It is a good time to replace windows and doors since you will be able to take advantage of tax credits and other incentives from your local utility company. I recommend you contact your local building department and utility company for current details and application procedures.
ENERGY STAR offers rebates. In order to be eligible for the ENERGY STAR rebate, you have to purchase windows which are listed and approved with the National Fenestration Rating Council (NFRC). Windows have to meet the minimum requirements of energy efficiency ? not every window is eligible.
Window and door replacement is very effective since most old homes have single-glazed windows with old wood frames (high air leakage = loss of energy). Windows, at minimum, should be dual-glazed, with a U-factor of 0.3 or lower, with low-e, and should be evaluated in comparison to the quality of the existing wall/insulation. It does not make sense to have an excellent window in a bad wall.
Standard product categories widely available are:
Considerations: What type of wood is used? Where is the wood coming from? Maintenance required, such as oil, wax, etc. Wood windows add a nice natural experience in the home, and are easy to recycle in the future.
Considerations: Offgassing of VOCs (volatile organic compounds) from vinyl; recycling is difficult.
Considerations: Aluminum requires a lot of energy in production, but is very durable, zero maintenance, and easy to recycle.
Wood windows with exterior aluminum cladding
Considerations: Again, what type of wood is used? Where is the wood coming from? Reduced maintenance (required only on inside), nice natural experience in the home, easy to recycle.
These are just a few choices and thoughts regarding residential windows and doors. A large factor for most of our clients is the cost, since there is big price difference between the products discussed.