[late]

[usermention=41202]

@late[/usermention]

By discussing greenhouses?

Yup.

Creating the appearance of controversy is a standard propaganda technique. Big Oil copied it from the tobacco guys.

I posted about this a few days ago:

https://www.politicsforum.org/forum/viewtopic.php?f=6&t=181311

[QatzelOk]

If anyone's planning on actually building their own greenhouse in order to see a microcosm of how the entire earth works, eBay has wood, and metal frames for greenhouses:

https://www.ebay.ca/b/Greenhouse-Frames ... olid=10001

I'm not selling anything, by the way. I'm just trying to help everyone understand how complex industrial pollution is to our fragile ecosystems. And the trend in this regard is building a greenhouse.

I guess everyone wants to grow weed and wait for the end of life for our species.

I appreciate a thread that changes the way we live our lives, like this one, pushing Internet geeks into DIY farming.

[ingliz]

@Truth To Power

We were discussing well-maintained garden greenhouses. And as a well-maintained garden greenhouse is a closed system (until you choose to open it), what's happening outside is irrelevant.

"a closed system"

Closed systems allow energy transfer but no transfer of mass.

[Pants-of-dog]

@Truth To Power

If convection is blocked, that means the air does not move, right?

If the air does not move, then the air at the top of the greenhouse stays there.

And if the air up there is unmoving, how does it make space for the ascending air?

[Truth To Power]

@Truth To Power

If convection is blocked, that means the air does not move, right?

Wrong. A chimney over a working fireplace works by convection. If you close the damper, blocking that convection, the hot air, smoke, etc. that would otherwise go up the chimney will just spew out into the room. The fact that the smoke will spew out into the room does not mean that the convection in the chimney is not blocked by the damper.

You will now contrive some disingenuous means to avoid knowing these facts.

If the air does not move, then the air at the top of the greenhouse stays there.

And if the air up there is unmoving, how does it make space for the ascending air?

Thank you for fulfilling my prophecy.

[Truth To Power]

@Truth To Power

We were discussing well-maintained garden greenhouses.

No we weren't. You just made that up. You must like to make $#!+ up: you do it a lot.

And as a well-maintained garden greenhouse is a closed system (until you choose to open it), what's happening outside is irrelevant.

"a closed system"

Closed systems allow energy transfer but no transfer of mass.

A well maintained garden greenhouse is not a closed system. Enough warm air can get out to keep its air pressure equal to the outside pressure.

[ingliz]

@Truth To Power

In a fully closed greenhouse, there are no open ventilation windows. Therefore there is no transfer of mass, no air escapes.

In some large commercial houses, there are no ventilation windows.

[Truth To Power]

@Truth To Power

In a fully closed greenhouse, there are no open ventilation windows.

So what? It's still not airtight, proving me right and you wrong.

Therefore there is no transfer of mass, no air escapes.

Yes, of course it does, to equalize pressure. Otherwise, it would blow up when the air inside was heated.

I'm right, you're wrong. You had better get used to that, as it will continue to happen every time you presume to dispute with me.

In some large commercial houses, there are no ventilation widows.

Another miracle of irrelevancy.

You're wrong. I'm right. Deal with it.

[Pants-of-dog]

Wrong. A chimney over a working fireplace works by convection. If you close the damper, blocking that convection, the hot air, smoke, etc. that would otherwise go up the chimney will just spew out into the room. The fact that the smoke will spew out into the room does not mean that the convection in the chimney is not blocked by the damper.

You will now contrive some disingenuous means to avoid knowing these facts.

Thank you for fulfilling my prophecy.

Your refusal or inability to answer the questions is noted.

Again, I am asking you to describe how the convection is blocked, and what how this heats the interior.

Specifically, what happens after the air ascends into the top of the greenhouse and what happened to the air that was there before?

[Truth To Power]

Your refusal or inability to answer the questions is noted.

Your continued baldly false claims about what I have plainly written are noted.

Again, I am asking you to describe how the convection is blocked, and what how this heats the interior.

Again, I am telling you that the convection that is blocked by a greenhouse's roof (and walls, to address your inevitable disingenuous contrivances to avoid knowing relevant facts) is the same convection that makes the open field adjacent to the greenhouse cooler.

Specifically, what happens after the air ascends into the top of the greenhouse and what happened to the air that was there before?

The warm air that has been heated by the ground displaces cooler air at the top of the greenhouse, which then descends to the ground, picking up more heat, and repeating the cycle. Because the greenhouse prevents the warm air from rising past its roof, its heat is retained, warming the greenhouse. The open field adjacent to the greenhouse has no roof or walls, so the air that is warmed by the ground continues rising, and its heat is lost to the open atmosphere.

I prophesy that you will now concoct some additional disingenuous contrivance to avoid knowing the indisputable facts of objective physical reality that I have identified (not much of a prophecy, granted, as your response is always the same).

