Low-e windows keep homes cool … but may set neighbours’ property on fire

Low-E Window Glass Raises Fire Risk When Used on Bowed Glass

A unique side effect of low-emissivity or low-E window glass, a popular green technology for regulating building temperatures, has been discovered. While the coated glass is effective at keeping homes warm in winter and cool in summer, its use on bowed glass can have an unintended consequence: a magnifying-glass effect that can ignite nearby flammable materials. This rare but potentially hazardous issue arises when sunlight passes through the low-E coated glass, focusing onto a specific spot and generating intense heat.

The low-E glass is coated with a thin layer of metal or metal oxide, allowing visible light to pass through while reflecting infrared radiation, thereby retaining warmth indoors during winter and repelling unwanted solar radiation in summer. However, when the glass is bowed or curved, it can concentrate sunlight, leading to an extreme temperature increase in a small area. This concentrated heat can ignite nearby combustible materials, posing a significant risk to neighboring properties.

As a result, homeowners and builders are advised to exercise caution when installing low-E window glass on bowed or curved surfaces. While the benefits of low-E glass in terms of energy efficiency and temperature regulation are undeniable, the potential fire risk associated with its use on bowed glass must be carefully considered and mitigated to ensure the safety of both the building occupants and neighboring properties.