John,

Are you referring to insulating the ceiling of the garage (i.e. cold floors above)?   Will you be dropping the ceiling or are you looking for options with minimal disturbance?

Hello John,

STEP 1.  This is a very common for homes with room(s) obove a garage.  Replacing the window (s) in the bedroom  may not solve your entire problem if the glass package you select does not include a high performance  heat reflectant type glass.   Which ever manufacturer you decide, its best to pay the additional cost and upgrade to thier best performance glass.  If you have already invested in new windows then check your paperwork to see if there is a greater performance glass option you can upgrade with for that type window .   This is a simple process and can greatly reduce your Solar Heat Gain for minimal investment.

STEP 2.  Select a certified insulation professional in your area to provide you with a "critical point air seal".  Properly applied by a certified professional at upper and lower rim joists in this room aproximatly  1' in width by 2" in thickness. Air sealing the upper and lower rim is a minimal investment  and provides  a significant and noticable change in comfort with a quick ROI.  Consider this service for the entire home.

Warm regards

Colorado Home Exterior