Electricity-free way to cool a home?

Mk Neal wrote:...I know on my block we actually get water quality problems from too LITTLE water usage (sediment builds up), so this might be worthwhile for my house.

Interesting.  I've never heard of such a problem.

Matthew Nistico wrote: It also won't work on a flat roof, like the tar or gravel roofs of some commercial buildings, or on the flat roof of an RV.

I’m thinking it would work just fine on those roofs (better, really, since they get hotter than sloped roofs) but you’d need a different way to disperse the water, like a sprinkler or soaker hoses. Flat roofs are not truly flat, they all have very slight pitches toward drains. But even if they didn’t, you just need to control the water flow so it keeps the roof wet but doesn’t create standing water, which would be wasted. On an RV, the water drains off the sides or ends. Again, just a slight misting to keep the roof wet is adequate. Where this will not work particularly well is on a steep metal roof, since the water will simply run off too quickly.
I like the idea of a solar panel to run the pump. Similar to the roof vent fan units that incorporate a solar panel to run automatically when the sun shines. If you have rain barrels, the downspouts are refilling them with any excess runoff. Once you had a sense of water usage, you could have spigot water on a timer to top them off, to compensate for evaporation loss.
The 12v RV pumps typically run a gallon per minute at 30 psi, which would be adequate. They draw less than 5 amps, which would be a 60 watt solar panel- less than $50 and not very large. So, yes, this would be very efficient compared to running A/C!

Julie Reed wrote:I’m thinking it would work just fine on those roofs (better, really, since they get hotter than sloped roofs) but you’d need a different way to disperse the water, like a sprinkler or soaker hoses.

Thank you for considering the idea so carefully.  You might well be right about the feasibility on flat roofs.  The idea of intentionally creating standing water - or as you point out, very very slowly draining water - even the thinnest layer of it on a flat roof just scares the hell out of me.

Yes, I also suspect that this concept would prove very efficient compared to central AC.  But the proof will (some day) be in the pudding, as they say.

Every time it rains hard you have standing water on flat roofs, nothing to be scared of. As I mentioned, they aren’t really flat, they have to be designed to drain! So they have multiple angles leading to drains, or sometimes simply one pitch to an edge which may have gutters or scuppers. Flat roofs are even more waterproof than pitched roofs, simply because they are designed to hold water for short periods of time. The only concern is snow load, in the north. (Interesting side point- our wasteful country, in the 60s, designed large buildings with deliberately poor insulation in the roof so that heat loss would melt the snow, which was considered far cheaper than constructing a stronger roof).
While the wet roof idea is obviously far less costly than A/C, it would be interesting to do a side by side comparison in 2 identical structures (storage sheds would make cheap test labs). I realize it would never lower inside temps as much as A/C does, but might be adequate. It could certainly reduce the cost of running A/C, and it would also be a great companion strategy with something like earth tube cooling.

Matthew Nistico - here is a project that sounds very similar to your idea, complete with lots of data!  Night Radiation Cooling of Water Flowing Over Roof

And for everyone, while I'm linking one of my favorite sites, here's a whole list of interesting ideas, projects, plans, etc - Build It Solar passive cooling

Great links C Jones! Thank you, can’t wait to spend some time on those when the rain keeps me inside tomorrow.

When i lived in the desert of Joshua Tree, we had a very real heat problem. The flatish roof was covered in the tar and pebbles of yesteryear. It worked very well with the wind and harsh conditions. However, between 3pm and midnight, we could feel the stored heat coming from the roof in the house and above if you were on the roof.

A 110 F this is a major problem.

So, being a midwesterner, i found the solution.

Simply water.

Now everyone will scream I am wasting water. Yes and no. Grey water got used up and POOF! it was amazing ow well it worked. It would literally steam right off. Especially in the evening once the sun went below the mtn tops, a quick spray and problem went away. Thus less waste w the swamp cooler or ac unit.

The reverse in the winter.

