Utility
Cross-Ventilation Analyzer
Does your room breathe well? Enter dimensions, window areas, and your layout — get air changes per hour, an NBC 2016 compliance check, and targeted suggestions to improve airflow.
Room
Floor area: 15.8 m² · Volume: 47.3 m³
Openings
0 for windows at the same height; 1.5 for clerestory / transom above a low window.
Site & climate
Southwest monsoon breeze; plateau elevation keeps speeds steady through summer.
Use this if you have a windy.com or ventusky.com reading for your exact location.
Airflow rating
Strong airflow — 11.3 air changes/hour, clearing the 6 ACH target for a living / dining.
Air changes / hr
11.3
target 6 ACH
Total airflow
535
m³ / hour
Effective opening
1.06
m² (paired)
Wind-driven
535 m³/hr
Stack / buoyancy
0 m³/hr
How to improve
- •This layout comfortably clears the target. Good candidate for a fan-off / AC-off strategy on mild days.
How this works
- Two airflow mechanisms. Wind-driven: pressure on the windward facade pushes air in, pulls it out the leeward side. Stack / buoyancy:warm indoor air rises and exits a high opening, drawing fresh air in through a low one — this is what makes jalis and clerestories so effective on still nights.
- Effective opening area. For cross-ventilation, Aeff = (Ain × Aout) / √(Ain² + Aout²). The smaller opening dominates — doubling just the inlet gives ~40% more flow, not 100%.
- Layout matters more than size. Cross-ventilation (opposite walls) delivers ~10–15× the airflow of single-sided for the same opening area. Corner / adjacent walls land in the middle.
- NBC 2016 Part 8. Minimum openable window area = 10% of floor area for habitable rooms (5% for bathrooms). This is a prescriptive minimum — clearing it doesn’t guarantee good real-world ventilation.
- What the calculator does not model: interior partitions, furniture blockages, balconies as wind shields, fly-screens (reduce airflow ~15%), security grilles, and wind approach angle. Real-world performance can be ±30% of the modelled number.
Related tools: Vastu Compliance · Sun Path Analyzer · Biophilic Score. Designing or specifying? The professional version adds NBC / ASHRAE compliance detail, discharge-coefficient tuning, and an SVG plan diagram.
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