Author Topic: cheapest ways to cool a greenhouse using little to no electricity ?  (Read 1508 times)

Avoman

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Looking for ideas to cool green house in summer ...I'm I better to build one into side of a hill or design passive cooling pipes 10 feet underground and vent the hot air out the roof trying not to use any electricity if possible.

Kevin Jones

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #1 on: December 27, 2020, 06:17:01 AM »
Passive cooling would be the cheapest ... My newer greenhouse... I designed with massive doors on either end that are left open during the warmer months... and plastic glazing that rolls up in the front for about 8 feet... still got pretty hot this Summer in the ceiling peaks.... especially for the taller plants.
I need to add some peak vents this year...

Best would be glazing that is totally removable for perfect ventilation.

I've been fantasizing lately about a Walipini style, mostly underground type greenhouse that would have its plastic glazing completely rolled up for full air exposure every spring... also easier to warm in the colder months.

Kevin

« Last Edit: December 27, 2020, 06:20:26 AM by Kevin Jones »

Galatians522

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #2 on: December 27, 2020, 07:24:18 AM »
Peak vents would be ideal. Hot air rises after all. Before AC, many homes here in Florida were designed to create a hot air draft that pulled cool air from under the house inside as the hot air rose to the peak. It works best on taller structures, and some wealthy people even had gas burners in little cupolas specifically to create this draft. I was shocked when I heard about this from an AC tech, but this was even before electric fans. People had no other way to move air.

TonyinCC

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #3 on: December 27, 2020, 08:30:45 AM »
Shade cloth can help. A thin coat of diluted white paint might work also.
« Last Edit: December 27, 2020, 09:03:56 AM by TonyinCC »

Plantinyum

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #4 on: December 27, 2020, 10:06:21 AM »
The upcoming summer will be the first for my greenhouse. I will place a shade cloth of maybe 30-40%. I also have two top windows and two doors which will likely be opened at all times. The temp in the gh now in december when sunny gets to 30C/86 F, it will be insane in summer .

Kevin Jones

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #5 on: December 27, 2020, 12:22:46 PM »
It froze last night... down to 27F... but I've got one of the doors open now to vent or it will quickly hit 100F+.

Kevin


brian

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #6 on: December 27, 2020, 02:20:18 PM »
Donít forget evaporative cooling.  Hose/sprinkler on a timer.  Or a constant drip and a bell siphon if it must be zero electricity.

Plantinyum

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #7 on: December 27, 2020, 03:34:26 PM »
Donít forget evaporative cooling.  Hose/sprinkler on a timer.  Or a constant drip and a bell siphon if it must be zero electricity.
I have also bought myself a mist cooling system, from the ones that get connected straight to the hose. I may use it for overhead watering , but my well water is rich in limestone .

Daintree

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #8 on: December 27, 2020, 04:07:06 PM »
Hi Avoman,
You are in the same climate as me (I'm in Boise).
I would go with your "side of the hill" idea, and what also works for me is that I situated my greenhouse under a maple tree.  In the summer, the tree helps shade the greenhouse, and in the winter the leaves have fallen and the sun helps warm the greenhouse.
I also have misters that I run from the house water (I hooked up an in-line de-scaler to keep the mister heads form getting clogged), shade canopies that I can move around if I need to, and airflow.  I do use electricity, so have an intake fan plus an exhaust fan, but you can probably use convection instead, if you are just building your greenhouse.  Having intake vents low-down on one side of the greenhouse and vents at top can force the air up and out.  High ceiling height should help also.

nattyfroootz

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #9 on: December 29, 2020, 10:28:15 AM »
I recently built a 12x25 off the grid hoop house that I'm using at an area with no electricity.  I had previousy experience working with snap fans, which are DC Solar fans for greenhouses and installed one in my new spot.  It's honestly pretty great and I plan on building more hoop houses for in the ground tropical plantings on my super sunny and hot SW slope.  Highly reccomend although they are kind of expensive.

https://snap-fan.com/

Avoman

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #10 on: December 30, 2020, 12:24:07 AM »
Some great ideas I didn't think about solar powered vent fans at top, shade cloth might not be an option on tall design unless below grade and large shade cloth kinda pricy, building into side of hill  seems like it would moderate temps in winter and summer both or going six to eight feet below grade seems like it could help alot, and yes I would use misters also if I struggled to keep temps down on 105 degree days outside temps.

