Detached garage insulation
So many variables to meet your requirements; type of siding, type of insulation, any exterior insulating sheathing foam board, vapor barrier, vapor retarder, wet vehicles being parked to add moisture, propane furnace adding how much moisture to room air, etc. R-19 (made for floors) is the lowest density fiberglass cavity insulation (lose R-1 just installing in 5-1/2" space) you can use in a 2x6 wall and is inherent with convective loops, and add the thermal bridging of the studs, 16"o.c. (R-1.25 per inch of thickness = R-7-) equals the whole wall R-value of R-13.7 (28% reduction). A 2x4 whole wall R-value is R-9.8 (11% reduction). So you lose with the price for the extra thick studs, the thermal bridging loss and the insulation loss if using foamboard on the exterior to raise the dew-point of the cavity against condensation. 2x4 is good to 12' high in the States, check w. your local AHJ.
Clothes taking longer to dry?
Clean the dryer screen in HOT water if using fabric softener sheets.
They leave a residue that impedes air-flow, costing you money.
Clean the ducting in the last six months? 17,000 dryer fires annually!