# Air movement



## Stone (Feb 19, 2012)

I was playing around with my fans yesterday thinking how nice it was to have a warm, humid breeze coming through the windows, and got to wondering, now that it's cold up north, how do you folks go about introducing fresh air into your enclosures? Do you do it every day regardless of temps. or only when the sun is out? I can feel Autumn just around the corner with heating hassles on the way :sob:

Mike


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## Gilda (Feb 19, 2012)

My orchids breathe what I do (meaning I grow in the house)...they seem to do ok  So only fresh air is when going in or out of the door.


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## SlipperFan (Feb 19, 2012)

Hmmm, lets see -- orchids are plants. They breathe in carbon dioxide and breathe out oxygen. So there is nothing fresher than the air in a greenhouse (or house) full of orchids. oke:


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## Stone (Feb 19, 2012)

SlipperFan said:


> Hmmm, lets see -- orchids are plants. They breathe in carbon dioxide and breathe out oxygen. So there is nothing fresher than the air in a greenhouse (or house) full of orchids. oke:



Er-- not quite Dot. The g/house air that might seem fresh to people might be quite stale to plants. I think air repalcement is very important for plants. not just leaves but roots are continually exchanging gases. Without an air change an imbalance of air chemistry would surely occur in an enclosed area? Not to mention creating a better evnironment for bugs.

Mike


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## NYEric (Feb 19, 2012)

I'm not worried about air exchange as much as temperature regulation. In my apartment its a battle to keep it from getting too hot with winter heat, I crack the windows at night and then close up as the temperatures drop from day/sun heat... then go through the process again!


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## Stone (Feb 19, 2012)

That's a good thing Eric, changing temps that way will change air at the same time.


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## paphreek (Feb 19, 2012)

Even the most efficient greenhouses probably have some leeks. I also get air exchange when I run my propane heater, which must exhaust air as it burns. It also helps to lower the humidity after watering.


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## Yoyo_Jo (Feb 19, 2012)

I open windows in our house at every opportunity, even now during the winter. We've had an exceptionally mild winter this year and there's only been a few weeks at the most where it was too cool to open the windows.


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## Rick (Feb 20, 2012)

The GH isn't airtight, and if leaked much more it would cost me $1000 a month to heat in the winter.

The plants seem to do fine with what leaks are present, and with me opening and closing the door a half dozen times a day. And there are plenty of fans to move the air around inside.


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## Rick (Feb 20, 2012)

SlipperFan said:


> Hmmm, lets see -- orchids are plants. They breathe in carbon dioxide and breathe out oxygen. So there is nothing fresher than the air in a greenhouse (or house) full of orchids. oke:



Well plants do this in the presence of light. But at night the respire like the rest of us.

However the next oxygen production by plants during the day is what created the habitable atmosphere that the respiring creatures of this earth depend on. So I would agree that during the day plants create fresh air. But it doesn't take much of anything leak wise to support a GH at night.

I guess the same question could be asked of how people can survive in their houses without suffocating at night (even thought the windows and doors are shut).

Then there's the semi hydro question with large amounts of roots immersed full time in water, generally with no photosynthesis taking place from algae, but those roots seem to "breath" just fine.


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## Rick (Feb 20, 2012)

paphreek said:


> Even the most efficient greenhouses probably have some leeks. I also get air exchange when I run my propane heater, which must exhaust air as it burns. It also helps to lower the humidity after watering.



I use a ventless propane heater to back up the electrics. So it typically only runs substantially on the nights below freezing.

Burning propane adds a bit of CO2 and water vapor from a ventless heater, so doesn't bother the humidity.

Even though its not nearly as cold in TN as it is up in your part of the world Ross, I can here my fogger turning on and off at night when the North winds are blowing. So that means that my humidity is dropping to below 70% to kick on the humidification system. Without the humidification system my GH humidity would drop to >30% with the electrics running and cold/dry North winds blowing.


