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Richmond, BC

We are having fantastic weather in the Pacific Northwest. I have a 420 cfm exhaust fan in my greenhouse and the temperature still reached a 100. Will a plant survive at that temp? What do you California guys do? Thanks
Richmond Dave

4/25/2018 5:32:52 PM

Torrance, Ca.

You don't want 100 Dave... When its 75 out I keep 2 doors open and it stays right around 85. On the warm days I open all 4 doors and turn the fans on and it stays right around 85. Play with it over the next couple weeks Dave and you'll get it down!
Make sure your temp gauge is accurate and not in direct sunlight.

4/25/2018 10:06:22 PM

Richmond, BC

So Chris, my thermometer is mounted on the shady side of the ridge beam. Of course that's going to be the hottest air. How high do you mount your thermometer? Maybe 3 ft would be a better indication of what the plant feels.

4/25/2018 10:24:18 PM

Mill Bay, British Columbia

Too hot Dave, tear it all down and take the year off.

4/25/2018 10:32:39 PM

Syracuse, NY

just an idea, but, if nothing else works, or as a supplement: a roll of cheap black plastic strategically unrolled and placed arc-wise over the GH and anchored properly may act as a filter, maybe a shade feature as well; i'm thinking along the lines of a shade tree's effect...

4/26/2018 1:35:22 AM

Eddyz@efirehose.net

your leaves will take it, your vine tips, not so much. Biggest problem is that the plants may look like they are handling it but your leaves will age faster with high heat As chris said try and keep it in the 80's

4/26/2018 2:36:28 AM

Central Illinois

I would place the thermostate where the plant is

4/26/2018 8:36:21 AM

Westmoreland, KS

Dave, first year greenhouse grower here.

I'm working through these same issues. In Kansas we'll get 100 plus degree days with 80 to 90 percent humidity.

When i built my greenhouse I dug geothermal. I have it running and i still had to add an exhaust fan just to remove the hot air out of the top of the greenhouse.

Since adding the top exhaust fan it has kept the temperature very nice but the true test will come when the really hot temperatures hit.

4/26/2018 9:20:32 AM

Torrance, Ca.

Yes Dave, I have a greenhouse thermostat inside the plastic housing. I keep it 1 foot off the ground and I've made a open wooden box to keep it in.

Like Eddy said, the plants will take it but the vines will grow faster then the leaves and your plants will stretch way out between nodes.
Open the doors more.

4/26/2018 9:50:19 AM

Richmond, BC

Thanks for all the help and replies. I think I'll lower my thermometer to get a true "plant "reading. And I'll need to open the rear end wide open for more circulation. Boy that sounds funny!!! I will also try some remay over the hoop house to see it that helps. I have done that in the past.
Cheers Dave

4/26/2018 12:41:44 PM

Midway, UT

If the beam is metal it may be heating up the thermometer, even if it is on the shady side. Even wood will heat up over time so it may be throwing the temps off some.

4/26/2018 3:09:28 PM

Weatherman

They put shade cloth on the green houses here in north east Ohio when it gets hot.

4/26/2018 4:41:53 PM

Richmond, BC

Thanks for all the help and replies. I think I'll lower my thermometer to get a true "plant "reading. And I'll need to open the rear end wide open for more circulation. Boy that sounds funny!!! I will also try some remay over the hoop house to see it that helps. I have done that in the past.
Cheers Dave

4/26/2018 6:43:32 PM

Richmond, BC

Ok so I opened up the back end of the hoop house and the temp was hotter than yesterday! 101 F ! Amazing ! Have I discovered a new form of Energy?

4/26/2018 6:46:04 PM

Mill Bay, British Columbia

Mine are mini hoophouses Dave, but I’ve put remay over top of the plastic to shade the young plants and cool it down a little.

I still think you should tear it all down, take the year off, no stress.

4/26/2018 8:59:15 PM

Syracuse, NY

RD---How thick is the Remay, and isn't it white? The entire reason for too hot is you are having a greenhouse effect. Too much sun coming in, no way for it to get back out.
You have mini global warming. Block the sun. White material will not help. At least not much. just MHO. eg

4/27/2018 5:12:12 AM

Rudolph

You'll need to get a bigger exhaust fan dave, 420 cfm is to small for your set up, I looked at the greenhouse in your diary I don't know the total area of the greenhouse but from the pictures you'll need more like 4000 cfm to exhaust the air properly.

4/27/2018 9:31:59 AM

Torrance, Ca.

lol,,, 101,, you have found new energy Dave! I know some guys don't agree for areas like ours but I've run the year with no shade and years with shade,,, I'll let you know now I have 31% shade over the whole patch unless its cloudy. I keep that on until the leaves have matured then I remove the shade for the remained of the season. Last year was the first year I did the shade until the leaves were mature and I had the best looking plants ever.

4/27/2018 9:33:57 AM

Weatherman

What is your outside temperature?

4/27/2018 1:21:34 PM

Richmond, BC

Green house is 14 x 20...6 ft high.
Front door is 24 x 60 and the rear door is 30 x 50. The doors open right to the top of the hoops so as much hot air can escape as possible.(My wife says I have too much hot air escaping!).
Outside temps are only around 72 F.
My neighbor offered me a construction fan. Will check the power/cfm and give it a try.

4/27/2018 3:16:58 PM

Mill Bay, British Columbia

pumpkinpal2, White remay offers 30% shade. We have used it here for years.

4/27/2018 4:53:36 PM

Syracuse, NY

Thanks, Glenn. I've been using Pro 19 Floating Row Cover from American Agrofabrics in Georgia and swear by it for like 10 years now for my 8' x 8' GHs until the plants outgrow them, and even then i have to cut 'gills', slits and triangular openings into the fabric to allow wind to flow through the TOP part of the GH. On the wind-facing ends, how i punctuate those depends on my mood and what patch i am headed to. They get removed and put aside upon outgrowth.
Probably like 90%+ light transmission. The main reason for a SUMMER GREENHOUSE at all is to prevent wind damage and to deter insects---they don't want what they cannot see. I had made a FRC GH in around '04 that was 220 feet long X 20W but i stupidly tore the fabric unrolling it and half of it was useless; what i USED worked awesomely---when the wind blew really hard, though, the back side of the GH tore away from my novice anchors and just blew in the wind, but THAT was OK!
I'm curious - where is the fan presently located? I could go on and on about my ideas. For one, the fan needs to be part of the circuit of airflow: as high as possible and blowing OUT, or as low as possible and sucking IN, with the fan installed INTO the plastic, protected from the rain---i know, i know, you don't want to cut into all that nice plastic, no one ever does, but...ok, gotta go...eg

4/27/2018 6:01:49 PM

Lymington UK

We are starting to vent at 58F while the plant is growing.
We will start venting at 70F when the pumpkin is set.
We need to use the greenhouse to smooth out the highs and lows.
Balancing heat with light is very important. Low light and high heat will give you long skinny plants.
I would do anything you can go keep that heat down and side vents on both sides of a poly tunnel work very well.
Ian

4/28/2018 4:58:47 AM

Richmond, BC

Thanks for the great tips Ian. Really enjoyed you two at the convention and am following the amazing/crazy things you're doing with botany. Cheers

4/28/2018 11:50:18 PM

Richmond, BC

Since the last post I have covered the greenhouses/hoop houses with remay. It is giving me 50% blockage according to my lux meter readings. Each hoophouse has an oscillating fan. The plants really responded well to this treatment and are growing well. Today the coolest reading I got was 91F° in the shade. The leaves did not droop. Our evenings are so warm I'm leaving the hoops wide open.

5/14/2018 9:03:56 PM