BBadger wrote:... the black shade cloth has a higher emissivity, which means it absorb and emit light (and heat). The light that it absorbs will usually be converted to heat and radiated back out...
This is the problem with taking partially understood information, and applying it out of context instead of accounting for all meaningful factors in a system. You can see how the total in some of the cases with dark vs. light interiors, it can end up elsewhere than one would reasonably intuitively expect it to.
tamarakay wrote:You can't beat 90% black . We have the white/blue color and it's nice, but the 90% black kicks serious butt.
There is reflectance and there is emmisivity. They add up to 1. And that is confused by visible reflectance vs. heat reflectance vs. total reflectance, and the same again in emmisivity (although they're much better than black asphalt roof tiles, the white roof paint documentation uses that to good effect to obscure how much light & heat the white absorbs). But things will absorb light into heat and heat into heat. Ignoring selective materials, if something is good at reflecting, it is poor at absorbing and equally poor at emitting. If it's reflectance is 92%, it's absorption is ~8%., it's emmisivity should be ~8%.
So yes, shiny aluminum will absorb less heat than matt aluminum, and matt aluminum less than white, and white in turn less than black. Lighter materials will have a more difficult time radiating their absorbed heat away. Where black is good at absorbing (both light into heat and absorbing radiated heat directly), it is equally good at radiating that heat out again. And it will radiate it away, unless something else happens to remove a portion of that heat. But this is in isolation from what happens when it interacts with the environment. Another twist due to the fact that surfaces aren't truly flat, but textured: a portion of the heat radiated away from a surface will encounter another nearby part of that same surface, and subject to absorption. So a white surface will reabsorb less of what it radiates compared to a black surface, such that a highly textured white surface can have a net emissivity greater than a smoother black surface. (edit. doesn't apply here, so you can ignore)
The wind on the playa will be working to remove whatever heat has been absorbed by the shade cloth, regardless of colour. The wind is providing a similar, if less efficient, benefit as the water does on the green house shade cloth (water is cooler than playa air and it has an additional swamp-cooler/evaporative-cooling benefit), in that the wind is removing heat from the shade cloth before it is radiated down.
The wind will be somewhat more efficient at removing heat from black than from white, as it is both conductive heat transmission and radiated transfer to the air blowing through/across it. As all of the shade cloth heat is not preserved to be radiated above and below the cloth, the differences between "silver" and white, while there is a real difference, are not as great as one would expect. Hence why
Trilo's recommendation works.
Now go back and read what can happen with black interiors for some
structures, and with some
with light interiors, keeping in mind reflectance & absorption add up to 1 and absorption ~equals emmisivity, and the wind removing a portion of the heat from shade cloth before it radiates.
So again, due to the weird way in which things can add up, we're still at:find out what worked on playa for the type of shelter you're considering: the type of material (cheaper cloth vs. shade cloth), it's shade/sun spec, and its colour, and even the orientation of the shelter relative to the sun. Hard to beat Playa-Tested©)'( designs and materials.
you can take the same info on reflectance vs. absorption, combining it with conductance and insulation, and look at the performance of the various treatments for enhancing the performance of coolers on the playa.
Odd. No bears to watch in the dump. Oh well, lets go across the road & pick blueberries.
... but don't harm the red dragon that frequents the area from time to time. He and I have an agreement.