October, 2012

An update and response to Gin:

We are still very happy with our earth sheltered concrete home, and it is performing as we hoped and expected.  It took 18-24 months for the temperature to stabilize (it was cool to begin with as the concrete cured)and now our electrical bills are pretty stable summer and winter.  During the shoulder months we do not either heat or cool as the house provides the stable temperature around 74 that we want.  The biggest problem here in TX is with the humidity, not temperature, and the house cannot really help with it.  So far it has not been enough of a problem to install a dehumidifier.  The heat pump system works as expected.

There have been no concrete cracks or leaks at all. We apparently planned well enough that there have not been any major corrections or additions we want to do that do not have wiring/plumbing available to them.

We are presently in the process of landscaping the yard, as soon as we get the plans from the landscape architect.The orange, lemon, kumquat and grapefruit trees make it through the winter with a little help and protection, and are all loaded with fruit in the process of ripening. The fact that they are planted under the overhang next to the heat retaining concrete walls helps, I am sure.  Most of the other trees (oaks, pecan, wild plum, pomegranate and Fantex ash are healthy and growing.  We have Texas Sagebrush and creeping lantana on the roof, which exist with virtually no care and no irrigation.  They do very well, as shown in the above  photos and should eventually spread to cover the entire roof. (And a Texas sunset, too!)

We do not have any open houses scheduled, though it is due to no requests rather than any other reason.  If enough people want to see the house we will schedule one.  I would direct people to other similar houses, but there is no good list or registry that I know about.  Maybe we need to figure out how to create one.

If people have specific questions I am happy to try to answer them.

Mike

We just had an open house for persons interested in the details of our home and prepared the following fact sheet. It serves well as a summation of the finished project:

ARANT EARTH SHELTERED HOME

Fact Sheet

Designers: Michael and Chris Arant
General Contractor: Michael Arant
Concrete Contractor: Ralph Smoot
Finish Work: Michael and Chris Arant (March 2008 to present)

Construction began in October, 2007, with the home occupied in March, 2008. Finish work continues (baseboards, counter trim, bookcases, landscaping).

Basic Design
2500 square feet, 2 bedrooms (can be 3), 2 baths on 3/4 acre lot.

The home is designed on four 24' square concrete modules placed on 2' footings. Each module was formed with aluminum wall forms producing 9” thick walls including reinforcing bars. Once the wall forms were in place an umbrella shaped form was raised in the middle of the room and attached to the top of the wall forms. Concrete was then pumped to the top of the ceiling form and allowed to run down to fill the wall forms. When the walls were filled the concrete continued to cover the roof form to a depth of 6-8”, including rebar. The roof is engineered for a load of 50,000 pounds per square foot. After the concrete had set the module was a single piece of (monolithic) concrete, walls and roof, with no seams. The floors were poured last, after all electrical and plumbing was in place. The roof and walls are waterproofed with an emulsion compound, special waffle weave fabric and plastic sheet. Water drains off the roof into the surrounding soil, then down to french drains which conduct the rain away from the home.
All penetrations (doors, windows, etc.) are framed inside the concrete forms before the concrete is poured, as are the outlets, switches and all wiring within the walls. There are additional framing details in place for future features such as a fireplace, lighting and the like.

Energy Saving ('green') features:
Concrete is a poor insulator, so all exterior walls have 2” of foam insulation on the outside under the stucco. Concrete does provide excellent thermal mass which levels the temperature throughout the year. With 900,000 pounds of concrete it took a year for the walls and ceiling to stabilize temperature at about 74 degrees. It appears the temperature will vary from about 70 to 74 on a year round basis, with a thermal flywheel effect giving the highest temperature in Oct/Nov and the lowest temperature in Jun/Jul. The concrete walls completely prevent air infiltration through the walls at outlets, switches, etc. (The average house changes interior air due to leaks about 4-6 times per hour. This home changes air 1-2 times per day.) The largest source of heat gain in the summer is the west windows, which are presently shaded with removable shade cloth and will eventually have shutter/shades.
Each room has a ceiling fan which runs constantly. This keeps the temperature within the home even and prevents any pockets of static air which could result in mold or mildew. We have had absolutely no problem with mold or mildew, and keep the indoor humidity at about 50% for comfort. Most of the ceiling fans are an energy efficient design from the Univ. of Florida. The fan blades are about 40% more efficient than the typical ceiling fan, allowing the use of a smaller motor. It is actually a commercial fan available at Home Depot (look up in their stores and you will see they use them too).
Windows are from Don Young Co. and are high efficiency all vinyl with thermal breaks. They are double pane with argon between the panes and a low emissivity ('low e') coating on the exterior.

