A grow room for home mushroom growing

The Fruiting Environment: Chosing a Grow Room Design for Home Cultivation

One of the most important aspects of growing mushrooms indoors is providing the right fruiting environment. Unless you have adequate temperature, humidity and air exchange, your mushroom block will dry up and not produce any fruit. Providing adequate air exchange while maintaining high humidity is difficult to master, but there are several possible solutions that will get the job done. Although different mushrooms have their own unique environmental requirements, once you have a basic grow area set up you can tailor it to the specific species you are trying to grow.

Straw logs hanging in the grow room.

When trying to design a grow area, think what causes mushrooms to fruit in nature- that is, high humidity and cool temperatures. That is why you see way more mushrooms outside in the fall when the rain is falling and cooler temperatures have settled in. Two other aspect that are not as obvious is the requirement for a high rate of air exchange, or more specifically low levels of carbon dioxide, and the proper light levels. Most mushrooms don’t grow well in the dark and require a threshold level of light to produce normal fruits. As for air, high levels of fresh air can be difficult to achieve when trying to maintain high humidity, and some experimenting will be required on the part of the home cultivator.

The Cheapest Option: The Shotgun Fruiting Chamber

Anyone just getting into the hobby might want to start with a shotgun fruiting camber. It is essentially a clear plastic tote that looks as if it was blasted with a shotgun, hence the name. This design is good for the small scale cultivator who just wants to fruit one or two small blocks, or a few PF cakes. A good fruiting environment can be maintained in a SGFC, but it requires a little more monitoring and maintenance.

Shot gun fruiting chamber SGFC

Start by getting a clear plastic tote that is big enough for whatever blocks you want to fruit. Drill holes in the tote two inches apart on all sides of the tote. This will allow the fruiting blocks or PF cakes to breath.

In order to produce and maintain humidity, fill the bottom of your SGFC with a few inches of perlite. Perlite is a porous rock like material that absorbs water. This water is slowly released inside your chamber which causes a humid environment. Before putting the perlite in your chamber, soak it in water for an hour so it can fill with water.

The last thing you will need for your SGFC is a spray bottle with a fine mist. Several times a day you will want to open the lid and fan to get some fresh air movement, and then spray water into the chamber. This should help to maintain high humidity. If you want to know where you are at, get a cheap hygrometer to monitor the humidity levels. It will also tell you the temperature. Keep your SGFC by a window or in room that receives a moderate level of natural diffuse light.

See full instructions on building a SGFC here.

The Dedicated Hobbyist Option: Mushroom Greenhouse Design

If you want to pump out a lot of mushrooms and want to be able to automate some of the process, you might consider stepping up to a mid size grow chamber. The most common type of indoor mushroom growing chamber is the 4 tier green house. This option will cost a little more, but is a great way to increase you mushroom growing potential.

The 4 tier greenhouse is typically used for starting plants indoors. They are very commonly found in garden centers, big box retailers or can be bought online for pretty cheap. You can even buy entire kits online- which saves picking up all the components individually. The 4 tier greenhouse can easily be converted into a mushroom growing paradise. It is big enough to hold several blocks, flat trays and lots PF cakes.

The main advantage of this design is the incorporation of the humidifier– which can be automated- and saves you from having to open the flaps and spray several times a day. You could just place the humidifier inside the grow chamber, and although that will easily maintain high humidity, you will still have to open the chamber several times a day to allow for fresh air exchange. A much better option is to pipe in the humidifier using a few pieces of PVC pipe. The humidifier has a fan, which will push fresh humid air into your chamber.

When choosing a humidifier, you have the option of either a cool mist or a ultrasonic humidifier. Both will work, but the ultrasonic is a far better option. Ultrasonic humidifiers produce a visible stream of vapor, using spinning discs that vaporize water droplets, and can increase the humidity in your chamber really quick. Cool mist humidifiers simply use a wick to draw water up and into an air stream and are much less effective. Make sure to clean your humidifier often to prevent contaminants from building up inside.

It is best to use a hygrometer in your grow chamber to monitor the humidity. You will not want to run the humidifier all the time, as it will will produce way to much moisture in your grow area. Typically, you will want to maintain at least 80% relative humidity. A good option is to get a timer that has multiple on and off setting, and playing around with your specific set up until you find a good on-off pattern.

If your grow chamber is placed on carpet or hardwood, make sure you place a sheet of plastic underneath so that the build up of moisture doesn’t damage your floors. Also, although the humidifier will pump in fresh air, it is not always enough, especially for air hungry species like blue oyster. You may still have to open up your chamber once in a while to fan in some fresh air.

