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Author Topic: Good greenhouse management site  (Read 815 times)

Mark in Texas

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Good greenhouse management site
« on: February 12, 2018, 08:07:53 AM »
http://www.greenhousegrower.com/technology/natural-ventilation-and-fog-increase-cooling-efficiency/

I found the comparisons between indirect greenhouse heaters and direct heaters, their effect on plant growth, efficiency, etc. really interesting too.

brian

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Re: Good greenhouse management site
« Reply #1 on: February 12, 2018, 04:24:15 PM »
Thanks for this.   I'm still very interested in setting up a fogging system for my greenhouse.  I'm not in a prime climate for evaporative cooling, but I'm hoping its still worthwhile.

I just browsed the daily weather for my area from last year.  If I look at midday hours where it was warm with clear skies, the relative humidity is usually around 50%.   A quick browse around suggests that 50% humidity is low enough to get a significant benefit from evaporative cooling, even if its not as good as in drier areas.  Using daily averaged humidity to judge effectiveness seems misleading to me, because my greenhouse only needs cooling when its sunny.  Most cooling guides are about air conditioning for people's homes, and they care about maintaining temperature even at night and when its cloudy and rainy. 

Mark, I just noticed you are talking about heating guides, but the link you provided is about fogger cooling.  Do you have a link to the heating guide you're describing also?  Maybe you pasted the wrong link.

I've been thinking a lot about heating also.  My understanding is plant roots like to be warm, but foliage can be rather cold.  I started dreaming of a fully hydroponic growing system using heated water, while running only minimal air heating.  Would this work?
« Last Edit: February 12, 2018, 04:45:00 PM by brian »

Mark in Texas

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Re: Good greenhouse management site
« Reply #2 on: February 13, 2018, 08:04:58 AM »
Thanks for this.   I'm still very interested in setting up a fogging system for my greenhouse.  I'm not in a prime climate for evaporative cooling, but I'm hoping its still worthwhile.


Then you need to check out Brad's hoop house thread.  He's done all the homework for us.  Look at his video....too cool. http://tropicalfruitforum.com/index.php?topic=26039.50

Quote
I just browsed the daily weather for my area from last year.  If I look at midday hours where it was warm with clear skies, the relative humidity is usually around 50%.   A quick browse around suggests that 50% humidity is low enough to get a significant benefit from evaporative cooling, even if its not as good as in drier areas.  Using daily averaged humidity to judge effectiveness seems misleading to me, because my greenhouse only needs cooling when its sunny.  Most cooling guides are about air conditioning for people's homes, and they care about maintaining temperature even at night and when its cloudy and rainy. 


Unless you have temps in the upper 90's or 100's, considering the high RH, I'd just inject or exhaust ambient air.  Whatever you do don't install a swamp cooler.  They're not only useless but a PITA to maintain.

Mark, I just noticed you are talking about heating guides, but the link you provided is about fogger cooling.  Do you have a link to the heating guide you're describing also?  Maybe you pasted the wrong link.

I've been thinking a lot about heating also.  My understanding is plant roots like to be warm, but foliage can be rather cold.  I started dreaming of a fully hydroponic growing system using heated water, while running only minimal air heating.  Would this work?
[/quote]

Bill Blevins

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Re: Good greenhouse management site
« Reply #3 on: February 13, 2018, 11:09:12 AM »
I'm still very interested in setting up a fogging system for my greenhouse.

I'm looking for a small scale fogging system that lets me spray 5 seconds every 30 minutes like what you find in the produce section in a grocery store. This would be for a small propagation box/tent and not for a whole greenhouse. If anyone sees anything like that when you are poking around the Internet...
Bill Blevins
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brian

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Re: Good greenhouse management site
« Reply #4 on: February 13, 2018, 11:57:19 AM »
Bill, you might be able to use a personal misting system designed for use in small rooms, attached to umbrellas, or near pools

Bill Blevins

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Re: Good greenhouse management site
« Reply #5 on: February 14, 2018, 03:28:22 PM »
Bill, you might be able to use a personal misting system designed for use in small rooms, attached to umbrellas, or near pools

That's a good idea. I have found some small misters but I've been stumped with the misting only for 5 seconds every 30 minutes part.
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spaugh

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Re: Good greenhouse management site
« Reply #6 on: February 14, 2018, 08:22:22 PM »
I'm still very interested in setting up a fogging system for my greenhouse.

I'm looking for a small scale fogging system that lets me spray 5 seconds every 30 minutes like what you find in the produce section in a grocery store. This would be for a small propagation box/tent and not for a whole greenhouse. If anyone sees anything like that when you are poking around the Internet...

That would be easy to do.  They sell on/off interval timers on amazon.  You could easily have it control a valve to run water to mist lines.
Brad Spaugh

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Brad Spaugh

spaugh

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Re: Good greenhouse management site
« Reply #8 on: February 14, 2018, 08:28:52 PM »
Thanks for this.   I'm still very interested in setting up a fogging system for my greenhouse.  I'm not in a prime climate for evaporative cooling, but I'm hoping its still worthwhile.

