Energy Efficiency

10 to 12 percent of a home’s heat loss is through its windows.

Up to 35 percent can be the result of uninsulated walls.

Getting Started

Windows are generally not the main culprit causing energy loss in a home. Blower tests can be done to see where air leaks are located in a building.

Easy fixes to reduce drafts in your historic home:

  • ♦  Weather stripping around doors and windows
  • ♦  Sealing cracks around doors and window casings

Effective, but relatively simple, ways to further reduce heat loss:

  • ♦  Insulate attic
  • ♦  Insulate basements or crawl spaces

Spray foam insulation is not good for historic building:

  • ♦  It conceals roofing members (necessary to assess building)
  • ♦  It isn’t reversible
  • ♦  Using a new product on historic material can be problematic
  • ♦  Historic tax credits do not allow spray foam insulation
  • ♦  Acceptable in new construction and additions

Old cellulose spray-in insulation can be problematic if there is no vapor barrier:

  • ♦  Dew point can be reached within wall cavity and damp insulation can fall into cavity and potentially rot

General Tips

Make sure all insulating measures are reversible.

  • ♦  Over time, what was once the “best” solution can cause problems in the future.

Each home is unique. Details, features, materials, and alterations in each building aid or hinder its ability to be energy efficient.

  • ♦  There is a balance in each building that if upset will cause problems elsewhere.
    • ◊  Consider the larger picture—see how each system affects the others.
  • ♦  Older buildings should not be completely airtight. Building are meant to have some airflow and to breathe.
    • ◊  Lack of airflow can result in moisture/rot and low air quality.
      • −  Mold can become an issue.
    • ◊  Paint can be affected when moisture comes through walls and begins to “bubble” paint layers.
    • ◊  Modern building requirements can require air exchanges, even new buildings aren’t “air tight”, it is just a predetermined airflow.

“Older and historic buildings are often inherently designed for energy conservation and respond to different regional environments. Overhanging roofs, porches, awnings, and shutters can maximize shade and provide insulation. Thick walls provide thermal mass and buffering. Large, operable windows provide natural light and promote air circulation. All in all, older buildings offer these “built-in” advantages.”

    • ♦  Landscaping and plantings can affect a building’s energy conservation as well.


“Saving Windows, Saving Money: Evaluating the Energy Performance of Window Replacement and Retrofit”—Study by Preservation Green Lab

Preservation Brief 3—Improving Energy Efficiency in Historic Buildings by Jo Ellen Hensley and Antonio Aguilar

Building Information Center: Insulation—National Trust for Historic Preservation

Weatherization Guide for Older & Historic Buildings—National Trust for Historic Preservation

Energy Efficiency Basics—Common Sense Preservation

Energy Advice for Owners of Historic and Older Homes—National Trust for Historic Preservation

The Fifth Fuel—Energy Audits

1 “Weatherization Guide for Older & Historic Buildings.” Sustainable Communities. National Trust for Historic Preservation, 2015. Web.