How to Handle Temperature & Humidity the Right Way

One of the linchpins of mushroom cultivation is getting the growing conditions right. To achieve that you have to think about

1) in which climate zone you are in,

2) what mushroom do you want to cultivate, and

3) how do you want to grow them.

All three aspects will determine the design of your farm in general and especially your fruiting room.

Let’s start with the climate zones first.

Climate Zones

Each region can be described according to the temperature and humidity. Figure 1 gives us an overview of Europe. As you can see, Europe is divided into several zones. While for example, Spain and Italy (red) are in zone 1&2 (hot and dry climate), Germany, France, and the UK (green) are in zone 4 (temperate climate).

Figure 1: NZEB climate zones combined with EHI and ECI

Figure 1: NZEB climate zones combined with EHI and ECI[1]

For North America (figure 2), we will find a total of 11 zones. Each region in this figure is described by the average minimum temperature.

Figure 2: Climate zones North America

Figure 2: Climate zones North America[2]

Mushroom species

If you know your climate zone, then you can think about a specific mushroom species (figure 3). To pick your best mushroom species you can use the mushroom value rating, which I described more in detail in my article What is the best mushroom strain?

Figure 3: Overview of growing conditions

Figure 3: Overview of growing conditions[3]

An overview of 26 Delicious Mushroom Species You Should Cultivate can be found if you follow the link to my article.

How important the humidity is can be seen in the following video. In it I talk about a research project in which the author investigated the influence of the water frequency on the growth of Pleurotus ostreatus.

Cultivation technique

After you have picked the mushroom of your choice, it is time to think about the design of your grow room. If you are living, for example, in a climate zone where the temperature is more stable than you can think about growing your mushrooms in a simple tent (figure 4) or shed (figure 5).

The advantage of these two versions is their low upfront costs. But on the other side, you are more dependent on the environment and have therefore less control over the growing conditions.

For example, a fluctuation of the weather will directly impact the growth of your mushrooms and therefore your yield. Besides, you prone to a higher contamination risk because contaminated air can easily go inside the tent.  

Figure 4: Mushroom house made of plastic (no insulation)

Figure 4: Mushroom house made of plastic (no insulation)

Figure 5: Oyster mushroom houses made of grasses

Figure 5: Oyster mushroom houses made of grasses[4]

If you want to have more control over your growing conditions and if you want to maximize your yield, than you should think about going inside (figure 6). This means that your fruiting room will be hermetically enclosure from the environment.

While you get control over the growing conditions, you are confronted with a higher upfront cost.

Figure 6: Mushroom houses (insulated)

Figure 6: Mushroom houses (insulated)

The next point on our list, how do you want to grow them. Here we have to talk about manually vs. automated. The advantage of manual production is the lower starting costs. But with this advantage, you are paying later a higher price.

1) Your business depends on you.

2) If you’re doing everything yourself you can’t focus on the things, you’re good at and which are bringing you the money. Moisturizing the mushroom isn’t on that list.

3) If you hire someone to do the work for you then you just increase your running costs anyway.

4) By doing many things manually you have less control over the results.

You have, therefore to think about what things should I now automate, and what things can I right now automate to improve my business? One of the things you should automate is your grow room.

Moisturizing and temperature control are one of the critical parts of your business. If you want consistency in your production than the automation of these two parameters is mandatory.

The first step towards automation is measuring. You need sensors that are telling you the current growing conditions. A relatively simple one would be a hygrothermograph (figure 9). This sensor measures and logs the temperature and humidity over a specified period.

Figure 9: Hygrothermograph[5]

If you want to prefer a more “advanced” version than a set of sensors is the way to go (figure 10).

Figure 10: Thermo-Hygrometer[6] 

Now that you’re monitoring and logging the growing conditions, you need to adjust if needed the conditions. You, therefore, need a controller like the one in figure 11. This humidity controller will activate and deactivate the humidifier (figure 12) accordingly to the set-points.

Figure 11: Humidity Controller[7]

Figure 12: Aquafog Turbo XE

Figure 12: Aquafog Turbo XE[8]

Now that we have control over the humidity, we need more control over the temperature inside our grow room. To achieve that you need an air conditioner (figure 13). The size or to be more correct the capacity of the air conditioner (in BTU) depends on the temperature range of your climate zone and the size of your grow room.

