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Important Metrics for Assessing Window Performance

Many window companies claim their products are the best on offer, but how can you be sure? There are a few ways to measure a window’s effectiveness. Read on as Renewal by Andersen® of San Antonio, a leading window installation company in the local area, shares a quick guide.


The U-factor is a measurement of the amount of heat dissipated by the window over a given period of time. The higher the window’s thermal resistance, the lower the U-factor. A U-factor of .30 or lower is considered good enough for an average household’s needs, although the best windows have a U-factor of .15 or lower.

Solar Heat Gain Coefficient (SHGC)

The SHGC is a measurement amount of how much radiation from the sun passes through a window. The lower the SHGC, the better the window will be at preventing heat from the sun from penetrating into your home–which translates to less work for your air conditioner on hot days. If you’re installing a large window like a bay window, choosing a unit with excellent an SHGC rating is critical to keep your home from over-heating during the summer.

Visible Transmittance (VT)

This metric is related to light. Windows with high VT will let plenty of light into your home, while those with low VT don’t admit as much natural light. Values between 0.3 and 0.7 are considered standard for double and triple-pane windows.

Condensation Resistance (CR)

This one is especially important for homes in areas that see significant amounts of rainfall. A window’s CR shows how good it is at resisting condensation. For example, multi-pane picture windows with high CR are less likely to experience condensation, which means a reduced chance of mold and mildew growth.

Learn more about window metrics from our team of specialists. Renewal by Andersen of San Antonio serves homeowners in Boerne, San Antonio and Universal City, TX. Call us at (210) 988-6466 or fill out contact form to request a quote.


"When we purchased 10 large windows from Renewal by Anderson, were able to do so because of the liberal finance plan offered. The work was done in a timely manner and they did a good cleanup. I would highly recommend them for any window replacement."

Valerie Faleski

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