How should ignition-resistant windows be integrated with proper sealing to prevent ember entry?

• A. Use tempered or laminated glass, multi-pane assemblies, and weather-stripping plus caulking around openings to seal gaps
• B. Use tempered glass only
• C. Use single-pane glass with no seal
• D. Use plastic sheeting instead of glass

Answer: (D)

The key idea is that protection from embers comes from both the glazing itself and the way the window is sealed into the building envelope. Ignition-resistant windows perform best when you use a strong glazing assembly—tempered or laminated glass, ideally in a multi-pane design—to resist heat, breakage, and ember penetration. But embers can still find their way through any gaps around the window, so sealing is essential. Using weather-stripping and caulking around openings creates a continuous barrier that blocks ember entry through joints, frames, and gaps between the sash and the wall, preventing embers from sneaking inside and igniting surrounding materials.

Why the other options don’t fit: relying on tempered glass alone doesn’t address gaps that embers can exploit; single-pane glass with no seal leaves multiple routes for ember intrusion; plastic sheeting isn’t a durable, reliable ignition-resistant window solution and won’t provide the same level of protection against embers or heat.