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 electric power provider.  

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 as frame parts 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 costly than buying new windows. Retrofit options do not offer the biggest energy efficiency upgrades, but can still help. A simple and effective first step is to use caulking and weatherstripping to seal the air leaks around a window frame. This is one of the most effective and inexpensive things you can do to boost efficiency, 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 and is effective to fill larger 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 can be easily replaced at a low cost.   

With caulking and weatherstripping in place to reduce air leakage, the next stage of retrofit options adds insulation and blocks 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 can save money on installation by preserving the frames, paint, siding, or 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

Includes removing old frames. It is more expensive but offers the greatest 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: