Anyone know the average daily values for evapotranspiration for Cannabis per sq ft?

L

logan9fingers

Well-Known Member
Now that there are commercial growers out there and people growing in areas of high humidity etc.

Anyone have a table of values or an average amount at say 26C, 60-70% RH.

Need to work out dehumidifier requirements. Being told I'm wasting my time if I cant exhaust. How do people in closed loop systems deal with high humidity? What kind of dehumidifier power you using for how many plants covering what areas?

Help please!
 
dstroy

dstroy

Well-Known Member
logan9fingers said:
Now that there are commercial growers out there and people growing in areas of high humidity etc.

Anyone have a table of values or an average amount at say 26C, 60-70% RH.

Need to work out dehumidifier requirements. Being told I'm wasting my time if I cant exhaust. How do people in closed loop systems deal with high humidity? What kind of dehumidifier power you using for how many plants covering what areas?

Help please!
Click to expand...
https://pubs.usgs.gov/wri/wri994079/text/evapotranspiration.htm

Here you go, you can adapt the equations to suit your purpose, which is smaller scale than their test area.

You can probably get more accurate than them since you’re gonna know how much water you’re putting in, the mass of the soil and it’s composition, and the average biomass for a given area. All of that stuff is difficult to estimate accurately large scale.

It’s cheaper to exhaust than it is to run a dehumidifier, which is why people aren’t going to understand why you want to use one. That’s ok.

To a point, plant count isn’t going to affect humidity, but if you start dealing with large numbers of pots that’s going to increase your exposed soil surface area which will cause humidity fluctuations after watering.

The thing that has the largest effect as I’m sure you already know is the transpiration area. So just do your calculations for the worst case scenario (a completely full area wall to wall). And you’ll never be above your dehumidifiers capacity.
 
Roger A. Shrubber

Roger A. Shrubber

Well-Known Member
there will be big fluctuations from the lights being on and off, expect a big rh spike about 45 min or so after lights out, that will last pretty much until the lights kick on again
 
L

logan9fingers

Well-Known Member
dstroy said:
https://pubs.usgs.gov/wri/wri994079/text/evapotranspiration.htm

Here you go, you can adapt the equations to suit your purpose, which is smaller scale than their test area.

You can probably get more accurate than them since you’re gonna know how much water you’re putting in, the mass of the soil and it’s composition, and the average biomass for a given area. All of that stuff is difficult to estimate accurately large scale.

It’s cheaper to exhaust than it is to run a dehumidifier, which is why people aren’t going to understand why you want to use one. That’s ok.

To a point, plant count isn’t going to affect humidity, but if you start dealing with large numbers of pots that’s going to increase your exposed soil surface area which will cause humidity fluctuations after watering.

The thing that has the largest effect as I’m sure you already know is the transpiration area. So just do your calculations for the worst case scenario (a completely full area wall to wall). And you’ll never be above your dehumidifiers capacity.
Click to expand...
Super interesting read man thanks. That's some heavy maths right there though for the calculation.

I ended up going for a 40 Litre per day domestic dehumidifier and can now keep RH of the recirculating air between 40 and 50. Its 2 rooms worth about 50m3 of air for my 4 x 4 tent.
 
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