Weatherization & Building Envelope

Insulation Diagram

The building envelope is crucial to ensuring an energy efficient building. Things to consider in the building envelope include: insulation, window fitting, caulking, and sealing. Insulation and window fitting is necessary to control the heat flow in and out of a building. Being able to control heat flow with insulation and proper windows allows for less energy to be used by heating and cooling systems. This in turn allows there to be less carbon dioxide emissions created and lower energy costs for the building.


Insulation should be installed in many places within a building. These include attic space, exterior walls, unconditioned ducts, and foundations of basements and crawl spaces. An opportunity to improve insulation can be when existing buildings are being reroofed or are undergoing repairs. During this process more insulation can be added in order to improve overall building envelope. 

Double Window Pane

Window Replacement

Another opportunity to improve the building envelope of an existing building, although expensive, is to replace existing windows with more energy efficient double pane windows. Or instead of complete window replacement, consider adding another single pane. It is also important to consider adding storm doors to entryways to prevent energy loss at this active area in the building. For new construction there are new Energy Star-rated window technologies that are designed for energy efficiency and the prevention of heat loss. Learn more about Energy Star windows.

Other Ways to Solve Energy Loss

There are many other areas in a building that can be the source of energy loss. Every building should also be checked for air leaks near electrical boxes and outlets, plumbing and ceiling fixtures, attic hatches, and other locations where it is possible for air to pass outside.

If any of these areas show signs of air leaks it is necessary to caulk, seal or weather-strip in order to prevent energy loss. For additional reading see Maine Home Performance Technical Standards and EPA's Do-It-Yourself Guide to Sealing And Insulating with Energy Star (PDF).


  • U.S. DOE Energy Efficiency and Renewable Energy. 2006 May 30. Air Leaks and Sealing. Accessed August 2008.
  • U.S. DOE Energy Efficiency and Renewable Energy. 2008 June 3. Building Envelope. Accessed July 2008.
  • U.S. DOE Energy Efficiency and Renewable Energy. 2006 May 31. Windows. Accessed July 2008.