drywall only. How much difference will the garage ceiling insulation make? Stay tuned, I'll have results in February.
Corrosion of Metals Under Thermal Insulation (Sulfates in Cellulose Insulation)
BlueJeansGoGreen.org - Denim Recycling