greenhouse Crappy nighttime temps and greenhouse climates ...

As some of you know Ive been shopping for a permenant greenhouse. I got one purchased and it showed up yesterday. Tomorrow we are going to get it all put together.
Anyway, its a really nice model.. 8x16', 8mm polycarbonate panels (commercial grade, twice as thick as the usual 4mm seen in cheaper greenhouses for better insulation), 113 MPH wind ratings, etc, etc.
So Ive been looking at heaters because our nighttime temps pretty much suck year round. Even in the middle of the summer our highs usually get only around 85-90 with night time lows around 50's or better (possibly up to 60).
Heres a link to our average temps:
Thats a little off in my experience. We had several 92 degree days last year for the highs and Im not sure of the nighttime lows but Im betting up to 60. As you can see though .. the night time lows really suck and all summer long you can be looking at around 45-55 degrees.
How can I combat this in my greenhouse so I can get pod production? Ive come across info that says night time temps below 65 will cause flower drop. Is that really the case? If so looks like Ill have to run a heater year round!
On the plus side we are at 7,000 feet up in the mountains of Arizona so our sun is really intense even in the winter time. Our lows rarely get to below zero and its usually only for a few hours a night.
If I get a heater with a thermostate. I was thinking of setting it to 50 degrees and letting it just do its thing. Will this not allow pod set though .. at 50 degree nighttime temps?
Is the 65 or higher night time temp really necessary? That seems awefully high and Im sure in most places those kinds of night temps would come with days that are above 95 ... so if thats the case no one would ever have pods lol.
Man don't be stupid... :D

You have all you need to get a solar heated gh going. Just position 4 black 55 gal. steel drums in it (use them as support for shelves). That's nearly a metric tons - 2000lb of water .

They will heat up during the day - effectively cooling your gh during the day - and release the warmth during the night - effectively warming up your gh when you need to .

Bang! Best of both worlds!

Look into solar heating
B. R. Al
Hi Al, thanks for your input.
Ive looked into the thermal heatsink approach as you suggest, but originally wrote it off because I dont want to sacrifice that kind of room. However... using the drums as a work bench is a great idea! Ill have to consider that a bit more.
I still may stick a heater on a thermostat in there though .. if anything the barrels will help out the electric bill. I guess Im just wondering if I really gotta keep the damn thing heated up to 65 degrees at night to get pod production. I think Ive heard of peoples chinese producing just fine at 50 deg night time temps as long as the day time sunlight and temps are appopriate.... do you guys agree with that or do you find you really need night time temps in the 60's?
With this greenhouse Ill be able to keep 80 degree days in the coldest part of winter.
Al - I appreciate the input.. Im sure I do have all the elements I need Im just a little lost on how to put it all together. Knowing what minimum night time temps I really need to achieve will help me figure that out.
Im open to ALL suggestions though. You guys are great!

EDITED: Upon looking into that ... the recommended water amounts are 2.5 gallons per sq foot. That means i need 6 - 55 gallon drums. Again.. eating up a large amount of space in a greenhouse thats already not quite as big as I wanted lol ... I dont mind running a heater, and with the 8 mm polycarbonate panels Im not sure it will tear me up to bad electric bill wise.
I'd start with 3 or 4 barrels - whatever works with your layout... Make sure that you have them painted flat black and on wood or foam board or the cold ground will suck the warmth out of them.

The heater is a good backup plan.

Good luck, Al
Here is my experience working with a greenhouse, though St. Louis and Flagstaff have vastly different climates.

Pods will set below 65 degrees, but if your nighttime temps are below 65 for long periods of time your pods will not fully mature and will ripen early, leaving you with small little niblet peppers that aren't great.

Air movement is KEY! Get a fan that has a SEALED motor, this is very important, a non-sealed motor will fail or worse (catch fire) due to humidity. There are fans rated specifically for greenhouse use. Without the air moving, and no pollinators, you will get flower drop due to poor pollination.

I use a 20,000 BTU natural gas heater for my 14x16 greenhouse. It easily keeps my temps at 60 through the winter, even when it is 10F outside. Keeping it above 65 is not cost effective though. Once it starts staying above freezing at night, 65 is maintainable. I also keep 1 55gallon drum as a thermal mass/water supply.

Another trick I use is radiant barrier (foil covered bubble wrap). I line the north facing wall with it during the really cold times and remove it in the Spring. This cut down my heating cost by about 1/3. Natural gas is pretty cheap here, my heating costs run about $30/month in Dec and Jan if I keep it at 60. Trying to keep it above 65 during those months makes the cost triple.

Ventilation is really important as well. I have the exhaust vent/fan set up to start venting at 85, it doesn't take much sunlight to get the greenhouse above that, even in the dead of winter. Temps above 95 will cause flower drop, so you have to make sure not to overheat things.

Here is what I am working with.

Picture by, on Flickr

This was in the winter 2011

100_0731 by, on Flickr
Thanks! Thats some good first hand experience there. Im not entirely sure that my goal is to get pod set the entire year. I may be fine with just letting them stall a bit during the coldest few months around Janurary or so and kick them back into gear come march. I think that should be easily obtainable.

