Sunlight, Heat, Redirection...

[Shroom Man 777]

So I have a problemo. In our stickbeating classes, we train in a backyard that's sauna-like in heat. The yard is under a tent. And it's got four walls around it, two of the walls are cement. The other two are... white-painted corrugated sheets of metal, like the ones for cheap roofing. The sheets reflect the sunlight at noonish and I kinda suspect it significantly contributes to the heat and humidity of our yard.



So what can we do? Would the reflected sunlight and heat be significantly reduced if the sheet metal was repainted? I suspect so. What would be an optimum color to minimize heat reflection?

I suspect that if we paint it black, the sheets would absorb the heat. I imagine, this would turn 'em into heat sinks and make the surrounding area cooler. BUT it could also mean that by absorbing so much heat, the sheets will also heat up the area?

How does this work?

[Darth Tanner]

Can you not put some trellis up and get some plants to cover the metal & concrete. The white will be reflecting heat but worse is that the metal and concrete will also absorb it and radiate it back at you. Ideally replace the sheet metal with just the trellis so you can get some ventilation too.

[Shroom Man 777]

Can you not put some trellis up and get some plants to cover the metal & concrete. The white will be reflecting heat but worse is that the metal and concrete will also absorb it and radiate it back at you. Ideally replace the sheet metal with just the trellis so you can get some ventilation too.

The sheets aren't our property but that of the people allowing us to use the area. I'm thinking repainting would be OK as opposed to outright replacing their stuff. Though yeah, I would prefer if the metal sheets were replaced with something that had more ventilation...

So my question's just regarding the thermal qualities of the colors I could use in repainting the sheets.

[Shroom Man 777]

Here is an image of the area, infer that the unshown, off-camera walls are the sheet metal ones.

[Sea Skimmer]

Flat black paint would be best for absorbing the heat and avoiding reflection, but that will only reduce the heating via reflected light on your body. Net it will increase heating of the air, because now much less is being reflected back into the sky.

The best option would be to spawn that gap with a white net I imagine, so you maintain ventilation but keep most of the light off the metal, and any heating of the net is suspended in the air above you where it will want to rise into the air.

[Shroom Man 777]

The best option would be to spawn that gap with a white net I imagine

Spawn?

[Sea Skimmer]

Yeah you know, like the creep from Starcraft helps spawn stuff and cools down planets by covering hot rocks with mushy living carpet. Or, span, whichever.

The net concept is basically the same logic as spaced armor, just protecting your body against the frigging sun. Which by internet logic means I just invented a way to make a human being immune to a nuclear blast.

[Vain]

The net concept is basically the same logic as spaced armor, just protecting your body against the frigging sun. Which by internet logic means I just invented a way to make a human being immune to a nuclear blast.

Well, I mean, if you had a sufficient quantity and thickness of nets...

[cadbrowser]

Photon is the quanta of electromagnetic (EM) radiation and energy carrier for radiation heat transfer. - Source

Not only is it currently reflecting electromagnetic radiation in the visible part of the spectrum, it is also reflecting it in the other ranges too. A flat black paint would be the best at significantly reducing the amount of reflection. However, that would also cause the sheet metal to absorb most of that EM radiation. It would then radiate that heat in close proximity to itself. Probably for quite a few hours.

Depending on how much distance there is between you and the sheet metal wall, you may not even feel it unless you were directly next to it. Even a slight wind would pull away most of the heat elsewhere.

[LaCroix]

They are selling Vantablack now, I've heard. Would be the perfectsolution for the reflection issue.

"Vantablack is now available in a spray-on form that blocks 99.8 percent of ultraviolet, visible and infrared light"

[Shroom Man 777]

Photon is the quanta of electromagnetic (EM) radiation and energy carrier for radiation heat transfer. - Source

Not only is it currently reflecting electromagnetic radiation in the visible part of the spectrum, it is also reflecting it in the other ranges too. A flat black paint would be the best at significantly reducing the amount of reflection. However, that would also cause the sheet metal to absorb most of that EM radiation. It would then radiate that heat in close proximity to itself. Probably for quite a few hours.

Depending on how much distance there is between you and the sheet metal wall, you may not even feel it unless you were directly next to it. Even a slight wind would pull away most of the heat elsewhere.

The sheet metal's a foot away from the part where the tent starts and where we walk/stand at.

