Greenhouse Construction help

PM your email address to me & I'll send you everything I've got.

 

Oh. Duh. I wish the software sent a warning.

 

If you go to 'Growing Area', 3rd page and about half way down, I have a post and photo's of my grow area and what's in it. It works fine for me.

 

My greenhouse is 9x12 - a trimmed-down version of the 9x14 Juliana premium (I trimmed it to fit the site). The foundation is a kneewall of concrete block and a floor of concrete sloped to a floor drain. A photo of the foundation & floor:
.


This greenhouse uses a Microgrow Growmate controller (really just a temp sensor & low voltage directional device) that signals a custom-designed motor control center that drives the powered equipment. You need both a logic controller with sensors (the Growmate) and an MCC with relays, contactors, etc. unless you have a unit that does both - most don't. Don't be fooled into thinking off-the-shelf greenhouse logic controllers will drive the equipment - you need the MCC also (at extra cost, of course). I designed the MCC and had it built by some friends in the industry but most logic controller companies (Microgrow, for example) will build you one as well. Photos - Growmate on the right & MCC on the left; second photo is the guts of the MCC:
.


I use exhaust fans & intake shutters instead of passive vents. I went this route so I could precisely and reliably control the climate with the computer - when I chose to - instead of relying on vents that opened and closed whenever the wax inside dictated. Also ... shade cloth and vents don't work and play well together. A couple of photos of the exhaust fans and motorized intake shutters that the computer operates in sync:
.

 

Cooling (beyond the exhaust fans, which is cooling stage 1), is done via a wetwall that's adapted from a commercial system. It uses a PVC pump basin that fills through a float valve connected to a municipal service line, a small submersible centrifugal circulating pump, and 4" thick pads. The wet wall system kicks in as cooling stages 2 and 3 (one exhaust fan vs. two). Our temps peak at 110-112F and this system has never let the internal GH temp exceed 88F. Couple of shots:
.

.


For humidity I tried (disastrously) overhead misters, against all recommendations. I learned from my mistake and later installed under-bench misters that, though not perfect, are a great deal better than the overhead units. The overhead system kept everything wet which, or course, didn't work for very long. The misters I use are low pressure - 100-110 psi - 0.012" units. I wasn't willing to spend the money for a high pressure system, which I'm sure would work better, and I'm reasonably happy for the time being. My five year plan includes a high pressure system that creates more of a fog than a spray. Everything is driven by a Greenair THC-1 humdistat that I hot-wired to operate a solenoid valve. Works quite well.

For water quality I consider myself lucky - I have high quality municipal water readily available. It's chlorinated, of course, as all municipal supplies are, so all I do is run it through a carbon block filter to kill the chlorine. I pass muni water through the filter and then into a basin through a float valve to moderate the temperature, and then I draw from the bottom of the basin with a commercial diaphragm pump with an internal pressure switch to pressurize a watering wand. The system works extremely well, is reliable, and I recommend it to anyone with good quality municipal water that doesn't need treatment. This photo shows the basin on the left, the pump, the carbon block filter, etc.
.


For air circulation I use the smallest HAF fans I could find - 8" Shaefer units. They are more than adequate. I have them mounted in opposing corners of the GH so as to produce a circular pattern of air movement. I often think I could use other fans to create better vertical mixing but I haven't gone there yet. It's on the list.

For heat I chose electric resistance heating because it was easy and cheap in the short term, not because it was the best long-term choice. I have access to natural gas but I needed heat now and didn't have the time to extend gas piping to the GH. I'll do it eventually but for now I'm in operation. The heater is a Dayton 5000W resistant unit that's controlled by the environmental control system (the logic unit's thermocouple). It's not the cheapest choice but it gets the job done, is very reliable, and acts as a suitable placeholder until I have the energy to deal with the gas piping.

 

What a fantastic post, T. migratoris! I appreciate your sharing this thorough documentation of your greenhouse. That control panel is impressive; so many breakers!

Was the permit process drawn-out and complicated?

 

A tall greenhouse is very good because the heat is allowed to rise to a higher level above the plants below, so your kneewall sounds great. The main challenge with humidification is pumping water into the air without wetting the plants. Mist and fog produced by misters, hydrofoggers and the like will condense on plants if there isn't enough of a buffer zone between the water output and the plants. Good air circulation is of course very important, but these same fans can if not situated ideally, pull and push water droplets in a way that cause them to condense on plants, causing grave problems on angraecoids.

I have three different growing spaces, two are outdoor greenhouse and I use Hydrofoggers to humidify both. I have had to filter out the largest droplets using multi-layer barrier off fibreglass window screen material. They are activated by hydrostats. I agree with T. migratoris that it is better to use a cooling system based on a wet wall on one end and exhaust fans on the other; it is the most effective and most efficient and gives you the greatest control both over over-heating and retaining humidity. While it's true that the new air brought in through the wet wall will pick up some humidity, in California at least this air input isn't usually much higher than 60% r/h. Angraecoids of course need 70% to do respectively, 80% is ideal, so you'll need to supplement additional humidity either by misters or other devices.

High pressure misters are the best, but they are pricey and the air-compressors that run them are loud! Misters beneath benches are probably the most popular method of adding humidity, but fans or even gentle air uplift can cause the spray from these to drift up to the benches, so do watch out for this problem.

Unfortunately the reality in California is that using fossil fuels is still significantly cheaper for heating than is so with electricity. I recommend buying a vented A-1 heater from Southern Burner Co. You should get a copy of the manual before you finish designing or constructing the greenhouse, as there are specifications that you will need to plan for (e.g. roof height, venting pipes etc.) ahead of time. You are lucky in southern California to have sunny days even in winter that will help you achieve decent diurnal temperature variation; up here I use a 2- stage thermostat to ensure I get warmer days during the cool, foggy, cloudy rainy days of winter and spring here in the SF Bay.

 

WOW!

 

Wow! Amazing greenhouse one day I will hope to have something similar fantastic, great job!! <3 your plants will be very happy in their new home

 

Great info in this thread!

Ang- How do you like the aluminet? How much do you think it dropped the temps in the gh vs. just having standard shade cloth.

 

Wowwwww that GH looks spectacular!