VT
visible transmittance
How much visible light the window lets through, 0–1. Higher means a brighter room. Separate from how much heat it blocks.
What it means for you
Why a heat-blocking window doesn't have to feel dark: VT and SHGC are different dials. You can have a low SHGC and still get plenty of daylight.
Where you'll see it
On the NFRC label, below U-factor and SHGC.
Related terms
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