Good luck.

just a thought, but many of the very old, pre electricity houses in Florida were built with very high ceilings and wrap around covered porch and large or lots of windows built under the best and biggest shade trees.

This is our problem.

Ran across misting systems when we lived in AZ… flex small diameter tubing, micro-nozzles and hook up to the house spigot. Line the perimeter of the roof (or in our case just the patio) with the line of nozzles and turn on the water during the hottest part of the day. Lowers the temps by about 20F and uses about a gallon of water an hour. Kept the plants hydrated too. We thought it would only be a benefit for the patio area but it lowered the temps in the house. We would have expanded the system around the other 3 sides of the house if we hadn’t moved to WA. We didn’t install it here for several reasons. It rarely gets hot enough here to justify the expense, materials or effort. The humidity here is much much higher and evapotranspiration is already happening so it probably wouldn’t lower the temps as much.

What about green roofs?
I understand that climatic conditions vary wildly within the US and Canada, but in some regions green roofs might help with cooling down the building. They are not only insulating both in summer and winter but also help cool down inner city climates because of evaporation. There are studies and numbers and everything but still there is no proper law here in Germany that regulates obligatory green roofs!

I saw a documentary once which showed some green roofs in Toronto where there is a law apparently, so there must be some kind of infrastructure (builders, suppliers of material and plants).

Our new neighbours built their home following all the latest technology in heating, insulation etc. and they have a flat roof over the entrance and part of the patio which is now buzzing with bees.

IN Australia i had a rental house with a basement.
The tenants would often sleep in it.
It was so much cooler than the rest of the house.
America doesn't know it yet but in many states folks will start building basements for this reason in the future.
you can also put gravel or sand in the lower part of it and fill it with water which can act as a water cooler when a fan is blowing on it.
hot air rises which is basements  are cool. It is good however to circulate the air out of it once a day as CO2 can be a little more prevalent . The house can also be cooled
by having many pipes deep underground absorbing the cool earth temps and then have a fan sucking the air through at one end. Its elaborate to build a system like this but it can also act as a warming ambient heater in winter too...

all the best

Growing up in Minnesota, our neighbors without air conditioning likewise slept in basement during heatwaves.

Swamp coolers only work in dry environments. When I lived in Utah we had one and it worked great but here in North Carolina most people don’t even know what a swamp cooler is because they just don’t work in the levels of humidity that we have.

Hi Hannah,
This is Jane Higginson. Mainly writing to greet you! My little hut in Dehesa on the land you have been to, had no electricity. The doors were open to the prevailing cooler breeze, which could pass through one door and out the other. If you could install windows in the garage orienting one toward the prevailing cool breeze and another opposite, and open them,  it might help a little. Other than that, it's hot anyway so I moisten a long-sleeved cotton shirt and wear it during the hottest hours. It's a personal swamp cooler. I also have a 500 gallon water tank that I soak in.
Hope you find something that helps!
Jane

The basement in my Mojave Desert house is below the frost line (6"). It runs from 80 to 89 degrees F all summer. I go down there to keep cool when it's between 124 and 133 F in the direct sun outdoors.
Think about excavating a basement when you build a house.

Hi,  Pipes are a very good way to transmit cool temperatures to warmer ones. If you fill those pipes with an inert gas, put one way check valves in them and run the pipes underground, through the walls and up in the attic roof  and back into the ground, you have a closed passive heater/air cooler. Do your research on this before buying parts for installation. You might also not be able to get it permitted.  

