Mushroom House Ventilation Calculator
Fresh air exchange for a mushroom fruiting room.
Enter your values
ⓘ Live results
Results
- Fresh air exchange
- 120 CFM
- Room volume
- 1,200 cu ft
- Target CO2
- 800-1000 ppm during fruiting (species dependent)
- Humidity note
- Pair with humidification since fresh air lowers RH — target 85-95% RH
Quick answer
Mushroom fruiting rooms need enough fresh air exchange to keep CO2 below about 800-1000 ppm, often requiring 4-8 full air exchanges per hour depending on growing density and species.
CFM = volume x air exchanges per hour / 60
How to use the Mushroom House Ventilation Calculator
- 1Enter the fruiting room's floor area and height.
- 2Choose an air-exchange rate suited to your mushroom species and density (oyster mushrooms want more than button).
- 3Balance the added fresh air with humidification, since ventilation dries the room.
Worked example
Using the values the calculator loads with:
Inputs
- Room area150 sq ft
- Ceiling height8 ft
- Air exchanges6 per hour
Results
- Fresh air exchange120 CFM
- Room volume1,200 cu ft
- Target CO2800-1000 ppm during fruiting (species dependent)
- Humidity notePair with humidification since fresh air lowers RH — target 85-95% RH
Frequently asked questions
Why does CO2 matter so much?
High CO2 causes long, thin stems and small caps ('legginess') because mushrooms sense it as a signal to stay underground.
Can I just crack a door?
For small setups yes, but a ducted fan with a timer gives far more consistent, controllable exchange.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.