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## Stone (Feb 20, 2012)

Rick said:


> > I guess the same question could be asked of how people can survive in their houses without suffocating at night (even thought the windows and doors are shut).
> 
> 
> 
> I guess the bigger your g/house -the greater the volume of air- the longer it will take before you need to change it So a very small enclosure will need more frequent changes. Bigger g/houses are also easier to manage temp. wise.


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## Rick (Feb 20, 2012)

I don't know about that.

When it got real cold here a few years back, and propane tripled in price, people with big houses moved everything into a few small rooms in the center of the house, and used space heaters to keep the core warm. Since then the trend has been to increase the sealing/insulation of houses. Reducing leaks and air exchange.

Air doesn't hold heat very well, so the more you have the more energy it takes to heat it. That's why the IR heaters are so popular since the energy goes preferentially to solids and water rather than air.


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## Shiva (Feb 20, 2012)

I live in an old house that's leaking like crazy. It's really like pores on the walls. Still, whenever the weather is warm enough outside, I open a window or two in the plant room for a few hours.


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## Erythrone (Feb 20, 2012)

I live in Eastern Canada where winter can be very cold (but not this year!!!).

The growing room is in our home in the basement and it if "full" of growing lights. Of course, it is not like a GH in Australia!

It would be quite hot if there was not air exchange almost all year round! The window is almost always open and there are holes in a wall for extractors that often run all day long, even at some winter nights. But I should say that I shut the window and the holes when there is a arctic winter outdoor (something like -25 C or less at night).


I just avoid cool breeze directly on plants. The breeze is diffused by strong air movement of fans. 

For me it was very important to add humidity to the air in winter. It is very important since cold air can’t hold as much moisture than warm. In Summer the humidifiers are oftent shut down but in Winter they are very important!


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## Ray (Feb 20, 2012)

paphreek said:


> Even the most efficient greenhouses probably have some leeks.


Not mine! I grow those in the garden (Sorry, Ross. Couldn't resist.)

A few years back I replaced a Modine heater that used greenhouse air for combustion and positive exhaust ventilation with a Reznor separated-combustion chamber design. It draws air in via a flue pipe that surrounds the exhaust pipe, using that preheated air for both. Obviously it's not forcing the air exchange that the Modine did,

The result: no loss of humidity or already-warmed air out of the exhaust, and a 40% reduction in fuel use. The plants are much happier, and so is my bank account.

While I absolutely agree in the need for _some_ air exchange, I've not seen any structure so tight that it causes any issues. Consider how difficult it is to maintain humidity in a home. Air is a lot harder to "trap" than is water vapor.


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## Lanmark (Feb 20, 2012)

Ray said:


> Not mine! I grow those in the garden (Sorry, Ross. Couldn't resist.)



:rollhappy: I was thinking the same thing. Then I got hungry for some potato-leek soup.


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## gonewild (Feb 20, 2012)

When Plants grow in an enclosed environment they certainly alter the atmosphere. If the environment was completely enclosed the the gases would become a problem if there is in fact only plants in the enclosure. But there are organisms in, on and around the plants that use use the gases the plants create for their growth and in turn release gases the plants use. 

I wonder how many minutes it takes a human to "recycle" the plant gases in a small greenhouse even if it were completely airtight? Or how many orchid plants it would take to produce enough oxygen to keep a human alive?


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## Erythrone (Feb 20, 2012)

I often think about air exchange (not only air movement) as a way to decreace the" airborne diseases" problems.

Mother Nature doesn't care about wetting the orchid's foliage many hours before night... But many owners like me seem to have problems with diseases in cool weather and we must take care with water splash and water early. And I don't think it is only because of cloudest days or short photoperiod because I grow under lights and I had many problems with rot with long photoperiod and high light level in spring. I don't think it is only because of the high humidity, because HR is almost always higher than 65 % year round.

OK.. maybe I am wrong... The disease is sometimes a fungus. So maybe it has been carried as a spore in the air... but what about bacterial rot?


