Just discovered some folks living in >100° summer temps will sometimes use mister / intermittent sprinkler systems on their roof / walls etc. Gave it a try - as our So Cal weather is WELL w/in the range above. We are at 109° right now ... & the garage is 115° with the garage roll up & side doors open. So ... with the prevailing 1mph breeze coming into the garage ... thought it may help to hose down the tile garage roof, asphalt street in front of the garage, as well as the concrete driveway. Boom shaka laka ... a few minutes later, the garage was a mere 100°. Since i'm soldering up an important project, & have to be out there ... yea ... cooling the garage is important! Some living out in the AZ desert actually use AC to cool the garage (what a stupid time to bring your car into the garage ... after driving around the the blazing sun & 300° motor heat) - but hey! ... i read that water evaporation is equivalent to 8,000 BTUs ... so ... why not! .
Does SoCal have enough water available for that application? I did find a nice side effect of a large rooftop solar system: the shade seems to keep the attic and ceiling cooler. Though determining the actual degree is confounded by multiple nearly simultaneous changes (e.g. reroofing with a more heat-shedding product, improved attic venting, and upgraded ceiling insulation, including discovering and remedying uninsulated portions that were beyond the view of building code inspectors). The eave overhang of this house is also set right to prevent direct solar heat gain from all south facing windows during mid-summer, the sun doesn't start getting low enough to get through any windows until late August. (And that is still minor today). But that eave shade never covered the lower portion of the patio slider door, so two years ago I finally hung a roll shade from the eave in front of it, intercepting the great majority of that heat gain outside. It is much more effective than any reflective shade inside. That dropped our AC use down to zero (not that we needed it much before, this is a mild climate zone). While hotter climates will still need AC, similar changes could reduce the load. It is similar to this:
that works well when it's dry, not in our humidity unfortunately many flat roof industrial buildings in arid climates use misting systems on the roof
The future is cold tubes. ‘Cold Tube’ Invented to Beat the Summer Heat More Efficiently Than Air Conditioning
yep ...... our roof is pretty much covered, with the panels being around 7" above the concrete tiles; Just over a year ago - we added 4 more panels - although we had to shift the original panels around as the newer panels were much larger. They are more powerful too - but panels sense the lower current & automatically de-rate to match Thank you satellite photo people That's what a now 8kW's AC rated system looks like. Paid for itself in under 6½ years. .
Likely NOT......because to actually do anything useful, the surfaces need to be kept damp ALL DAY and an hour or so after sunset. Moreover, if there are minerals in the water, you will NOT like the residue that is left. And if the surface is metal, you won't like the rust that forms either. Overall, a BAD idea.
There are new building techniques which are more practical to deal with this if you were building a new dwelling Here are just a couple of examples; This is a solar board for building it has a silver reflective side to reflect radiant energy back instead of into the dwelling Roof Sheathing: Silver Side Down - Fine Homebuilding Passive home ventilation systems will remove heat from your attic and roof areas Proper Attic Ventilation is Needed on Every Home | Solar Blaster Heat reflecting shingles Solar Reflective Shingles in States like California there are products like metal roofing materials that reflect solar energy and are flameproof and resists ignition from embers to help make the entire home flame resistant. A Metal Roof is a Fire Resistant Roof | Classic Metal Roofing Systems All these may be a better alternative then using a precious natural resource like water in an area that has limited amounts of the resource. For existing dwellings option are limited.
it is a mist system, very little water. it cools the air above the roof you want to see water wasted in the desert? drive down the street at sun up and watch the rivers of sprinkler water
As is often the case, there are a few elements not mentioned with the notion above where I said 8000 BTUs "cooling" energy via 1 gallon of water misting a rooftop. There is that small consideration, the most powerful lifting pumps in the world. California Aqueduct. Getting huge volumes of water over the Tehachapi Mountains so that California can send water down their gutters, hose off their cars, run their outdoor fountains, etc. That's said, the cost of compressing refrigerant for our old central AC dinosaur is still more pricey, because our greedy electric utility jacks up our electric rates to a higher tiet - 28¢ / kwh after the first 600 kwh - so .... "LET the Watet Misters Continue! " It's not like the water is truly wasted in our example, as it's simply evaporated back up into the clouds, or it comes back down as precipitation, percolating down into the many local aquifers, or ends up somewhere else back in the biosphere. Right? .
water is a funny thing. the quantity never changes, just the quality and location. i suppose it's just a matter of weighing the energy necessary to get clean water to your door vs whatever other options there are.
Thermal management of human environment in a very broad perspective: MIT’s Asegun Henry on “Grand Thermal Challenges” to Save Humanity From Extinction Due to Climate Change Perhaps in some ways a bit overstated but that's in the eye of the beholder. == Specific colutions: Global Cooling Prize
Growing up in Oklahoma, we had: swamp coolers four sack cloth wetted down But that was before every creek and ditch went into a pond. The climate has become distinctly humid compared to what I grew up in. Bob Wilson
perhaps being the operative word .... but then nothing evokes concern more - than labeling a concern on par with future death of our children. as kids, it was often so dry our lips would crack open and bleed. Now? 2 or 3 days in a row of arid heat is much more a rarity. .
6 homes in California that already have taken the new net 0 home mandate into real time https://www.builderonline.com/design/projects/six-california-homes-that-are-ready-for-2020_o
