Northern Greenhouse on a Budget 2012

[krazay]

I have done a fair amount of research into building a 20x60ft greenhouse this year but as a primarily indoor med grower, have some unanswered questions from lack of greenhouse experience.

I plan to build this greenhouse out of rebar, pvc, and wood.

I think it would be easiest to back a truck in and dump out a few yards of peat/perlite and feed with a general hydroponics feeding program. Rather than pots, is there a difference vs dumping soil on the floor than using these 100gal pots i keep seeing?

This greenhouse would be used for the summer season from june-september in a location where average lows get to 40f and record lows are 25f in the summer and average highs are 70f record highs are 90f

I plan to buy a kit like this

http://www.growerssupply.com/farm/supplies/prod1;gs_greenhouse_kits-gs_greenhouse_equipment_kits;pg104813kit.html

the heater is 120,000 btu and should be able to give a temperate rise of 20f during any cold summer nights that dip below 65f

the ventilation fan should be able to exchange greenhouse air at 1 time per minute when temperatures rise about 80f also it should be able to control humidity, there is no need for a dehu in a greenhouse correct?

louvres will be places at the opposite side and thermostats in the center.

Plant spacing would be something like a 1 to 4 ratio of whats seen in this picture

The greenhouse kit is 1700, poly pvc rebar and wood I plan for 1000, food and soil another 1000. I budget 4k for the greenhouse plus another 1-2k for addes misc expenses like gas and kids.

I do not plan to have roll up sides or roof vents, just a ventilation fan and heating system. Will this be enough to control humidity and temperature? I am not pouring a concrete pad or using humongous pots but will look for sandy soil with good drainage or use alot of perlite to compensate for drainage will this work just as well or am I asking for disaster?

I plan to run a cable and pipe to the greenhouse to supply power and water.
Plants will be fed out of a res barrel with a sump and water wand once or twice a week as needed.

Is this overkill can I get away without a heater and ventilation fan or is this underkill am I cutting corners and do I need a better foundation for drainage or huge pots?

Any input would greatly benefit me as well I'm sure as anyone in the ICmag community looking to build a large greenhouse in northern climate.

 

[kmk420kali]

Looks good to me!!
In my experience, the biggest problem you will have with that, will be humidity--
If you have the means, I would have one side be passive vent, and the other I would put a large, slow moving large blade fan for exhaustion--
Drag fresh air in across the plants, and exhaust it...you will be dealing with a lot of humidity with all that damp soil--
Other than that...you look golden!!
Oh, and as short as that first pic looks...you need to keep on top of topping-- lol

 

[Sinkyone]

No vents is asking for trouble. There is absolutely no way a single ventilation fan could handle a greenhouse that large. You need a lot of air movement and ventilation in a greenhouse or your temps and humidity will get too high. IMO something as large as you are talking should have several exhaust fans, vents, several fans inside the greenhouse to move the air along, and probably roll up sides as well. Not sure what climate you are in, but doing a GH with no vents and minimal fans is a death wish for your plants where I am at - it just gets too hot in the summer.

Also I would recommend better drainage as well. You need to get your run off out of the GH or you will have endless humidity problems. Just relying on the soil to drain it all away will likely cause problems. You don't need a real foundation, but you do need SOMETHING. This could be as simple as laying down a thick layer of gravel at a slope to ensure the water drains away from the GH, it doesn't have to be complicated or expensive.

 

[kmk420kali]

No vents is asking for trouble. There is absolutely no way a single ventilation fan could handle a greenhouse that large. You need a lot of air movement and ventilation in a greenhouse or your temps and humidity will get too high. IMO something as large as you are talking should have several exhaust fans, vents, several fans inside the greenhouse to move the air along, and probably roll up sides as well. Not sure what climate you are in, but doing a GH with no vents and minimal fans is a death wish for your plants where I am at - it just gets too hot in the summer.

Also I would recommend better drainage as well. You need to get your run off out of the GH or you will have endless humidity problems. Just relying on the soil to drain it all away will likely cause problems. You don't need a real foundation, but you do need SOMETHING. This could be as simple as laying down a thick layer of gravel at a slope to ensure the water drains away from the GH, it doesn't have to be complicated or expensive.

His GH is the top picture, not the bottom one...at least i think-- lol
A 48 or 50 inch exhaust on one end would be fine for that--

 

[Z-ro]

the greenhouse in the first picture is an 11x20 from an online build tutorial, i have it in my bookmarks bar, i helped some friends build a similar 20x40 one last year to dep in.

unless youre so far north that you have to keep heat in during the day, or are not on site at all times, i would just run it open ended during the day, but with closable poly flaps on the ends, and just button them up at night at kick on mad dehuys then reopen again in the morning.

 

[krazay]

They are different greenhouses, just examples.

There will be fans for airflow and the exhaust fan in that kit is 36" and 12,000 cfm

@kmk that was exactly my plan the kit comes with an aluminum louvred shutter for one end and a 36" fan for the other end.

@sinkyone Kit also comes with 4 12" airflow fans. What kind of experience do you have with greenhouses? 12,000 cfm should be able to exchange air enough to keep humidty down. I'm trying to keep away from roll up sides to keep things unseen. Gravel sounds like a great idea maybe i can lay a layer of plastic down then gravel at a slope then soil?

@Z-ro the record and average night temps for the location is 25f-40f.. way too cold for our friends... I don't want temperatures to dip below 65f (in greenhouses they keep tomatoes at 62f minimum) I'm not sure buttoning up the ends would be enough to keep things warm when nights get cold.

 

[Mrs.Icetoker]

wow MAN!!! I´ve got a 12m2 greenhouse and this is just a kick in the ASS for me....thanx,man,,,,I´m gona use it a bit more now...love your work.