What Are Fenestrations?

Doors (walkthrough and overhead), windows, skylights, louvers, and storefront glass.

Why Focus on Fenestrations?

Fenestrations are an integral part of the building envelope, yet contractors often overlook them. Per the IECC and ASHRAE Standard, these components have important performance requirements. When reviewing code compliance for fenestrations, typically a designer will use the default option in COMcheck™, which can lead to a mistake in the building envelope. Instead, contractors and designers should get the actual performance rating of the products that will be used, since they are better performing than the default code values.

What to Know

Doors – both walkthrough and overhead – are required to pass the ASTM 1363 test. This is a performance test of the entire door. This is important, since a typical walkthrough door may have a leaf R-value of 5 or 7, but an ASTM 1363 test of the entire door could result in a total R-value of 2.5. Keep in mind that, by code, the U-values for these products assume the ASTM 1363 test is passed.

Windows and skylights require a different test, which is regulated by the National Fenestration Rating Council (NFRC). The NFRC rating has two results:

  1. U-Value
    The U-value consists of the total window, including glass and frame.
  2. Solar Heat Gain Coefficient (SHGC)
    SHGC is the fraction of incident solar radiation admitted through a window, both directly transmitted and absorbed, and subsequently released inward. The lower a window’s solar heat gain coefficient, the less solar heat it transmits.

Solar heat gain can provide free heat in the winter but can also lead to overheating in the summer. Other factors that affect SHGC are climate, orientation and shading. Since there’s an SHGC requirement for each climate zone, it’s important to understand the following tables.


Expert Building Envelope and Fenestration Knowledge

Check back for my next post in May, which will focus on a common challenge faced by many contractors: Air leakage in the building envelope and fenestrations.

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