Plantinyum

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #11 on: December 30, 2020, 02:19:37 AM »
Anyone knows if using misters on tap water is safe for plants. I know they put chemicals and chlorine . Anyone using their tap water for misting and overhead irrigation in their greenhouses?? I apologise to the OP if i'm hijacking the tread too much , thought to just ask here and not make a separate tread .....

nattyfroootz

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #12 on: December 30, 2020, 10:08:15 AM »





A couple of pictures of my set up, can get up to 110+ in full sun at my site, and will get into the 100's in the GH due to the arrangement. Ventilation on N side, should be opposite but im limited by my access. 

turpentyne

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #13 on: December 30, 2020, 10:47:47 AM »
Anyone knows if using misters on tap water is safe for plants. I know they put chemicals and chlorine . Anyone using their tap water for misting and overhead irrigation in their greenhouses?? I apologise to the OP if i'm hijacking the tread too much , thought to just ask here and not make a separate tread .....

If the water's got too much stuff in it, yeah, I think it could be bad. Where I live, there's salt in the water so it's not a risk I like to take. The salt collects on the leaves, then burns and could cut off transpiration.

Plantinyum

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #14 on: December 30, 2020, 10:57:09 AM »
Anyone knows if using misters on tap water is safe for plants. I know they put chemicals and chlorine . Anyone using their tap water for misting and overhead irrigation in their greenhouses?? I apologise to the OP if i'm hijacking the tread too much , thought to just ask here and not make a separate tread .....

If the water's got too much stuff in it, yeah, I think it could be bad. Where I live, there's salt in the water so it's not a risk I like to take. The salt collects on the leaves, then burns and could cut off transpiration.
tanks , I am actually thinking of having a retentive tank or something, for collecting rain water and then feed it to the misters by a pump of sorts ...I also have aces to well water , but its rich in limestone and makes the leaves on the plants white couse of the deposits .

spaugh

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #15 on: December 30, 2020, 11:12:51 AM »





A couple of pictures of my set up, can get up to 110+ in full sun at my site, and will get into the 100's in the GH due to the arrangement. Ventilation on N side, should be opposite but im limited by my access.

I put roll up sides on mine and leave both long sides and the back wide open for 6+ months a year.
Brad Spaugh

fruitnut1944

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #16 on: December 30, 2020, 11:36:25 AM »
Cheapest is seldom best and usually not close. My greenhouse can do 800 chill hrs in 40 days for those plants needing chilling. And then do 6-7 months of main crop fig harvest. Or grow about anything else you want. It gets no hotter than low 90s in summer but has 300 days a yr of heat, 80-92F. 1725 sqft. Wet wall and three 36 inch exhaust fans. Heating cost $500-1000+ depending on what one wants.

In any place with dew points below 60F in summer evaporative cooling has a huge benefit/cost ratio compared to nearly anything else. It allows both the chilling in winter and cool summers. We average 60/30 in winter and 92/62 summer with 75% sun all year long.
« Last Edit: December 30, 2020, 11:51:57 AM by fruitnut1944 »

brian

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #17 on: December 30, 2020, 01:55:05 PM »
Foggers work incredibly well for me.  However even with city water that is only moderately hard I still get scale buildup on the plants closest to the misters.  I tried with and without a phosphate filter, but I get scale either way.  The citrus plants seem to tolerate it okay, though, so I just ignore the scale. 

If you have hard water you will definitely get scale from sprinklers/misters/foggers.  However if you sprayed the water directly on the ground it should still have a cooling effect.

forumfool

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #18 on: December 30, 2020, 02:50:46 PM »
Lots of good ideas just to mention another phase change materials. Iím going to experiment next year build a small greenhouse and put coconut oil in plastic container. Changes phase at 76 degrees

Plantinyum

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #19 on: December 30, 2020, 04:04:46 PM »
Foggers work incredibly well for me.  However even with city water that is only moderately hard I still get scale buildup on the plants closest to the misters.  I tried with and without a phosphate filter, but I get scale either way.  The citrus plants seem to tolerate it okay, though, so I just ignore the scale. 

If you have hard water you will definitely get scale from sprinklers/misters/foggers.  However if you sprayed the water directly on the ground it should still have a cooling effect.
by scale u mean the mineral deposits by water, not the insects right ??. I measured my tap and well water's tds (total dissolved solids) and the tap water came at 005 , the well water was 040 , I found a chart for hardness of water according to which both are soft. I do not really understand what those numbers mean thought.
I also wonder if whatever things they use to clear tap water are present in it at all times , and do these chemicals leave a footprint in the tds measurement as a example.

Kevin Jones

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #20 on: December 30, 2020, 04:24:51 PM »
In my town... and most others... the municipal water facility adds lime to the water to adjust the ph... not to mention chlorine for purifications... and other chems too.

