Earth Sheltered Home in Texas

[Mike Arant]

Thanks, Rob, for the email and reminder about new posts.

We are in the process of building an earth sheltered home about 20 miles east of Austin, TX. While we are not being strict with regard to nothing but green, we do think it probably qualifies as a Green House. We know the definition is very fluid and some may not agree it is green, so please take it for what it is.

We are about 1/2 way finished with the basic shell. You may follow our progress on our blog at: marant1946.blogspot.com (or just google it at 'arant earth shelter'). We will continue to post to the blog as we progress through completion.

Generally, it is about 2500 sq ft, including the one car garage and mechanical room. It will have a floating concrete floor and high performance low e windows. It will be very tight (to the point that we are making sure we bring in outside air) and should use about 25% the energy of the average house. The biggest problem will be to keep the humidity controlled, which will be done with a combination of ceiling fans and a high performance (though small) hvac system.

We would appreciate any and all comments, preferably on the blog itself, or, if you wish, directly to: errantventures@gmail.com. If you have specific questions just send them to the email address.

Mike

[Joe Blake]

Mike,

Just on the point of controlling humidity, have you considered using a water condenser to take the water out of the air and turn it into drinking water?

http://airwatercorp.com/products.aspx

I've got a small (20 litres per day) machine which sits in my kitchen and gives me all my drinking and cooking water, and depending on relative humidity, it only needs to run 6-7 hours per day. It draws 450 watts, and my measurements indicate that the (dry) exhaust air is only 1-1.5 degrees warmer than ambient temperature, due to a very neat design twist which takes the cooled air and blows it over the heated coils, thus recycling a large portion of the "cool", which means it runs more efficiently.

It certainly won't solve all the problems, but if you have a HVAC system, you are probably going to have "waste" condensed water so why not put it to good use?

Regards,

Joe

[Mike Arant]

Joe,

Good idea, I will check it out. I already intend to see how much water the hvac puts out and have made arrangements to collect it, as well as rainwater. The house has a french drain around the back side which can also be collected if it produces enough to be worth while.

Mike

[Rob Beckers]

Mike, that is some house you are building there!
I would be interested to hear a little more about the technical details of your construction. Is the house designed for passive solar on the 'open' side? Thermal mass is clearly not an issue with all that stone around. Since your roof is concrete, is that water-proof enough in itself (thinking about the inevitable cracks that always seem to appear in large concrete panels), or do you put a membrane on top of this? Similar question for the buried walls. What are you using for insulation? Concrete itself has an R-value of only 0.08/inch. Insulating under the floor slab and then using the floor slab for radiant heat (and thermal mass) would seem a good way to go. Is this in the plans?

I would imagine that you won't need very much cooling in summer, despite the Texas climate. Being underground and with the large thermal mass should keep things pretty cool.

Any RE plans for this house? Some PV or wind?

Please keep us posted about the building progess Mike! Feel free to liven it up with a few pictures (I know, you have pictures at Blogspot, but it's so much easier to see have them inside the thread with the story).

-RoB-

[Mike Arant]

Rob,

No, I really have no pv or wind plans. The state of Texas is really quite primitive in its approach to incentives. There is a tax moratorium on the value of the re system, but that is about it. At this point it is just not economic, though I have designed the house for future installation.

As for insulation, we will put some insulation on top and under the stucco on the sides, mostly to protect against heat rather than cold. The thermal mass and earth sheltering will keep the interior at a temperature swing of about 10 degrees year round.

As to heat in the floor, I considered it, but with the heating requirements being so low it just was not economic. Next time(?) I may consider it with active solar hot water and storage, but not this time.