Off Grid Home Forums Technical Discussion How you design an off-grid home to deal with extreme heat

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    We have been trying to deal with the AC problem for years. Our biggest concern here in the south is humidity. We can’t open windows at night when it is high because we have no way to remove it without adding heat to our home. We have thought about trying a wholehouse dessicant dehumidifier that also does some cooling. Without humidity we can simply use fans to keep us cool till about 80 degrees. Another problem is we don’t have any duct work in our home. We thought we could use our wholehouse fan at night so we never installed any. Boy do I regret it now. 3 days ago we set the all time record high for heat here. Ductwork would at least help with the humidity. No way yet to run central air, uses to much power. Geo-thermal is too expensive.We need to invent an AC unit to run on DC…so solar panels could run it all day…don’t need it at night so much if it stayed cool all day!


    Hi HippyChic

    “Dessicant dehumidifer” – does that mean silicon crystals that soak up the moisture? And what does the cooling?. Are there no DC coolers at all? That is suprising as there are DC fridges (though they add heat).


    Traditional Homes in India and the Middle East are built at low cost to withstand extreme heat and promote cooling breezes, but that kind of lesson is not learned in most modern American homes.

    With aircon breaking down for millions on the Eastern side of the US right now, and an extreme summer perhaps on the way – what tips are there to stay cool while off the grid?


    No ductwork? No DC refrigerators?

    Although it may be too late to cope with the present heat wave, several things can be done in short order. Homes in hot climates tend to have white or reflective exterior surfaces. Lots of insulation is good, more is better. Yes it sounds counter-intuitive but consider this. You can cool off partially at night then keep heat from invading living quarters during the day. Even something as simple as shiny aluminum foil can be a radiant heat barrier. Reflectix is a bubble wrap product coated one side with silver foil. It is often used in attics to reflect the radiant heat from dark roofing tiles back up instead of down to living quarters. In the longer run consider installing light or even white or silver colored roofing materials as oposed to darker colors.

    Duct work is not that expensive. It can be retro fitted in attic or under floor or in basements. Worst case it can be run on shady side of house. Granted it may not look great but its a choice of comfort or appearance.

    Even something as basic as hanging up towels soaking wet to give some cooling as water evaporates will provide some relief. Fans will speed up this process even in humid climes.

    Yes I am aware swamp coolers are not as effective in coastal area compared to desert climates. But it does work.

    While working on survey crews in blazing summer heat I learned to wear long sleeved white shirts and a hat. Soaking the collar and sleeve cuffs and the hat gave me some relief even on hot humid days. Better than heat stroke any day.

    If I was building from scratch I would put R40 insulation in walls and ceiling. Exterior siding would be a white color. The roof would be the new metal sheeting in a silver color. If house was built on a slab I would place a large trunk duct on slab then tee off to various rooms. The slab being in shade and in contact with ground would be the coolest place in house on a hot summer day. It would help cool the trunk duct.

    When I built a house in the Great Lakes region I designed ducting for central air conditioning but discovered I did not need it. Just fans.

    If DC power is all you have either get a small inverter to power an icemaker or buy a DC refrigerator. You can blow a fan across a bowl of ice cubes for an effective cooler. More elaborate setups are also possible given some DIY skills.


    We live in oklahoma. Our house is 800 square feet. We insulated it well when we built it. Passive solar -porch roof shades the windows, no windows to catch the sun on the east side in the a.m., etc. Our solar system will run a box fan nicely and that’s usually enough at night in the window blowing across the bed. Our solar system will not support air conditioning of course. We have a small propane generator that will run two small window unit a.c.’s at a cost of about $10.00 per day. Summer is about the only time we run a generator and if we have to do so for 10 – 12 weeks in the summer we do so, figuring that we still save overall on electricity when averaged throughout the year. We purchase propane once a year when the demand is low and the price cheaper. Several households in our area buy at the same time and we negotiate a price with the company.


    Admin had written:

    “Traditional Homes in India and the Middle East are built at low cost to withstand extreme heat and promote cooling breezes, but that kind of lesson is not learned in most modern American homes”.

    The lesson has been learned by architects but the general public has ignored it. I first heard of such simple and inexpensive house building tricks in the sixties when I worked summer jobs for an architect. Later on I saw several designs applying these techniques but the general public kept ignoring such design innovations. I don’t know if it is a case of the building industry seducing people away with more appealing looking houses or simply because people were more interested in fashion and status than practicality.

    Most libraries will have books on how to build solar and passive designs. The information is already there you just have to dig a little bit to find it.

