Window Replacement

In the case of heating, replacing windows can save 2 to 3 therms ($2 to $3) per year per window, resulting in a payback period of over 100 years. Individual conditions should be considered before a decision is made.   Jalousie windows or super leaky units without storm windows could see better savings.

In the case of cooling, it’s more cost effective to try shading windows with landscaping, solar screens, or window film.

Heat gain / loss from windows come from:

  •  Solar gain is direct sunshine or solar reflected from white concrete driveways, patios, swimming pools or lakes etc.  Solar gain is good in heating season bad in cooling season.  In all but the most northern climates, the use of solar control glass provides significant energy savings. Solar heat gain is a serious problem particularly in buildings with large areas of south or west facing glass. In warmer climates in buildings with more than 25 percent glass, consider using landscaping, exterior sun screening, window tints or reflective coatings to reflect up to 90 percent of the solar heat striking windows. 
  •  Normal conductive gain is heat transferred through the window frame and glass.  Aluminum frames are particularly bad.  Thermal glass is good.
  • Infiltration is air leakage through and around window frames and walls.  Smoke candles can be used to detect this leakage on a windy day.  Caulk may fix the problem.