Louver Cross Ventilation Calculator
Computes minimum louver opening area required to deliver target air changes per hour in cross ventilation from room volume and wind speed.
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Sizing louvers for cross ventilation
You get cross ventilation when openings on opposite walls let the outside wind pass straight through the room. The opening area you need comes from A = (V · ACH) / (3600 · v · Cd) where V is the room volume, ACH the air changes per hour you are after, v the outside wind speed and Cd the discharge coefficient (≈ 0.6 for louvers). For bedrooms, NBR 15575 asks for a window area of at least 1/6 of the floor area for ventilation.
Two openings facing the prevailing winds beat one big opening on a single wall. The stack effect (warm air rising) plays a smaller part. A high outlet helps clear out the hot air that pools near the ceiling, which matters most on those still summer afternoons.
Applications
Passive design in tropical climates, NBR 15575 desempenho, LEED IEQ credits, and ventilation standards for schools and hospitals (ANVISA RDC 9/2003 covers healthcare buildings).
FAQ
How many ACH are enough? Figure on 3-5 for bedrooms, 8-12 for bathrooms, 10-15 for kitchens and 4-6 for living rooms.
What if there is no opposite wall? Reach for clerestory windows or roof vents and let the stack effect push the air upward.
Are louvers better than sliding windows? Louvers keep the air moving during rain without letting water in, which is why they show up so often in tropical homes.
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The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.