Article No: 85
By: Carole McMichael
Although several states have their own "tornado alley," Oklahoma is widely known for it. This makes Oklahoma prime real estate for concrete homes. Vester Adams, owner and builder of an ICF home in Norman, Okla., initially checked out concrete for residential houses because he had seen the devastation tornadoes wreak on stick-built homes.
Photo courtesy of Insulating Concrete Homes
"In 2002, a big tornado passed just five miles away from where I lived," Adams said. "A week later, when I drove through the area, I was shocked at how some of the houses were gone, down to the slab. And I thought, if we were hit, what in the world would we have done?
"Then I saw some tests on TV with different materials being hurled through walls. That got my attention. On the Insulating Concrete Homes (ICH) Web site I saw that the company offered some seminars. I went to a couple of them and also learned about ICF's energy-efficiency and termite resistance. With that, I decided it would be worth going into."
Adams drew up some house plans incorporating all the features he and his wife Sharon wanted and made a model. Then he took the plans and the model to architect Charles Custer who had worked with ICH and done some designing for ICFs before.
The house is a blend of styles, mixing Mediterranean and Southwest. The 3,300-square-foot hacienda was built on two levels, with a main floor area that has an open ceiling. To stay true to the Southwest flavor of the design, Adams ordered doors and ceiling materials (the Santa Fe vegas and latillas) from Mexico. There are two bedroom wings on a lower level, one for the master and one for the children.
The exterior has an adobe color, but is finished in synthetic stucco by Senergy. It has Adobe-style rounded corners and several arches. Stucco in a lighter color was used on the interior walls. The rounded corners were built up with extra foam from the ICF and rasped into the softer shape. The house also used carved posts and corbels. For the roof, Adams chose a high-end asphalt shingle, which has the terra cotta color, but was less expensive than ceramic tiles.
ICFs in Oklahoma
Over the years, hundreds of concrete homes have been built in Oklahoma. Insulating Concrete Homes has been distributing Amvic and subcontracting Amvic shells for about three years. They build about 50 residential concrete homes per year.
Michael Summers, sales manager for ICH in Oklahoma City, said concrete homes are gaining in popularity in Oklahoma in line with the nationwide trend, and because of the high winds and tornadoes as well.
"Initially, I was intrigued by the differences between concrete and stick and the end-result product. What sold me on concrete? Not just concrete as much as ICFs. I believe the ICF is a far superior building method to conventional stick frame. I found working with concrete to be easier and, in a way, kind of foolproof. To build, you stack it, you pour it and brace it and you are done.
"With an ICF, the concrete is encapsulated in polystyrene, producing great R-factor and all the other benefits associated with it. It was really a no brainer.
"When ICFs first came out about 20 years ago, there were a lot of odd concepts and notions on what a block should look like inside--the grid or post and beam types. Now they all seem to be migrating to a flat wall system, which is what Amvic has."
"We used Amvic on the Adams house," Summers said, "because we wanted a product with a flat-wall block. It is stronger than ICFs that rely on steel ties on 12-inch centers. The Amvic ties are made of polypropylene on 6-inch centers. Also, the ties are submerged in foam, so if a finish, like stucco, is needed, it goes on easily and you don't have to refoam it. It provides you with a stud on six-inch centers, as well. We are really satisfied with this product."
He said the reason a flat wall is such a benefit is that there is less form impeding the flow of the concrete.
"You don't have to worry about voids and blockages inside the walls. I don't have to worry about blowouts. In fact, I haven't had blowouts since I moved to this block. Because they are manufactured differently, the factory molded corners and 45-degree angle blocks prevent blowouts in what used to be considered weak-spotted areas. This block also has a Lego-style interlocking system that helps keep the block in place. Tongue and groove tends to shift from side to side."
The blocks are stacked like bricks to maintain the strength and rigidity in the stack. Amvic core widths range from 4 inches up to 6, 8, and 10 inches. Block dimensions (6-inch core) are 16 inches tall by 48 inches long by 11 inches wide. They include 2 1/2 inches of polystyrene on either side. For the 10-inch core, Amvic goes up to 24 inches tall by 48 inches long by 11 inches wide. The 10-inch core is used more for straight, long spans and for structures below grade where a stronger block is required to handle backfill pressure.
On the job
There were two unusual features in the Adams house. First, the house sits on two levels, requiring step-down footings; and second, the bedroom wings have long ceiling spans (16 to 20 feet), requiring a concrete cap.
"Normally we do the footings," Summers said, "because it is a lot easier to schedule. Any time you have more contractors, it makes the job more complex, especially because we do a wet-set procedure. To make our footings and stems one, we wet set the blocks in green concrete footings and then stab in our connectivity steel."
After a ditch is filled with the steel configuration, the concrete is poured in the footing. The crew has set up batter board and string lines all around the structure. They know the outside edge and the height of the stem. Using one course of Amvic block and an insulated stem, they wet set it down in the green concrete and build the stem on top of that footing. That will adhere the block to the concrete. Then, they place connectivity steel with a 90-degree end bend into the footing in the middle of the block. It comes up 3 feet to provide the connectivity. The next day, the crew comes back and fills the stem with concrete almost to the top. Then they leave and let HVAC, plumbing and electrical contractors come in. When they are finished, the crew sands up and gets a slab up to the top of the block for the first course, which went up 8 feet in the Adams' house. From there, the connectivity steel ties the system together, and they come back and stack the next phase.
"If plumbing needs to be throughput, as for dryer vents," Summers said, "we try to forecast that so we can get it in before we pour the concrete. Other plumbing and electrical services can be chased inside the foam with a chain saw or hot knife. One of the neat things about ICFs is its flexibility with building. No extra insulation or furring strips are required. Another thing is that it encapsulates the concrete, preventing air filtration; and that and its thermal mass keep the heat really stable."
The second unusual feature--the bedroom wings--required the long span of ceilings, but also was intended to provide extra protection against possible tornadoes; so they needed a closed concrete envelope. For this, Summers chose Lite Deck, an insulating, stay-in-place joist form for concrete floors. Wood bracing was used for most of the erection work, but metal shoring jacks were kept in place for the ceilings until the concrete cured. In the master suite, Summers built one of the closets to double as a safe room.
"I put in a geothermal system for heating and cooling," Adams said. "There is no exterior condensing unit. Basically you are using the temperature of the ground, which is always 60 degrees. The system pumps a glycol antifreeze solution and water through a ground source loop. That transfers the heat from the heat pump. To cool, it reverses the cycle. The ducts are run under the slab. The system itself is run from the attic, down through the mechanical room in the garage into the slab. So if something goes wrong, you can access it easily. It is very energy efficient. I also designed the house to make the most of solar orientation. There are few windows facing north, but windows facing south take advantage of the winter sun. I decided against radiant floor heating because that works best where you have consistent need for heat. Here, the frequent fluxuation in temperature doesn't make it practical."
Summers said that when you build with ICFs, you are building a wall system that registers an R-52 factor.
"Windows are going to be the greatest source of loss in the wall; so it makes sense to use as energy-efficient window system as you can. In choosing, you need to pay attention to the NFRC (National Fenestration Rating Council) stickers that gauge the energy efficiency of a window system. On the sticker, you should look for the U-factor and solar-heat-gain co-efficient number. In our climate, it needs to be at .50 or under.
Spreading the word
More and more customers are driving the market and from the builder perspective too, according to Summers, because they are challenging builders to build one of these homes. Clients may be leery of builders who are just starting out with an ICF system, but companies such as Summers' have the answer: They don't build whole houses, but rather install the shell as subcontractors and allow the builder to do the rest. This way builders and clients can rely on an ICF subcontractor who has years of experience.
Summers may be contacted at noSpam("msummers", "insulatingconcretehomes.com"); firstname.lastname@example.org at insulatingconcretehomes.com.