Greenhouse engineering tradeoffs.

14 years ago

Looking to build a greenhouse. Most likely double poly gothic hoop house.

I live in a northern climate (central Alberta) and would like to use the green house for starting bedding plants, forcing lilies, forcing shrubs during spring, growing tomatoes, peppers eggplant during the summer (we don't get enough hot days to ripen a tomato outside most years) and extend the growing season into the fall.

I'd like it to be efficient to heat in spring, but ventilate without fans in the summer.

There's a whole bunch of design differences -- roof vents vs. roll up side vents. etc etc.

Anyone point me to a good info source for the various tradeoffs?

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Comments (4)

eaglesgarden
14 years ago
Size would be a huge determining factor for this, I would think. What size are you considering?
Sherwood Botsford (z3, Alberta)
Original Author
14 years ago
That partly depends on what I can scrounge. 1000-2000 square feet. I've got a possible line on a 30x50 frame.

After reading up, I'm trying to run a high tunnel in two modes: Heating mode -- where the tunnel is keeping plants from actually freezing, and Summer mode, wehre it's just trying to keep things 10 degrees warmer than outside.

I've concluded that my best compromise are inflatable roll up sides. That is, the rollers have a latch so you can fasten them down for the heating season.

Add to that:

* Raise the frame an extra few feet by putting in taller foundation posts. This creates a larger stack effect.

* Put both high and low openings in the end walls for controllabe ventilation.

* Insulate the margin of the greenhouseduring the heating season with a row of straw bales. (This may be the way to hold the rollers down.
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calliope
14 years ago
I have one g'house with roll up sides. I have a heater in it, but don't use it for heated crops unless I am overflowing the regular houses and in a pinch. You usually don't inflate the part you roll up, just the main. Obviously you'd have to let out the inflation on the side to roll them. LOL. Don't even think about those inflatable sided jobs because in a power failure, they collapse exposing your crops when you least want them to.

Roof vents are the bee's knees if you want natural ventilation. When I installed my houses, they weren't available. A grower up the road has them in one of his houses and they work well.
poppa
14 years ago
I'm just a hacker at this greenhouse stuff and i have yet to go through a summer with my new GH (22x50) but what i did was open the gable ends of the GH 1/3 of the way from the peak down.I am told heat rises so i figured the best place to ventilate is at the roof peak. Works well so far. had One day break 90F and i was able to work in there if i left the doors open (I only have doors at one end).

I have not heated it yet and was surprised that cold weather crops planted in the fall survived (outside temps were down to 0F) and grew all season albeit slowly. My peas are now flowering and about 4 feel tall (planted in november). Picked my first raddish today and lettuce mix last week.

My gh is built along the solaroof design with a 30" dead air space - double walled GH, though i have yet to build the insulation bubble machinery yet.

Zone 5/massachusetts

Still playing!

Poppa