Diy steel hoop house.

[redlaser]

A possible option for cooling would be incorporating an evaporative cooler into the incoming air.
I have one that covers slightly more than 3/4 the width of the end of the greenhouse. It’s good for 10-15 degrees of a decrease in temps.

There is a guy on IG who uses Home Depot/lowes wall mount evap coolers on a 2,400-3,000 sq ft greenhouse. He uses four that are 3’x4’ in size, one would easily do your greenhouse. Jayplantspeaker is his IG name.

Thought it was a little on the hoopty side at first, but it’s really all that is needed.

At least you have a few weeks to get your night time humidity issues in check. A combination of heating and burping or one or the other will get it under control.

 

[Zeez]

The ambient humidity is too high for evaporative cooling.

The easiest fix looks to be having ducts on the fans taking the warmest air from the ceiling out.

Edit;

Heating and burping? So you heat the air to soak up the humidity and then vent it out?

Here's the beginning of the first duct prototype.
It looks kind of weird, but I can compare the temperature recordings in a few days to see how well it works.

 

[Zeez]

 

[redlaser]

They look healthy Zeez, looks like you might have pulled a few out for more room.

That ducting probably helps with heat , are there any vents on the opposite side of the exhaust fans?

If it’s sealable tight enough to heat that would solve most of your night humidity issues, if not could run exhaust fan all night, would still get humid but not as humid, and moving air would cut down and possibly prevent a botrytis or similar outbreak too bad.
Still would likely get a little at least in less air movement areas like corners.

The burping could be be used with or without a heated situation, depends how humid it’s getting. It adequate heat was there, it shouldn’t be needed, because humidity will be low enough. Just keep air moving inside with fans anyway.

If it’s borderline it could help to exhaust a few minutes, reheat and repeat. It seems wasteful but it’s worth it if it puts a dent in humidity.
If the building is not able to be easily heated, I would just run exhaust all night to keep air moving , and that will cut humidity in the 10-14% range.

I don’t have double poly on my building, so it’s not easily heated, and have just run straight exhaust all night. Have attempted to heat it as well, adding 10-12 degrees difference. Not in same year. Actually had pretty similar results, and the straight exhaust year was ran an extra month into the fall with lights for an extra veg. month.
I know you have high humidity, mine is 20% during the day but 80-90% at night.

 

[Zeez]

A couple of males got pulled along with a few I was babysitting / rehabbing for someone who messed them up. Gave some away too.

The sides are screened up to about 6 feet so there is plenty of air coming in. The duct works pretty good pulling out hot air of the closed 2.5 foot roof peak above the screened lower. There is a hurricane fan in there too keeping it moving around and breaking the stratification. Next year I will add an upper roll up going from the mid section to the peak and screen it. That way convection will move the warm air out. For now this is working pretty well with the duct. Plants are very happy.

There are allot of humid days here. there's not much to do about it except for keeping the rain out and having the plants well trimmed for ventilation. That's a good plan to run the fans through the evening temperature drop to prevent humidity spikes. There are 3 sensor push recorder/ monitors in there at different levels. The humidity spike happens early evening with the cooling and then it evens out. Thing is we're just getting into the muggy season and PM would really suck. These plants are way better off than outdoor grown.

 

[redlaser]

The non moving air is the enemy when coupled with a high dew point, so the fans will help with that.
It looks like you have screen all the way around that can be covered with plastic. That seems to help with your cooling in summer, but it will affect the efficiency of exhausting air.

I wouldn’t call it a criticism, but rather a preference to want to have an intake on opposite wall of exhaust to more thoroughly exhaust humid air.

Possibly with enough air movement from within with fans would keep that from being an issue

 

[Zeez]

The non moving air is the enemy when coupled with a high dew point, so the fans will help with that.
It looks like you have screen all the way around that can be covered with plastic. That seems to help with your cooling in summer, but it will affect the efficiency of exhausting air.