I cant stress enough how intense our sun is being in Arizona, and THEN being at 7,000 feet. A local guy at the nursury told me last week that "full sun" here is 4 hours direct sun. No more. My plants have been handling 5 hours but its morning sun from sun up until about 11 am. They still got a bit crispy at times even so Im excited for the UV shielding properties of the greenhouse.
Not only that, but its pretty damn sunny year round so daytime temps during the middle of the winter, especially in a greenhouse thats as well insulated as this, should be no problem.
Its just the night time temps that are out of whack because our days will be mid 70's with strong sun from April to October easily. Inside a greenhouse I could achieve 70-80 degree daytime temps year round. Problem is, during those times our nights are around 25-40 degrees. Hell all June we will have 40 degree nights with 80 degree days. Peak of the summer our average highs are 80-85 degrees with night time temps in the 45-55 range. Thats as good as its gonna get before temps start to cool off again in August.

Keeping it cool is going to be an issue so Ill have to look into ventilation. Luckily our highs are usually mid 80's with a few days here or there hitting 90 degrees. The greenhouse has 3 automatic vents on the roof and a 54" wide door that I can leave open during the summer to keep temps down. I also have a shade cloth. Im guessing theres going to be many, many months where Im running a heater at night and a fan during the day. Either that or I lug pots in and out of the greenhouse every morning and night... Ild rather not do that!
I think thats probably my goal with the greenhouse is to have production from March to November, then in Dec-Feb Ill just keep it at 40 degrees and let the plants go semi-dormant/stall for a few months. Ill just have to see how the temps react to things such as heating and ventilation.
Honestly, I think I have a handle on heating. Im still a little unsure of what Ill need for ventilation.
Do you think Ill need an actual exhuast system with summer highs in the mid 80's and a 54" door plus three 2'x2' roof vents open? Or could I just get away with a large fan sitting in the doorway blowing air in.. or something along those lines?
I really appreciate the input ... any other greenhouse growers Im all ears on what your setups are like and what you do with them.
You will definitely want to use that shade cloth in the summer. We put our 60% shade cloth on 2 weeks ago, and it will stay on till October probably.

Honestly, you are going to be amazed at how quickly your greenhouse heats up. Like I said before, my ventilation system kicks on at 85F, and it will kick on in January with snow on the ground and outside temps of 20F. It will vent for about 5 minutes until the temp drops, then shut down for 15-20 minutes.

Even with the shade cloth and my door wide open, if it is sunny, the vent will be running non-stop. As long as the daytime highs stay under 90, you might be ok with fans/auto vents.

For my setup, I have to run an evaporation cooler in July-August to keep temps below 100. That is in addition to everything else I am doing to keep it cool.

I highly recommend something like this for your greenhouse, they are pricey, but they are sealed and will run for a very long time.;gs_cooling_fans-gs_exhaust_fans;pgcf1750_CF1750.html
I dont doubt it! A buddy just set up a greenhouse and the temps are soaring to 120 degrees with 70 degree temps outside. They dont have any type of exhaust system nor do they have the width of front door and venting I have but still.
Thats a great looking component, Im assuming it would be best to just install it in one of the roof vents?
Also... Ill probably need some sort of thermostat Im guessing too. Ill probably put in the shade cloth now and leave it on. Ill get direct morning sun from 6:30-11:30 am through the left side of the greenhouse, and then direct evening sun from about 4 -7pm from the other side of the greenhouse.. the way I have it positioned. Also, my shade cloth is a 62% transparency, the sun will be directly overhead from 11 - 4 or so.
Really appreciate the help!
You would want to install it near the peak, at the wall opposite the door. Generally you would also have an automated intake on the end with the door, which would allow you to not have to keep the door open all of the time. This is important in the winter when you are trying to delicately balance the temp in the daytime.;gs_shutters_vents_louvers_1;pg106052_106052.html
I have one of these on the front of the greenhouse with an actuator (which opens/closes the vent) wired to the same thermostat that controls the exhaust fan. When the temp hits 85, intake opens and exhaust turns on, when it drops below 85 the opposite happens. Its pretty neat stuff.
You could also very easily just find a manual vent and open it in the morning and close it at night.
Thats perfect ... thanks a ton!
Ill shoot you a link to my GLOG once I get it all up and running. Construction begins tonight!
Im pumped..
Planning on containers as of now. had to stop halfway through assembly last night apparently we drank to much lol
Done ... It took all weekend but now Ive gotta get the exhaust system figured out... it was 77 outside and 110 inside the greenhouse today. Im still messing around with the automatic vent openers so I have the shade cloth hanging for now. Also, I have to get a dumpload or two more of that rock. This greenhouse begins the backyard renovation. I bought this place a year ago and the back yard is a half acre, but its completely undeveloped. Last year I put up a new privacy fence on the front and rocked the front yard (It only took 40 tons of landscape rock), and planted 10 fruit trees but other then that I havent gotten to it.
Its gonna be a lotta work but should turn out nice from the plans I have drawn up.



Lol...thanks. I'm really liking it. Just gotta get the temps in check and I'm off to the races ...
I don't have a greenhouse, but the nighttime temps in my area are nearly always in the 50s during my growing season. I've never had any pod setting issues, and I grew most of the common superhots last year. Ymmv, but hopefully that gives you some perspective.
Thats extremely helpful fireface ... I was seriously questioning that statistic because I know lots of areas that dont have 65 degree or better nights and the peppers still seem to do fine. I may shoot for around a 55 degree setting on my heater then and see how it goes.
Im looking into ventilation now.