Double Rafter Louver: what is a key action?

• A. Roll two rafters
• B. Roll one rafter
• C. Use four rafters
• D. Remove roofing material

Answer: (C)

In vertical ventilation, the double rafter louver is about creating a controllable vent opening by forming two hinged leaves from rafters. The key action is to use four rafters to build that double-louver structure, giving you two operable panels that can be opened for efficient smoke and heat release. Using four rafters creates a larger, balanced opening while preserving roof structure, which is why it’s the best choice. Rolling or removing only one or two rafters won’t yield the true double-louver setup and won’t provide the same ventilation effectiveness or structural control. Removing roofing material alone also increases exposure and can compromise the roof, rather than establishing the specific louver mechanism.