An essential part of a sustainable renovation or retrofit is installing quality, energy-efficient windows.  It is no secret that windows are responsible for many leaks in a building envelope and often show up as a deficiency in home energy audits.  There are a few major attributes that an energy-efficient window will have in order to eliminate drafts and help maintain indoor temperatures.

The most recent innovation in efficient window technology is a triple glazed, vinyl or fiberglass frame, with low e- coated panes and filled with argon.  Triple-glazed means the window will have three panes of glass separated with space in between them, one pane will be inside the building, one outside and one in between.  The spaces between the window panes are usually around 1/8” thick and will be filled and sealed with argon.  The argon gas is particularly effective in insulating and will slow down the convection of heat in the air from the first pane (exterior) to the second pane and even more from the middle pane to the interior surface of the window.  The low-e coating will prevent harmful UV rays from penetrating interior space.  The UV rays are responsible for glare and heat gain inside a home.  

Some of the best energy efficient windows on the market today include several windows from Serious Windows fiberglass and vinyl collections.  The windows from the fiberglass collection exceed the Energy Star standards up to four times.  These windows can lower energy bills and even decrease the size of the necessary HVAC unit.  It also will contribute to LEED credits.

Passive house standards use this type of window to combine with their superinsulated walls.  A Passive House window with a U-value of .8 W/(m 2K) or less guarantees high thermal comfort.  
Windows may be the most expensive component to your renovation but choosing the right ones can really pay off.  Don’t be afraid to make the investment and take advantage of the new
Home Energy Retrofit Act.