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How To Choose The Most Energy Efficient Impact Windows

Posted by Jimmy Hawley on Nov 26, 2013 1:55:44 PM

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In addition to needing durable, impact-resistant hurricane windows to protect against storms, Southwest Florida homeowners in Naples, Fort Myers, and Port Charlotte also want to have windows that protect them from the hot Florida sun and high humidity throughout the year.

The best energy-efficient windows meet ENERGY STAR standards, as defined by the Department of Energy, and are rated by the National Fenestration Rating Council (NFRC) for energy-efficient properties. But what does that actually mean, and why does it matter? Here's what to know.

 

What Makes an ENERGY STAR Window?

ENERGY STAR-compliant windows have a mix of high R-values, low U-values, low E coatings, low SHGC (Solar Heat Gain Coefficients), high VT (Visible Transmittance), and AL (Air Leakage). Many of the values assigned by the NFRC are noted on a sticker affixed to each window. That all sounds like a lot, and a great way to get confused, but it doesn't have to be. This is what the designations for energy-efficient impact windows mean:

  • R values measure the resistance to heat.
  • U factors measure the amount of heat that is transferred to a material.
  • Low E, which stands for low emissivity, indicates that the window has been treated with a metallic coating that reflects and radiates heat energy.
  • SHGC indicates how well the window transmits solar radiation, as measured on a scale of 0 to 1 (0 means the window is more like a wall that permits no solar energy to enter, 1 means that it lets solar energy in.)
  • VT values are also measured between 0 and 1 and refer to how much sunlight comes through the window.
  • AL notes how much air leakage passes through the cracks in the frame.

When you're trying to find out what windows to choose, or searching online for things like what are the best impact-resistant windows, it's helpful to know what those values stand for. Then you can find the right energy-efficient impact windows for your needs.

 

The Importance Of Proper Construction

Proper construction is the first critical step in manufacturing impact-rated windows that are also energy efficient. You can't get energy star windows, for example, that haven't met criteria and passed rigorous testing and requirements. Not sure about the windows you already have in your home? Here's how to tell if you have impact-resistant windows:

Impact windows are made of impact-resistant laminated glass, with special silicone glazing to keep them secure in their heavy-duty frames, even under duress. The double-pane windows themselves are made of glass, bonded together with a layer of polyvinyl butyral (PVB), and filled with argon gas, which is heavier than air and stays in place to provide insulating properties.

In Southwest Florida, that is a great feature. It lets you sit near a window and not be aware of how hot it is outside. The interior glass remains close to room temperature and does not produce radiant heat like a single-pane window would.

Some critics argue that having insulating gas between the window panes adds unnecessarily to the price of the window, but the gasses play an important role in reducing solar gain, which is the increase in temperature in your room from the sun. As temperatures rise, having insulating glass reduces the need to crank up the air-conditioning, and saves you money on your power bill.

Additionally, having the windows protected with a low-E coating can help block the sun by reflecting more of its rays. Since the coating can degrade when the window is exposed to rain, the coating is protected by the second pane of glass. Newly formulated versions of this coating work in Florida with single-pane windows, too, though they are less effective.

 

Desired Values For Energy Efficient Windows

In our climate, the most effective windows have these values posted on the sticker:

  • U Factor — Lower than .75. Below .6 is even better
  • SHGC — Lower than .4
  • VT values — Between .3 and .8 is common, depending on the amount of light you want to let in
  • AL — Lower than .3

Your window should be "spectrally selective," which means it should have a low SHGC and VT rating. The R-value, the reciprocal of the U-factor, may not be posted, but it should be between 2 and 3. Low-E is reflected through the SHGC and VT values.

 

Buy By The Numbers at Storm Solutions

Storm Solutions services the cities of Naples/Marco Island, Fort Myers/Cape Coral, and Port Charlotte/Punta Gorda in Southwest Florida, with the highest quality energy efficient impact windows. You can depend on us to carry windows with optimum values that translate to the most energy-efficient products we need in Southwest Florida.

We carry WinGuard® Impact-Resistant Windows from PGT that meet the most stringent code requirements for hurricane-force winds and flying debris. These custom windows will help provide year-round security against thieves and intruders, dramatically reduce outdoor noise, and also filter out 99% of the UV light that enters your home and causes fading. When combined with our insulating glass, you have energy-efficient impact windows that can significantly reduce cooling and heating costs.

Just visit our website and download our free information sheet "12 Things You Need To Know About Impact Windows," or give us a call at (239) 567-9772 to learn more and schedule your no-obligation consultation. We're here to help keep you cool, comfortable, and protected in your home, through quality windows you can rely on.

 

Impact Window FAQs

Topics: Impact Window Installation, Impact Windows, Energy Efficient Windows, Impact Windows FAQs, hurricane windows, Hurricane Impact Glass