8 ms·
Trees are a much better solution to urban heating. Proven with millennia, eco friendly, and makes cities beautiful and desirable to live https://creativelyunit
by slt2021 3y ago
Trees are a much better solution to urban heating. Proven with millennia, eco friendly, and makes cities beautiful and desirable to live
https://creativelyunited.org/wp-content/uploads/2019/02/temperatures-with-and-without-trees.jpg https://creativelyunited.org/wp-content/uploads/2019/02/temp...
- jjoonathan 3y agoTrees are swamp coolers. Consuming freshwater for outdoor air conditioning isn't necessarily a bad idea, but you aren't cheating thermodynamics.
- ComputerGuru 3y agoNative, grown trees need no watering, even in a (one- or two-off) drought.
- jjoonathan 3y agoSure, but less evapotranspiration = less cooling. You aren't cheating thermodynamics.
- ComputerGuru 3y agoApparently a good part of the reason (parts of) the Midwest can get uncomfortably humid some summers despite being so far from large bodies of water is the evapotranspiration from the crops (mostly the corn). So too much evapotranspiration is not always a great thing! (Of course those are being watered regularly.)
- kgermino 3y agoTrees are so much more than swamp coolers. Leaves block the Sun relatively high off the ground, meaning people are in the shade during the hottest part of the day and feeling as much radiation off buildings and streets in the evening. Beyond cooling they’re also good for water management. Most street trees don’t need any watering (at least in the Midwest) they live off rainwater. When it rains, water pools on the leaves and evaporates from there, reducing the amount of run off and keeping the street drier and less humid on days with light rain. In cooler months (and places where this is relevant) the leaves fall and you can still get the warming benefit of sunlight.
- jjoonathan 3y agoI love trees and want more of them in our cities, my only point is that they are not usually a substitute for HVAC unless your climate is in a precise sweet spot of plentiful water, dry air, and not too much heat. Rather than letting wishful thinking snowball into bad policy and disappointment, let's promote trees by focusing on what they do well (what you've mentioned plus aesthetics and sound damping) rather than by ignoring the limitations of evaporative cooling.
- kgermino 3y agoI guess we disagree on what trees do well. I’m in the Midwest with warm semi humid summers. Trees keep the area around them massively cooler, not by evaporation but by shading. Maybe it’s a disagreement of terms? I guess they aren’t technically “cooling” the area in an active sense, but they absolutely keep it cooler even when it’s 95 and the dew points over 70
- jrockway 3y agoThe shade is the important effect. Air conditioners have to use energy to remove heat from the indoors. That means that if the indoors are less hot, then you need to move less energy out of the room. Trees are great here, because the trees stand in the way of our solar system's largest energy source and the indoors. To be fair, things like insulation are also good here. You want something outside to get hot when the sun shines on it instead of whatever space you're cooling. (There are, of course, many heat sources inside that are annoying. I was running some fuzz tests yesterday and was annoyed to watch my air conditioner scale up in power to remove the heat that was wasting. I guess that's why people use The Cloud for everything. You can heat up someone else's city while enjoying the comforts of home!)
- freddie_mercury 3y agoDew point over 70 doesn't sound that high? I live in Vietnam. It is 8am right now and the dew point is 80. It only 80 at the moment but is supposed to get up to 90 later in the day. I assume the dew point will also go up to around 90. AccuWeather says the "RealFeel" will be 97 and "RealFeel Shade" will also be 97, so being in the shade does almost nothing, since it is overcast and raining very slightly at the moment. We're not in a heat wave or anything, this is just normal weather basically year round. If anything it's been especially rainy and cool the past few weeks. Trees are nice but are not remotely a substitute for air conditioning. Trees do not lower humidity enough to stop the average European/American from sweating constantly just sitting still here.
- uoaei 3y agoWith enough trees the microclimate changes enough that precipitation is more likely in that immediate area, which compounds the cooling effects on average.
- andsoitis 3y agoWe can do both.
- zdragnar 3y agoI can't- the solar company I talked to said there's too much shade on my roof for too much of the day, there's no way to place the panels to make financial sense before the panels need to be replaced. It seemed a bit odd, because my roof is fully lit up, but only for a few hours a day- one half is covered most of the morning, and the other half most of the evening. Sadly, it's not even really nice trees, just gigantic cottonwoods that litter leaves and twigs and sticky leaf pods like crazy.
- cassepipe 3y agoDon't worry, a sizeable part of the tree population we are used to live by are going to die because of climate change. Problem (soon to be) solved.
- parineum 3y agoIf you want to play that game, a sizeable part of the tree population is just going to migrate north/south. The more immediate problem with climate change isn't that there won't be enough places to live/farm, it's that it's all going to move causing destabilization of societies. The long term effects of running out of arable land are a considerable distance in the future.