So far it appears energy usage will average less than 1000 kwh/month, and 10 gal of propane/month.
All water fixtures are water saving, with low flow faucets and shower heads. The toilets are dual flush low flow Toto units from Japan. Exterior water requirements are minimal, with drip irrigation used where needed. The primary hot water heater for the home is a wall mounted Takagi TK3 point of use propane water heater that will provide up to 7 gpm of 50 degree rise water constantly (until we run out of propane!). There is a backup electrical hot water heater that is turned off most of the time.
All electrical appliances, including the heat pump for heating and cooling, are Energy Star or similarly certified. All lights except a few accent fixtures use compact florescent bulbs or LEDs. Cooking and primary water heating is with propane, with one 250 gallon tank lasting about 2 years.
The xeriscape landscaping is primarily of native, low water use plants. The grass is a combination of Blue Gramma and Buffalo grasses that need only 7-12 inches of water per year. If the summer is very dry they will become dormant, to come back green with the fall rains. The roof has 1-3 feet of soil covered with Lumite weed cloth which prevents penetration by weeds but allows rain to pass through. We have planted Texas purple sage and purple trailing lantana which will eventually cover the entire roof, providing shading and controlling erosion. For additional insulation the mulch on the roof will be 6” of pine needles under the sage and lantana. The citrus trees (NC 33 navel orange, Rio Red grapefruit, dwarf Improved Meyer lemon, Mexican lime, and Miewa kumquats), bananas and orange Esperanza will be drip irrigated. Pride of Barbados are planted along the fence line. Live oak, burr oak, western soapberry, Texas persimmon, wild plum, pomegranate and thin shell pecan trees have been planted throughout the yard and will receive only rainwater.

ADA features:
The home is designed and built to be primarily handicapped accessible. It is on a single level with no stairs. All doors open with levers, as do all bathroom fixtures. The toilets are raised, and there is blocking within the walls for the installation of grab rails where needed. There are no steps or impediments to wheelchairs anywhere inside the house, with all doors 36” wide and full wheel-in access to the master shower. All light switches are press pad style. The dishwasher and front loading laundry are raised about 6” for easier access. Dish storage is in pull out drawers in the base cabinets.

Safety:
The entire structure can serve as a storm shelter in the event of a tornado or hurricane, with the mechanical room providing complete protection to virtually all hazards except earthquake.

Summary:
We are very pleased with our home and would definitely do it again. So far it is performing as we hoped, with few problems other than design features we would do differently. Ralph Smoot did a great job and is a wealth of information and experience on earth sheltered building. We would not do it again without him.

The kitchen-dining room. This room has only the two windows shown, but it also has the large Sun Dome in the center of the ceiling which, when the sun is out, makes it the brightest room in the house! We can tell the weather just by looking at the Sun Dome, from the passage of clouds to rain. The house is so well insulated for sound that the only way we can tell it is raining without looking outside is the sound of it beating on the Sun Dome.

This is the last entry on the blog, as the house is now finished (if any house one builds and finishes oneself is ever finished). So far we are very pleased and would do it again. It performs as we hoped, with the average electrical usage for 13 months through the end of June (including a record heat wave last summer and another this summer) of 900 KWH/month. We use propane for hot water and cooking and used about 125 gallons during that period. It appears most of the savings come in the fall and spring as we do not need to run any space conditioning from about October to April, just using the fans to circulate the heat stored in the walls. We will probably need to turn on the AC sometime in early May.

Thanks for your interest. If you wish to ask any questions just post them to the blog and I will answer as soon as I can after I receive notice of the posting.

The living room showing the large windows and amount of light. Though it is an earth sheltered home there is no sense of being in anything other than an ordinary house.

Every room has a ceiling fan that runs 24/7. They keep the temperature even and prevent any stagnant air that could cause mold. We have had absolutely no problems with humidity in the house, and are able to maintain 50% or less in the house all the time. This particular fan is an exceptionally efficient design from the U of FL. It uses about 40% less energy than the normal fan and can move prodigious amounts of air. It is actually an industrial model fan available very inexpensively at Home Depot. We have 3 of them in the house.

Closeup of the stain showing the variety of shades possible and the irregular nature of application. We are very pleased with the results.

This is the drive after staining. The stain commonly used on concrete is acid based, requiring protective gear and the protection of plants. It is also quite expensive, particularly for the large area we had to color.

We learned about an alternative and decided to try it. It is Iron Sulfate, which is an acid type fertilizer. (Referred to as Copperas in TX.) It is merely mixed with water and applied with a hand sprayer. Any runoff benefits the grass. There is only one series of shades, all of an orange-red hue, depending upon the concentration and number of coats applied. Since it was the same general color as the house it was perfect. It is permanent, does not fade much, and really muted the brightness and glare of the native concrete. Enough to do the entire drive cost $5.

Driveway shortly after pour before staining. There is about 5,000 sq ft of concrete, which is really glaring and ugly. We knew we needed to do something about it.