keeping plants cool the computer way

[iann]

But now your computer will overheat

[Ernie]

[ralphrmartin]

My fans are circulation fans, positioned fairly high up, in the hope that this will also pull cooler air in from outside. as there are paired ridge vents along the length of the roof.
Point taken that intake fans could well be rather more effective.

Ernie, my reference to scams was a response to your remark "there are a lot of growers in the UK who use all manner of fans, they cannot all be wrong".
Just because a lot of people do something is no guarantee of correctness. I was trying to justify my point with a counter-example to your proposition: many people fall for scams, and they are all wrong in their belief that the scam is genuine in some way.

In fact, the effects and effectiveness of fans are complex:
- some may just act to mix the air, which can help to prevent localised hot spots (and thus scorching), without reducing the average temperature
- mixing may also lead to some cooling on average if the glass is cooler than the inside temperature
- some may pull in cooler air from outside
- some may cause a large enough airflow over transpiring plants / buckets of water to cause evaporative cooling
- and perhaps other ways I have not thought of

[Pattock]

My fans are circulation fans, positioned fairly high up, in the hope that this will also pull cooler air in from outside. as there are paired ridge vents along the length of the roof.
Point taken that intake fans could well be rather more effective.

In fact, the effects and effectiveness of fans are complex:
...
...
- and perhaps other ways I have not thought of

I had thought that part of the reason for fans was also to prevent localised high humidity, in a damp corner or at the base of recently-watered plants or on the dead flower junction of the plants.

For day-breathers it helps mix up the CO2 levels next to the leaves as well. I'll have to think about whether that works for our night-breathers. My first thought is that I don't see why not when they are growing fast, even though they are not usually producing a dense and complex canopy like a tomato. Edited to add, of course some have a dense, impenetrable coat of spines or fur that could slow CO2 exchange when the stomata are open.

An intake fan can also reduce flying pest invasions. Having a fine mesh over the intake will sieve them out. The positive pressure inside the greenhouse will mean you have a constant flow of air out of any open doors/gaps which will stop an undetermined flying pest from getting in. They can still walk, of course.

Considering the temperatures you have in there, you could plant an avenue of tropical bushes up to the door.

[ralphrmartin]

I had thought that part of the reason for fans was also to prevent localised high humidity, in a damp corner or at the base of recently-watered plants or on the dead flower junction of the plants.

Indeed, my main initial motivation for installing fans was to prevent stagnant air which makes it easier for fungus spores to settle and grow (Botrytis being my concern). That problem has been overcome.

An intake fan can also reduce flying pest invasions. Having a fine mesh over the intake will sieve them out. The positive pressure inside the greenhouse will mean you have a constant flow of air out of any open doors/gaps which will stop an undetermined flying pest from getting in. They can still walk, of course.

On the other hand, circulating air might help to spread any pests already inside, particularly very small ones.

For mites and thrips, I suspect you would need such a fine mesh over the intake that it would seriously impede the airflow.

[Ernie]

Ralph said Ernie, my reference to scams was a response to your remark "there are a lot of growers in the UK who use all manner of fans, they cannot all be wrong".
Just because a lot of people do something is no guarantee of correctness. I was trying to justify my point with a counter-example to your proposition: many people fall for scams, and they are all wrong in their belief that the scam is genuine in some way.

Sorry Ralph I still have no idea why the subject of scams got brought into a thoroughly innocent genuine post by me explaining my simple system to keep the air moving. (Important in winter. My mainly succulent collection needs a minimum of 5 degrees. The heater fan keeps the air moving when supplying heat. The other fans keep the air moving.) We all have ideas that work for us and mine works for me so please accept that I am happy with it. I am sure there will be those, free spirits, who may want to try it and others who think its rubbish. That's fine but please accept that reference to scams was just out of place. I have my faults but being a scammer is not one.
In one of my other hobbies, hydrodynamics and aerodynamics are very important considerations but not so in this one. BTW If you want to see what I mean check youtube for Bluebird K7 Lazenby. Getting that to work well at high speed required detailed knowledge of both hydrodynamics and aerodynamics. Scratch built by me with a real jet engine I built. https://www.youtube.com/watch?v=y2ANJAVRQpQ
Peace-keep well.

[Pattock]

For mites and thrips, I suspect you would need such a fine mesh over the intake that it would seriously impede the airflow.

Looks like the Econet 1515 screen mesh was designed for you! Though I don't know if you will be able to buy it in less than wholesale quantities. In a city you would have to clean the screen regularly.

https://www.ludvigsvensson.com/en/clima ... n-screens/.

[MikeT]

I have a fan running continuously. In winter the rationale is to improve air flow to reduce botrytis/fungal infection risk. In summer it's to reduce scorch risk since air in a 6' x 8' greenhouse can get locally hot enough to cause damage. I am sure that scorch is a risk because it's happened. I haven't done a controlled double blind experiment; I'm relying on my anecdotal evidence that both problems are much reduced since I adopted the continuous fan approach.

[Ernie]

I was discussing this thread with my wife who said why don't you get into the technical side of the issue.
I gave it some thought and decided that discussing fan blade shape/ pitch/rake/diameter/ RPM/type of motor and volume of air being moved would send everyone to sleep faster than Boris with his latest mutterings.
Keeping it simple is best. Whatever works works! I often say, people have a fridge, they know it works but don't need to know or indeed don't want to know why it works. Keep it cool fan or no fan

[ralphrmartin]

Ernie, I sincerely apologise if I have given you the wrong impression unintentionally. I was not in any way trying to suggest you were somehow connected with scams.

As a scientist, I am sure you would appreciate the point that a lot of people believing in something does not make it true. I was just using an example to illustrate that point, perhaps not a well chosen one.

Anyway, please accept my apologies, and let's get back to cacti and succulents and growing them.