WPSC

Whole-Building Energy Conservation and Windows

Author: Bob Yapp

In every building, windows are a part of the overall energy footprint (energy footprint is the total of what each component of a structure contributes to energy loss). In the testing at The Pine Mountain Settlement School in July of 2011, it was determined that the windows made up 11% of the energy footprint before the window work and 7% of the foot print after restoration and weatherization.

Information from other window energy studies shows 7% to 12% is the average range of the contribution windows make to the entire energy use footprint for many structures. Structures with a higher than average number of windows would put that number higher.

Some replacement window companies make false claims that their windows will save 35% to 55% on energy costs.

Additionally, in February 2012 the Federal Trade Commission charged five window companies made false claims of 35% to 55% energy savings on heating and air conditioning when consumers install their disposable, replacement windows (Source: FTC, http://www.ftc.gov/opa/2012/02/windows.shtm).

While 7% to 12% is not insignificant, in the scheme of the overall footprint, windows are a small contributor even with un-weatherized windows. The primary purposes of windows are ventilation and light transmission. Beyond that, glass, whether single, dual or triple glazed/paned, is a terrible insulator and constitutes the minor price we pay in energy efficiency to increase our quality of life.

As shown in the Pine Mountain Settlement School window testing, air infiltration through and around windows is the primary concern. In fact, the three fully weather stripped openings tested showed that with sash weatherization and a quality, weatherized storm window, these windows exceeded the 2012 International Energy Code (IEC) for air infiltration. Even a simple to make, low-cost, interior air panel/storm, over un-weather stripped primary sashes, met this IEC standard.

Every structure is different but most old and historic buildings used windows for air flow. The current trend to make windows "fixed" and inoperable, which began in the mid-twentieth century, has contributed significantly to the sick building syndrome. Taking time to understand how windows affect the air flow in a building can save money on air conditioning costs while replacing stale air with fresh.

Bob's original submission:

How Window Treatment Relates to Whole Building Energy Conservation

By Bob Yapp

In any historic or old house/building, windows are a piece of the overall energy footprint (energy footprint is the total of what each component of a structure contributes to energy loss). In our testing at The Pine Mountain Settlement School in July of 2011, it was discovered the windows made up 11% of the energy footprint before the window work and 7% of the foot print after restoration and weatherization.

More and more data from many different window studies shows 7% to 12% is the average range of contribution windows make to the entire energy efficiency foot print for any given structure. There are certainly some structures with a higher percentage of windows that would put that number higher.

Additionally, in February 2012 the Federal Trade Commission came down hard on five different companies making false claims of 35% to 55% energy savings on heating and air conditioning when consumers install a disposable, replacement window (http://www.ftc.gov/opa/2012/02/windows.shtm).

While 7% to 12% is not insignificant, in the scheme of the overall footprint, windows are a small contributor even with un-weatherized windows. The primary purposes of windows are ventilation and light transmission. Beyond that, glass, whether single, dual or triple glazed/paned, is a terrible insulator and constitutes the minor price we pay in energy efficiency to increase our quality of life.

As we've shown in our Pine Mountain Settlement School window testing, air infiltration through and around windows is the primary concern. In fact, the three fully weather stripped openings tested showed that with sash weatherization and a quality, weatherized storm window, these windows exceeded the 2012 International Energy Code (IEC) for air infiltration. Even a simple to make, interior air panel/storm, over un-weather stripped primary sashes, met this IEC standard.

Every structure is different but most old and historic buildings used windows for air flow. The current trend to make windows "fixed" and inoperable, which began in the mid-twentieth century, has contributed significantly to the sick building syndrome. Taking time to understand how windows affect the air flow in any given building can save money on air conditioning costs while replacing stale air with fresh.

OK, some minor editing on this. Check it out to make sure all your points still stand.

I suspect our Adviser, David Clark, will have some suggestions and contributions on this topic. He's visiting me here in Maine next weekend, so I'll be sure he sees this.

Let's push this right on out there.

_________________
John
Standards Co-Founder
Standards Editor

http://www.HistoricHomeWorks.com

Just wondering how much the weatherized window used at Pine Mountain with weatherized storm window surpassed the IEC code for air infiltration? I think Pete Carroll asked a similer question regarding the incremental affects of adding a weatherized stom window over a non weatherized storm window. Is it cost affective to add weather stripping to a wood storm window is my real question?

Windows get a bad rap basically because of the aggressive advertising campaigns permeated by the replacement industry. Adolf Hitler once said "tell a lie often enough and people will believe it". And so it goes with the replacement window myth. As a BPI trained Building Analyst, I know that air sealing, thermal bypass elimination and attic insulation are the better places to spend money for the greatest energy efficiency increases, but it is a tough sell. Mr. Yapp's observations from his Pine Mtn. tests illustrate that the true "energy hogs" are not the windows. As preservationists and restoration professionals we must keep "beating the drum" in order to save as many great old sashes as possible. Armed with knowledge and documented facts, you can many times convince the brainwashed homeowner.

The "tell a lie..." quote is attributed to Goebbels, Hitler's Minister of Propaganda.

_________________
John
Standards Co-Founder
Standards Editor

http://www.HistoricHomeWorks.com

You are certainly correct sir, I should have researched the statement, rather than relying on my diminishing memory.
However, I hope my point remains clear.