- midoridensha 3y agoMaybe I'm missing something, but I don't see how we'll ever run out of arable land. The Earth has been warmer than now, in the distant past: there were times when the poles were not frozen over. Of course, this means the sea level was higher than now, so melting all the glaciers means a lot of our cities (and probably most of Florida) will be underwater, and it isn't so easy to pick up a city and move it to higher ground. A warmer Earth probably means more deserts, but there should still be arable land, in places that are currently cold tundra perhaps.
- demandingturtle 3y ago[dead]
- rowanG077 3y agoI disagree. No amount of trees will take my 30 degree indoor temp down to 22.
- lionkor 3y agoHave you lived in a house covered entirely in tree shade?
- jjoonathan 3y agoI can look at the wet-bulb temperature and see exactly how far trees will get me. This time of year, it isn't far -- which checks out, because I have plenty of trees and they don't stop the heat. Swamp coolers (trees are swamp coolers, thermodynamically speaking) are brilliant if humidity is low and freshwater is plentiful, but if either of those wheels come off no amount of wishful thinking will make evaporation work comparably to a refrigeration cycle. Where I live, it's the humidity. Fortunately, I do have real AC, and even better, my power mix is predominantly nuclear so I can crank that AC and get real cooling without pumping legions of dead dinosaurs into the sky. Damn it's nice to live in the 21st century. Or the 20th.
- BeetleB 3y agoI don't know exactly how many degrees the shade will bring the temperature down, but just today my portable temperature sensor reported an 8F degree difference compared to one in the shade - both were in the same area of the house, but one happened to be where sunlight was coming in from a narrow window. And the sensor was in the sunlight for under an hour when I recorded the difference. Of course, this is spot heating, and over a whole house the effect will be diminished, but it tells you how quickly things can get hot.
- jjoonathan 3y agoNo, I did not forget that shade exists. It's still uncomfortable in the summer. Once RH hits 100%, evaporation stops cooling and your options are to go without or to use a different thermodynamic cycle. We've got plenty of freshwater in these parts, but in other places freshwater availability will be the limiting factor. Famously, swamp cooling works great in the desert if you can spare the water. Trees are great, let's just be real about what they can and can't do.
- jeffchien 3y agoWith regards to temperature, there are more levers to pull, like the aspect ratio of the street (narrower = cooler). Architects in Taiwan and southern China have been studying arcaded streets (qilou/騎樓), which seem to be as good as trees for shielding pedestrians [1], except in situations where the sun might shine through the sides or ends. Of course, trees are great for many other reasons like air quality, but for temperature fundamentally they're just big evaporative coolers. I wish cities in more water-stressed areas would consider arcades + rooftop solar. [2] https://www.mdpi.com/2071-1050/11/5/1355/htm https://www.mdpi.com/2071-1050/11/5/1355/htm
- AlDante2 3y agoThe big advantage trees have ove most man-made shade is that heat can convect through them. If you’ve ever sat underneath an umbrella at a café versus a beer garden under trees you’ll notice the difference. The umbrella shades, but traps reflected heat, re-radiating it below.
- agsnu 3y agoTrees also provide a significant cooling effect by releasing water vapour into the air from the soil (evapotranspiration), which you won't get under an umbrella.
- samcheng 3y agoQilou seem much more oriented around shelter from the rain than for shelter from the sun, though. I agree that they're a great addition to urban streets for pedestrians!
- BurningFrog 3y agoTrees can shade one story houses, but hardly any multiple floor apartment buildings. Which makes it a good solution only to suburban heating.
- another_story 3y agoIt's a huge benefit to the crowds at street level, and keeps the city cooler overall because all that concrete is not being turned into a heated surface. They're not generally there to shade the buildings, but the people and roads.
- throw3823423 3y agoI think of the cities in Spain with the hottest climates, and I don't see a lot of crowds being protected by tree shade: Instead, the traditional design is narrower streets which aren't straight for very long, and even white cloth hanging across the street to provide the shade directly. It's not that there's no trees, but you'll see them in parks and boulevards that might as well be narrow parks. If anything, I see far more trees in the American midwest. Here the streets are very wide, with basically no foot traffic to speak of, and too much road for the number of cars that use the street in urban areas. You can definitely fit trees here, but that's because so much of that concrete is waste. The extra trees just mean more distances, and more distances means more parking lots and more concrete.
- lucidguppy 3y agohttps://www.energy.gov/energysaver/cool-roofs https://www.energy.gov/energysaver/cool-roofs Paint roofs white - and then go plant some trees.
- brentis 3y agoOddly houses in Dallas are going with white brick and pure black rooftops. Looks hideous to me and not solving our plight. Some modern neighborhoods are trying living roofs with grass. Haven't taken off and the grass hasn't survived either. Lastly, other day saw post about leaving grass uncut reduced surface temps notable amount.
- crazygringo 3y agoSorry, do you mean trees on roofs? Since the person you're responding to is talking about solar panels on roofs and you're suggesting trees instead?
- ehnto 3y agoYou will still want airconditioning in a great many cities. It gets to 45c in the forest here, no amount of trees will help the city, although of course they are still part of a good solution. As always it's likely a combination of solutions, and rooftop solar is a good idea for more reasons than just heat.