What is the primary effect of Low-E coating on glass?

• A. Blocks most infrared but transmits visible light
• B. Blocks infrared and UV
• C. Reduces radiant heat loss by reflecting infrared while transmitting visible light
• D. Increases radiant heat loss

Answer: (C)

Low-E coatings control heat transfer through glass by shaping how it interacts with infrared and visible light. The primary effect is to reflect a significant portion of infrared radiation back toward its source, which reduces radiant heat transfer, while still transmitting visible light so daylight isn’t blocked. This means you get daylight with less heat loss in winter and less heat gain in summer, boosting energy efficiency. Some UV light may be blocked as a secondary benefit, but the defining feature is infrared reflectance paired with clear visible transmission. The other descriptions aren’t accurate because blocking infrared entirely would also block daylight, and increasing radiant heat loss is opposite to what Low-E coatings are designed to do.