[Pants-of-dog]

Your continued baldly false claims about what I have plainly written are noted.

Again, I am telling you that the convection that is blocked by a greenhouse's roof (and walls, to address your inevitable disingenuous contrivances to avoid knowing relevant facts) is the same convection that makes the open field adjacent to the greenhouse cooler.

The warm air that has been heated by the ground displaces cooler air at the top of the greenhouse, which then descends to the ground, picking up more heat, and repeating the cycle.

Yes, this is what I explained to you when I pointed out that the convection of interior air is not blocked.

Because the greenhouse prevents the warm air from rising past its roof, its heat is retained, warming the greenhouse.

Yes and no.

First of all, thanks for admitting that solar radiation is the way the greenhouse heats itself.

And yes, some of the heat is not dissipated to the exterior as quickly if exfiltration is blocked, but also that heat goes to heat the cool glass roof. This cools the air, and then the air descends, which means the convection is bot blocked.

The open field adjacent to the greenhouse has no roof or walls, so the air that is warmed by the ground continues rising, and its heat is lost to the open atmosphere.

I prophesy that you will now concoct some additional disingenuous contrivance to avoid knowing the indisputable facts of objective physical reality that I have identified (not much of a prophecy, granted, as your response is always the same).

All of this is irrelevant.

[Truth To Power]

Yes, this is what I explained to you when I pointed out that the convection of interior air is not blocked.

No, it was a contrivance you concocted to evade the fact that greenhouses work by blocking convective heat loss to the open atmosphere. You then compounded your despicable, disgraceful and loathsome behavior by disingenuously trying to change the subject to the irrelevant convective circulation of its interior air that the greenhouse's blockage of external convection initiates.

Yes and no.

No, only yes.

First of all, thanks for admitting that solar radiation is the way the greenhouse heats itself.

First of all, thanks for once again confirming your invariable practice of misleading readers by falsely and disingenuously implying that I only reluctantly "admitted" a fact that has been self-evident from the outset, and which you are fully aware I never disputed.

And yes, some of the heat is not dissipated to the exterior as quickly if exfiltration is blocked, but also that heat goes to heat the cool glass roof. This cools the air, and then the air descends, which means the convection is bot blocked.

If convection is not blocked, why does the warm air in the greenhouse stop rising when it reaches the greenhouse roof? Why doesn't it go on rising, as the warm air rising from the adjacent open field does? (This should be good.)

All of this is irrelevant.

It proves you wrong, so you have to contrive some disingenuous means of evading it. Simple.

[Pants-of-dog]

No, it was a contrivance you concocted to evade the fact that greenhouses work by blocking convective heat loss to the open atmosphere. You then compounded your despicable, disgraceful and loathsome behavior by disingenuously trying to change the subject to the irrelevant convective circulation of its interior air that the greenhouse's blockage of external convection initiates.

No, only yes.

First of all, thanks for once again confirming your invariable practice of misleading readers by falsely and disingenuously implying that I only reluctantly "admitted" a fact that has been self-evident from the outset, and which you are fully aware I never disputed.

Your insulting and rude behaviour aside, you seem to finally be getting it.

You have conceded that the air does not stop when it hits the roof, nor does it heat the greenhouse space down where the people are.

Let us move on.

If convection is not blocked, why does the warm air in the greenhouse stop rising when it reaches the greenhouse roof? Why doesn't it go on rising, as the warm air rising from the adjacent open field does? (This should be good.)

For the fourth or fifth time, the air descends after it ascends to the roof.

This is what we mean when we say the convection is not blocked.

You seemed to argue that is magically stayed there, and now you seem to agree with me that it cools then descends.

It proves you wrong, so you have to contrive some disingenuous means of evading it. Simple.

You do not even know what “it” is here.

[ingliz]

Otherwise, it would blow up when the air inside was heated.

Bollocks!

It’s a good idea to have an airtight greenhouse - the heat can’t escape (not quickly anyway) - that way, you get to choose when to let the warm air out.

And choosing is good; too high or too cold a temperature can kill the plants.

An airtight example

Yes, 100% sealed: a commercial hermetically sealed greenhouse.

[Truth To Power]

Your insulting and rude behaviour aside,

Unfortunately, under the forum rules, I am not allowed to behave as rudely and insultingly as your behavior merits.

you seem to finally be getting it.

Wish I could say the same...

You have conceded that the air does not stop when it hits the roof,

Because the roof blocks the convection that would otherwise take the heat in that air and release it into the open atmosphere.

nor does it heat the greenhouse space down where the people are.

No, that is false. It heats the greenhouse space all the way to the ground because it is still warmer than the outside air, thanks to the roof (and walls) blocking convection.

For the fourth or fifth time, the air descends after it ascends to the roof.

I asked you why it doesn't keep rising, given that it is warmer and less dense than the surrounding atmospheric air, not whether it stays up at the roof.

I repeat: WHY doesn't the warm air in the greenhouse continue to rise after it reaches the roof? It is certainly warmer and less dense than the atmospheric air around the greenhouse. What stops it from continuing to rise by convection?

Such a mystery.

To you, that is...

This is what we mean when we say the convection is not blocked.

No it isn't. If convection is not blocked, what stops the warm, less dense air from continuing to rise once it reaches the greenhouse roof, hmmmmmmmmm?

You seemed to argue that is magically stayed there, and now you seem to agree with me that it cools then descends.

No I did not seem to argue any such thing. You simply made that up and then falsely and disingenuously attributed it to me, as is your wont. I never said or implied that it stayed there, magically or any other way. I stated the fact that the roof stopped it from rising and thus carrying heat from the ground away into the open atmosphere by convection.

You do not even know what “it” is here.

Wrong again. "It" is the factual content I identified in my previous post.

Why do you always feel you have to make false and disingenuous claims about what I have said, what I mean, what I know, etc.? Is it because you know you have nothing factual or relevant to offer, and are afraid readers will discern the truth?

[Pants-of-dog]

Unfortunately, under the forum rules, I am not allowed to behave as rudely and insultingly as your behavior merits.

Wish I could say the same...

Because the roof blocks the convection that would otherwise take the heat in that air and release it into the open atmosphere.

No, that is false. It heats the greenhouse space all the way to the ground because it is still warmer than the outside air, thanks to the roof (and walls) blocking convection.

No. Air above humans does not warm humans. The air has to be touching the humans to warm them.

The air warms the roof, as I explained and as you acknowledged.

I asked you why it doesn't keep rising, given that it is warmer and less dense than the surrounding atmospheric air, not whether it stays up at the roof.

I repeat: WHY doesn't the warm air in the greenhouse continue to rise after it reaches the roof? It is certainly warmer and less dense than the atmospheric air around the greenhouse. What stops it from continuing to rise by convection?

Because it is too,busy descending after cooling the roof.

As I said, the convection current is unbroken and the air inside the greenhouse keeps moving,

Prove me wrong.

Such a mystery.

To you, that is...

No it isn't. If convection is not blocked, what stops the warm, less dense air from continuing to rise once it reaches the greenhouse roof, hmmmmmmmmm?

Because the air warms the roof and cools itself in the process, then descending into the lower part of the greenhouse.

And you agreed with this.

No I did not seem to argue any such thing. You simply made that up and then falsely and disingenuously attributed it to me, as is your wont. I never said or implied that it stayed there, magically or any other way. I stated the fact that the roof stopped it from rising and thus carrying heat from the ground away into the open atmosphere by convection.

Wrong again. "It" is the factual content I identified in my previous post.

Why do you always feel you have to make false and disingenuous claims about what I have said, what I mean, what I know, etc.? Is it because you know you have nothing factual or relevant to offer, and are afraid readers will discern the truth?

Then you were incredibly unclear about what happens with the air.

Once the sun heats the floor and the air, the air ascends. What happens after that? Explain in clear detail.

If you say that it displaces the existing air against the roof which has cooled, and the cold air moves over to allow for this newly heated air to rise, then you are agreeing with me.

[Truth To Power]

Bollocks!

Fact.

It’s a good idea to have an airtight greenhouse - the heat can’t escape (not quickly anyway) - that way, you get to choose when to let the warm air out.

Garbage. As soon as the internal pressure rises because the air is warmed by the sun, it escapes, equalizing the pressure. If it didn't, the greenhouse would pop.

An airtight example

Yes, 100% sealed: a commercial hermetically sealed greenhouse.

No it isn't. It just uses controlled and filtered rather than natural ventilation, including fans to maintain consistent positive pressure to prevent pathogen ingress. It is not in any sense "airtight."

[Pants-of-dog]

Fact.

Garbage. As soon as the internal pressure rises because the air is warmed by the sun, it escapes, equalizing the pressure. If it didn't, the greenhouse would pop.

Not necessarily.

The glass could easily keep in the heated air, as long as the air does not build above whatever pressure it takes to break the glass,

Also, this is not a problem if the internal air pressure can be controlled mechanically, which seems to be the case.

No it isn't. It just uses controlled and filtered rather than natural ventilation, including fans to maintain consistent positive pressure to prevent pathogen ingress. It is not in any sense "airtight."

It is in the sense that the building envelope is airtight.

You seem to be arguing that it stops infiltration of air by always having positive pressure pushing air out. But since the webpage also notes that insects and vapour would also not be able to enter or exit, it cannot be simply positive pressure.

[ingliz]

@Truth To Power

They use heat exchangers and solar to power them; no venting required.

[Truth To Power]

@Truth To Power

They use heat exchangers and solar to power them; no venting required.

The fact that they use heat exchangers without venting shows the greenhouses are not airtight: the pressurized air is escaping through tiny apertures, and even into the ground. What would stop it?