The trick to a successful 4-tier grow tent is trial and error in order to figure out what set up works best for your specific area, season and type of mushroom.

Here are some things you might need. In particular, we have used the tear drop humidifier with mush success.

See what works for you!

Mushrooms require a specific balance of humidity, temperature, fresh air and light. The above options are good choices for the home cultivator, but you can get creative and come up with a design that works for your situation. Part of the fun of growing mushrooms at home is the experimentation. Post pictures of your set up below!

Thanks for reading and good luck with your grows!

-spread the spores-

Comments 28

    1. Post

      Hey Patrick thanks for reaching out! I usually just keep a 4 tier in the garage and the temperature stays pretty steady throughout the year. If not, you could always try a portable air conditioner and a small heater fan used to either heat up or cool down the room in which the 4 tier is placed. It would be heard to try and heat/cool a 4 tier directly, unless you too the extra steps to insulate it, which might not be worth the effort. Let me know how it goes though!

      1. you could always use a hydro innovations heat exchanger with small 4″ inline fan with a small waterchiller/and water pump add a thermostat to fan. Walla closed loopchilling. with a 4″ dustshroom hepa air filter you can open loop exchange air and filter and cool at same time think ” three birds one stone”.

      2. I had same problem with my greenhouse. I put an adjustable fish heater in a 2 liter plastic juice bottle after filling it mostly to the top leaving a 3/8 inch air gap at top and siliconed it in place. Then i bot some cheap foil faced sheet foam insulation and shored it and folded it around the greenhouse on all 4 sides and cut a separate piece to cover the top and bottom and punched holes for air lines to go thru. didnt take long at all and brought up temp about 4 degrees to 68- 70. If I moved the humidifiers inside it would raise into 70s easily, but king oysters require much fresh air and these temps seem ok.

        1. Post

          It’s not entirely necessary although it does help. Oysters in particular will fruit pretty good without a sudden temperature change. For commercial growing definitely, but for growing at home generally not needed.

    1. Post

      Not at the moment, but I’ll sure put one up – stay tuned. The new set up I have with the 4 tier is a lot better. Using a 5 gallon bucket with a floating disc pond fogger, with humidity being pumped in through PVC pipe with a blower fan. Works like a charm!

  1. Hi there.

    We have opted for 4 tier greenhouse setup, but unfortunately we have encountered a lot of condensation and dripping. We are pumping in humidity with a simple humidifier/tube setup. Would you have any tips on keeping the humidity level in check?

    Also, how exactly should we go about the inevitable pooling in the bottom of the greenhouse. I see in the picture above the seems to be a PVC frame wrapped in plastic? Is it meant to be emptied every so often? How exactly would we go about it with a similar setup?

    Any and all help would be greatly appreciated.

    1. Post

      Hey Gabriel, thanks for reaching out! A 4 tier mini grow chamber is a great choice! If the humidity is too high, try running it for less time, using an on/off timer. Also, you can try running it with the door unzipped all the way. The pooling at the bottom is an unfortunate result of the humid environment. Obviously, the best way to fix this would be to place the 4 tier over a drain. If you don’t have this option, you could use a large tote or tub place under the 4 tier to collect the water. You can either towel it out every-other day, or install a small drain and drain pan to collect the water. Not a perfect solution, but you’ll just have to find a way that works for you. Hope that helps!


    2. Run the tubes into anywhere from 1 to 3 empty juice bottles . I run a tube from humidifier into bottle about a half inch.(laying on its side, cap on ) and run another tube out to the greenhouse. Mist condenses inside bottle and catches lots of the excess water. you can even run into and out of extra plastic bottles as required. just empty the condensate out every day or so. I melted holes into bottle for lines to enter with an appropiately sized socket i heated.

  2. Hey, I had a greenhouse grower + humidifier + hygrometer, but my mycelium kept getting beat out by some green fungus that took over the environment before it was able to.

    How do I create a more sterilized chamber/place to inject mycelium into the jars??

    1. Post

      I am thinking that the problem might be not with the fruiting chamber, but in the creation of the blocks. Once the mycelium has fully taken over the substrate, it should be pretty resistant to contamination. You may need to re-evaluate the way you make your fruiting blocks to make sure there are no opportunities for contamination to get a foot hold before you start fruiting. As for the chamber, you can try spraying the walls down with a light bleach solution every few days (5% or less) and making sure you put fresh water in your humidifier every couple days. Hope that helps!

