Sunday, November 22, 2009

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:

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.

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.

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.


Term paper said...

It’s great to see good information being shared and also to see fresh, creative ideas that have never been done before.

Anonymous said...

Michael, I have only read a small portion of your data and look forward to reading more as my interest in Leadership in energy and environmental design drives my curiosity. I hope to get a chance to visit your place some day.

Mike (The pine needle supplier)

Thanks for taking time to talk today - 3-6-2011

Anonymous said...

I liked the house that you built. It is simular to the montolithic Homes that are being built.More people should be conceidering a home like your family. Thank you for sharing.

Plumbing Fittings said...

So glad to see you updating on your homes you are building. Hope that one day it will be my house you will blog about!

mike said...

Very nice blog!
I'm getting ready to build an earth shelter house in central texas and wondered if I could talk to you about your experience with your earth sheltered home.

Gin said...

Hi Mike, I'm looking into building a home very similar to yours. Now that you've been in your house for nearly 4 years, have you discovered anything you'd do differently? Will you ever have another open house? I'm having a difficult time finding any finished bermed homes to view.

Gin said...
This comment has been removed by the author.