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Four Affordable Ways to Improve the Energy Efficiency of Old Windows

Before you replace old windows, consider exterior shades, storms, and window films

Posted on Jun 21 2011 by Peter Yost

There are many reasons to replace windows, but energy efficiency is not the best reason. Replacing the windows in an older house is one of the most expensive energy upgrades you can make. To improve performance of existing windows, consider storm windows, window films, and exterior roller shades before buying replacement windows.

But which option is the best bang for the buck?

1. Replacement windows -- the most expensive option
You have three options when replacing windows: full window replacement, insert windows (the old sashes come out and a whole new window inserts into your old window frame), and sash replacement (primarily for double-hung windows, this option requires jamb liners into which new sashes are installed). A typical full window replacement (a window 30 inches wide and 60 inches tall) will run about $400 to $600**; insert replacements cost about $300 to $400, and sash replacement kits cost around $250 to $300.

For the time being, tax credits are likely to be available for some window replacements (those with glazing that meets IRS requirements) and a few other window attachment options.

The best place to go to get unbiased information on window replacement options is the Efficient Windows Collaborative.

Remember that you might not need to replace your windows unless they are actually falling apart, if they are unsafe, or if they no longer operate. If your windows are sound and function well, consider other window attachment options.

2. Low-eLow-emissivity coating. Very thin metallic coating on glass or plastic window glazing that permits most of the sun’s short-wave (light) radiation to enter, while blocking up to 90% of the long-wave (heat) radiation. Low-e coatings boost a window’s R-value and reduce its U-factor. storm windows deliver a lot of performance
Newer, airtight storm windows with low-e coatings can rival the performance of just about any window replacement. Interior units are easy to install, although exterior units do a much better job of protecting your existing windows. And now you can buy low-e storms with high solar heat gainIncrease in the amount of heat in a space, including heat transferred from outside (in the form of solar radiation) and heat generated within by people, lights, mechanical systems, and other sources. See heat loss. for colder climates and low solar heat gain for warmer ones. Double- and triple-tracked storms come with operable screen panels so you can easily operate your windows for natural cooling.

For that same size window (30" by 60"), you can get a low-e storm window, installed, for about $60 for interior plastic single fixed panel (not low-e) to $160 for exterior low-e triple-tracked storm windows.

3. Window films can be temporary or permanent
There are two primary types of window films: more permanent, surface-applied films and the stretch-plastic that you install temporarily to interior window trim. Surface-applied films are now rated by the National Fenestration Rating Council and have a wide range of performance properties: U-factorMeasure of the heat conducted through a given product or material—the number of British thermal units (Btus) of heat that move through a square foot of the material in one hour for every 1 degree Fahrenheit difference in temperature across the material (Btu/ft2°F hr). U-factor is the inverse of R-value. , solar heat gain coefficient(SHGC) The fraction of solar gain admitted through a window, expressed as a number between 0 and 1., and visual transmittance. Standard solar control window films run about $80 installed while spectrally selective films are about $125 per typical window.

The stretch-plastic seasonal film kits you tack onto window trim can be installed relatively airtight for better thermal comfort and reduced heating in cold climates and typically run about $15 at any local building supply or hardware store.

4. Exterior roller shades keep the sun out
If keeping the heat out is your main concern, the most effective window treatment options are exterior; you keep the sun out before it gets in. While retractable awnings and even fixed awnings tend to be a bit pricey, economical exterior roller shades are available for as little as $25 per window.

New information resource on window attachments
While the best place for clear, unbiased information and guidance on replacing windows is the Efficient Windows Collaborative, there is a new resource dedicated to information and guidance on window attachments. The site includes information on products to purchase as well as a Q&A forum where you can post any question, including questions (and then get answers) for your particular situation.

Special note: What about lead-based paint?
While most window attachments can be installed without any sort of lead-based paint disturbance or legally-required management, don’t let the issue of loose and peeling lead-based paint slide as you work on any aspect of your home(s), but particularly windows. For more information on managing the lead-based paint hazard, see EPA resources.

