Use Energy Efficient Low-E Window Coatings to Keep Your Home Cool

By Vernon Trollinger, September 23, 2013, Energy Efficiency, Save Money

Use Energy Efficient Low-E Window Coatings to Keep Your Home CoolEarlier this year, I wrote a blog post on how to install Energy Efficiency Windows. In the article, I outlined that energy efficient windows are rated in “U-factors” to describe how the glass conducts heat — either from the inside or the outside. The lower the window’s U-factor, the better the performance. To increase this energy saving performance, energy efficient windows can also have a “Low Emissivity” (or Low-E) coating applied to them to reduce heat conduction.

We have a hallway at the top of our stairs on the south side of the house. The door has a large window that does not have Low-E glass. The smaller window next to it DOES, as I installed it in conjunction with writing that blog post in March. Not surprisingly, the door feels a lot hotter.

Experiment

I recently got myself an infrared thermometer, and during one 100°F afternoon, I decided to test it out by seeing just how much heat was being conducted through the windows. In terms of the conditions, our thermostat is set to 76°F. That day, the temperature of the wood decking outside was over 130°F, and our roof was 149.9°F.

Use Energy Efficient Low-E Window Coatings to Keep Your Home Cool

Here’s the smaller, Low-E window (note the white sash and latch in the background). The temperature of the glass on the inside of the house reads 88.7°F.

Use Energy Efficient Low-E Window Coatings to Keep Your Home Cool

Here’s a picture of the temperature in the window that does NOT have Low-E glass. The temperature on the inside of the house reads 103.5°F. Yes, it is THAT HOT.

Use Energy Efficient Low-E Window Coatings to Keep Your Home Cool

Here’s the same door and window, but with a sheer curtain over it. The temperature dropped to 92.2°F, since the curtain absorbed and radiated the heat, which is why we often recommend using curtains as a method to lower your electricity bills by reducing the temperature of your home.

Results

A Low-E coating meant the difference of 14.8°F between the two windows. Putting up a little swag of light weight fabric also cut the heat from the door window by 11.3°F, but heat was absorbed and radiated by and into the curtain. Putting the same curtain over the Low-E window resulted in further temperature drop of only 2°F — hinting that the Low-E coating eliminated most of the heat being conducted.

Though not an entirely accurate scientific experiment, it does indicate that Low-E windows are highly efficient in reducing the amount of heat getting into your home and can lower your air conditioning costs.

For more information, we recommend that you visit the websites for top-brand window-makers like Pella, Jeld-Wen, Andersen, and Marvin, as they provide window specs and installation instructions online for all their energy saving window products.

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About 

A native of Wyomissing Hills, PA, Vernon Trollinger studied writing and film at the University of Iowa, later earning his MA in writing there as well. Following a decade of digging in CRM archaeology, he now writes about green energy technology, home energy efficiency, DIY projects, the natural gas industry, and the electrical grid.

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