cooling a greenhouse

[Halfathumb]

Built a 12' X 8' greenhouse for LOML last year. having trouble keeping it cool. We live in SW Mo., the GH is a lean-to facing the west. We've installed a sunscreen on the roof and west face and a 10K BTU window AC. She grows microgreens so a mister unit can't be used (Ugh!). We have our eye on a used 24K window unit for a decent price. Any similar experiences with a possible solutions?   

Jim

[R Clark]

I'm not a greenhouse expert, but have given "half a thought" to building one at our place.  In my research, I've seen thermostat controlled vent windows at the top of the greenhouses that open and close to moderate high temps.  The ones I've seen tend to use screens and those vent windows, either automated or manually-controlled.

I wouldn't think misters are a great solution in your area anyway.  Misters rely on evaporative cooling and the effectiveness decreases as humidity rises.  I've never heard anybody from SW Missouri say, "It's a dry heat!"  

[MichaelMouse]

Built a 12' X 8' greenhouse for LOML last year. having trouble keeping it cool. We live in SW Mo., the GH is a lean-to facing the west. We've installed a sunscreen on the roof and west face and a 10K BTU window AC. She grows microgreens so a mister unit can't be used (Ugh!). We have our eye on a used 24K window unit for a decent price. Any similar experiences with a possible solutions?   

Jim

Oil-expansion (~70) widow openers and a thermostatically controlled attic fan installed on the opposite wall.  Sunny days go to 88.

[fixtureman]

When we had our greenhouse we used white shade spray and the roof vents to try to keep it cool.  Ours probably was a little bigger then yours as it covered 1 1/2 acres

[JosephP]

Green Circle Growers (Lorain Co Ohio) has a 5 acre green house they air conditioner to manipulate the timing of orchid flowers...maybe more.  It's been at least 12 years ago I toured their place.  They have grown more than the 80 acres under roof it was then.

[EightFingers]

Wow, orchids in Ohio!

[JosephP]

In a greenhouse...in Ohio.

They supply most of the Home Depot stores around Easter.

[EightFingers]

I bet their utility bills are on the high side!

[JosephP]

I visited when they were installing the new heat system.  They were switching from boiler to hot water for heat.  A boiler required an operating engineer on site 24/7.  At that time it was the largest hot water system in the eastern hemisphere (may still be?).  I was there as a Forester because it is a wood-fired system.  We were trying to convince them to use chips from the woods - especially Ash because emerald ash borer was just getting going.  They didn't like the idea of inconsistent moisture so were planning to stick with all ground up pallets.  The expectation was 20 semi loads a day during the winter.

But their kWH for running AC in the orchid house is probably right off of the grid?  Fortunately, I think they only need that to ensure bloom once per year in the spring, so not like they are trying to cool it when it is 90 degrees for long stretches.

[Cooler]

Evaporative cooling works great.  Depending upon the humidity it can lower the temperature from 5 degrees to 25 degrees.  But be aware of condensation inside the greenhouse.  It can cause rust (steel), white rust (aluminum oxide on aluminum) or rot (on wood and wood products).  It can also condense so much that it will appear to rain indoors.

A perforated garden hose "sprinkler" would work great for this application.

Here is some information on cool misters:  https://www.growspan.com/news/the-summer...l-it-down/