Builders of new homes, multifamily buildings, and commercial buildings have a golden opportunity to lock in lifetime savings while improving the comfort and durability of their buildings by installing new high-performance windows. Windows account for a disproportionately high amount of the heating and cooling load of a building. While they comprise only 7% of the overall envelope for single-family homes, typical windows account for 48% of heating energy loss; and in commercial buildings where they account for a slightly higher average percent of the building envelope, they account for 53% of heating energy loss on average. Poor performing windows cost U.S. building owners $Billions each year in heating and cooling costs.
For owners and managers of existing buildings, secondary glazing can be a realistic retrofit option that can increase thermal comfort while reducing glare, drafts, and noise transmission. Interior or exterior secondary glazing offers a minimally disruptive, less expensive alternative to full window replacement and research has shown that adding secondary glazing can reduce heating and cooling bills by up to 20% while improving occupant comfort. For mid to large size commercial buildings with low-performing (single-pane or clear double-pane) windows, secondary windows can achieve similar performance to full window replacement for 30-50% less cost.
Insulating cellular shades and exterior solar screens are other retrofit options for increasing occupant comfort while decreasing costs.
AERC Ratings & Certification
The Attachments Energy Rating Council (AERC) recognized the potential of secondary windows and prioritized the development of a commercial rating and certification program in order to provide the industry with credible data on the energy performance of these products. The AERC uses rigorous performance metrics in its ratings including U-factor, Solar Heat Gain Coefficient (SHGC), Visual Transmittance (VT), and Air Leakage.
Commercial secondary windows are ideal for
- Small, medium, and large commercial buildings with fixed or operable windows
- Retail, office, hospitality, schools, healthcare, and historic buildings
- Buildings constructed before 1990 without low-e coatings on windows
- All-electric buildings with single-pane, clear windows.
Secondary glazing with a low-emissivity coating was installed on this commercial building to reduce heat losses in winter and solar heat gains in summer for a quieter, more comfortable interior space that reduces occupant turnover.
Installation of interior storm windows, like those shown in this retrofit of a 1960’s era commercial building with single-pane windows in eastern Washington, can reduce heating and cooling bills by up to 20%.