  3. Hey, do you have more info on your new fruiting chamber build with the disc pond fogger, 5 gallon pail, fan, and piping it into your 4 tier grow chamber ?

    Big thanks in advance !

    1. Post

      Not yet, but I will put something up shortly. Feel free to get creative though! I basically just piped PVC into the fruiting chamber, and ran the line through a 5 gallon pail with a fan on a timer. Ill do a write up on it soon!

  4. hi tony,
    i’m planning to build a greenhouse for white oyster mushroom. what is the recommended temperature, humidity and carbon dioxide for such type mushroom?
    can i utilize defective refrigerator for my greenhouse by installing exhaust fan, humidifier device and sensors.? thanks.

    1. Post

      Hi James! Feel free to experiment, because ideal conditions will depend on the strain… but in general, 18-20 degC, and >85% humidity will be ideal for growing many types of Oysters. You could definitely try to build something out of an old refrigerator, but you can easily do with a less complicated set-up. All the best!

  5. Thank you so much for all of this! I’m struggling with the exhaust fan issue- I understand I need exhaust piping but what can you do with the air leaving the chamber short of making a hole in your house and pumping it outdoors? Not sure what to do about spores leaving the chamber?!?!?

    1. Post

      Hey Jewlell!

      For the exhaust, as long as you don’t have a ton of humidity exiting all the time, it shouldn’t be much of a problem, since the volume of your house is much larger than the volume of the grow chamber. For larger grow areas, pumping it outside is advisable. As for the spores, I have never found this to be much of an issue. Best practice is to harvest the mushrooms before they drop too many spores. You could also consider filtering the air leaving the grow chamber, although the grow chamber would have to be otherwise airtight for this to be effective.

      Hope that helps!


  6. Hi Tony,
    I am running a small farm for oyster mushroom. the problem is the lighting. how much light can be allowed inside the room. if the room is completely sealed, what category of lighting will be preferable.
    Thanks in advance.

    1. Post

      Hi Marshal,

      Light is important, but not for the same reasons as plants, so it is not usually a huge concern. Best practice is to use florescent lights. I used 2 ballasts each with two 4 ft bulbs for a 4 ft x 8 ft grow chamber, and it worked out pretty good.

      Hope that helps!

  7. Contaminated blocks? That’s from not sterile enough substrate, pre-inoculation, or not having a sterile inoculation environment…if you think your substrate block is not the problem, the look at your inoculation…can you build a still air box? If so you can build ridiculously cheap, one time use, or a damn good one like mine out of a tote, some flanges, elbow leanth rubber gloves, window/door weather strip tape, and 91% alcohol…I’ve lost 3 jars in 54…that’s pretty good…I’d say that was more likely inoculation contam not substrate, since they were 3 different batches…

  8. Also, another option is to build yourself a flow Hood…you can make them as simple as you want but you’ll sacrifice quality control, or you can go elaborate like I did (plans for the future) and large and it’s working great…36 blocks in 3 batches…only 3 blocks lost…all from our first batch…

  9. Out of curiosity, what containers are you using to create your mushroom logs. They don’t look like the standard 5 gallon bucket.. Also, thanks for providing this info – very helpful indeed. I recently purchased the teardrop humidifier and greenhouse tent to finish the fruiting chamber which is currently controlled via an Arduino. Put up white plastic on most of the outside walls to help refract more light. My next task is to place waterproof LED lights inside the tent so that most everything is encased in the “mycohouse”. Cheers!

    1. Post

      Hey Marsh!

      Looks like you have a great set-up going there! For the mushroom logs, I use poly tubing, 14″ inch lay flat diameter. But ya, the buckets are just standard 5 gallon Home Depot buckets.

  10. Hello Tony,
    I want to set up a greenhouse to start my experience with mushroom growing.
    I’ve seen that some producers have two different chambers for the two different phases of the fungus life.
    Should I create two different environments, if possible?
    One for the growth of the mycelium: humid, “high” temperature and dark;
    And another one for the fruiting phase: fresh aired, decrease temperature and a little light?
    Thank you!

    1. Post

      Hey Marta!

      It really depends, you don’t necessarily need a separate room for incubation, but it will definitely help make the process more efficient and streamlined. For oysters though, typically you can just place them straight in the grow room for both processes. They do not need to be in the dark, and high temperature can often end up causing contamination rather than faster growth.

      Happy growing!

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