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Greenhouse Construction help

Discussion in 'Growing Areas' started by Ang, Apr 25, 2012.

  1. Ang

    Ang New Member

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    So with all the master orchid growers knocking about the forum, I thought I'd appeal for info/help on greenhouse setups.

    I'm planning on building in Los Angeles a 12'x16' greenhouse with twin-wall poly and a 3' kneewall since I'm pretty tall and like the extra headroom. In my area, the highest temp is around 100F and lowest is 40F. Building the actual structure isn't what I'm concerned about, but rather the environmental controls. I'm mainly interested in your opinions about what I actually need for a GH this size: exhaust fan system versus auto vents, evaporative pad coolers versus under bench misters versus humidifiers, RO systems, circulation fans, heaters, etc. I grow mostly Angs, so an intermediate GH is what I'm shooting for here.

    Your opinions are greatly appreciated!
     
  2. T. migratoris

    T. migratoris Active Member

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

    Marni Well-Known Member Staff Member Supporting Member

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    If you haven't yet checked the archives, it is worth checking. A search on titles with "greenhouse" or "construction" should come up with some info.

    For California's climate (mine is similar to yours), I think a swamp cooler, several fans, a passive (oil or parrafin filled) vent up high, a heater and shade cloth (or shading compound) are essential. Things like under bench misters, RO system can be added as needed.
     
  4. Ang

    Ang New Member

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    I tried sending you my info but your inbox is full. Let me know when you clear up some space. Thanks!
     
  5. T. migratoris

    T. migratoris Active Member

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    Oh. Duh. I wish the software sent a warning.
     
  6. John Klinger

    John Klinger Active Member Supporting Member

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    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.
     
  7. T. migratoris

    T. migratoris Active Member

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    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:
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    GH 001.jpg

    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:
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    Controls 2.jpg GH controls 004.jpg

    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:
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    GH 013.jpg Evap cooler guts.jpg
    GH 001.jpg Controls 2.jpg GH controls 004.jpg GH 013.jpg Evap cooler guts.jpg
     
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  8. T. migratoris

    T. migratoris Active Member

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    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:
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    Evap cooler 2.jpg
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    Evap cooler sump 1.jpg

    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.
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    Controls 4.jpg

    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.
    Evap cooler 2.jpg Evap cooler sump 1.jpg Controls 4.jpg
     
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  9. Uluwehi

    Uluwehi angraecoids, dendrobiums and more Supporting Member

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    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?
     
  10. Uluwehi

    Uluwehi angraecoids, dendrobiums and more Supporting Member

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    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.
     
  11. Kitty

    Kitty AKA\Debby

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    WOW!
     
  12. Ang

    Ang New Member

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    It's been a while since I've been on the forum due to going back to school, but I finally got a break to take some pics and show you all what your feedback built. I actually finished the gh in September 2012 but had to wait to set up the evap. pad cooling system till this summer. It took a lot more work than I thought, but the plants think it was worth it. GH1a.jpg
    14 x 16 SolarGro Greenhouse on knee-wall (faced with leftover stone) Sill is stained redwood. Shaded with 50% Aluminet
    GH2a.jpg
    All in all, it came out to be ~14 ft. tall from ground to eave.

    GH3a.jpg
    Found some commercial sized shutters to use with the evaporative pad. Makes a perfectly sealed gh when not running. GH4a.jpg


    GH5a.jpg











    GH6a.jpg
    Simple control setup, but it works perfectly to control humidity, heating and cooling systems.
    GH7a.jpg
    Next project is to set up a bigger and better setup for hanging plants.

    When I get more time, I hope to post some backlogged pics. Thanks again to everyone who helped build my dream greenhouse!
     

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  13. KellyW

    KellyW Orchid wonk Staff Member Supporting Member

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    Wow. That is really nice. Did you do it all yourself?
     
  14. Ang

    Ang New Member

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    I can't take all the credit. I designed it with a CAD program to get all the measurements correct. Luckily, I decided to build the gh at the same time we were doing major renovations on the house so I put the electrician and plumber on the gh for a day to do their thing. Knowing that everything is wired, piped, and hooked up correctly is a nice peace of mind. The heater was hooked up to gas and vented by our HVAC guy too. I did do all the digging, drainage, foundation work, and woodwork, but got help to finish the knee wall in two days. I purchased the evap-pad system and installed that myself. Overall, I got a lot of help building the thing but always had my hand in the mix.
     
  15. Marni

    Marni Well-Known Member Staff Member Supporting Member

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    Congratulations! A job well done. And thanks for giving us the update. I hope you will let us see how your plants are responding.
     
  16. LJeziorska

    LJeziorska New Member

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    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 :)
     
  17. keithrs

    keithrs Member

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    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.
     
  18. juanriog

    juanriog Barcelona, Spain. Inter GH.

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    Wowwwww that GH looks spectacular!