How to Calculate Ventilation Rate
What is Ventilation Rate?
Ventilation rate specifies fresh air exchange required for indoor air quality. Codes typically require 0.3-0.6 air changes per hour.
Formula
Calculate: Air change rate = ventilation flow / room volume
Step-by-Step Guide
- 1Calculate: Air change rate = ventilation flow / room volume
- 2Typical: residential 0.3-0.5 ACH, office 4-8 ACH (per code)
- 3Energy cost: heating/cooling outdoor air increases with ventilation rate
Worked Examples
Input
Office 100 m³, requires 0.5 ACH minimum
Result
Ventilation = 50 m³/hour fresh air needed
Balances air quality and efficiency
Common Mistakes to Avoid
- ✕Over-ventilating (energy waste without air quality gain)
- ✕Neglecting filtration (outdoor air quality varies)
Frequently Asked Questions
Does higher ventilation always improve air quality?
No, diminishing returns exist. Outdoor air quality also matters; mechanical filtration sometimes better.
How do you reduce ventilation energy cost?
Heat recovery ventilators (HRV) capture 75-85% of exhaust air heat; significantly improves efficiency.
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