I could imagine putting some mulch on the roof and keep it moist. This will stay moist maybe for the day and collects dew in the night, Make a dense layer of soft mulch (grasses, herbs, leaveses mix) and a rough irregular layer which is loose (woody herbs, branches of bushes) so that the nightair can move through it and can condense water on the surface of the mulch. The condensed water will drop into your soft dense mulch which soaks it up. The sunlight and warm air can then evaporate moisture from the dense layer of mulch during daytime which results in a cooling of the roof surface. If you plant seeds of such woody herbs and bushes into the dense layer of mulch befor putting the loose mulch, you will get a almost mainenance free natural cooler. Take care to have an uneven mulch- or canopy surface on your roof to have a big surface for the air to condense water. I've seen somebody in California studying which plant species are the best water collectors in the night. Maybe you can find the Website and the plants she found. It's likely that her study is already finished now. then you can combine such plants to a low uneven multistory open canopy. Bill Mollison has scetches of such uneven canopies for big forests in his Permaculture - A Designers' Manual. What you'll end up with is such a canopy in miniature. There are even very small palms (red palm) and Bamboos (Multiplex and Japanese) which reach around 1m hight.

I love the idea of a green roof, but fear it would be unsafe in the event of wildfire...

I love the idea of cooling water spray on the roof, but fear that is not "water wise" (wasting potable water, likely municipally treated or from an aquifer/well) or environmentally friendly; be it long-term or if it became popular.

Seems to me the solution is better planning/thinking/building...incorporate both passive cooling (clerestory windows, basements, wind towers) and passive heating (appropriately placed, double hung windows that can open top down or bottom up, insulation, thermal building materials, overhangs, ceiling fans...) is the truly whole environmentally sound concept that is ideal.

Planning buildings for our changing climate(s), with greater wind and temperature resistance would likely be the best solution.

With that said, I THOUGHT we had done so, and yet during the West Coast "Heat Dome" of June 2021 all the extra insulation and ventilation options we installed did not suffice... Now, we did experience Temps 10 degrees above what is normal for August (and yet it was June); perhaps this was a one off anomaly? Sadly, I think not.

As much as I have always eschewed A/C, not sure 40+ Celsius Temps are something we can exist in without resorting to A/C....

We have invested in a super pricey "Vornado" large room air circulating fan that DOES seem to work well as a push/pull fan (evacuating hot air out or blowing cold air in at night). I am hoping that with a second when the outside Temps drop, and we throw open all the windows this MIGHT keep the A/C at bay; if only we had a basement....

Lorinne said, "I love the idea of a green roof, but fear it would be unsafe in the event of wildfire...

We have had some discussions of sod roofs here on the forum.  To me, they sound like what I would want in the event of a wildfire.

a foot-deep sod roof.

https://permies.com/t/6489/permaculture-sod-roof

Lorinne Anderson wrote:I love the idea of a green roof, but fear it would be unsafe in the event of wildfire...

A very good question!  Unfortunately, I don't know the answer, and so cannot further expand that line of inquiry.

Lorinne Anderson wrote:I love the idea of cooling water spray on the roof, but fear that is not "water wise" (wasting potable water, likely municipally treated or from an aquifer/well) or environmentally friendly; be it long-term or if it became popular.

Seems to me the solution is better planning/thinking/building...incorporate both passive cooling (clerestory windows, basements, wind towers) and passive heating (appropriately placed, double hung windows that can open top down or bottom up, insulation, thermal building materials, overhangs, ceiling fans...) is the truly whole environmentally sound concept that is ideal.

These are excellent points.  I have incorporated pretty much every passive solar cooling/heating principal you named into my own home design.  And I am STILL interested in cooling my roof with water, at least in concept.  It seems a promising technique with minimal investment and minimal operating cost.

Having said that, I live in a water-rich environment.  There is ample rainfall and plentiful lakes and rivers here.  If I lived in a desert, I might well reconsider how "minimal" the value of the additional water consumption actually is, both ecologically and in terms of $.

Also, I am installing no A/C in my home.  I will depend on these alternate cooling strategies for 100% of my summer comfort.  Based on my preliminary observations - since I'm still not living in the home under discussion - I would probably do fine as is, without additional "active" cooling strategies like roof irrigation.  But I still wish to explore and see how well they work.  If roof irrigation ends up consuming little and bumping my summer comfort level from 90% to 100%, then I want to know that.  I would also consider it a good hedge against the possibility that, in a warmer future, I might need more cooling capacity than I'm currently designing for.  As you well pointed out.

