If the outside walls of your garage are insulated, you may be eligible for the energy efficiency federal tax credit for updating garage doors. Garage doors with a U-factor of 0.30 or less qualify for the tax credit. ENERGY STAR does not label garage doors; therefore, you will need the help of your retailer to determine if specific garage doors qualify.

If you are considering insulating the outside walls of your garage, all insulation qualifies for the federal tax credit, regardless of its R-value. You can refer to ENERGY STAR's R-value recommendations when deciding what type of insulation to add. However, depending on how you use your garage, it may not be advisable to insulate. If you keep a car, paints, chemicals or a lawn mower in the garage, the fumes from these items could leak into your house if you insulate your garage.

If the improvements were completed by Dec. 31, 2010, you could qualify for the 2010 federal tax credit. The credit is equal to 30 percent of the cost, not including installation or labor costs, up to $1,500. If the work is completed in January 2011 or later, you could qualify for the 2011 federal tax credit. The credit is equal to 10 percent of the cost, not including installation or labor costs, up to $500.

Additionally, in Boulder County, you may be eligible for insulation rebates of up to $600 through Source Gas'Excess is out Program if your garage could be considered a residential dwelling. All R-values appear to qualify for rebates, although an R-value of 19 is suggested.