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## Rick (Feb 20, 2012)

gonewild said:


> When Plants grow in an enclosed environment they certainly alter the atmosphere. If the environment was completely enclosed the the gases would become a problem if there is in fact only plants in the enclosure. But there are organisms in, on and around the plants that use use the gases the plants create for their growth and in turn release gases the plants use.
> 
> I wonder how many minutes it takes a human to "recycle" the plant gases in a small greenhouse even if it were completely airtight? Or how many orchid plants it would take to produce enough oxygen to keep a human alive?



http://en.wikipedia.org/wiki/Biosphere_2#Biosphere_2

These people might help you figure it out.


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## Rick (Feb 20, 2012)

Erythrone said:


> Mother Nature doesn't care about wetting the orchid's foliage many hours before night... But many owners like me seem to have problems with diseases in cool weather and we must take care with water splash and water early. And I don't think it is only because of cloudest days or short photoperiod because I grow under lights and I had many problems with rot with long photoperiod and high light level in spring. I don't think it is only because of the high humidity, because HR is almost always higher than 65 % year round.



This observation was one of the reasons I worked on the low K fertilizer system. The problem isn't the air, or the microbes present, but the plants lack of resistence to disease caused by poor nutrition.

One of the articles I found demonstrated how common agricultural plants (like beans or potatoes) were more susceptable to Erwinia and Botrytus (to of the common bacteria and fungal orchid disease genera) when leaf tissue concentrations of K exceeded the concentrations of Ca/Mg.

Since going low K the plant leaf consistancy is much tougher and glossier. My incidence of mealybug and erwinia problems has dropped substantially. I don't need to use chemicals, and I can water almost whenever I want (the fogger comes on anytime the humidity is below 70%, which could be in the middle of the night).


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## Stone (Feb 20, 2012)

Rick said:


> I don't know about that.
> 
> When it got real cold here a few years back, and propane tripled in price, people with big houses moved everything into a few small rooms in the center of the house, and used space heaters to keep the core warm. Since then the trend has been to increase the sealing/insulation of houses. Reducing leaks and air exchange.
> 
> Air doesn't hold heat very well, so the more you have the more energy it takes to heat it. That's why the IR heaters are so popular since the energy goes preferentially to solids and water rather than air.



Maybe it's different in the northeren hemisphere where the temps can be more extreme, but I find that the bigger your enclosure is the less temperature fluctuation you get. 
Yes air doesn't hold heat very well but once the space has been brought up to temp in a big glasshouse it remains much more stable regardless of a sudden drop or spike on the outside which we often get here. - a kind of buffering effect- which is more condusive to good grrowing.
For instance, my g/h is 11mt long x 5mt wide and 4mt at the apex. If we have a warm sunny day say 30c, the inside- with shade up- will slowly climb from 15c to 30c and may take 4 hours to get there and the same is true in the afternoon even if we get a thunderstorm and the temp suddenly drops from 30 to 20, you would hardly notice it inside.
If on the other hand I had a small commercial unit of 4mt x 2mt x 2mt, the cooler and heater would going on and off all the time.
I think it's also important to have your g/house crammed full of plants including ground covers under the benches for extra humidity and as a heat bank.
Of course having your growing area inside the house will give you that same-or better- temp buffering.


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## keithrs (Feb 20, 2012)

Erythrone said:


> I often think about air exchange (not only air movement) as a way to decreace the" airborne diseases" problems.
> 
> Mother Nature doesn't care about wetting the orchid's foliage many hours before night... But many owners like me seem to have problems with diseases in cool weather and we must take care with water splash and water early. And I don't think it is only because of cloudest days or short photoperiod because I grow under lights and I had many problems with rot with long photoperiod and high light level in spring. I don't think it is only because of the high humidity, because HR is almost always higher than 65 % year round.
> 
> OK.. maybe I am wrong... The disease is sometimes a fungus. So maybe it has been carried as a spore in the air... but what about bacterial rot?



My theory on root rot and such is that mother natures plants are covered with beneficial bacteria that protect the plants from harmful diseases. I think if we started to use beneficals and stopped with the physan routine, we would have much healthier plants. 

