How to Grow Mushrooms: Ventilation and Humidity
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Mushrooms love fresh air and moisture. The two are a large component of a healthy grow room environment, and an essential balancing act for the growth of high quality, restaurant ready mushrooms.
Ventilation
- The air in our grow room is replaced roughly once every two and a half minutes. Larger grow rooms can get away with longer replacement times. We use equipment that’s over-powered for the environment that we’re creating so that we have some leeway as wear and tear takes the efficiency down over time.
- It’s important to take the time to find the right balance between CO2, temperature, and humidity for your situation. Ultimately, you won’t know you have it right until you start growing your first mushrooms. Every time you change your stocking rate your settings may need to change as well. Daily checks are essential to keeping the balance.
- While our lab is positively pressurized, we use negative pressure in the grow room. Instead of pushing air in, we pull air out and send it outside. This prevents spore filled air from being pushed out of the grow room and into the lab or the house.
- At first, we tried using a filter over our fan to catch the spores, but we were going through so many that we realized it’s more cost-effective to clean the fans with a pressure washer and replace them when they break down. They’re changed out roughly once a quarter, which isn’t too bad with how cheap they are and the work they do.
Humidity
- The relative humidity in our grow room ranges between 70 and 90 percent. This is a good place to start, but depending on your local conditions, you may have to adjust your high end to keep from overdoing it. This helps keep the contamination down and the mushrooms growing strong because it mimics the fluctuations they’d experience in nature.
- Our reservoir is from Lowe’s. We cut 3 holes in the lid: for the power cord, for the collar and for the quick connect for the fan. This allows everything to be taken apart, cleaned, and put back together easily.
- A waterproof fan goes through ducting into the water reservoir, which has a 12 disc fogger and an automatic refill valve from House of Hydro in it. (Use code Mossy at checkout for free discs) Cool air comes over the water, collects the mist, and comes out the top of a 4 inch PVC pipe, then gets mixed into the air being pulled into the room through the door.
- Our automatic refill valve is plumbed into the house and has a shut-off valve for emergencies or maintenance. A T-joint near the entrance with another valve for the pressure washer helps make cleaning easier.
- The humidity sensor is tied to a shelf and plugged into the humidistat controlling the transformer. When the humidistat is getting readings of lower humidity, it kicks on the transformer for the fogger, and when it reads higher humidity it will shut it off.
With our set up, the fresh air and humidity are able to sink through the room before being pulled back up and exiting through the ducting with the fan near the ceiling. This enables an even spread through the room, so the mushrooms at the bottom of the shelves have as high quality air as the ones up high.
How to Grow Mushrooms: Ventilation and Humidity
You guys are doing a great service to those interested in growing gourmet mushrooms. You have some of the best looking mushrooms I’ve seen so far. Keep up the good work, and can I say( keep spawning culture y’all)? Lol
Thank you! One of our goals is to encourage more people to jump into growing mushrooms, so it’s nice to hear we’re being helpful. Keep spawning culture. 🙂
Hello,
This question is concerning the maintenance required for the 12 disc fogger. You mention ‘hard water of Tennessee’, is your water supply a private well or city water and do you know the mineral level of your supply? There is a fair bit of mineral plating out on the fogger. So, for the 12 disc fogger, how often do you need to change the disks and ????
Thanks,
jdg
Ah, that’s a good question. The short of it is, not sure on actual mineral levels, and we change the disks when the fog output drops. They can actually handle a bit of scale ok, but the output slowly drops off. In practice it’s been every three months or so, but that will change based on local water hardness and humidity levels.
Hey there!!! Mossy crew, awesome vids! so encouraging! wondering about the distance between the 2×4’s. Also i noticed the wall its naked, what kind of sealant or paint did you use? or its not a problem having Hi humidity all the time on the walls?
tanks!
We space our 2x4s 30-40 inches, maybe even wider at the end of an aisle. We used a waterproof paint, but I don’t remember what kind right at the moment, so I’d have to get back to you on that.
Good morning. I have seen where some growers cycle their humidity levels to fully saturate their mushrooms, then dry them out a bit with lower humidity? Have you tired that approach or do you stick with a constant humidity once you have found the right balance? Thank you for providing this service.
We’ve stuck with constant humidity. It works well for us.
Hmm, that’s not accurate. We cycle humidity from around 70-95%, though the exact high and low level gets adjusted according to how the mushrooms look. Time of year, and freshness of disks in the humidifier affect how wide we set the range, but we always use the mushrooms as the gauge. If they start looking wet, we will lower the range a bit, if they start getting dry edges we raise it up.
How do you handle condensation on walls / floor? What prevents this from wrecking your place?
p.s. your videos are awesome – thank you
Before we set up the grow rooms, everything was protected against water. Constant cleaning helps, as well.
We also use a negative pressure setup in the grow room. The fan pulls air out of the room through the duct and so if there’s any leak or hole in the wall wrap it will tend to draw external, dry air in and not let the moist air out into the house. The fan runs constantly, so there’s no backflow into any other part of the house.
Good afternoon Mossy
Ernest from South Africa.
I have watched some of your ” YOU TUBE ” great content thanks.