Now that Heat Domes have become the latest expression of climate chaos, I'm wondering what folks are doing for electricity-free cooling.
What works when things get so extreme?
What no longer works?

What's a solar chimney? Or lunar cooling panels?

Great thread.

We just built our home with a full daylight basement. (faces south so no sun coming in during the summer, stays cool)
Toying with keeping the house cooler I have found that if I run just the "fan circulate" on the furnace, it circulates that cool 60's air from the basement through the home.  Stays in the low 70s.
But, if outside temp's hit 95 and higher inside temps seem to warm up a bit more, high 70's.
I run the A/C then.

I run the sprinkler up wind of the chicken coop during the hottest part of the day.  Sure keeps the girls cooler.

Also have a mister on our outside patio.  Love it !!

Rebekah Harmon wrote:What's a solar chimney? Or lunar cooling panels?

Rebekah, here are some threads that will explain a solar chimney:

https://permies.com/t/143626/Solar-Chimney-Earth-Tubes

https://permies.com/t/146268/work-solar-chimney-sucking-tube


And the lunar cooling panels is best explained here:

https://permies.com/t/14038/Electricity-free-cool-home#734262

https://permies.com/t/44467/brainstorm-super-green-modern-ice#359546

That concept is also known as "Night Sky Radiant Cooling".

“Exactly. The moon has nothing to do with it. I just like calling them Lunar as opposed to Solar. Technically, the darkest part of the sky would be best.”

Whereas sunlight heats, The moon actually does have a cooling effect. It has been measured. Direct moonlight is cooler by almost 10 degrees than the space next to it that’s not in direct moonlight. There are you tube videos on it.

I would think that just like having a green house set up to be South facing, you would also want your Lunar cooler to capture as much direct moonlight as possible for maximum cooling effect.

hannah ransom wrote:What are things that you do? We don't have air conditioning, but do have ceiling fans which I would prefer to not use. We live in a garage and it gets HOT. Hopefully we will be insulating the ceiling soon, but I doubt that will help much with the heat...

Window shades on the East in the mornings and on the West in the afternoons - IF you have windows.
If North and South facing windows shades pulled for whatever time the sun shines in either of those.
The same for a fan bringing in the cool air at night and off in the morning should help matters.

Suggestions for a swamp cooler are right on! That was our cooling system in a huge old house in Texas one summer. It is amazing how cool it can keep a large area like that old 2 bedroom, living room, dining room, kitchen, and back porch. The fan forcing humidity into the rooms as well as the cool air did a great job. Not like Air Conditioning, but makes it livable in a house.

Our primary savings comes from not wearing clothes! The difference is so incredible when putting  clothing on when guests arrive. The clothing is so very evident as uncomfortable, wasteful and unnecessary.

I have also taken to sitting on Japanese Tatamis and also low furnishings like desert people in northern Africa. There is a wonderful evident cool mass, like where you would crawl to avoid smoke inhalation in a fire. I notice the difference when I stand up and walk around, again more sensitive without the clothing.

We are also more sensitive and conscious of the temperature enough to know when to close the windows and to open them at night.

When the day tops out at 102F, I won't turn the cooler on but a couple of hours in the afternoon. Thermal mass does the rest, holding in the cool. My bills are very low. A ceiling fan circulating is great in milder weather.

A Bernoulli tube effect can make for better cool air flow. Choosing a canyon, or man made, or local hills will give that extra breeze to increase the prevailing winds.

Planting trees and ground cover, instead of dirt and rock, is worth several degrees and pleasing.

As for bang for buck, spending less on clothing and washing is even better than $20 spent on paint for the roof. It feels good generally, too.

I am considering installing an extraction fan to remove the heat in the vaulted ceiling portion (half) of our home (Spouse thinks I am nuts).  