Air exchange also brings up the topic of CO2.... What's optimal PPM for orchids? 1200 PPM? Greenhouse farmers often double the amount of CO2 than we see on a normal day. Should we be dosing CO2 during the day?


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## Stone (Feb 20, 2012)

keithrs said:


> My theory on root rot and such is that mother natures plants are covered with beneficial bacteria that protect the plants from harmful diseases. I think if we started to use beneficals and stopped with the physan routine, we would have much healthier plants.
> 
> Air exchange also brings up the topic of CO2.... What's optimal PPM for orchids? 1200 PPM? Greenhouse farmers often double the amount of CO2 than we see on a normal day. Should we be dosing CO2 during the day?



I think beneficial bacteria and fungi are a good thing if you can arrange an environment for them to prosper but it doesn't get away from the fact that the air exchange/movement in our g/houses is really pathetic compared with habitat where there is constant breezes and WIND. That's where most of our pest and disease problems come from.


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## paphreek (Feb 20, 2012)

Rick said:


> I use a ventless propane heater to back up the electrics. So it typically only runs substantially on the nights below freezing.
> 
> Burning propane adds a bit of CO2 and water vapor from a ventless heater, so doesn't bother the humidity.
> 
> Even though its not nearly as cold in TN as it is up in your part of the world Ross, I can here my fogger turning on and off at night when the North winds are blowing. So that means that my humidity is dropping to below 70% to kick on the humidification system. Without the humidification system my GH humidity would drop to >30% with the electrics running and cold/dry North winds blowing.



My problem is just the opposite, with RH in the 90+% range after watering. With the short days, I use the propane heater to intentionally lower the humidity. My main source of heat is in floor, off peak electric. This may be why my humidity stays so high. As the gravel floor is heated, moisture in the gravel evaporates into the air. After the RH is lowered to a more acceptable 80% or so, I switch back to in floor heat and the propane heater becomes the back up for the rest of the week.


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## keithrs (Feb 20, 2012)

Stone said:


> I think beneficial bacteria and fungi are a good thing if you can arrange an environment for them to prosper but it doesn't get away from the fact that the air exchange/movement in our g/houses is really pathetic compared with habitat where there is constant breezes and WIND. That's where most of our pest and disease problems come from.



Being that I grow outdoors I don't have air movement problem.... but that still didn't do anything to fix the rot problems I had last winter... and the winter before that.

I have been using a bacteria product for about 6 months and I have only lost one plant to black rot(which I had for two weeks while I was switching to k-lite and not using the product) and zero cases of root rot as of yet. Temps here have been in the low 40 for several weeks @ night and low 60 during the day.... rained about 4 or 5 days off and on. With temps that low and that much rain anyone would most likely have rot problems... instead I have new roots grow from the older roots along with new roots and there only getting about 3 hrs. of sun a day. Though it may be do to the combo of low k and beneficial's.... either way I'm happy as a clam!!!!


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## Erythrone (Feb 20, 2012)

I thought about that too... but since I don't write English very well nor quickly, I decided to not write it. 

Scientific works have been made and we can now use some microbial antagonists to control some diseases. I guess there should be some microbial antagonists near many orchids in nature.

Actually, there may be several explanations for diseases in our collection... not enough air movement, not enough air renewal, no antagonist, etc.

Nutrition problems, like Rick said? Why not. Since I read the threads about K, I think about a kind of "fertilizer renewal"... But I must be « sure it is broken before I fix it ». 

Sometimes a plant is simply not adapted to a new pathogen and the species is simply decimated.

Examples : Dutch Elm Disease killing american elms. Native walnut tree, Juglans cinerea (butternut), dying everywhere here because of a foreign fungus whose name is almost impossible to remember.

And of course, we must sometimes admit that pathogens are simply part of an ecosystem... The same for many insects!


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## Rick (Feb 20, 2012)

Stone said:


> I think it's also important to have your g/house crammed full of plants including ground covers under the benches for extra humidity and as a heat bank.
> Of course having your growing area inside the house will give you that same-or better- temp buffering.



