Improving Window Performance

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Improving Window Performance
Shades, shutters, films, quilts, and more can give your old windows improved energy performance without breaking your budget.
Installing window films
Installing window films without leaving bubbles can be tricky—it’s usually a job best left to professionals.
New window putty
New window putty helps seal a window pane and minimize air leakage.
Fitting exterior storm windows
Fitting exterior storm windows in preparation for colder weather is often a rite of fall.
Operable awnings - open
Operable awnings can provide summer shade, yet be retracted for winter solar access, wind protection, or to avoid snow accumulation.
Operable awnings - closed
Operable awnings can provide summer shade, yet be retracted for winter solar access, wind protection, or to avoid snow accumulation.
Hinged shutters
These hinged shutters also have adjustable slats to let in some light and view.
Roller shutters
Roller shutters can provide effective shading and some ventilation.
Installing an interior glazing panel
Interior glazing panels are an inexpensive way to boost a home’s energy performance without compromising its architectural integrity.
Quilted window covering
Quilted window coverings and their valances can provide an attractive method to reduce heat loss through windows.
Insulated cellular shades
Insulated cellular shades contain multiple layers that produce a honeycomb-like structure that can add from R-1 to R-4 to a window’s thermal performance.
Improving Window Performance
Installing window films
New window putty
Fitting exterior storm windows
Operable awnings - open
Operable awnings - closed
Hinged shutters
Roller shutters
Installing an interior glazing panel
Quilted window covering
Insulated cellular shades

Boost window performance without the high expense of complete replacement.

Windows play a unique role in our houses. They provide views to the outdoors, introduce natural light, deliver passive solar heat, and provide natural ventilation.

But they are expensive. A top-quality window can cost $50 per square foot or more—$600 for an average-size (3- by 4-foot) window. A state-of-the-art, triple-glazed replacement from Germany can cost more than $1,000. Count up the old windows in your home, and you’ll quickly see that replacement can be expensive, often costing thousands—or tens of thousands—of dollars.

With 130 million houses, mobile homes, and apartments in the United States—and a majority of them with poorly performing windows—it’s unrealistic to think about replacing most of them. This article looks at alternatives to replacing windows while still significantly boosting their energy performance.

There are affordable options for reducing heat loss in the winter and reducing unwanted heat gain in the summer and in warmer climates year-round. Some treatments can do both. And if implemented well, such window treatments or attachments can enhance a home’s appearance.

Applied Window Films

Transparent films can be applied to windows to reduce unwanted solar heat gain and reduce heat loss. These plastic films, which are typically made of polyester, are usually applied directly to the interior glass surface, though some products are for the exterior. They are most commonly installed in southern climates to reduce solar heat gain, though some newer, low-e films are more transparent and help reduce heat loss.

While there are window-film kits for do-it-yourselfers available at home centers, the best installations are done professionally by trained installers. Most films are 2 to 7 mils (0.002 to 0.007 inches) thick and come in 36- to 72-inch-wide rolls.

Applied window films are fairly permanent modifications. They cannot be adjusted like most other window treatments, and they are difficult to remove.

The energy performance of applied films is certified by the National Fenestration Rating Council (NFRC). In fact, this is the only window treatment with NFRC certification. Ratings are provided for U-factor (a measure of the heat loss through windows); solar heat gain coefficient (a measure of how much solar heat enters through the window—which can be desirable or undesirable); and visible transmittance (a measure of how significantly films affect visibility through the windows). Tinted films, for example, will dramatically reduce solar heat gain and visible transmittance, but have little impact on U-factor, while newer low-e films may reduce the U-factor (lower U-factor means less heat loss) with minimal impact on the visible transmittance.

Benefits

  • For cooling-dominated climates, films are useful for reducing solar heat gain
  • Use of low-e films reduces heat loss
  • Some films are designed specifically to reduce glare
  • Blocks 95% to 99.9% of UV light 
  • Enhances privacy (especially films with high reflectance or “mirroring”)
  • Enhances security and safety (some films designed specifically for these benefits)
  • No operation or maintenance required

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Comments (8)

Edgar Zeitler's picture

Quick overnight response from these folks to my email inquiry about vertical blind slats.

Edgar Zeitler's picture

A very interesting product indeed, the videos on their website are informative. Just requested a quote for their vertical blind slats.

Robert Crosby's picture

I didn't see mention of a product called "solarize inflector", which looks interesting. It appears to be a reversible window insert that either passes or rejects radiant heat flow depending on which way it is turned.

Wondering if anyone here has experience with this product. Their youtube videos look impressive.

https://www.youtube.com/watch?v=B4Y...

Michael Welch's picture

Seems like a brand new product that might not even be available yet. The product's web site sure doesn't work.

Edgar Zeitler's picture

While living in Maryland I covered half my windows in each room with aluminum screen frames covered with clear heat shrink. The rest of the windows were covered with 1" styrofoam panels. Both installed inside. Really reduced heating costs even tho my windows were all double glazed with low E treatment. Easy to store between use.

Fred Golden's picture

The 1" styrofoam will reduce heat gain on a sunny day, and yes reduce heat loss at night, or in the mornings/evening when there is no sunlight coming into the window. At the same time, not having daylighting can increase the use of interior lights and that can increase the electric bill.

So some sort of night time only shutters, or styrofoam installed each afternoon, and removed during daylight heating times would improve the heat gain while reducing heat loss.

My sister's home in Phoenix AZ has screens on both the opening and fixed windows. This reduces sunlight hitting the glass, and thus less heat gain to the windows. Air can still circulate to remove any built up heat between the screen and glass. She would benefit from styrofoam covering the windows, yet it would give a "Cave" like feeling too. She would rather have more daylight and higher A/C bill.

The electric shades also look very promising. I know people who have them installed on motorhomes, and there is a wind sensor that brings them in at 15 MPH winds to avoid damage to the awnings.

IndowWindows's picture

Thank you for this informative article! There are so many other options than window replacements and I hate seeing those beautiful old windows go into landfills. Alternatives are more eco-friendly and can be just as efficient as a replacement. Save those historic windows!

samuel chamberlain's picture

One option which is not mentioned is the use of bubble wrap , this of cause is only suitable for out buildings or where the need for improved performance out weighs aesthetics . whilst it can be stuck to glass with water I have found that fixing to the frame is better as this cuts down on air leakage . The bubble wrap can be ripped/cut in case of emergency exit .

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