Planning a 15ft x 24ft greenhouse - need help+advice!

Discussion in 'Greenhouses' started by walterego, Nov 20, 2011.

  1. Hey guys,
    So i am planning a greenhouse grow next year. I have experience indoors, but this will be my first time growing in a greenhouse. Have some questions and concerns, hoping some peeps can shed some light.

    I'm looking to create a 15ft x 24ft greenhouse with glass or polycarbonate walls.

    #1 - Construction. I see companies online such as Santa Barbara Greenhouse Co selling kits of all sizes. But they are pricey. For the 15ft x 24ft size it's $12-$16K (!!), depending on whether you want the panels pre-assembled. I think i could save a lot of money by buying the raw materials and designing it myself. And that also allows more flexibility on size etc. The kits I've seen have pretty low ceilings. But not sure what materials to use exactly, wood and glass or wood and polycarbonate ideally (no plastic film or tarps etc). But also want it to be air tight and bug / pest tight etc. Basically: I have no ideal WTF i am doing re: building a greenhouse! I am handy with tools etc., but just want to create a solid, functional, secure (as can be) structure vs a shanty. Are there plans online? I see sites that want to charge for them, but that seems like bullshit. What's the best source for polycarbonate panels? Tap Plastics? What about framing them? Or is glass better?

    #2 - Growing in ground vs. pots. I have seem some people recommend growing directly in the ground vs. in pots. My soil is not good here at all though, so that would mean some digging etc. But i have a jackhammer! LOL But are the advantages definitely worth it? Obviously in containers allows more flexibility with moving plants, etc., and worst case they could be moved if there was a problem. But seems the ground allows a lot more root growth, and in happier, bigger plants in the end. I had thought about laying a concrete slab as a floor for the greenhouse, but it seems that leaving natural dirt floor would be better here?

    #3 - Ventilation / odor. I plan on running big inline fans and having constant air circulation. But am concerned about odor come that time of the grow. I will be using carbon filters, and ideally the greenhouse would be relatively airtight. Is this enough for odor control? I live in a small town in a small neighborhood… but there technically are neighbors (I do live in a medical state). I think getting ripped off is a bigger concern, but ideally i would just like no one smelling a thing if that's possible. No troubles or problems! That's what i need :)

    #4 - Pests, molds etc. Are there extra precautions that have to be taking when growing in a greenhouse? Seems like bugs and mold etc would be more of a problem? Any advise here? Read about spraying neem oil every 2 weeks until thc starts to form?

    #5 - Making walls opaque / privacy. I have read about this stuff you can paint on glass to make it milky and opaque (white/gray and cannot see thru). But not sure about light transmission. What's the best way to let light in while keeping privacy?

    And any other advise for an aspiring greenhouse newbie? :)

  2. Unless you will have a good heating system in your greenhouse, you'll really need to keep an eye out for mold on your plants when it starts getting cold outside. Towards the end of the season, try to keep your greenhouse warm inside and keep the air circulating. In the summer you will not likely be needing a heat source but good air circulation is still a must.
    Here's a helpful link on vapor pressure deficit and how to use it in preventing mold friendly conditions in the greenhouse. The chart is especially helpful in my opinion because relative humidity and temperature can easily be monitored. Using this data, the VPD can be determined and adjustments can be made if it is too low (turn on the heater and fans). It is suggested that a VPD value lower than .06 is favorable for fungus and at .03 fungus and disease can be very damaging.

    Hope that helps.
  3. i REALLY want to throw this computer out the FUCKING window right now, because i just typed up like 4 in depth paragraphs and i recieved an error when i hit quick reply. grrrr........ill re-type it.

    you should really consider polyethylene over polycarbonate. it is way more economical, because you have to consider everything else you have to buy. HAF fans, poly tubes, a heater (a natural gas heater would be the cheapest to run), a foundation, ect. unless you plan on investing $30k, i wouldnt go with polycarbonate right of the bat. if you do, dyna glas is a good company, but it is not double layer. like i said, you should look into a double layer polyethylene house. they are cheap and REALLY easy to set up. glass has the highest transparency rate, than polycarbonate, than polyethylene. polycarbonate needs to be replaced every 8 years or so i believe, due to UV radiation. polyethylene is every 6.

    dont forget to install all intake fans on the windward side of the house.

    unless you have a boiler, or some other means of steam pasturizing your bedding after every cycle, than it would be best to go with pots.

    you are right about the air circulation. make sure you have a really efficient ammount of it, because molds/mildews can grow extremley easily in the house. it will also help reduce algae growth within the house.

    now about the smell, you are SOL there. even if you have carbon filters and such, at some point air will escape your greenhouse, without getting filtered. its inevitable. if a fan shuts off because it is cool enough your gonna smell it. at least you live in the country & a medical state.

    keeping the greenhouse as clean as possible (no weeds inbetween the cracks, ect.) and well ventilated is key to preventing pathogens in a greenhouse. it all depends on the temprature and RH of the house. The more the RH is around 50%, the less molds and problems you will encounter.

    you may want to think of getting a swamp cooler for the summer months.

    you can put white glazing on the walls, but glazing's purpose is to reduce light intensity during the summer months. in fact, during the winter you should probablly put some extra 400W HID lights in there. you will have little success vegging a plant in december. the extra HID lights will help contribute to yeild, as well. so, polyethylene walls are naturally opaque and it can help, but i think your SOL again trying to hide the plants.