Figure 13: Mini Split Air Conditioner[9]

But we not only want to control the temperature and humidity of the air we also want to have better control over the air quality. Therefore, the installation of a filter (figure 14) is recommended.

Figure 14: HEPA Filter[10]

We are almost done. Depending on the size of your fruiting room, it makes sense that you put in a second ventilator (figure 15), which will circulate the air inside the fruiting chamber.

Figure 15: Floor Wall Fan[11]

If we put everything together, we just talked about, we will get something like figure 16. This figure describes the path of the air from the intake (A), through the conditioning (1-3) to the exhaust (C).

In this example, the first step is adjusting the air temperature accordingly to the requirements. In the second step, this air is now filtered through a HEPA filter, and finally in the third step moisturized.

Depending on the amount of water you need to reach the necessary humidity, the temperature of the air will decrease. You have, therefore, to adjust the setpoint of the air conditioner accordingly. Which means the air temperature after the air conditioner has to be higher.

Figure 16: Air conditioning – 1: Split Air conditioner, 2: HEPA Filter Air conditioner, 3: Aquafog, A: Air intake, B: Conditioned Air, C: Exhaust[

Figure 16: Air conditioning – 1: Split Air conditioner, 2: HEPA Filter Air conditioner, 3: Aquafog, A: Air intake, B: Conditioned Air, C: Exhaust[12]

If you condition the air the way I just described, you will maybe be confronted with hot and cold as well as dry and wet zones inside the fruiting room (figure 17 and figure 18: red areas). These zones depend on several factors. Which I will describe below.

  1. Size of the fruiting room.
  2. Location of the temperature and humidity sensors.
  3. Position of the air intake system.
  4. Spray angle of the Aquafog system.
  5. Power of the Aquafog system.
  6. Position of the first shelves.

The larger your fruiting room, the more likely you will run into these kinds of problems. Therefore, it would be a good idea to reduce the size accordingly. As an alternative, you can install additional ventilator(s) (figure 15) which will circulate the air.

If you measure for example the humidity only in the first half of the room than it could be possible that the mushrooms on the last shelves don’t get that much humidity and the mushrooms to the first shelves too much.

The same goes for the temperature. If you are using an air conditioner (figure 13), the temperature probe will usually be located next to it. A better location would be more in the middle of the room.

As seen in figure 18, the vertical position of the air intake system is critical because it will impact how far the conditioned air will be sprayed into the room. If the air intake is positioned too low, then you’re risking that the last shelves don’t get enough humidity.

Depending on the spray angle of the Aquafog system (figure 12), the first shelve may not get enough humidity. It is, therefore, crucial to position them accordingly, or you use additional ventilator(s) (figure 15).

Not only the spray angle of the Aquafog system will impact your mushrooms but also the power of the system itself. The more power the system has, the farther, the conditioned air will be pushed into the room. Again, adjusting the airflow through the installation of additional ventilators (figure 15) can compensate for that to some extent.

And as already mentioned the position of your shelves will impact the airflow throughout the grow room.

Figure 17: Location of potential dry zones (red); A: air intake, B: conditioned air, C: exhaust, 1: air conditioning system; top view

Figure 17: Location of potential dry zones (red); A: air intake, B: conditioned air, C: exhaust, 1: air conditioning system; top view[13]

Figure 18: Location of potential dry zones (red); A: air intake, B: conditioned air, C: exhaust, 1: air conditioning system; side view

Figure 18: Location of potential dry zones (red); A: air intake, B: conditioned air, C: exhaust, 1: air conditioning system; side view[14]

If you don’t place a ventilator in position (C) the air inside the grow room will be then passively exchanged, because of the overpressure. This higher pressure also prevents contamination can enter your grow room.

With that said, the points discussed in this article will help you to get better control over the temperature and humidity inside your grow room.


[1] Pvsites 2016

[2] Source

[3] Own figure based on Paul Stamets (1993) Growing Gourmet and Medicinal Mushrooms

[4] Mushroom Growers Handbook Volume 1

[5] Oakton WD-37250-00

[6] Ambient Weather WS-3000-X5 Wireless

[7] IHC200 Inkbird Humidistat

[8] Source

[9] Senville SENL-12CD, 12000 BTU (1000 BTU/h ~ 293Wh)

[10] Novatek F4030 HEPA Filter Novair

[11] Lasko 20“ High Velocity QuickMount

[12] Own figure

[13] Own figure

[14] Own figure

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