Mar 4, 2015

Final Report: Window Retrofit Technologies

Christopher Plum, Gustav Brandstrom


This white paper explores the potential for energy savings with window retrofit technologies, specifically window panels and surface applied window films, in residential and commercial buildings across Minnesota. The retrofits are permanent products, unlike shrink-wrap plastic that is applied over a window frame for seasonal use. The report includes a literature review, the results of computer simulations of the products in commercial and residential buildings, information from product suppliers and building owners, and recommendations for increasing market adoption of the effective retrofits.

The total annual energy savings potential of window retrofits is 13 trillion, of which 80% is in houses. The commercial building sector uses a comparable amount of total energy per year (about 340 trillion Btu) to the residential sector (395 trillion Btu)1 , but windows represent only about 10% of the energy load in commercial buildings, compared to 30 to 35% in houses. The cost-effectiveness of window retrofits is also better in houses, both because of a large number of product suppliers and the cost savings offered by self-installed products. 3.4 trillion Btu, or about 26% of the total savings potential, can be achieved with retrofits that pay back in 15 years or less, based on energy cost savings.

This report considered five specific window retrofits:

1. Clear window panels;

2. Window panels with a low-e coating;

3. A moderate solar heat gain, low-e applied film;

4. A low solar heat gain, low-e applied film; and

5. A tinted window film.