Setting up a Grow Room

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When designing a grow room, it’s important to know that keeping your room hospitable for growing mushrooms is a constant balancing act between five main factors. Perfection isn’t necessary, or even attainable, but it’s essential to realize that often when one element changes, another will have to as well. It’s a push and pull to get the correct combination, but your mushrooms will tell you what they’re needing, if you pay attention.

Fresh air exchange

• One of the biggest mistakes made by growers is not bringing enough fresh air into the grow room. We stock the room heavily and have an exhaust fan that is adjustable, but allows us to replace all the air in the room in 2 minutes when running full speed.

• Bigger environments are more adaptable to shocks, so complete air replacement doesn’t need to be quite as often as a smaller, more densely stocked area.

• A CO2 meter is nice, but unnecessary. Each mushroom has tell-tale signs that your room isn’t breathing enough. Oysters in particular will grow tall and stemmy. Get to know your mushrooms, and they will tell you what they need.

Humidity

• The second biggest mistake growers make is not increasing humidity when increasing the fresh air flow. We keep our humidity cycling between 70 and 90 percent, creating a more natural environment for the mushrooms. We avoid ultra-high humidity, though, because once you get much above 90% you start to get condensation, which encourages unwanted bacterial and mold growth.

• The best system that we’ve found for humidity is the Ultrasonics from House of Hydro. The particles they put in the air are incredibly fine, staying airborne longer, and they don’t feel like they’re sticking in your lungs. We like this system because it feels like a dry fog, giving the room humidity without excess moisture.

Lighting

• We use T5 6500k spectrum lights on a 12 hour on, 12 off cycle on a timer. They don’t have a very high heat output, are easy to replace, and are a lot cheaper than LEDs.

• Proper lighting improves the quality of the mushrooms, encouraging them to grow large and gorgeous, but it is possible to overdo it. Too much light isn’t a problem, but with that light comes heat, and even low heat lights add up.

Temperature

• Growing strains that are naturally suited for the season will help you adapt to seasonal changes in temperature, but it’s still essential to avoid extremes. We do this by pulling in fresh air from the rest of the house, allowing us to utilize our home unit.

• Placing a mini-split or window AC unit just upstream of the grow room would provide additional help, but avoid placing them in the room. Mushroom spores are hard on heat exchanger coils.

• Keep in mind that the room itself generates a fair amount of heat. At any given time we may have 3 tons or more of mushroom compost exhausting heat and CO2 into the room, as well as lighting that, while lower than many alternatives, still outputs a substantial amount of heat in this small space.

Space Utilization

• Sturdy shelving is essential, but it doesn’t have to be expensive. Our racks are ¾” schedule 40 PVC pipe run through holes drilled through pressure treated two-by-fours. They are easy to assemble and clean, provide excellent airflow, and were very budget friendly.

• Our design is 10.5” wide at the end, which gives a 6” space between the rails for our fruiting blocks to straddle. Make sure to leave at least 2” of space between the rack and the wall, or your fruiting blocks will tend to fall out into the aisle.

• We found 12” of vertical space between shelves to be ideal, starting 6” above the floor. We made the bottom shelf out of wood to stabilize the racks.

• 36” is what we found to be the minimum width of the aisles. You may be able to push it a little, but you want the room to be comfortable to work in, as well as space efficient.

• All together, the minimum width of an aisle with shelves is 5’ per aisle. That’s 2” of space behind the rack, 10.5” of rack itself, 36” of aisle space, and the second rack and space behind it. (technically, that comes out to 5’1”, but I’m sure you can figure out how to save an inch somewhere.)

While we didn’t include cleaning in the push and pull balancing act of these five factors, setting up an easy system that is performed on a set schedule is just as essential. Setting up effective systems for each of these five things, as well as a consistent cleaning routine, will benefit your mushroom business by providing you with high quality mushrooms consistently.