Cold floors in rooms above garages are typically caused by air gaps between the sub-flooring above and the fiberglass batt insulation below. Any time insulation does NOT touch the surface you are trying to keep warm or cool...it will NOT work!
See how big the gap between the floor and the insulation is in this Sterling Virginian Home WOW!!!! This might have been the worst we have ever seen...Might be 2-3 feet of a gap!
Our team spray foamed the gaps to ensure no air leakage. These floors are now much more comfortable!