Should I Use Low-E Glass or Window Film to Block Out the Heat?

Scott Dylan Westerlund
Updated January 3, 2022
woman with pen, paper, and cup of coffee sits next to window in early morning
Westend61/Finland via Getty Images

While low-E (low-emissivity) glass windows are more expensive than window film, they often provide a better return on investment when upgrading windows in your whole house

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What is right for your home: low-E glass or window films? Low-E glass windows increase your home’s value while also fixing drafty windows. However, window film offers a quick, low-cost, less permanent solution for reducing UV rays.

What’s the Difference Between Low-E Glass and Window Film?

Heat-blocking, low-emissivity (low-E) windows and films both work to reduce your heating and cooling bills by blocking out UV rays. They also prevent the general transfer of heat. That means that you're preventing heat loss in the winter and stopping heat entry in the summer. 

When choosing between low-E glass and window film, the difference comes down to how big you want the project to get and the quality of your window frames. 

If you have an older home with drafty windows, installing low-E glass along with repairing the frames is a great option. You won’t get any benefit from applying a film if the window itself is poorly fit and allows heat transfer. If your windows are well-fit, you can opt to apply a blocking film instead. 

Upgrading to low-E glass means hiring a local window repair contractor for a total house upgrade to avoid mismatched windows. Applying film is a DIY project that lets you just cover the windows that need blocking.

Which Is Better: Low-E Glass or Window Film?

Should you pick new windows with low-E coating or heat-blocking film? Take a look at the pros and cons of both.

Low-E Windows

A permanent, built-in solution, low-E windows are "low emissivity" windows that filter out the long wavelengths of heat while allowing the short wavelengths of light to pass through. Windows with low-E coatings deflect UV and infrared light back outside.

Pros:

  • Increase energy efficiency

  • Won't obscure your view

  • Won't obscure sunlight

  • The EPA estimates that low-e windows reduce heat loss by up to 50%

  • Durable

  • "Invisible" benefits that don't alter the look of your window

  • Keeps window cleaning costs and efforts low

  • Repels dirt and sand

  • Repels water particles from sticking to glass surface during rain

  • Reduces condensation

  • Protects floors, walls, and furniture from UV damage

Cons:

  • $300 to $1,000 per window 

  • Expensive installation compared to normal glass

  • It's necessary to upgrade all windows in a home for a uniform look

  • Upgrading just one window won't boost efficiency by much

  • View can be mildly hazy compared to normal glass—most people say it’s unnoticeable

Window Film

A sun-blocking window film or tint can be a good cost-saving option. The average cost of solar reflective films on the market is between $6 and $14 per square foot.

Pros:

  • Inexpensive

  • You can pick and choose which windows to cover

  • Doesn't require window removal and replacement

Cons:

  • Can peel after a few years

  • May darken your view

  • Can make windows look shiny

  • Won't fix the problem if the underlying heat-loss cause is window fit

  • You'll need to fix drafty windows first to get the benefits

  • Applying aftermarket films can void the window manufacturer's warranty

woman on phone next to large, ceiling-height windows
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Which Is More Energy Efficient: Low-E Glass or Window Film?

Wondering which energy-saving window solution is right for your home? Take a look at the key categories to consider when strategizing for lower energy bills.

Best for Older Homes: Low-E Windows

If you have an older home, a window film may not be enough to reduce your energy bills. Your heat loss could come down to insufficient window frames. Before spending money on heat-blocking window films, have a pro assess your windows for energy loss.

Best for Newer Homes: Sun-Blocking Window Film

If you recently built a home without low-E windows, your newer windows are probably still energy efficient. While replacing your newer windows may not be economical, adding window film can boost the energy efficiency that's already there.

Best Whole-House Solution: Low-E Windows

If you're ready to replace the windows in your entire house, this is an opportunity to upgrade to low-E windows. While the project cost will be higher, this is a chance to "seal in" the entire house and lower your lifetime energy costs.

Best Solution for One Room: Sun-Blocking Window Film

Adding low-E windows to just one room or portion of your home because you need a window repair or replacement won't create a "sealing" effect the way that redoing all of your windows will. 

As a result, replacing just one window with low-E glass may not give you a good return on investment. This is where sun-blocking window film allows you to enjoy the benefits of reducing heat transfer in a strategic area of your home without the big financial investment.

Best Budget Option: Sun-Blocking Window Film

With an average expected cost of $730 per energy-efficient window, you can expect to pay $300 to $1,000 per window during your low-E upgrade. Compare that to $150 for each 3 by 5 window in a house.

Best Option for a Forever Home: Low-E Windows

If you plan to stay in a house for the long term, you'll get back your investment in reduced energy savings. While high-efficiency windows do help resale value, you're not guaranteed to recoup the full return on investment if you do a whole-house window upgrade.

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