The U.S. DOE Studies Historic Home Energy Efficiency

Aileen’s mission was to boost historic home energy efficiency for her Seattle house. She got rid of her oil furnace and electric baseboards. She air sealed and insulated. She even participated in an energy efficiency study by the US Department of Energy. But she wanted to go further and the one element that remained unaddressed in her historic home energy efficiency project was incredibly important: her windows.

interior view of indow window inserts for historic home energy efficiency

Aileen began searching for window efficiency ideas and was impressed when she learned that Indow window inserts could provide as much comfort and energy efficiency as high-end replacement windows. Indow is AERC certified. AERC, the Attachments Energy Rating Council, is an unaffiliated organization that rates window attachment products on energy efficiency by measuring various factors such as Air Leakage (AL) and U-Factor.

Aileen decided to put energy-efficient Indow inserts in 27 of the single-pane windows in her 1916 Seattle home. And it’s made a world of difference.

Related: Farmhouse Window Treatments in Kitchen Remodel of 1917 Home

Historic Home Energy Efficiency Made Easy

A follow up energy efficiency study for the U.S. Department of Energy prepared by the Pacific Northwest National Laboratory found that the Indow window inserts reduced her heating, ventilation and air-conditioning energy use by more than 20%! She would have had to have gotten high-end double or triple-pane windows, at great expense, to achieve that level of savings.

indow window inserts installed in historic home for energy efficiency

That’s important when you consider that energy use in residential homes has increased to 22 percent of total energy use in the United States. Reducing energy loss through windows is one of the most important steps individuals can take to address climate change.


“You can take a 100-year-old historic home and by doing some effective things, you can make it as energy efficient as a new building. The biggest difference I noticed was the sound reduction, I’m on a residential street but you get a whole lot of noise penetration with single-pane windows.”

– Aileen Gagney, Home Owner, Seattle Washington

Read more case studies.

Additional Benefits: Reducing Window Condensation and Window Noise

The extensive air sealing Aileen had done as part of an earlier energy efficiency upgrade had caused condensation on her single-pane windows. When she installed the Indow inserts the condensation disappeared. The inserts prevented the warm, moist interior air from coming into contact with her cold windows.

Not only did it do that and lower her energy use, but it had the unexpected benefit of making her home much quieter.

two windows in historic home with Indow inserts for energy efficiency

Historic Home Energy Efficiency Saved $273 a Month

With all the energy efficiency work taken together Aileen has seen her energy bills drop from more than $300 a month to $27 a month. “I’m trying to reduce our impact on the environment to save the environment.”

She’s not alone in improving her energy efficiency with Indow. Amy, another Indow customer, also decided to install Indow window inserts after completing an energy assessment of her home. You can read about it here.

closeup of Indow window insert used for energy efficiency in historic home

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bedroom with window with Indow inserts installed for soundproofing in San Francisco


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