How to Look

at a House

A home inspection blog
with answers to your questions about home inspection
and maintenance

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We want you to be an informed homebuyer, and each blog post is a question that we have answered for our friends and customers over the years. Hope they help you make a good choice for your next home.

  1. B)Solar Heat Gain Coefficient (SHGC) measures how well a window blocks the transmission of heat from the sun through the window. SHGC is expressed as a number between 0 and 1. The lower the SHGC, the better the product is at blocking unwanted heat gain, which is particularly important in hotter, Southern climates like Gainesville where the homes are air conditioned part of the year.

  2. C)Visible Transmittance (VT) measures how much light comes through the window, and is expressed as a number between 0 and 1. The higher the VT, the higher the percentage of sunlight that penetrates the window for better daylighting.

  3. D)Air Leakage (AL) measure how much outside air comes into a home through the window. AL rates usually fall between 0.1 and 0.3. The lower the AL, the better the window is at keeping air out. It is an optional rating, and not all manufacturers choose to include it on their labels.

  4. E)Condensation Resistance (CR) measures how well an window resists the formation of condensation. It is expressed as a number between 1 and 100, with higher numbers indicating better resistance to condensation on the window.

    For more details about the rating system, visit the NFRC website at:

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
©2015 - McGarry and Madsen Inspection.

Sample label - National Fenestration Rating Council

  1. A)The U-Factor is a measure of the insulating ability of the window: how well it prevents heat from entering or escaping through the window. U-Factor ratings generally fall between 0.20 and 1.20. The lower the U-Factor, the better the window is at insulating. To convert a U-Factor to an R-Value (the number used to rate the insulating ability of other building materials), divide 1 by the U-Factor. So, a window with a U-Factor of 0.25 would have an R-Value of 4 (1 divided by 0.25 = 4). A low U-Factor is more important in cold climates, where it is important to keep the heat from escaping .