    Here in the north mobile homes are often fitted with a ‘winter roof’ consisting of a peaked roof over top of the mobile. The steeper angle sheds snow and coincidentally provides shade with an air gap below, but above the original mobile roof. This alone provides for about 15 degrees reduction in interior temperatures on a hot summer days. In the interior mountains it is not unusual to get 100+ degree daytime temps.

    Shade and ventilation and some evaporation goes a long way to alleviating summer heat even if you do not have utility power.

    Keep ‘er cool!


    We live in a mobile that is upgraded as per description in previous post. So far the interior is keeping much cooler than outside. Walked up to highway to get mail and it just about did us in. What a relief to get home again to the cool interior. We have not even needed to run a fan yet.


    Well, I talk a lot about this is some of my articles at I have friends who are in mobile home, camper and

    a storage shed that was turned into living space. We have talked about ways

    to keep them cool in summer, last summer was bad for them in Arkansas as they live in a deep hollow with no air stirring. Their problem is like most

    peoples problem lack of money and ability to do any upgrade work.

    They do have a/c in a camper, window unit. Ben the son goes out back several times per day and fills a bathtub with cold well water. He then soaks in it. Evenings tend to be cool though and even require blankets some nights. Though that’s not normal in Arkansas with the humidity.

    I say if you are in a hurry and have little money and ability then make a small

    space comfortable and forget the rest of it. Shutters, moveable insulation, thermal barrier mentioned above are all great ideas. I heard of one guy that sleeps on a water bed that lays on the concrete in the garage where it can cool off to near ground temps before nightfall. I’m sure he keeps insulation over it during the day hours.

    Geothermal or getting below ground is more difficult. Geothermal is not without cost and takes time to pay off. Excavation, engineering and protection

    from water all make underground construction somewhat costly and difficult if

    doing it yourself all depending.

    Quick and dirty underground might be earth bag dome, with dirt bermed partially around it (above grade). Thermal barrier and insulation can be used here as well near the exterior.

    I think we talked about this last summer on the forum but hay or straw insulates well. Though hay is only a very temporary solution. And this is only a great idea if you bail your own hay or straw in square bails. If you made a box 2 bails deep on all 6 sides it would be more well insulated than a commercial freezer. Put a small window unit a/c on it and you would have some cheap a/c for the summer. I wanted to try this just for the heck of it but I have yet to come up with money for materials. You would still want to use thermal barrier.


    In my house and Earthship, the tire walls keep it cooler. There is less solar gain from the tilted windows. It got up to 92*F here at 8,880′ 39* latitude, but the tire wall areas stayed around 72*F. In Phoenix, Arizona the underground temperature is 70*F and an Earthship there faces north. Unless you have ground water problems, going down into the ground can cool a house.


    I found this website with an article showing how buildings were air conditioned as much as 1500 years ago. Note how modern architects have sucessfully adapted the ancient concept and modern architecture design.

    The sentence concerning how construction costs were also reduced really intrigued me.

    At the same website you will also find articles and diagrams on how to make food storage containers that will keep food safe for many days without electric refrigeration.

    Pre-history off-grid anyone?


    It is no wonder that ancients lived in caves, some of which were even cooler with water deep in them. The water is both thermal mass with the cool rock and has an evaporative cooler effect. Thick stone or adobe walls were found to be cooler in the day and warmer at night—thermal mass.

    My Earthship has the catchment water tank and transpiration of the plants to also cool it, but the humidity it adds has to be vented. The lower buried tire walls tend toward the ground temperature year around, with the angled glass and brown lower walls and mass absorbing solar thermal gain in winter and releasing over days, and otherwise acting like other mass wall types like adobe and thick rock.

    It works well, both the evap, deep underground parts, and mass in dry and warm/hot climates, but in places like England and Scotland the thick castles are damp, and overly cool places.

    In places like the southeast US, underground could be done with waterproof concrete type, but would still need that power using dehumidifier.


    I don’t suppose 40°C (104°F) would be considered extreme heat by some of you but the house we built is nice and cool in the summer (And lovely and warm in the winter too !)

    I have a set of photos in Flickr to show some of the principles we used to build the house.


    that looks like cordwood masonry? am I right? or is it rock? You should draw up the design for you place with a free simple cad program like STD CAD Lite.


    It’s stone from our land.

    I used pen and paper at first then once I’d got the solar panels up I used Sketchup to design the extension.

    I’ll have a look at that other program, thanks.



    I wouldn’t count out earthips and earth bermed building. The reasonings are great. First off, it will be easier to heat and cool, but everything has to be built correctly or things turn into a train wreck. But built correctly, they typically require less mainenance, less energy, keep a more steady temperature year round, are safer as well as preserve more of your yard to be put to better usage.

    Eventually I plan to build an small earth bermed home on on my largest pasture to retire into once the kids are out of the house..

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