Ventilation and indoor air calculators
Ventilation and indoor air quality tools: fresh air from CO₂ readings, air purifier sizing, heat and energy recovery and whole-house fans.
CO₂ Ventilation Rate Calculator
Estimate outdoor-air ventilation per person from indoor and outdoor CO₂ (steady state), or the indoor CO₂ a ventilation rate would give.
Answers: How much fresh air is a room getting, judging by its CO₂ level?
Air Purifier CADR Calculator
Find the clean air delivery rate (CADR) a room needs, or the air changes per hour an air purifier gives, following EPA guidance.
Answers: What CADR air purifier do I need for my room?
ERV / HRV Heat Recovery Calculator
Find the supply-air temperature and heat recovered by an energy or heat recovery ventilator from its sensible effectiveness, and the heating energy it saves in a season.
Answers: How much heat does my ERV or HRV recover, and what does it save?
Whole House Fan Size Calculator
Size a whole-house fan from floor area and ceiling height, using DOE guidance of one-half to one house volume per minute.
Answers: What size whole house fan do I need?
Fresh air and clean air
Ventilation brings in outdoor air to dilute what people and their homes produce; filtration and air cleaners remove particles from the air already inside. These tools estimate ventilation from CO₂ readings (with NIST generation rates), size portable air cleaners from EPA guidance, show what a heat or energy recovery ventilator recovers, and size a whole-house fan from DOE guidance.