I wouldn’t call it a criticism, but rather a preference to want to have an intake on opposite wall of exhaust to more thoroughly exhaust humid air.

Possibly with enough air movement from within with fans would keep that from being an issue

It's never a criticism. The whole point is for everyone to benefit.

There is a Hurricane fan in there that oscillates with a parabolic motion. It seems to create plenty of air motion inside to the point where more fan might be too much. With the large amount of screen wall the only demperature differential is the roof area. I have never seen condensation.

Check this out. This is the concerning part. When the temp comes down in the evening the humidity (also dew point) comes up. I just changed the fan program but suspect the outside ambient air does the same. It almost has to right? Humidity can not be calibrated so it's only representative.

 

[AgentPothead]

Sorry if it's been asked already, thread is kind of long, but what is the average cost for one of these hoop houses?

 

[Zeez]

No worries AP. 12 x 18 - about $1k. It can be done cheeper. The tube is from Lowes - chain link fence top rail. Each hoop is two 10' tubes $12 each. Plastic was $70. I'll loan you the bending jig.

 

[redlaser]

It's never a criticism. The whole point is for everyone to benefit.

There is a Hurricane fan in there that oscillates with a parabolic motion. It seems to create plenty of air motion inside to the point where more fan might be too much. With the large amount of screen wall the only demperature differential is the roof area. I have never seen condensation.

Check this out. This is the concerning part. When the temp comes down in the evening the humidity (also dew point) comes up. I just changed the fan program but suspect the outside ambient air does the same. It almost has to right? Humidity can not be calibrated so it's only representative.


View Image View Image

Hopefully the hurricane fan will be enough to prevent condensation, it likely will be needed to get maximum benefit from the greenhouse covering.
Cooler air cannot hold as much moisture, you could be at 100% humidity at 68 degrees, but be at 50% humidity same day at 95 degrees.
Getting into flowering it would be ideal to keep it no higher than mid eighties as far as humidity, because botrytis/gray mold issues will occur when 3 things are present:
92% humidity
free moisture
Plant injury’s/ dead material (dead pistils)

You could get a minor outbreak, increase air circulation and it may not spread.
Some variety’s are much more resistant, and nutrition up to that point plays a large role.

When I just run exhaust fans throughout the night there is only a couple percentage point difference in humidity, and it’s possibly just a gauge/calibration difference error.
The main benefit is the amount of air flow preventing dead air pockets and preventing any condensation buildup as much as possible.

Greenhouse seems like a solution to moisture issues, but unless you can adequately control the interior, it’s really just creating a different set of issues.

 

[Zeez]

With the sides rolled up almost half of this greenhouse is screen. Not getting into VPD, I followed the humidity levels with evening cooling comparing fans on and fans off. Maybe it's the large amount of screen area that has the humidity inside and outside even out after about an hour. In the first hour of evening cooling the humidity spike is about 10% less with the fans on. Next year the house will be 2/3 screen.

I've been thinking about a second interior fan for under the canopy. Maybe it's over kill, but like you say, condensation or standing moisture is the big problem. The plants are pretty well trimmed at the cores so moving air underneath should be effective.

Inkbird has a new temp / humidity controller. I'm told that it could trigger the fans by either temp or humidity. Still looking for clarification and setting values before purchasing but that would be sweet if it does the job. Just have to turn it off manually when it rains but the sides have to be rolled down too.

 

[redlaser]

I haven’t seen the inkbird controller that does both temp and humidity, but I like the 30$ ones that do one or the other.
The temp ones will control both heat and cooling, with 10amp max power usage.

I have a 600$ controller that does both plus co2, but find the inkbird controller is enough since I’m not adding co2 or humidity devices. Running exhaust throughout the night keeps humidity at 81%, which is not terrible with a lot of air exchange.

Is the 2/3 screen for next year more or less than what you have now?

 

[Zeez]

I guess I'm about 50% screen now and monitor temps humidity at three levels. One week into August it's all going very well. Next year with improvements it will be even better. It turns out that the Inkbird controller will not do what the amazon seller said.