Could you please show close pictures of the fans you use for the Humidifier as well as
the the negative flow ventilation. Can you also give me the air flow specifications of the fans
ie cubic metre’s or feet per second/minute/hour that the fans are rated.
Keep up the good work we really appreciate
Kind regards Ernest
Hey y’all! Me and my partner just started our new farm in Alton, IL. We are having issues with excessive condensation buildup in our grow room. We also began our op in our basement. Our temp is on the cooler side but should be good, our exhaust runs all of the time but it may be too strong for our little room because it seems to make our fogger kick on constantly. Our humidity is set to 85% but it just won’t hold humidity.. the floor, shelves and blocks are overly condensated. Any tips on this issue? Thanks so much.
Try slowing down your exhaust fan. Should help with your temperature, too.
Like!! Really appreciate you sharing this blog post.Really thank you! Keep writing.
Hi! This info is great! My issues are currently the condensation which I will look to get the exhaust fan you guys mentioned. However since my grow tent is in my garage I don’t have an option to “suck air out” of the garage. The tent is unfortunately not near the window of the garage. Any ideas of how I can properly ventilate the room and lower the condensation? I am currently running a ultrasonic humidifier running at 22 degrees Celsius, and 85 percent humidity. Thanks so much!
Is there any way you can get some tubing and connect it from the tent to the window?
Can you tell me what type of filter you are using on your door?
We don’t use filters on our doors, they’re lined in plastic.
Hi Andrew and Samantha great great great vlogs both of you
I literally follow hundred of channel out there but content like yours is pretty rate (full of knowledge , and reason behind your doings)
I have few questions for you though
I’m Aniket from india btw
About substrate combination you use 50:50 saw dust and soy hull both are fine powder like substrate dont they cause aeration problem , coz i tried same combination (soy hull replaced with rice husk) and my mycelium run was patchy , didn’t went throughout the block where substrate was dense
2ndly people do sterilization with different timing some with just 15 min some with couple of hours and some like you for 36 hr straight , can you please tell me the reason with this difference everyone gets good flushes
Thank you so much , I expect your rply and keep posting good contents 🙂
We use pellet forms of soy and wood. Powders can indeed be a pain to work with. Did you mix the bag up to get the inoculated spawn evenly throughout the substrate?
There are many different methods for a lot of things that generate good results. It’s all about finding the methods that work best for you and your business.
Hi what is the brand name of the extractor fan for your fruiting room?
There’s a link to one in the post. At the rate they’re replaced, finding a cheaper one that functions is just fine. It’s not worth it to shell out for a more expensive one, because the spores are going to destroy it eventually anyway.
How does fan direction influence mushroom growth? like side flow, grow sideways, top flow, grow up, etc…?
I have no information about fan direction influencing the direction of mushroom growth. Maybe you could run some experiments and track your findings?
Do you guys filter the passive air intake into the fruiting room? If so, what filters would you recommend?
Thank you for sharing such excellent content!! Youre a gem to the mushroom community.
The air coming in was just the air in the house when the operation was in the basement. Some parts of the operation have changed with the switch to the warehouse, so we may need to do updates before too long.
hello my name is Kevin I’m from CT I’ve been growing indoors in a Martha tent. I am upgrading to a 4×8 Vivosun tent and I am unable to vent out a window or any were else but in the room. I wanted to know if you had a solution. my idea was to use a hepa filter but I’m not sure how to reduce the amount of moisture that will be ruining the filter. thx for any info you can provide.
I’m not sure of a solution. Have you joined our growers’ group on Facebook? There are a lot of fantastic people in there that could likely give you wonderful advice.
Hello!
Wondering what you would say is the optimum % humidity for harvesting? I’ve heard it’s best to lower the humidity pre-harvest so the mushrooms aren’t too wet, which will lessen shelf-life….but not sure to what level exactly? I’ve been keeping my grow tent at around 88-92% humidity for fruit development.
Our humidity cycles constantly, and we don’t change anything before harvesting.
Hi, is it important where the exhaust fan mounted in the very small volume room? Closer to the floor / ceiling or in between?
We’ve always had our fan installed toward the ceiling, in part because it pulls and mixes the air effectively (helping to exhaust co2 and spores) and in part because of the ease in which we can change it without being inside the room via the outside catwalk. It’s important that you are able to change the fan without being in a co2 producing area for very long, preferably not at all. It’s additionally important to choose a fan appropriate to your square footage and production density to ensure the appropriate fresh air exchange, and you’ll notice your room stays cleaner in general if it’s powerful enough to keep spores at bay but not so powerful it removes optimal humidity. I’d also round up in size rather than down if the space is in between sizes.
Hello! I was wondering how you sync up the humidistat with the fan blowing into the tote. Do they turn on and run the same duration? Or just have the tote fan on all the time?
Thanks for this great video. You mentioned keeping the mist maker cool. I’d like to know more about this. We have a 10×10 foot grow tent. When we were running an AC to bring cool air in, our humidifier was working constantly and got warm. We also had over saturation like like Adam mentioned above. Do you have any suggestions for keeping both the humidifier and the space cool?
Hi, Great community guys.
How are guys handling Green Mold issues, whilst growing White Button Mushrooms ?
Thanks – Keep up the good works