What if the backside of the sheet metal, the side not facing us, was still painted white? Would that have some effect? One side absorbs, the other reflects? Does it work that way?

[cadbrowser]

The sheet metal's a foot away from the part where the tent starts and where we walk/stand at.

What if the backside of the sheet metal, the side not facing us, was still painted white? Would that have some effect? One side absorbs, the other reflects? Does it work that way?

I would imagine that you'd have to be just a few inches or closer from the heat being radiated from that sheet metal in order to feel anything significant.

Yes, one side would absorb and the other would reflect. Now, I don't know how much difference it would make, but based on my understanding, it should help. Definitely better than all that EMR being reflected on you in that space. What would happen, I think, is that with that black/white configuration, the heat dissipation for the whole piece would be lower.

Something else that might help as well is to get an oscillating fan on a stand and run an extension cord from the house. While you are out there training, have that create a breeze to assist with removing the excess heat from the area.

That Vantablack stuff sounds very promising!

EDIT: The humidity that you are experiencing would be due to the moisture content of the air and ground. There isn't much you can do about that, unfortunately. And I'm not sure how well a de-humidifier would work in a large, open area like that.

[Shroom Man 777]

I would imagine that you'd have to be just a few inches or closer from the heat being radiated from that sheet metal in order to feel anything significant.

Is this for sure? I don't wanna inadvertently end up making the place have HOTTER HEAT by repainting it.

[cadbrowser]

Is this for sure? I don't wanna inadvertently end up making the place have HOTTER HEAT by repainting it.

You can easily test it.

Hover your hand above asphalt that has been baking in the sun all day. How close do you have to hold it to the surface before you feel the heat radiating?

[Shroom Man 777]

Is this for sure? I don't wanna inadvertently end up making the place have HOTTER HEAT by repainting it.

You can easily test it.

Hover your hand above asphalt that has been baking in the sun all day. How close do you have to hold it to the surface before you feel the heat radiating?

Unless this is a trick question, I think the answer would be opposite to say white sand beaches where even without placing your face on the sand, during sunny days its already hard to look at the sand without shades because the sunlight and the heat coming from the sky is reflected off the sand and everything is burning!

[cadbrowser]

Or, I could be completely wrong.

[madd0ct0r]

You've got three things going on. Direct sunlight heating, reflected sunlight heating, and delayed heat coming off the concrete and the floor where it warmed up under direct sunlight earlier.

Skimmer's white netting to try and avoid anything getting warmed up in the first place is the best idea if you ask me. The metal sheet dosen't have much heat storage capacity, while the concrete and the floor will remain hot for hours. Spraying the area down with water and setting a fan on it before the session starts will help.

[Shroom Man 777]

Or, I could be completely wrong.

I don't distrust or doubt you. I just worry that if the black-painted sheet/wall absorbs heat TOO well it might end up somehow making the place catch fire or something.

There's a lot of dry leaves in the area.

[cadbrowser]

I seriously doubt it will get hot enough to burn a place down like that. Here in the Midwest, the temperatures during the summer months can peak well over 100 degrees (F) with heat index reaching up to 120 (F) at times. A white metal door that has been baking in the sun all day can get hot enough to cause 1st degree burns if you place your hand on it long enough. However, you still have to be a few inches away from the door to actually feel the heat radiating.

Heck, even recently, I left work to go home at my regular time (15:30). I have a white Dodge Ram. The temperature reached, IIRC, in the high 80's/low 90's. I rolled my window down. Placed my arm out the window. The black window weather stripping was warm, but that white metal door panel as soon as it hit skin was EXTREMELY hot. Was not fun.

If you are that worried about a fire hazard from the dry leaves, get a rake.

I'm not sure how easily you can hang netting over the area(s) in question to reflect the heat back up and out. But that and hosing the area down before you do training is a really good idea too.

[Sea Skimmer]

I don't distrust or doubt you. I just worry that if the black-painted sheet/wall absorbs heat TOO well it might end up somehow making the place catch fire or something.

There's a lot of dry leaves in the area.

When was the last time you heard of the shining sun starting a wildfire in an open field? Its not possible without a magnifying glass or glass bottle acting as being involved, and in that case a WHITE wall would be the real risk, because it would reflect more sunlight back into the magnification device to cause a point ignition.