Yes thermal mass adds a lot of heat stability. Anything to take up air volume and replace with heat holding solids and liquids will help. Storing tanks of water under the benches, piles of bricks, plants.....

I guess if you also replace dead air with tanks of water, rocks, brick.....then whatever air leaks in/out will increase the effective exchange rate.


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## Rick (Feb 20, 2012)

Stone said:


> I think beneficial bacteria and fungi are a good thing if you can arrange an environment for them to prosper but it doesn't get away from the fact that the air exchange/movement in our g/houses is really pathetic compared with habitat where there is constant breezes and WIND. That's where most of our pest and disease problems come from.



The air is full of fungus and mold spores all the time. Bacteria and virus don't travel all that far except in water vapor. Just recently heard an interview with a fungus expert who noted that if you sample air (out in the ambient) you would probably be shocked to see how much life there is out there.

Granted in an enclosed environment you will get higher levels of microbes in the air. But swab around healthy plants and you can probably find low levels of your favourite pathogens all the time. They're just waiting for the right stressor:evil:


Do you have a number for optimal air exchange rate? I can't afford to heat / humidfy any more than my present leaks will allow so my plants are just going to have to live with what they get.

This is probably better than I get in my bedroom each night (which is smaller and better sealed than my GH!


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## Stone (Feb 20, 2012)

Rick said:


> > The air is full of fungus and mold spores all the time. Bacteria and virus don't travel all that far except in water vapor. Just recently heard an interview with a fungus expert who noted that if you sample air (out in the ambient) you would probably be shocked to see how much life there is out there.
> >
> > Granted in an enclosed environment you will get higher levels of microbes in the air. But swab around healthy plants and you can probably find low levels of your favourite pathogens all the time. They're just waiting for the right stressor:evil:
> 
> ...


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## SlipperFan (Feb 20, 2012)

Stone said:


> Er-- not quite Dot. The g/house air that might seem fresh to people might be quite stale to plants. I think air repalcement is very important for plants. not just leaves but roots are continually exchanging gases. Without an air change an imbalance of air chemistry would surely occur in an enclosed area? Not to mention creating a better evnironment for bugs.
> 
> Mike






Rick said:


> Well plants do this in the presence of light. But at night the respire like the rest of us.
> 
> However the next oxygen production by plants during the day is what created the habitable atmosphere that the respiring creatures of this earth depend on. So I would agree that during the day plants create fresh air. But it doesn't take much of anything leak wise to support a GH at night.


I hope everyone understands that my post was a bit tongue-in-cheek.



Rick said:


> The GH isn't airtight, and if leaked much more it would cost me $1000 a month to heat in the winter.
> 
> The plants seem to do fine with what leaks are present, and with me opening and closing the door a half dozen times a day. And there are plenty of fans to move the air around inside.


That's my theory, also.



paphreek said:


> My problem is just the opposite, with RH in the 90+% range after watering. With the short days, I use the propane heater to intentionally lower the humidity. My main source of heat is in floor, off peak electric. This may be why my humidity stays so high. As the gravel floor is heated, moisture in the gravel evaporates into the air. After the RH is lowered to a more acceptable 80% or so, I switch back to in floor heat and the propane heater becomes the back up for the rest of the week.


Clever, Ross!


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## Stone (Feb 20, 2012)

Rick said:


> > Do you have a number for optimal air exchange rate?
> 
> 
> 
> ...


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## Rick (Feb 20, 2012)

Stone said:


> Rick said:
> 
> 
> > So during very cold weather you could probably reduce this drasticlly but still try to change your air at least once or twice/day? to replace co2.
> ...


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## Stone (Feb 20, 2012)

Rick said:


> Stone said:
> 
> 
> > Burning propane with a 30,000 BTU ventless heater will replace plenty of CO2 without opening any vents in my little GH. Given that the low O2 sensor has never shut down the heater, I must have adequate ventilation to feed O2 to the burner.
> ...


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