    put alot if plants in there; in a greenhouse setting, you never know what pathogens may attack.

    i would use neem cake & my other organic methods to prevent pests/pathogens. actinovate is expensive but works great at fighting harmful fungi. the neem cake should take care of every bug except gnats. mosquito dunks will take care of gnats.

    i dont mean to offend, but how long have you been growing? not just MJ, either. If you have like 5+ years than youll be cool, but greenhouses are just alot of work :smoke:

  4. Thanks, J-dubb! :) I am saving that PDF you linked, pronto! Looks very useful. Thank you! :hello:

    And yeah i think emphasis on super air flow and circulation is critical. And I might want to get a heater for the colder months towards the end of the season. It doesn't get THAT cold here in Oct... so maybe could get by w just lots of circulation.

  5. DOHHHHH!!! I hate that shit!! Thats the worst. Thanks for retyping it! I appreciate all the input :)

    I have never heard of the polyethylene. I will check it out, thanks! Everything i have been reading just compares polycarbonate vs. glass. I have been looking a lot at these pre-fab kits, and they mainly just offer the two choices.

    Noted ;) :)

    Yeah that seems to be the general consensus. I dont want to go digging up the ground every cycle anyhow. Another grow i was reading about used 100gal smart pots in a 20ft carport greenhouse grow. Worked great! So I'll prob rock something like that.

    Yeah i am gonna be super agro about this!! Cant take any risks there. Thanks for confirming that i do indeed need to be aggro about it! Cant fuck around w mold.

    LOL, yeah... pretty much. I mean i am sure the smell will escape. Even in the tightest of greenhouese the dank smell will permeate a bit i would think. Just didnt know if the ones that advertise airtight would be nearly smellproof... or if i would still be reeking up the neighborhood.

    So would i want to use a dehumidifier at times to keep that in check?

    yeah i figured as much... i mean walls that are more opaque would be better than crystal clear! But i imagine more people would see it or smell it as they walk on the street. Which is not ideal... but prob more of a prob w rippers vs police. But who knows. I just think its better to be more stealth than not. I am planning on also building a big fence :D And its not a super busy street.

    Never heard of Actinovate, but will def check it out. And I have previously sprayed on a light mixture of neem oil. But have never used the cakes. Will check that out too. Thanks for all the great tips and info here! :)

    I have been growing regular plants my whole life. Houseplants, outdoor plants, farm plants (fruits, veggies, etc). I have grown indoors MJ before, but never outdoors and never any sort of plants in a greenhouse, MJ or otherwise. I know i'm opening myself up to a whole new world here so to speak... but that's part of the beauty of it. I am excited about the concept of a greenhouse, but I also know it will be a lot of work!

    Buy THANK YOU for all your help here! VERY MUCH appreciated! you are a wealth of knowledge and i really am grateful for the time and energy you put in (twice!) to this post :) THANKS! :D
  6. Budget for automatic shade pullers, and plan to mount lights. You can grow some fine stuff year round that way, and take a LOT of control over your photoperiods... and get more grows in under the sun.
  7. I saved it too and even printed the graph out. I just wish it was a little easier to read.
    I've gotten by without heating sources because I am usually able to harvest in early-mid october but this past season was different. Next season I'll probably throw in either a space heater or dehumidifier when it starts to get really cold.
  8. Not sure where you live. I'm south of Santa Barbara and last year I built a greenhouse out of 2x4 cedar fencing and that plastic wavy stuff from Home Depot. By wary spring I ripped off all plastic on the sides and replaced it with screening. Basically not sure where you live but if its airtight then your system for air and humidity better be awesome. I would have rather gone screen all the way do from the roof but I got dogs and kids I had to keep out. Best of Luck.
  9. Greenhouse tips...face the house north to south for hoop house..south facing for glass house...lots of air flow...lots of fans..I am trying a sulpher burner next coats every thing with a fine sulpher and raises PH and mold and PM wont they say?...i sulphered out my indoor and so far so good

  10. DAMN... yeah many peeps have mentioned humidity. I guess i better go MEGA on the fans and ventilation.

    And I live near Yosemite national park in the Sierras. About 3000ft elevation. It actually gets quite hot here in the summer. But more dry than humid.

  11. Yeah i have heard good things about the sulfur too, esp w mildew. And that's looking like its gonna be a MAJOR concern w the greenhouse. Mega airflow gonna be the key!

    The area where i plan on building it is South facing, so should get plenty of sun. Admittedly i am a bit overwhelmed by the project, as its gonna be a pretty full on structure when it's said and done. But then again... i have lots of motivation ;-)
  12. #12 OhioStateBuckeyes, Dec 6, 2011
    Last edited by a moderator: Dec 7, 2011
    ventilation really is the key to keeping your humidity levels par.

    do you guys get alot of snow there? im guessing yes lol. have a nice line of trees about 30 feet north of your greenhouse. it should help reduce the cold + wind.

    theres just alot of things to consider when choosing your plot. location is key. i live in the great lakes area. we have hot, extremley humid summers and very cold, snowy winters (with lots of lake effect snow). so i guess you can say i am accustomed to the extreme chaos weather can cause. :smoke:

    you have lots of experience, soyou should be fine with your greenhouse. as long as you take all the "what-ifs" into consideration (like winter wind, humidity, shade cloth, ect.)

    edit: check this site out

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