• [A]
• [B]
• [C]
• [D]
• [E]
• [F]
• [G]
• [H]
• [I]
• [J]
• [K]
• [L]
• [M]
• [N]
• [O]
• [P]
• [Q]
• [R]
• [S]
• [T]
• [U]
• [V]
• [W]
• [X]
• [Y]
• [Z]

Net free area

The effective operating area of a vent after adjustments for insect screening, louvers, and weather coverings are accounted for. AKA net free ventilation area, or NFVA.