Low-E Glass

No, it’s not the name of Troy’s favorite rapper! The term “Low-E” is an abbreviation for “low emissivity” which means that a surface radiates (or emits) low levels of radiant energy (in our case – think sunlight.) From a science perspective, a surface that is 100% reflective has an emissivity rating of 0 while a surface that completely absorbs the energy has a rating of 1.

Unglazed glass has a rating of 0.95. That means that the radiant energy from the sun passes through into your house. That makes it difficult to run your air conditioner efficiently in the summer. It’s not that great in the winter because the radiant heat energy in your house will pass through the unglazed glass to the outdoors.


Low-E GlassA Low-E coating is a microscopically thin, virtually invisible, metal or metallic oxide layer deposited directly on the surface of one or more of the panes of glass to help reduce the energy loss by as much as 30-50%. So how do you figure out what works best for your house and what do all those ratings mean?

Here’s a quick tutorial. The “U-Factor” is the rate at which a window conducts non-solar heat flow. The lower the U-factor, the more energy-efficient the window. The Solar Heat Gain Coefficient (SHGC) is that fraction of solar radiation that makes it through the window and is release as heat inside the home.  A product with a low SHGC rating is more effective at reducing cooling loads during the summer by blocking heat gained from the sun. The SHGC you need for a window, door, or skylight should be determined by such factors as your climate, orientation, and external shading. VT, or Visible Transmittance, is the amount of visible light that is transmitted through the window. A product with a higher VT transmits more visible light. VT is expressed as a number between 0 and 1. The VT you need for a window, door, or skylight should be determined by your home’s day lighting requirements and/or whether you need to reduce interior glare in a space.

When properly selected and installed, energy-efficient windows can help minimize your heating, cooling, and lighting costs. Iron Crafters offers a wide range of window options including vinyl replacement windows, aluminum replacement windows, and storm windows. Each window is specifically designed to fit a particular opening in your house as one size does not fit all! Every window product we offer is made from the highest quality materials. Our vinyl replacement windows and aluminum storm windows are backed by a Lifetime Limited Warranty. Our aluminum replacement windows come with a Lifetime Limited Transferrable Warranty.

Before the summer heat starts bearing down on us, pick up the phone and call Iron Crafters (or send us an email.)

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