Thinking about the idea of a wind tower that funnels hot air up and out, I question if this could this be done mechanically.  My thought is to take the dead space above the closet in the vaulted ceiling area and install air vents on three sides with a powerful heat extraction fan that would exhaust either into the attic or directly outside (this would be the non windy side of the house).  The pull of the high, heated air being extracted "should" have a secondary effect of pulling in the cooler, lower air/prevailing winds from outside, through the open windows.  In winter, this fan could easily be sealed off from the inside, within the closet, to prevent heat loss when it is cold out.

We do not have a/c, nor am I a fan of it due to noise and energy use.  We live in a newer "manufactured home" of 1500 sq ft, with scads of insulation, no basement, but elevated a couple of feet of the ground, fully sealed (siding extends beyond home down to a 4 inch wide concrete curb the entire periphery of the home).  We currently operate on a strictly passive system of monitoring of outdoor vs indoor temperatures to "shut down" (close all windows, blinds and curtains) when temps outside exceed indoor temps and "flushing" out the heat by opening all the above when outdoor temps fall below those indoors.  

We have multiple 48 inch, super efficient ceiling fans (one in each room) and two window extraction fans, as well as the bathroom and kitchen exhaust fans.  Unfortunately we do not have double hung windows, so even when fully open, there is still about five feet above the opening, to the ceiling.  Lately, by 8 or 9pm, the outdoor temps (generally reaching a high of 35-40C) have fallen below the indoor temps, and all windows, blinds and curtains are thrown open, and it is 25-27C, both indoors and out.  Within an hour, the outside temps have fallen several degrees, whilst the indoor temps have dropped maybe half a degree.  By 4am, lately, it is 15C outside but still mid to low 20's in the house, and does not seem to fall anymore.  By 8am the indoor temps start to rise, and we shut everything down.  The internal temp is MUCH slower to fall and never seems to equalize with the lower outdoor temps, before they begin to heat up the following day.  I suspect this is due in part to our excessive insulation both in the walls and attic, our vaulted ceilings, and heat producing appliances (fridge and two deep freezers) in the vaulted portion of the home; but that the biggest issue is the style of windows, that open only from the bottom.  It seems to me that the that the hot air is stuck up high and cannot vacate the building efficiently due to our lack of double hung windows.

Sorry if I sound like a whiner, but I do NOT do heat well, and anything above 25C is just about unbearable for me.  IF we could cool the house down at night, just a bit more, I think it would offset the daytime highs, indoors, that are so challenging for me.

Any engineer types out there?:    Is my theory sound?  Would this actually work?  Is the expense worth the cost to install and run such a fan.  Lastly, what size of fan (CFM) and type of fan would be most effective for a 1500 sq ft home?  Thanks for your input!

For hot climates, my son found this video by his favorite Chemistry Professor:


He had been looking up the concept for making a type of "air well" for collecting dew. Reading he's done suggests as a roof paint it's quite appropriate for hot climates, but not a net gain as far north as we are. He's also read that it's not that difficult to make your own "paint" with the Barium Sulfate as the added colour.

Hi,

L. Anderson wrote,
Thinking about the idea of a wind tower that funnels hot air up and out, I question if this could this be done mechanically.  My thought is to take the dead space above the closet in the vaulted ceiling area and install air vents on three sides with a powerful heat extraction fan that would exhaust either into the attic or directly outside (this would be the non windy side of the house).  The pull of the high, heated air being extracted "should" have a secondary effect of pulling in the cooler, lower air/prevailing winds from outside, through the open windows.  In winter, this fan could easily be sealed off from the inside, within the closet, to prevent heat loss when it is cold out.

Attic fans have been around for a long time.  If we didn't clean the fireplace the ash would go all over the house. The fan needs an unrestricted flow to do its purpose, such as in the hallway ceiling. Also the closet may have dirt pulled into it getting on whatever is in it. I might recommend whirlygigs in the roof,  or vents on the side of the home. Without knowing the configuration of the home it is a little difficult to imagine a cost and energy saving solution.