**All cost estimates presented here are ballpark numbers obtained from discussions with remodelers and manufacturers or actual purchase.

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  1. BuildingGreen

Jun 23, 2011 12:07 PM ET

Another Option - Window World
by Kevin Dickson, MSME

I've mentioned these guys before, but believe me I'm not a shill for them.

I don't like storm windows compared to window replacement for many reasons:

`Window World operates in most of the US, and they standardized their price at $189 per window including installation, with a five window minimum. Just my opinion, but this is better value than the storm window options you cite in the article. No low e at that price, and many folks may object to vinyl as a material for any product

Let's hope Window World will transition to fiberglass pultrusions soon, and not have to bait-and-switch just to get Low e glass.

Jun 29, 2011 6:41 PM ET

Reducing window heat loss option
by David Bearg, PE, CIH

Additional options for reducing window heat loss include custom movable interior insulated shutters (see examples at, store bought interior insulated shades (Symphony and Window Quilt) and clear interior storm windows.

Jun 30, 2011 12:47 PM ET

Window retrofits
by Peter Gutmann

Check these out. Acrylic window inserts that improve R-value and air sealing and reduce noise.
I've got a couple of them in my house already, and they're amazing!

Jul 1, 2011 8:02 AM ET

window refrofit options discussed above
by Peter Yost

Thanks for the tip on the insulated shutters; we will be taking a closer look at these on

Window insert replacements can certainly be competitive with various window attachments, such as storm windows, but there are a lot of factors affecting the decision. See especially the Overview document at

Indow windows are one of the options referenced at


Jul 2, 2011 12:29 AM ET

Old windows
by Mike Legge

My observation is that old windows are leaky. Is a touch of sealant and new catches not a significant cheap fix? Lack of tightness comes before insulation gain, as I understand it. Cheers Mike Legge

Jul 2, 2011 9:16 AM ET

Edited Aug 1, 2011 12:28 PM ET.

repairing/upgrading old windows
by Peter Yost

Hi Mike -

This was a tough one to decide on when I wrote this blog. Repairing older windows and making them more airtight can be very inexpensive and mean a new window, or sash, or attachment does not have to be made.

But, generally, air tightening an older window by itself does not give enough of a thermal performance benefit; it needs to be coupled with something like a low-e storm window.

For more detailed information on window repair/upgrading, there is a fact sheet on dedicated to the topic:


Jul 4, 2011 2:49 PM ET

where can I purchase triple track low E storms?
by ken fink

I'm in Michigan. I've tried all the links that are suggested in this article. Only the Larson link takes me to a dealer in Michigan but Larson does not make a triple track. Any ideas?

Jul 4, 2011 9:14 PM ET

Respone to Ken Fink
by Martin Holladay

Any storm window dealer that offers triple-track storm windows can order low-e glass. You just have to request it. When I asked the question from a local dealer, they said, "Sure, we can do it. Not many people ask for it, but it's available."

Jul 5, 2011 9:30 AM ET

availability of low-e storms
by Peter Yost

Hi Ken -

You tried all of the listings here?

I am forwarding your email to a member of our Advisory Committee for who specializes in storm windows and will post his response.

Thanks - Peter

Jul 6, 2011 10:21 AM ET

where to find low-e storms
by Thomas Culp

Ken, I am a consultant working with a number of low-e storm window manufacturers. Why do you say you want a triple-track storm? New design double-tracks offer the same functionality, more streamlined appearance, and less air leakage. As for getting windows, you can ask any manufacturer to get low-e glass, but they may gouge you on price for the special order. Better to go to established low-e storm window suppliers. Quanta Technologies ( is in PA, but ships. Larson sells through dealers in Michigan, and through Menards. Here in Wisconsin, they have low-e storms in stock in Menards, but you may need to order for your specific sizes (custom order is common in storm windows, and turn-around is usually quick).

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