Zero Energy Earth Home in Texas?

Kelly and Owen,
I’d like to thank you for all of the wonderful information you have offered for free to the world! I’ve been following along for about a year now and it just keeps getting better and better.

I have a question about insulation and thermal mass. I live in Austin Texas and our summer nights are a lot of times only 20 degrees cooler than the day time high. Which that day time high can get to over 110F. If I build with only earth/adobe filled bags, I don’t think that the house would be very comfortable during the summer months. I’m planning on rebuilding a small dilapidated shed in about a year using the hyperadobe method. The shed will have plumbing and electrical. Basically I’m going to build it just like I would build a house for our family to live in full time. This is going to be a proof of concept to show my lovely wife that it’s not a bad idea and that a house built in this fashion can look professional.

So my question is, how would you go about insulating a building built with the hyperadobe method, or would you build using a different method?

Thank you for any information!

Hi Michael,
I just looked up what the year-round underground temperature is in Austin, TX, and noticed that it is 71 degrees F. You couldn’t ask for a nicer temperature to live in! A substantially bermed or underground home in that locality could easily become a zero energy home, as far as heating and cooling goes.

You are right that a solid adobe-walled home there would be too hot in the summer for sure. Yes, it can be insulated, either with exterior insulation, or by filling the bags with an insulating material, and this would help keep the interior more comfortable…but you are still going to need air conditioning most likely.

If it were me, I’d go underground!

[Owen: This can include building above grade with earth berming/earth sheltering to reduce the risk of flooding.]

18 thoughts on “Zero Energy Earth Home in Texas?”

  1. I just came across this and I think it would be very helpful for you to go look at the homes of early Spanish, German and U.S. settlers of central Texas. These structures have these things in common: thick, dense walls of native limestone- some up to foot more, with plastered finishes, some only interior at then later the exterior was added, rubble trenches, many had pounded dirt floors with boards laid over them in a pier support and then broad porches, front and back, frequently added at a later date if need be with the early homes, later encircling porches were added. These homes are cooler than you realize in Texas summers, I know, many of my relatives had them. I hope to build my own when I get back to Texas. Granted the concrete is not green, but it’s a matter of balances here. The continual demand for cooling costs over years and maintenance of conventional home or slip-formed insulated rock home that can that can take the worst of Texas weather.

    • There are many examples of traditional building practices like the ones you mention being superior to the methods used today. This is one reason architecture is so fascinating to me. It would be tragic if these great ideas that evolved over hundreds and thousands of years were lost.

      I can’t help but compare earthbag to stone houses. Both are high mass and would provide the cooling effect you describe. However, earthbag walls can be built in a fraction of the time of stone walls. Of course, speed isn’t everything. I very much love the look of stone. So I’d be inclined to combine the two by incorporating a stone entry, fireplace, etc.

  2. What’s Going down i am new to this, I stumbled upon this I’ve discovered It absolutely useful and it has helped me out loads. I am hoping to give a contribution & aid different users like its aided me. Good job.

  3. Hi there,

    I am working on putting together a medical retreat centre in the Caribbean, on an island where pumice sand is very cheap. Would using pumice sand make the buildings any cooler or would one still need any insulation?

    Glad for the input.

    Kind regards,

  4. I’d like to thank every one for the input! Seems I have some places to visit and books to read. I’m really looking forward to building a house that will last and won’t cost an arm and a leg to heat/cool.

  5. We will be building a 1000 sq. ft. adobe home in the north Chihuahuan desert of Texas (Big Bend area). Our blocks walls be 12 thick and insulated with a 4-6″ thick straw/clay mixture on the exterior. Covered with another 2-3″ thick skin of plaster, the walls will be 18-20″ thick. The thick staw/clay mixture is a recent decision to replace the 2″ poly-foam we originally intended. The insulation properties of the straw/clay will be about the same, but less expensive (not including labor) than the foam panels. This is referred to as ‘hyperadobe’ by the adobe folks in New Mexico. As Quintin Wilson commented, it is like ‘adobe on steroids.’

    The properties of the straw/clay layer increase the insulation, but the real gain is the thermal delay and conductive properties of the entire adobe/hybrid wall. Other designs in the structure will also aid in cooling: a breezeway with large doors on both ends, all windows with exterior shutters, a small basement for food storage AND conduction of geothermal cooling to the above structure, earhen/adobe floors, and a double-layer roof designed to shade in summer and allow solar gain in winter months.

    Simone Swan, an adobera that has built many adobes in deserts around the world (her place is also in Big Bend), advocates internal courtyards as the most efficient design component for hot weather buildings. Thousands of years of living in earthen buildings in Middle Eastern deserts confirms that design. While we will not have an internal courtyard, we will probably incorporate one open on one end to the north, which will be shaded all day in the summer.

    Because our place is on flat ancient seabed of caliche and limestone, a bermed structure will not work for us. However, a local woman (Bonnie Wunderlich) built a partially-bermed adobe/rock home: (click on the photos for larger image and description). Another interesting individual built a rock ‘adobe’ house in the area that is completely cooled by a basement he pick-axed into the limestone. The rock walls are double layered so that cool air from cellar flows through and into the house while hot air escapes through ceiling/roof soffits.