Now, it's a 12' hoop with 2' sides below the hoops. The screen goes from the ground to 10 o'clock on both sides. Next year a second screen and roll up plastic will go from ten o'clock to 12 o'clock (the top). This way the heat can go up and out.

 

[CrushnYuba]

Zeez: does your screen obscure view?
Why won't the inkbird work? What do You want it to do?
I feel like mid summer, the best thing to do is run the greenhouse as open as you can. Just rock your natural climate. Adding the ridge vent will help tremendously. I wouldn't stress about humidity much. Just get your horizontal air flow bumping and the plants will love the extra humidity. Your greenhouse is very small. It should be easy to move around.
I didn't see, do you have HAF fans? Mine hang right above the canopy. HAF is more important then humidity #s.

 

[Zeez]

The screen only partially obscures the view. I think there are some that do more.

The inkbird I looked into had both temperature and humidity for $70. I wanted it to switch on the fans if either the set temperature or humidity was exceeded. Mainly the idea was to blow out the air that got water saturated with the cooling after sunset. So one outlet would be controlled by both functions. The seller said it would work and the manufacturer said no way.

https://www.amazon.com/Inkbird-Temp...ords=inkbird&qid=1565294129&s=gateway&sr=8-15

I have two 1800cfm exhaust fans for a GH with 1700cf inside. The fans wouldn't fit at the peak so I had to jury rig it with a duct. It works, but next year there will be screen and a top roll up for natural convective ridge vent cooling. There is a 40% shade cloth on top. Those really obscure the inside.

We bored holes in the ground and pounded in base pipes leaving two feet above ground for side walls. The hoops fit inside the base pipes and were bolted through. For extra security The base pipes were lag bolted to the landscape timbers for extra security in wind. It could be moved or lifted but it would be a project. The structure is rigid and strong.

The hoop spacing looks a little weird. We ran into rocks. The parallels on the end are for light dep (overlap) next year.

 

[CrushnYuba]

But do you have HAF fans? All i see is the one oscillating wall fan. That's tubulant air flow.
You need to hang small fans above your canopy so you can get a horizontal air flow loop. Hang 2 small fans going down one side of the greenhouse and 2 small fans returning air down the other side in a loop. I use 12$ Honeywell fans in my little 12' wide house.

Google "HAF greenhouse". Every university and greenhouse manufacturer recommends HAF loops. You can run 90% humidity with no rot.

Why don't you just try a 15$ sonoff th16. Like your z waves. It can run off humidity and temp. Change settings from the app.

 

[Zeez]

The HAF greenhouse is a real good idea. All new to me and good stuff. Thanks

The Sonoff looks good initially. Looking in to it. Simple If Then commands will do it.

There is a zwave switch to control the light dep motors easily. Way better than the timer relay setups.

Check this out.
https://www.amazon.com/gp/product/B01MPZEU12/ref=ox_sc_saved_title_8?smid=A1XO9WGZO0A93O&psc=1

 

[p0opstlnksal0t]

What's the largest hoop bender? I've seen 24 foot jigs I'm guessing that's as big as it goes without making my own.

I will be building a 24x40 or 50ft long and will probably go double inflated poly. Would I block too much uv if I use a frosted plastic for privacy sake on one of my double layers?

 

[CrushnYuba]

That little zwave thing will only do 2 amps so It couldn't run the motors. It could trigger a relay but really anything could. It's only on and off. It does not reverse polarity as far as i can tell do It couldn't reverse a dc motor. It being 50$ is what really turns me off. For what it can do you could use any 10$ smart switch to trigger the appropriate relay.

Sonoff makes a smart relay that is 4 channels and is din mountable so it will mount easily with your other components. It's about 25$. It can run off 24v. You can do allot with 4 channels of you want.

 

[Zeez]

You're right. The small motors are 80 watt but they're 3.8 amp.

Most all of the information I had building the greenhouse came from this thread. Appreciate it.