I just browsed the daily weather for my area from last year.  If I look at midday hours where it was warm with clear skies, the relative humidity is usually around 50%.   A quick browse around suggests that 50% humidity is low enough to get a significant benefit from evaporative cooling, even if its not as good as in drier areas.  Using daily averaged humidity to judge effectiveness seems misleading to me, because my greenhouse only needs cooling when its sunny.  Most cooling guides are about air conditioning for people's homes, and they care about maintaining temperature even at night and when its cloudy and rainy. 

Mark, I just noticed you are talking about heating guides, but the link you provided is about fogger cooling.  Do you have a link to the heating guide you're describing also?  Maybe you pasted the wrong link.

I've been thinking a lot about heating also.  My understanding is plant roots like to be warm, but foliage can be rather cold.  I started dreaming of a fully hydroponic growing system using heated water, while running only minimal air heating.  Would this work?

If you are adding a lot of moisture and its already 50% humidity, you may end up with mold or mildew issues. 

If your greenhouse is small, you maybe better off with an air conditioner.  Window units or mini splits are fairly cheap.
Brad Spaugh

Mark in Texas

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Re: Good greenhouse management site
« Reply #9 on: February 16, 2018, 12:21:31 PM »
Mark, I just noticed you are talking about heating guides, but the link you provided is about fogger cooling.  Do you have a link to the heating guide you're describing also?  Maybe you pasted the wrong link.

It's on that site.

Millet

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Re: Good greenhouse management site
« Reply #10 on: February 16, 2018, 01:03:30 PM »
From reading the article (and thank you for posting the article), both systems, fan and wet pad, and fan and fogging work best in hot dry locations such as Arizona, as it is written in the article --  " The high-pressure fog works best in a dry climate, he says. If the outside air is humid and hot, the cooling capacity of an evaporative cooling system is very limited to just a couple of degrees Celsius."   What about a humid area such as Brian's ?   Here in Colorado, the area is a dry area, and evaporative cooling works really great, and I assume fogging would also.  I use what is called a wet wall evaporative system, which works wonders during the summer months.  Brain, does your greenhouse have roof vents?
« Last Edit: February 16, 2018, 01:05:37 PM by Millet »

brian

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Re: Good greenhouse management site
« Reply #11 on: February 19, 2018, 12:56:38 PM »
spaugh, my greenhouse is 575sq ft and 15ft tall.  I believe cooling with regular AC unit would be extremely expensive.  I do have concerns about humidity.  I may simply have to experiment and see how it works out.

Millet,  the limited research I've done into evaporative cooling says that Colorado has the best possible climate for this, while Pennsylvania is "reduced effectiveness", and in areas like Florida & Alabama it is totally ineffective.  What I am hoping is that I will get decent results because the system would only be running when it is bright and sunny, when relative humidity is at its lowest (for the area) as compared to cloudy/rainy days and nights when humidity is 80-100%. 

I do not have roof vents on my greenhouse, only two 24" high-CFM fans paired with two 36" vents.

brian

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Re: Good greenhouse management site
« Reply #12 on: February 19, 2018, 02:14:38 PM »
http://www.greenhousegrower.com/technology/natural-ventilation-and-fog-increase-cooling-efficiency/

I found the comparisons between indirect greenhouse heaters and direct heaters, their effect on plant growth, efficiency, etc. really interesting too.


Ah I finally saw the article you describe on the side.  I've always wondered about vented (indirect) vs unvented (direct) heaters.  I had read that unvented is bad because of the emitted carbon monoxide (for people) and ethylene (for plants).  However... I've run unvented propane heaters for a couple years now and never set off my carbon monoxide sensor or noticed harm to plants.   This article seems to claim that the unvented heaters gave better results.  Though, they add a lot of humidity which is already a problem for me. 

I'm still trying to think of a root zone heating system that doesn't rely on expensive electricity.  Piping radiant-heating-type water pipes around root zones might work but would be a lot of work to set up.

spaugh

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Re: Good greenhouse management site
« Reply #13 on: February 19, 2018, 07:03:27 PM »
Have you looked into rocket mass heaters?

There are some awesome setups out there.  They heat up several tons of rocks with it during the day and the heat is release over the next 24hrs.

For the cooling, only one way to find out. 

On my mist system, I have the pump on a humidistat set to 40%.  It wont even run unless the humidity in the hoop house drops below 40.  It basically kicks on only when the vents and fan are running which is maybe 20% of the time.
Brad Spaugh

brian

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Re: Good greenhouse management site
« Reply #14 on: February 20, 2018, 04:50:24 PM »
I had never heard of rocket mass heaters, and that is a really neat design. 

 

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