Improvement for a small greenhouse

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About four years ago, we set up a 8x6 harbor freight greenhouse in my outdoor growing area. The goal was to extend the outdoor growing seasons for my cooler intermediate growers and anything that needs a cool dry rest. Over the winter, I use an oil filled heater controlled by a programmable thermostat to heat. I also bubblewrap it for additional insulation during the cold months. The greenhouse is not used year round. Generally, cooler appreciating orchids transition into the greenhouse in April when temps are still unpredictable in Ohio. These plants come out if the greenhouse when chance of frost is over. Most of my collection is outside June through October. Then the greenhouse in back in play October through January. Somehow we always seem to get a snow storm in January/February that knocks out the power for 12+ hours while temps are in the teens. At that point anything in the greenhouse is brought into the house and does not go back until April. The option to provide an extended cool period has really helped.

I would like to use my greenhouse more in the summer but it can quickly heat to 100F with the sun. I use shade clothe, auto-venting windows and have a fan running 24hours a day. A couple of years ago I installed a mister. It helped minimally. And now it is time to replace it. Before i replace it in kind, I am wondering if there are other improvements to consider.

It is such a small space temperature swings are inevitable. Just wondering if others have small greenhouse and what they do to make them work better. Summer and winter recommendations are welcome.

And no. I can not build a larger greenhouse...yet;)

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eds

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A few ideas to consider;

I'd look at fitting some ventilation low down to help get air moving through the greenhouse and carrying the hot air up and away. Leaving the door open when it is warm enough will w also be a big help.

How big is your fan? You may need a larger one to really move the heat around.

I'm surprised you need shading as the greenhouse looks pretty well shaded by the trees, but if you do, I'd look at something external to stop the heat getting into the greenhouse in the first place.

Try black containers full of water under the benches could help offset the small size and reduce temperature swings (they will absorb heat during the day and slowly release it at night).

Also what's under the floor? Can you soak the floor or will it all just run away? Perhaps replacing that with a concrete poured floor might allow you to retain more moisture in the summer.

Finally perhaps an evaporative cooler (swamp cooler) might be worth a look instead of a humidifier?
 
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Thanks eds and Tony! I appreciate the ideas.

Ed's - my fan is 18" and oscillates. It seems to move a fair amount of air. The floor gravel and marble chips. When we put it up, we dug a foot deep for the footers. Soaking is certainly an option. The bins are also.


When I can I leave the door open despite critter concerns. I forget to close it at night.

Thanks for the lead Tony! So I take it you leave your greenhouse closed?
 

CarlG

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Make sure your shade cloth is perhaps a foot or so above the roof. If it sits on the roof, it'll shade, but will transfer heat into the house.

You could also try something like aluminet (if that's still available), although then your greenhouse will look like it's wrapped in foil.
 

abax

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Darlene you might install an automatic, shuttered fan in the front and
a larger exhaust fan in the back. My greenhouse is 12' x 28' and I have
two shuttered fans (I've forgotten what size) and a large exhaust fan.
A cheaper option than a swamp cooler and they sure keep the air
moving. On really hot days, I flood the concrete floor with very
cold water a couple of times.
 

Ozpaph

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Aluminet as the shade cloth is good for 'heat reduction' in summer.
You would probably be better with an ultrasonic fogger rather than a mister
 
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All great idea! I will have some research fun to do day.

My shade clothe is not Aluminet, but I am familiar with it. I only need a small amount. Only two panels get direct sun in the hottest part of the day. Also I did not know the shade clothes need to be above the greenhouse and not directly on it.

Thanks all! I will update you on the improvements.
 

Ray

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Aluminet can be laid right on the structure and will help reduce the temperature. Gothic Arch Greenhouses in Mobile AL will custom-make a cloth to your specs for a very good price.

A swamp cooler will have its own blower to push the cooled, humidified air into the greenhouse. It should be installed to blow the air in near the floor, then it will rise, pushing the warmer air out vents higher in the structure.

My greenhouse in PA was surrounded with woods, so humidification was not much of a concern, so I just installed screen-covered, louvered vents on either dose of the door. They opened and closed with temperature controlled “wax motors” when the interior temperature was 65F. If the ambient conditions caused the temperature (I had Aluminet, too) to reach 80, a 48”, 10,000 cfm exhaust fan in the upper part of the rear of the greenhouse came on to pull fresh air through the structure.
 

richgarrison

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@Ray Hey Dude...

thanx a ton for the screen covered louver vent link... i was about to start figuring that out this weekend, and this certainly kickstarts the process...
 

richgarrison

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@Djthomp28 some other cooling options for you.

I'm in PA, and cool the greenhouse in the summer with under bench misting. It's setup on the water supply with a sprinkler system solenoid valve to control the flow. A timer opens the solenoid valve for 30 seconds every 15 minutes. You could probably do the whole thing on the cheap for about 150$ using some of the newer electronic timers.

Also, for shading i use the good old greenhouse paint. I used to use shadecloth (aluminet), but wanted to maximize the transmission throughout the season. I spray on a 10-20% coating at 3 different times during the season. mid -april may and june. The rain tends to wear the coating off over time, so that by september, i just brush what is left off to be left with the clear roof for the winter. I use a garden sprayer to apply it. A lifetime supply (a gallon) of Kool Ray liquid shade is about 40$ give or take. If you go this route, i would suggest transferring the unused portion into some kind of plastic container since the paint can rusts over time.
 

Ray

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@richgarrison - I obviously cannot speak for Darlene, but in my greenhouse, under-bench misting would certainly have raised the humidity, but probably would not have cooled much. Just too wet to start with, so there wouldn't have been much evaporation.
 

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