Ventilation Graph
Example Data Table
| Room Type | Volume m³ | ACH | Airflow m³/h | Suggested Use |
|---|---|---|---|---|
| Bedroom | 36 | 4 | 144 | Basic comfort |
| Office | 72 | 6 | 432 | People occupied |
| Workshop | 120 | 10 | 1200 | Higher pollutant load |
Formula Used
Room volume: Length × Width × Height.
Airflow by ACH: Room Volume × Air Changes Per Hour.
People airflow: Occupants × Fresh Air Rate × 3.6.
Final airflow: Greater airflow value × Safety Margin.
Duct area: Airflow in m³/s ÷ Air Velocity.
Round duct diameter: √(4 × Area ÷ π).
How to Use This Calculator
Enter the room length, width, and height in meters. Add the needed air changes per hour. Then enter expected occupants, fresh air rate, duct velocity, and safety margin. Press the calculate button. The result appears above the form. Use the CSV or PDF buttons to save your result.
Air Ventilation Size Calculation Guide
Why Ventilation Size Matters
Ventilation sizing helps move stale air out of a room. It also brings cleaner air inside. Good airflow supports comfort, safety, and moisture control. It may also reduce odors and heat buildup.
Understanding Room Volume
The first step is room volume. A larger room needs more air movement. Volume depends on length, width, and height. A high ceiling can increase the required airflow a lot.
Using Air Changes Per Hour
Air changes per hour shows how many times room air is replaced each hour. Low values suit simple rooms. Higher values suit workshops, kitchens, gyms, or busy spaces. This calculator uses ACH as the main physics method.
Occupant Based Airflow
People also need fresh air. The calculator compares occupant demand with ACH demand. It then selects the larger value. This helps avoid undersizing in crowded rooms.
Duct Size and Velocity
Duct size depends on airflow and air speed. High velocity can create noise and pressure loss. Low velocity needs larger ducts. A balanced velocity gives practical sizing.
Safety Margin
A safety margin covers filters, bends, grilles, leakage, and real system losses. It is useful for planning. Final design should still follow local codes and professional advice.
FAQs
What does this calculator estimate?
It estimates airflow, duct free area, and round duct diameter using room size, ACH, occupants, velocity, and safety margin.
What is ACH?
ACH means air changes per hour. It shows how many times room air should be replaced during one hour.
Why does occupant count matter?
People need fresh air. A crowded room may need more airflow than a simple room volume calculation suggests.
What air velocity should I use?
Many comfort systems use moderate velocities. Lower velocity is quieter. Higher velocity can reduce duct size but may increase noise.
Is this a final engineering design?
No. It is a planning calculator. Final ventilation design should follow local rules, building codes, and expert review.
Why add a safety margin?
Real ducts have losses from filters, bends, grilles, and leakage. A safety margin helps cover these practical effects.
Can I use feet instead of meters?
This calculator uses meters. Convert feet to meters first. One foot equals 0.3048 meters.
What does duct free area mean?
It is the open area needed for air movement. Grilles and screens may reduce effective free area.