Window Retrofit Technologies

A team from CEE and the University of Minnesota’s Center for Sustainable Building Research studied the savings potential of five different commercially available window retrofits: two types of interior mounted window panels and three kinds of applied window films:

  1. Clear glass or plastic window panels;
  2. Window panels with a low-e coating;
  3. A moderate solar heat gain (0.46), low-e applied film;
  4. A low solar heat gain (0.30), low-e applied film; and
  5. A tinted window film.

Climate specific energy modeling was used to simulate the energy impact of the five retrofits on residential houses and sixteen different types of commercial buildings. The climates of both southern and northern Minnesota were modeled separately.

Contrary to some literature claims, researchers did not find any examples where the simple payback was three years or less. The impact of retrofits in commercial buildings is more variable than in residential houses because of the impact of building use and construction characteristics. For this reason it is not possible to prescribe a simple energy saving solution that works for all commercial buildings. While most building types will save energy savings with at least one of the retrofits, at current energy prices the payback for commercial buildings are often over 20 years.

Full report (PDF):
Window Retrofit Technologies Final Report


*This project supported in part by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program. And with co-funding by CEE in support of its nonprofit mission to advance research, knowledge dissemination, and program design in the field of energy efficiency.