Assessing Options

Repairing or replacing your windows is an opportunity to improve your home’s energy efficiency and lower your monthly utility bills. A good starting point is an energy audit, in which an expert evaluates the weak spots in your home’s energy use. Audits are often available through your local electricity utility.  It is possible to boost the efficiency of existing windows if they are in good condition. There are two main signs windows are in bad condition:  

  • Water and moisture damage, as well as mold or mildew on or near frames, can negate the benefits of making repairs. The window should be removed, and the surrounding walls repaired first. 
  • Lead-based paint was commonly used on frames before 1978, at which point health concerns led to a ban. For walls, this problem is solved with a fresh coat of paint, but windows create an additional challenge because of the dust created when windows are opened and closed, causing parts of the frame to rub against each other. Solutions include lead-safe window replacement or hazardous paint removal. For more information, consult the U.S. Environmental Protection Agency’s Renovate Right guide.  

Retrofit Existing Windows

Windows without these problems can be repaired or improved, which is less expensive than buying new windows, and boosts a home’s energy efficiency. A simple and effective first step is to use caulking and weatherstripping to seal the air leaks around a window frame. Sealing these leaks is one of the most effective and inexpensive efficiency upgrades, and the savings on monthly utility bills usually exceeds the cost of the upgrades within a year. 

Caulking is a waterproof sealant that goes on wet and dries in place. It is effective to fill cracks, gaps, and joints up to a quarter-inch wide. Follow instructions on the tube to get the best results.  

Weatherstripping is made of foam, felt, plastic, nylon, or another spongy or squishy material. When closed, a shut window should compress its weatherstripping, sealing air leaks in the process. Weatherstripping loses effectiveness after several years but the replacement cost is low.

With caulking and weatherstripping in place to reduce air leakage, the next stage of retrofit options adds insulation, to block heat from passing through windows in particular in hot climates: 

Replacement Options

If your window frames are in good condition, whole windows can be inserted into them. This is called an insert-window replacement and is less expensive because it preserves existing frames, paint, siding, and interior finish. This is a good option when: 

  • the old sill and frame are in good condition 
  • the insert can be installed into the existing construction in a that is structurally sound
  • casing and trim must remain in place 

Full Window Replacement

Opting for entirely new windows, including removing old frames, is more expensive but offers the largest efficiency gains. Full replacement is a good option when: 

  • the old window frame is deteriorated, or cannot accommodate a new window
  • a larger opening is required by choice or by the local building code 
  • energy efficiency is the top priority

If you choose to replace windows: