Greenhouses receive solar radiation through the glass. Essentially all of that energy has to escape back out of the greenhouse. The only place for it to escape is back out through the glass.
Heat flow between two points is proportional to the temperature difference, and also proportional to the thermal conductivity. The glass has low thermal conductivity, so the temperature inside the greenhouse has to rise to keep the heat flowing out at the same rate it is coming in – creating a large temperature drop across the quarter inch of glass.
Without the glass, the heat would escape much more efficiently, and the temperature would be lower. The energy flow through the system is the same with or without the glass, but the temperature is higher with the glass in place.
I agree on the radiation and conduction components.
The glass also separates convection into 2 zones. Natural convection (sans glass enclosure) would rapidly carry that heat energy upwards and away from the gardening area. The glass creates a separate, localized convection environment, limiting heat losses from the greenhouse system to (essentially) only radiation and conduction.
There’s a simple way to test the hypothesis and that is to open a window flap leaving the glass ajar so that it is still blocking the hole but leaving a gap around it. If the heat were constrained by thermal conductivity, then as the glass is still largely in place there would be almost no impact on temperature from conduction. It also has very little impact on radiation transfer.
So, if opening such a window did cause a significant drop in temperature this proves that heat is lost from convection.
davidswuk says:
24th November 2014 at 3:09 pm
All very well, but – just gaze into a Northern red sunset and wonder why then your retina do not fry………..
well there`s still ONE HUNDRED/m2 or so WATTS of ENERGY at around 0.8um lighting-up the sky whereas, in the LIR world, at 15umt (CO2`s blocking frequency) there is LESS THAN FIVE for Co2 to take a nibble at.
And so, when it comes to real heat, 0.8um at about 120c and 15um near 20c, 3why is it we BELIEVE that Co2 is any sort of a problem warming-wise and not cooling??
Reply
I didn’t address any mechanisms, so difficult to see what it is that you could possibly be disagreeing with.
the relevance of low grade heat/energy to the concept of AGW
dq = -k dT/dz, except at NCDC, where dq = k dT/dz, by Executive Order
Well, no. The sunlight causes a disequilibrium state where heating occurs in proportion to the exchange of energy occurring. In practice, the sunlight is not constant; equilibrium is never reached, just passed through on the way up and the way down.
Also for these purposes, glass is a poor insulator. Just ask anyone who has to keep a glasshouse warm.
Your comment is extremely annoying and a waste of space.
Its only annoying because your analogy is sloppy. You’re capable of better.
Reblogged this on IF THE TRUTH BE KNOWN…BLOGGING BAD w/Gunny.G….
Whenever you introduce a solid of any kind into your metaphor, you block convection. The atmosphere does not do this. Lose the solid.
There is no convection at the top of the atmosphere. There is plenty of convection inside the greenhouse. Try again at finding petty differences.
Are you familiar with the Wood experiment?
The Wood experiment just showed that suppression of convection was the dominant effect warming a glass greenhouse. It demonstrated nothing one way or another about the atmospheric greenhouse effect.
Did anyone put a greenhouse inside a greenhouse? This would more or less eliminate convection as a factor. Would the inner greenhouse get warmer than the outer?
How does the greenhouse work?
Not by the greenhouse effect.
Isn’t some of that energy taken up by the plants?
Yes NancyG……but Steve here will tell you that it’s heat which is taken up by the plants.
He either can’t get nomenclature right, or he dosn’t know the difference between energy and heat. http://stevengoddard.wordpress.com/2014/11/23/proper-use-of-principles/#comment-461921
The light which was taken up by the plants would have turned to heat without the plants. You need to go make your senseless posts on skepticalspeudoscience or RealClimafia where that is the norm.
Well Steve says that the contents of the glasshouse (plus the plants) ABSORB HEAT.
I was always given to believe they absorb EM Radiation, ie energy ,ie light.
Btw Morgan, I’m a total denialist of the “Greenhouse” effect., so don’t get upset.
They absorb what would have been heat. Petty nitpicking is just annoying.
Well you’re cleverer than me if you can figure out Steve’s comment ,Morgan….but..give a pig wings and whether it would fly or not ..would be petty nitpicking?
Scientist: “The plants absorb some of the heat”
3rd grade science teacher talking to one of her slower students: “The plants absorb light which would have turned into heat if the plants weren’t there”
The scientist above assumed the listener didn’t ride to the lecture on the short bus
Pretty sure that heat is energy, i.e., the vibration of molecules as mechanical energy when they absorb radiation. I’m also pretty sure the molecules can transform that energy by emitting photons thereby going to a quieter state. Think light bulbs. They can also lose the energy by exciting the molecules around them.
There aren’t any plants in this greenhouse.
Ok, thanks. I didn’t mean to cause a disagreement. I only asked because you had said, “Essentially all of that energy has to escape back out of the greenhouse.” I thought that if there were plants then “all” the energy wouldn’t have to escape the greenhouse, some would be used by the plants. Realistically, a greenhouse might also have a gardener going in and out which would also allow heat to escape. So you’re talking about something like a sealed terrarium without the plants. Got it, I think.
Yes NancyG,(the peacemaker 🙂 ) but I have to say that sealed terrarium seems to me like a “closed system” contrary to Steve’s assertions in his comment. When is a closed system not a closed system….when the gardener opens the door.
Exactly, which is nothing like the way a free flowing gaseous atmosphere works. Using the term “greenhouse gas” puts two mutually exclusive terms together to create a nonsensical concept.
If I was to start talking about “rock food” then you would be challenging my english language skills for the same reason.
And yes , it is nothing like a free flowing gaseous atmosphere works. I wrote recently that the velocity of transfer of absorped radiation is extremely fast. Through glass and insulators it is’ perhaps, 1000 times slower. The velocity of radiation energy transfer is what dictates the temperature in the greenhouse.
Beware, transfer through the glass will almost certainly be through kinetic transfer rather than radiation transfer, IMHO. I have not done the experiment.
“Kinetic transfer”? Perhaps you mean conduction?
Heat loss from the greenhouse will be by both conduction and IR transmission back out the glass.
The greenhouse will become hotter the more energy is input. When the energy input is levelled out the greenhouse will stop heating and also level out. This is always the point where energy input is equal to energy output.
The same occurs in reverse.
Certain conditions cause momentary or possibly more permanent increases / decreases in input and a corresponding change in the greenhouse temperature, such as cloud cover.
Agreed Truthseeker, but “greenhouse” gas is still a good analogy. Although a greenhouse contains the same gas mixture as outside, it’s the glass covering that’s the insulator, being the analogy for the “gas” that slows the heat transfer.
Is there a name we can all agree on?
No Olaf, it is not a good analogy. It is a very bad analogy that immediately takes the discussion in wrong areas like blankets, electrical resistors and the like. There is no layer of solid matter in our gaseous atmosphere.
It is even a worse analogy when you consider this use of lapse rate and pressure to get the 33 degrees difference between the S/B modelled temperature and the observered average temperature.
http://hockeyschtick.blogspot.co.uk/2014/11/derivation-of-entire-33c-greenhouse.html
As for terms, how about “lapse rate” or “atmospheric heat capacity”.
Now that’s better
“Heat flow between two points is proportional to the temperature difference, and also proportional to the thermal conductivity. The glass has low thermal conductivity,”
That has got to be the dumbest explanation ever given.
Stick to reporting facts and numbers, the rationales and physics is beyond your powers of description.
Polycarbonate has even lower thermal conductivity than glass. It’s a reason soda in plastic bottles takes far longer to cool in the fridge than glass bottles.
The glass in the greenhouse has a lower thermal conductivity / thermal transfer capability than the convection without it.
Forgot to add:
PJ – Why not cite your explanation as to why Steve’s was “the dumbest”. If you can’t attack the theory with facts of your own, you attack the man?
Lame, dude. Pick up your act.
q = k A dT / s
PJ that is the conductive heat transfer equation. (don’t care about whether the minus sign is in front of the k) Please note that it is what Steve says. The “s” is usually an “L” in other forms of the equation.
Conductivity of the glass has almost nothing to do with how a greenhouse works.
A greenhouse primarily works because it stops convective currents and that is why very thin poly-tunnels with almost no material between the inside and outside are still very effective. It would work even with the thinnest possible membrane – so e.g. if you sit in a bubble bath and put bubbles on top of you, it insulates even though the “greenhouse” is a few molecules thick.
It’s also why a greenhouse with only a small ventilation window can be cooled so effectively.
Yup – see my post above. Convection is a more powerful transfer mechanism where permitted, such as in a gas, but not in a solid, where conduction rules.
I once got asked whether I could design a “parrot incubator”. It seemed a trivial task – my main interest being in the electronics. And then I was told the parrot had to breath and that there had to be air flow – and suddenly a really trivial problem of sticking a temperature controller on a box became a nightmare of air flows and cooling spots and why don’t parrots come with datasheets? What’s the maximum and minimum temperature for a parrot?
Heh. That’s the problem with finicky things such as animals – they need too much oxygen and aren’t too efficient at it. So welding them into a box doesn’t do them much good for long.
The best way is use a larger cardboard box with a smaller opening at the top and hang a single red (IR) light bulb in a corner. The parrot should move either to or from the heat source to regulate its own temp. Should be close to human temp I’d imagine – 96.8F or for us Engerlandish-speakers – 36C.
I think the minimum for a Norwegien Blue is about zero C if you put it in the freezer.
I think the following would be on-topic for this post. That is, if I understand what Steve Goddard was trying to say with that short post.
“Derivation of the entire 33°C greenhouse effect without radiative forcing from greenhouse gases”
http://hockeyschtick.blogspot.com/2014/11/derivation-of-entire-33c-greenhouse.html
I much prefer the term “atmospheric effect” as it is descriptive and has no propaganda component. The heat/energy transfer in thick atmospheres is dominated by convection in the troposphere up to the tropopause. In the tropopause we find that the atmosphere is too thin to sustain convection and so radiation becomes the dominate force to cause cooling of the stratosphere and above.
Good one! And in contrast to some of the other posts by others above, neither impolite nor condescending.
“The heat/energy transfer in thick atmospheres is dominated by convection in the troposphere up to the tropopause.”
Completely agree with that statement. Thermodynamic and hydrostatic equations completely describe thick troposphere differentials of temperature, pressure, density (mass/volume) while temperature gradients remain linear without any radiation considerations at all. I have spent the last two years studying this exact topic as applied to four different atmospheres and you cannot deny what you are saying, it is true.
The key is density which you rarely hear even mentioned. Any local influx of energy that is absorbed immediately decreases the density and all planetary atmospheres are strictly sorted vertically by density, not pressure or temperature though temperature and pressure track density closely vertically by well established thermodynamic and hydrostatic equations. Leave density out of the picture and you will always be outside reality to some degree or the other. Density rules the convection/subsidence within gases in a gravitational field.
Hey Wayne! Yes, radiative effects, while real, are completely overwhelmed except in special cases. Convection, (the obvious outcome of density variations (which is to say “temperature variations”) in the atmosphere) is enormously efficient at transporting heat. Throw in the phase changes of water and the increased albedo from clouds and I suspect that any radiative effects would be hard to even measure. About the only times where the presence or absence of GHG becomes a real-world factor is when speaking about water vapour as a GHG. As for CO2 — it might be a factor in the deep interior of Antarctica where water vapour is negligible, or maybe in the high Atacama Desert, but otherwise it is a gnat on an elephant’s behind.
Yep, Scottish Sceptic, that was proved and published by experimental physics more than a century ago. The “global warming” nonsense ignores experimental physics and is based on non-science wacko theories long disproved.
If you want to trap heat or avoid doing so, use insulation according to the medium and the application.
You can warm a gas inside a steel cube by heating it through direct contact of the steel to the heat source or bathing it in IR. Ultimately the gas will be heated by conduction through the steel and internal convection of the gas, providing gravity or physical manipulation exists to create convection of the gas inside. Convection is only necessary to speed up the process.
This can be avoided by insulating the steel from the heat source, either through a non-conducting layer or a reflective one.
The most effective way to trap heat from the Sun in a greenhouse is use an IR-transparent insulation that protects against loss that would occur through convection. Almost any material is useful as an insulator in this instance because convection in this application is the greatest source of heat loss, however the insulator is best transparent to IR.
If not using the Sun, use a silvered inner surface glass or heat resistant material and set fire to the plants.
Olaf.. in my opinion you are missing the point. Very few disagree with your description of an insulator. What many of are saying that water vapor is gas, not a solid insulator. Gasses expand when heated and rise.
How insipid.
People still bedwetting over the term “greenhouse” in every sense of the word, without actually inventing the one they desperately want. How about it then:
1. Atmospheric effect – or more accurately;
2. Adiabatic effect
There’s not much of a better and simple physical example to show how an atmosphere works INSIDE AN ATMOSPHERE than a greenhouse analogy. Yet you guys still cry that the glass isn’t actually gaseous as it should be and blah blah down to critical minutiae until your soup is full of tears.
Either come up with a better term or analogy than greenhouse or shut up.
Olaf…
Debunk this ….
http://www.principia-scientific.org/why-not-backradiation-the-amazing-nature-of-light.html
The greenhouse effect is bunk because greenhouses are square and the earth is round. Make a round greenhouse and we can talk.
Edmonton – Backradiation exists, so I don’t need to debunk it. Besides, it’s not particularly what was being discussed.
Morgan – See what I mean? Round or square doesn’t matter in this simple analogy. Why even bother arguing about that? Now go wet your pants because greenhouses aren’t spherical.
If not using the Sun, use a silvered inner surface glass or heat resistant material and set fire to the plants.
You have experimental data on this no doubt. 🙂
Vast.. VAST data 😉
Unless the glass have a selective surface
http://solar.org.au/papers/10papers/10_66_GENTLE.A.pdf
So how many greenhouses are built using quarter inch plate glass dummy?
Not many. 0.25″ is heavy & expensive.
The large industrial type that require protection from large hailstones. Lots of them.
My greenhouses uses 1/2 inch polycarbonate by Lexan
That’s probably the best.
It’s taken four days to produce, now finally here is what I hope is a thorough review of the physics underlying the so called “greenhouse gas” effect:
A scientist’s guide to greenhouse warming
It’s not a law, it’s not even a theory – it’s just the practical overall effect of adding CO2 to our atmosphere.
E/A = ?T4
Without the SB factor, 5.67e-8, in the above this will not work.
davidswuk says:
24th November 2014 at 3:09 pm
All very well, but – just gaze into a Northern red sunset and wonder why then your retina do not fry………..
well there`s still ONE HUNDRED/m2 or so WATTS of ENERGY at around 0.8um lighting-up the sky whereas, in the LIR world, at 15umt (CO2`s blocking frequency) there is LESS THAN FIVE for Co2 to take a nibble at.
And so, when it comes to real heat, 0.8um at about 120c and 15um near 20c, 3why is it we BELIEVE that Co2 is any sort of a problem warming-wise and not cooling??
Reply
Oops! & Thanks. Doesn’t change conclusion, but it’s obviously needed.
Wouldn’t the system need to be measured through a full 24 hour cycle to fully illustrate the energy balance of the system?
Also doesn’t the increased CO2 common in greenhouses have the added effect, beyond being fertilizer, of reducing the heat ceiling even further than if there was no CO2; with this concept being what is the “greenhouse effect?”
So we have a greenhouse within which we can observe the unfortunately coined “greenhouse effect.”
Also, wouldn’t the geographic location have a major effect on the conditions in the greenhouse; as well as the date upon which we measure the greenhouse at any given location?
The amount of heat leaving the greenhouse is equal to the amount of heat entering the greenhouse
If a pound of air at 60 F and 20% RH (15.3 grains/lb dry air) absorbs water vapor through latent evaporation and increases its RH to 80% (61.9 grains/lb dry air), its heat content increases by about 8 Btu/lb. No sensible heat added, no dry bulb temperature change.
For that same pound of air at 60 F and 20% RH to absorb the 8 Btu/lb mentioned above without absorbing more water vapor the dry bulb temperature would have to increase by 30 F! (90 F, 7.3% RH, same 15.3 grains/lb dry air)
Water vapor is a serious heat mover/absorber/releaser. Air is pathetic.
So the heat leaving does not equal the heat entering by the difference of the heat absorbed by the water evaporating into the air. During the night the process reverses, the water condenses, cooling and removing heat.
It’s the water vapor cycle that runs the climate, not CO2 & GHGs.
Nickreality65 you may enjoy this photo.
http://climaterealists.com/?action=report&uid=8100&id=9004
Nick…. I agree but we need a rebuttal to the idea that water vapor near the surface of the earth slows down heat flow and thus warms the surface like an insulator [according to Tony] if I am correct in my understanding of his statement.
You may be more capable in this regard than me.
You need to cool a greenhouse in more southern (N.Hem) climates as compared to more northern climates. In some northern climates heating may even be suggested. That without considering the volume of CO2 if ambient or artificial.
When?
(If that was always true, the greenhouse wouldn’t warm up in the first place, would it?)
Reblogged this on Centinel2012 and commented:
Basic science at work here, the science of the earths temperature is some what different and is not a true greenhouse effect as just described. There is a warming effect its just based on different principles.
The so-called “greenhouse effect” of glass blocking thermal radiation going out but not blocking radiation going in was disproved experimentally and the results published in physics journals more than a century ago. Green houses work by blocking CONVECTION of heat, the motion of warm air, not by blocking radiant heat. The greatest heat loss form an open garden (no glass) is from warm air moving away. A glass panel blocks air motion and stops convection transfer of heat. A glass panel has NO effect on radiant heat. It does not block radiant heat leaving the green house, and does not raise the temperature by capturing more thermal radiation from inside. Basic science needs to keep reading its own experimental results and stop with the wild harebrained theories that have long since been proved false.
The fact that glass greenhouses inhibit heat loss primarily by blocking convection in no way disproves the atmospheric” greenhouse effect.
The idea that “a glass panel has NO effect on radiant heat” would be news to thousands of scientists and engineers who select glass panel materials based on their radiant absorption properties. Technical glass catalogs are full of graphs showing the radiation absorption spectra of different types of glass.
Which direction does the glass absorb or radiate?
“Without the glass, the heat would escape much more efficiently, and the temperature would be lower. The energy flow through the system is the same with or without the glass, but the temperature is higher with the glass in place”
Radiant energy/heat has no appreciable inertia and can only increase in temperature by using a medium that can retain it. Thus the greenhouse analogy is erroneous as it is not differential IR causing the higher temperature within but it and the structure/contents of the greenhouse retaining heat due to lack of comparable cooling.
the same rule must apply to alleged GHG`s with H2O being the rather obvious heat sink.
So if C02 is directly comparable to the glass in a greenhouse should we be very safety conscious when exhaling? I mean we don’t want to cut anybody.
In fact I might go up to my greenhouse which still has some tomatoes on the vine but a couple of sheets of glass missing and I can replace them by exhaling my co2 in the green house.
It is freezing point here in London tonight but I’ll try it in the morning.
Because a diesel engine isn’t exactly the same as a gasoline powered engine, it obviously can’t power your vehicle.
Glass is solid Co2 hardly exists and I believe that at 400 parts per million is also quite porous, have I misunderstood that fact?
Because a diesel engine isn’t exactly the same as a gasoline powered engine, it obviously can’t power your vehicle.
No if I put diesel in a petrol driven combustion engine it would be disasterous
In truth
I have an electric car powered by turbines………………….steam heated by coal .
Steve do you have indigestion or something
IMO people who do not agree with GHG Theory [GHGT] or the Green House Effect [GHE] do NOT say the GHGs do not exist. They say that it is a misnomer. It is called a radiative gas.
Believers in the GHE say that GHGs slow down the transfer of heat from earth’s surface to the upper atmosphere. NON-believers of the GHE say that GHGs/Radiative Gasses speed up the transfer of heat to the upper atmosphere, and are coolants. The water cycle cools the earth. I cannot see how water vapor near the earth’s surface retains heat.
Some people did an experiment wrt this:
See here: http://okulaer.wordpress.com/2014/11/16/the-greenhouse-effect-that-wasnt-part-2/
Try staying warm overnight in a desert or arid zone. You’ll be wishing you were in a tropical one.
if the greenhouse is sealed obviously –
I have quite a large greenhouse and can open the windows and door a notch, In the Summer to cool the greenhouse down I open these windows and doors a notch and open the windows in the much cooler room adjoining. I would expect this room to warm and the heat to disappear through here, in fact what happens is you an feel a drought immediately coming through the windows of the adjoining room into the greenhouse, I guess this is the ” Stack effect” What surprises me is it doesn’t happen the other way around , drought from green house to adjoining room and out.
The greenhouse cools quickly from convection.
If the greenhouse windows are higher off the ground than the doors then the draught will leave through the windows. Hot air rises. thanks to gravity.
My humble position:
GHG block heat transfer by radiation very efficient in the lower atmosphere. The atmosphere are heated by direct sunlight and indirect by evaporation and convection from Earth surface. The incoming heat from the sun is very efficient transfered to the atmosphere, but not by LW IR. Heat transport in the atmosphere by LW IR is also very low especially in the lower humid atmosphere.
GHG block heat transfer by radiation int he lower atmosphere.
The atmosphere is cooled only by radition to space. By GHG. The altitude this can be done without that the efficient GHG block this transfer is different for different GHG.
For C02 is this altitude where the atmosphere is about 220K all over the earth. That is the altitude of the lower stratosphere where temperature is stable with altitude. More C02 will att this altitude have a cooling effect. And that is stratospheric cooling.
“In the stratosphere, this emission of heat becomes larger than the energy received from below by absorption and, as a result, there is a net energy loss from the stratosphere and a resulting cooling”
http://hockeyschtick.blogspot.se/2014/08/why-does-co2-cool-stratosphere-warm.html
Edmonton Al says:
November 25, 2014 at 2:09 am
“I agree but we need a rebuttal to the idea that water vapor near the surface of the earth slows down heat flow and thus warms the surface like an insulator [according to Tony] if I am correct in my understanding of his statement.”
I never cared for the notion that I have to prove someone wrong. It’s on them to demonstrate their position is correct. I don’t understand how water acts as an insulator or slows down heat flow.
As I understand it, CO2/GHGs heat the air and that heat has to go somewhere – into a hotter atmosphere. So where did the hiatus heat go? IMO, into water vapor, higher relative humidity, clouds, etc. IPCC AR5 TS6 admits low certainty about the precipitation cycle. Water is a wonderful fluid, it absorbs and releases heat – without changing the temperature.
I know the greenhouse concept has it flaws, but…
Take two identical faux greenhouses, big glass boxes, one totally dry, other one with a swimming pool, circulating pump, and misters. Set them out in the sun. (high school science faire) Install temperature instrumentation and relative humidity meters. Track data for several nights and days.
My hypothesis? based on decades of casual observations.
The dry box is going to get very hot as well as experience wide temperature swings between night & day, aka the desert.
The wet box will not get as hot nor have the wide temperature swings, aka rain forest.
Water vapor is the great moderator of the climate. Always has been, always will be. It’s water that really makes the earth unique.
So you think that the rest of the world, which has accepted greenhouse gas theory for a century. is obligated to keep explaining over and over again why you are wrong?
“Experts” considered the earth flat and central for centuries and that phlogiston was the source of fire.
I’m not doubting the theory that CO2/GHGs can add heat to the atmosphere, just that the overwhelming compensating power of water vapor is not getting the recognition I think it deserves.
BTW, your thoughts on Miatello’s paper?
I am trying to establish a groundwork of basic principles before any discussion of more complex topics. That is the mistake which almost everybody on both sides of the debate makes.
Apart from H2O radiative gases do not have I think sufficient capacity to slow neither the arrival nor departure of radiant HEAT – The experiment to determine the outcome of colliding Solar frequency radiation with the relevant gases would be so easy to construct that the proof,one way or the other lets say, must be out there,somewhere………………………………
The problem is Steve intelligent or not stupid at least people, still find it hard to see co2 as a very effectual gas in terms of effectiveness as an insulator. The fact that what you hoped would put an end to any doubt for once and for all shows that either many are too thick to grasp the scientific principles or they are bright enough but just come to different instinctive conclusions, not me by the way as I’m not clever enough to say yes or no. I have to go with the experts, I mean I know a couple of amps can kill me and so far I’ve trusted the experts on that one and always ensure I turn the mains off when replacing electric sockets or ring wiring.
“I am trying to establish a groundwork of basic principles before any discussion of more complex topics. That is the mistake which almost everybody on both sides of the debate makes.”
Kind of begs my question. Have you not read Miatello or do you have no comments on his paper?
So I went to Wiki for the groundwork in GHG theory basics.
1,366 W/m2 at the outer atmosphere.
235 W/m2 at the surface.
“However, recent measurements indicate that the Earth is presently absorbing 0.85 ± 0.15 W/m2 more than it emits into space (Hansen et al. 2005).”
Imbalance of .85 W/m2 +/- .15 W/m2 (That’s +/- 17% uncertainty for crying out loud.) attributed to man.
.85 is .36 %! of the 235, 0.062%! of the 1,366. 0.85 is nothing but noise in the data!!!!
0.85 watts is 2.89 Btu/h. That much heat could be absorbed by raising the RH at 60 F from 20% RH to 44% RH. No increase in dry bulb temperature. More clouds. Big deal.
A “Glass Greenhouse” works by preventing convective heat transfer in the large, and by restraining re-radiation in the small. Advantageously, by allowing artificially induced CO2 increases to promote plant growth. Whatever other statements might be made on this subject are factually irrelevant.
THE GREENHOUSE EFFECT…YAY OR NEIGH
When a horticulturist considers the functions of a greenhouse, radiation isn’t on top of the list, it may even not be on the list at all. Temperature is an important function but still not the most important.
The key function of a greenhouse is to restrict convection IN ORDER TO RETAIN MOISTURE IN THE AIR. Moisture retention is the goal, not the restriction of convection.
There are various low cost options if a horticulturist wanted to control temperature. Basic shades of all sorts for example. But retaining moisture in the air takes a building.
The huge advantage of moisture retention is that it restricts evapotranspiration, meaning plants retain their water better hence spend less energy sucking up water through the roots. The saved energy is used for growth instead. Plus the horticulturist uses less water.
The capability to control temperature is a big big bonus.
Why do horticulturists use greenhouses? BECAUSE THEY WANT TO REPLICATE TROPICAL CONDITIONS that plants seem to adore.
This structure that man has copied from nature is called a GREENHOUSE, yet when the same conditions in nature is called a GREENHOUSE people get upset. Go figure.
A green house operator might consider heat storage, barrels of water, stone pathways, brick planters, etc. Helps moderate the temperature swings, cloudy days.