    Two excellent reference books are “The Barefoot Architect”, by Johan van Lengen, and “Design Primer for Hot Climates,” by Allan Konya and M. Vendenberg. For ideas on low-energy ‘real’ buildings (aka built by and lived in by owners) in Texas hot climates, visit the Big Bend area. Many rock and adobe structures built in the mid-1900’s still remain, and most of the local residents (especially in south Brewster and Presidio counties) build their own energy efficient, low cost homes, many of them off the grid. They don’t have air conditioning or central heating, and live there year round in comfort. Most people also have a shaded outdoor kitchen which can be used year round, but most valuable during summer.

    Terlingua also has an annual home tour every late February. My partner Ed was there for it this year (photo album: One home was an earthbag in progress. Another local is building a modified Earthship.

    There are a few rammed earth buildings in the Austin area that are extremely energy efficient and comfortable without use of summer AC. A facebook page for adobes (Adobe Doings) is mostly TX and NM oriented. Project Somos is an excellent resource for earthbag building in hot humid climes (they also have a facebook page). And, of course, Dr. Geiger’s is the most diverse resource page that I follow. :)
    Sorry for the long comment.

  6. I had the chance to do some work on a large horse ranch near the Pala Indian Reservation several years ago. The ranch included several historic adobe building dating back to the early settlement of California. The ranch was huge and had a state of the art equestrian hospital.The owners had built all the new structures out of adobe, so as to not distract from it’s historic past. The equestrian hospital was probably near 4000 sq ft in size with 22 ft tall walls. The walls were 20 inches thick and the roof had large timber trusses covered with T&G. Mission tile was used as the final roof covering. I was there in late June and early July. The noon day temps were between 97-101F. The hospital had no air conditioning or fans. The inside temp of the building even with the large doors open was in the 70s. There was a consistent difference of approx 25 degrees at room level.

    My suggestion is to create a structure with enough height and ventilation so any radiant heat can be allowed to rise and escape. Cal Earth designs their domes with air scoops. The scoop looks much like a fireplace stack, except the top opening is on the side. Hot air can rise and escape and the scoop catches evening breezes and directs the air down into the building. Cal Earth is located in the Mojave Desert. Temps in Hesperia have reached 115F. Although night time temps on average drop a bit more then Austin, the climate during the summer is pretty close. The domes at Cal Earth are comfortable during the day time heat of July and August.

    Another option that isn’t really discussed much is landscaping. Trees planted in strategic areas can lower building temps considerably. Consider deciduous trees on the south. They provide shade during the summer and allow you to collect solar heat during the winter.

    • Air scoops and chimneys are a integral component of vernacular architecture in African and Middle Eastern buildings. The physics also apply to the composting toilets. The two books I mentioned in my other post address them to the best extent I have seen yet. We are considering incorporating one in our place, but don’t know yet how. Another component is domed or barrel vaulted ceilings (Simone Swan’s expertise).

      Jerry’s house with the double rock walls, basement and manually-controlled soffits stays incredibly cool in the summer. Without air chimneys, but the same principle applies and works quite well. Visiting his place overturned our conviction that a basement or in-ground building of any type in that area was impossible. (Jerry dug it mostly by hand, pick axe and buckets!) And he’s building another house nearby with same basic design! (btw, he’s also in his 70s’)

  7. But … but … I live in Austin, too, and we don’t have basements, root cellars, or in-ground much of anything except swimming pools. The limestone is just under the ground. In our yard, it is between 2 – 7 feet down until you hit it. If you dig it out, it fills up with water. This whole place used to be a shallow sea. How would that work?

  8. I was thinking more(dangerous!) I kind of thought about this To make a cool room for storing food.I would shade the earth berm and line the inside with rock.Ive seen a porous stone used as an room cooler,that and some lite misting to help cool things off.The occasional block of ice might help.

  9. I always wondered what it would be like with double baled walls,only a few layers high and dug down about four or five foot.A shed roof with bales?Super insulated. Some earth berming to.

    • That would work great temperature wise. But you never want to put bales below grade where they’re susceptible to moisture damage. Use gravel bags below grade. No need for double walls because there’s a point of diminishing returns. And don’t do this wherever there’s risk of flooding (which is most everywhere) or your house will turn into a swimming pool.

  10. Hey Mike,

    I’m building an earthbag home a bit north of you guys, and I have the same problem. One thing I considered is Rice Hulls, which are easy to mix in, and add a lot of insulation value. There’s a farm just out side of Austin that could deliver all you need. (for me a full 144 cu/yd live bed trailer was ~1700, but the lion share was the freight charge. They are working on big sacks people can come and pick up. Its worth considering:.

    I hope that helps,

    Sam Dodosn

  11. The key fact here is temps don’t cool off much at night in this area, so the thermal mass walls (earthbag, adobe, whatever) will remain warm/hot day and night, and make the house uncomfortable.

    Read Patti Stouter’s articles on designing and building in hot/humid climates. There are lots of things you can do to improve the design (improved ventilation, wide roof overhangs, etc.).


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