Taking my game to a new level with VPD

[PacificNorthWest]

I am so excited I have to share this.

I thought I was good before. But I think I am taking the next step to becoming great. I hope some of you can give me some constructive criticism.

I just spent the weekend wrapping my head around Vapour Pressure Deficit and plant biology in general. I can't believe something as important as VPD wasn't at the forefront of my mind before. I'm thinking I was intimidated by the concept a few years ago when I set up my tent because I don't even remember stumbling across the term.

I blast the light in my 4x4 tent (2x 315watt CMH). I needed heavy cooling. I opted to take in fresh air from directly outside in the pacific northwest with about 500CFM. I wrote off ever being able to control humidity because of that (What's the point of a dehumidifier when you are exchanging the air so quickly right?). And it is humid here in the winter. Even still...I grew a few good harvests. REMO nutrients are great. Good genetics was even better for sure. Help from Pennywise and InTheShed was invaluable.

However, after discovering VPD charts, I realized that all too often...I am NOT in that sweet zone. And in order to hit that sweet spot of transpiration, I don't need to change the humidity, I can change the temperature!!!

Boom. Fast forward to me now waiting for my WIFI thermostat that I can REMOTELY change the setpoint temperature of my tent!!!

My plan is to have a 200CFM exhaust fan run at all times, and use the 500CFM fan for heat removal when the setpoint is overcome. I'm not too worried about heating the space as it's rarely too cold. Although I may discover different now that I have the ability to monitor temps at night from my cell-phone. I could easily add a heater to the passive intake wired to the thermostat.

Then I will monitor the government website for the humidity in my neighbourhood, and then remotely change the setpoint of my tent as per the VPD chart to get where I want to be.

WHOOO HOOOO!!!! WHO USES REMOTE THERMOSTATS?????

Game changer or no???

 

[HydroponicFireman]

Sounds like you are dialing in your setup, let us know how it goes!

 

[PE636]

Sounds plausible though the quick air exchange rate makes it tricky in my experience. I'm assuming your RH is usually lower than ideal according to the VPD chart? I'm sure you've read all up on this but remember this is Relative Humidity. That is to say, relative to the maximum the air can hold at the given temperature. If you heat air that's say 20 degrees and 50 percent RH outdoors, the RH will drop. Conversely, cooling air that is at 50 percent RH will increase the RH. The air in your house is likely lower RH than the outdoors to begin with. Keep an eye on the dewpoint (temp the air would become saturated at) if your gov't site lists it as it may provide some insights on your ability to control it. I wouldn't expect to have a great deal of control but maybe a little. The thing is you're controlling the temperature by replacing the air so it's an ongoing battle. Be interested to see how it goes for sure!

 

[PacificNorthWest]

Summertime RH is slightly lower than the ideal. Wintertime is the opposite. But I see where you are coming from. I am just so excited to have learned about VPD.

After a few days of thinking about the changes I am about to make...I see it as less "dialing in my setup" as opposed to just eliminating the major swings. I never thought I'd be the guy with a wifi thermostat. But here I am.

Thanks for the input. I'll update this post in a week or two.

 

[bobrown14]

For VPD all you gotta do is be "in the ball park"

You need air exchange and filtering yes but remember 1 very important factor = the plant.

The plant has the ability to create a micro-climate at the leaf surface and its one reason you see the plants leaves move about and you never understood why they just dont all point to the light. The VPD is the reason.

Just get it in the zone or close don't have to be perfect.

I've grown beautiful plants in high heat, cold and dry, cold and wet and hot and humid. The hot and dry is the toughest - we had a drought this summer.

Genetics come into play as well. Think about where the plants originally were grown and the climate.

Not only should we have good air exchange but we also need good air flow thru the plants at all times 24/7. I run several fans along with extraction.

Try monitoring your grow space with a thermometer and a humidistat put it slightly above the canopy in the room/tent. My flower room has its own climate. Plants transpire quite a bit too so watering comes into play big time. Dont water enough the plants will suffer even tho conditions are perfect.

For me, watering proper is the key the plants can regulate the rest again if the environment is within reason. We have a pretty decent size window at certain temps and comfortable hoo-man temps are perfect for plants.

 

[Koolbudz]

I went sealed instead of full time air exchange, my room leaks take care of air exchange LOL