Kevin


cen

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #21 on: December 31, 2020, 04:01:32 AM »
I don't have a greenhouse, although I want one.  I'm going to try to describe an idea, based on post #3. Actual construction details will vary, and the order given is just to describe the unit.
1. Assuming the frame of the greenhouse is in place, but no covering, run a large diameter plastic pipe to a height higher than the roof of the greenhouse. Near the top, several large holes are drilled in the sides, perhaps from near the top down to roof level.
2. Drape a large plastic sheet, large enough to reach at least to the roof of the greenhouse. Secure the plastic to the top using a black, plastic, angled sewer pipe connector. The opening should be on the south side of the greenhouse (assuming . northern hemisphere). Cut a hole in the plastic on the inside of the pipe. Extend the pipe vertically about a foot, Install some sort of chimney rain cap.
3. Build a box on the south side with at least one open side. Paint it black. Run a black sewer pipe from the top of the box to the pipe connector.
4. Finish covering the greenhouse.

The plan is for hot air to rise and accumulate at the peak. The holes allow the air to enter the pipe and exhaust out the top. Air in the black box will heat faster than air in the greenhouse and vent out the top pipe. This warmer air will entrain the air already rising from inside the greenhouse and pull it out the top of the chimney.

Variation: Built the black box and run large diameter black pipe straight up several feet higher than the roof. The top of the black pipe has a reducer. Attach a smaller diameter pipe with an angled connector facing down.The smaller pipe is capped with a large pipe adapter, and then topped with a short length of larger diameter pipe and a rain cap. The top of the greenhouse chimney has a 45į connector and runs pipe over to the black pipe chimney. The purpose of this is to create a venturi to better entrain the air from the greenhouse. Maybe in this case the black chimney is made with ventilation pipe rather than plastic pipe. Maybe the box does not have to be on the south side, but can be at one of the greenhouse ends to avoid blocking light to the greenhouse.

This is just an initial idea, so perhaps people could suggest improvements. After writing this, I imagine someone has done this and described it on the internet or made a YouTube video, but I have not searched for either.

Edit: Maybe with the large diameter black chimney, we can dispense with the peaked greenhouse chimney and just use a top mounted or side mounted exhaust box. Part of the reason for the peaked greenhouse chimney was to provide support.
« Last Edit: December 31, 2020, 05:01:48 AM by cen »

fruitnut1944

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #22 on: December 31, 2020, 10:03:58 AM »
Cen your idea may have merit but is hard to visualize without pictures. The key with natural ventilation or your enhanced version is volume of air movement. On a sunny afternoon natural ventilation requires one air exchange per minute in order to hold temperature rise to 15F increase inside vs outside. So the key to any system is how much air is exchanged. In your location 15F above outside might be just what you want. In areas where temperatures rise above 100F that gets awfully hot.

Any natural ventilation system requires large openings at the top to vent hot air and large openings at the bottom to let in outside air. no matter how big the openings are it will be warmer in the greenhouse than outside.

A wet wall and exhaust fans capable of one air exchange per minute can keep it as cool inside as out, sometimes even cooler if dew points are low. Right now during chill cycle I can hold inside 5-12F cooler than outside. It will do the same in summer with low dew points, 90 inside with outside 100F and dew point of 40F. If dew points are about 60F it will hold inside about the same as outside when outside is near 90.
« Last Edit: December 31, 2020, 10:06:05 AM by fruitnut1944 »

nattyfroootz

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #23 on: December 31, 2020, 10:14:53 AM »





A couple of pictures of my set up, can get up to 110+ in full sun at my site, and will get into the 100's in the GH due to the arrangement. Ventilation on N side, should be opposite but im limited by my access.

I put roll up sides on mine and leave both long sides and the back wide open for 6+ months a year.

I unfortunately didn't include hipboards on this greenhouse lol.  So I'm not sure I can do roll up sides unfortunately, haha. But I will be doing that on the newer ones I build out.

spaugh

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Re: cheapest ways to cool a greenhouse using little to no electricity ?
« Reply #24 on: December 31, 2020, 12:49:02 PM »





A couple of pictures of my set up, can get up to 110+ in full sun at my site, and will get into the 100's in the GH due to the arrangement. Ventilation on N side, should be opposite but im limited by my access.

I put roll up sides on mine and leave both long sides and the back wide open for 6+ months a year.

I unfortunately didn't include hipboards on this greenhouse lol.  So I'm not sure I can do roll up sides unfortunately, haha. But I will be doing that on the newer ones I build out.

You can easily add it.  I dont have hip boards.  What you do is get the double wiggle wire rails and attach it about 6ft up on your hoops and clip the poly onto the top rail. 

I'll post a pic of mine later today.  I did mine as an afterthought and its the best mod I've done hands down must have. 
Brad Spaugh

 

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