Article No: 137

2006-05-02 14:23:32
ICF success in the Twin Cities
By: Carole McMichael

Photography courtesy of Vogue Homes, Inc.

John Vogstrom is the general manager and builder for his Twin Cities-based company, Vogue Homes Inc. Vogstrom had a long career as a stick-frame builder, but started building concrete homes about seven years ago with his sons Eric, president of Vogue Homes, and Paul, the company's designer.

"I saw the first concrete home built in this area," Vogstrom said. "I thought it was interesting, but it was a very square design and more expensive than stick. Still, it was a very good way of building. Five years ago, we teamed up with Cemstone, a large concrete company and Reward Wall distributor, and put up a house in the Minneapolis Convention Center in four and one-half days. Of the ICFs I've tried, I like Reward forms the best for a number of reasons - but the primary reason is that there is less waste.

"When you cut the forms in half, you can just turn them over and use them. All the corner angles are pre-made, so the ties that hold them together are in the right spot for the sheet rock. It was a lot easier to attach any type of siding. Two and a half years ago, we started building only concrete homes."

Vogstrom develops new business in two places. About 40 percent comes from referrals and clients for whom they have built homes in the past. The remaining 60 percent comes from having project homes included in the semi-annual Parade of Homes. Vogue Homes has one or two houses in every Parade, which draws people from the five-state area around Minnesota. Visitors to the Parade see the house of their dreams, and are then met with a surprise: The home is made of concrete.

To educate potential clients, forms are set up in the garage with bracing to illustrate how ICF walls look. Visitors can also view films made on the building process on big-screen televisions. Vogstrom noted that some of the clients are already well-informed and that he no longer has to explain the benefits.

Starting out
One of the recent Twin Cities Parade of Homes included an extraordinary Vogstrom-built ICF home in a hilly subdivision. The home's site is on a very steep hill, dropping about 45 feet to the road. At the bottom of the hill rests a small, pristine lake. Setting the three-story, 7,200-square-foot house into this unusual site was both a design and building challenge.

Accommodating the clients' wish list with the restrictions of the site meant the design needed to keep the three levels of living space to a small footprint. The preplanning team included the client, the Vogstroms and the structural engineers, who would sign off on the plans. Once they were finished, the plans were sent to subcontractors for bidding, with the exception of the concrete and excavation people, whose subs are scheduled on a day-by-day basis.

"We use the same subs each time," Vogstrom said. "We learned how to work with the Reward Wall System ourselves, and then taught others to do it. We got the training from our distributor, which had a technical representative onsite through the first pour. The technology has changed quite a bit in the last few years, but I can't say it was any harder to learn ICF systems than to do stick-built. And now, there are more and more people in the area doing it.

"To help get code approval, we use the manufacturer's specifications; our engineers prepare stats so we have them ahead of time. If worse comes to worse, we bring in samples of the forms or have them call up other cities where I have built concrete homes and see what they thought of it. Once the inspectors see how strong concrete walls are and the amount of rebar and how superior they are to stick-built, they accept it."

The details
The house's lower level is a walkout, and includes a large library, an office and extra storage. A secondary kitchen dedicated to entertaining, a half-bath and a large theater room with raised seating complete the floor. This level is also the floor level of a two-story atrium that houses exercise equipment and plants.

The middle floor is home to the bedrooms, including the large master suite, which overlooks the atrium and accesses the lower level via a spiral staircase. The suite also has a luxury bath with a spacious walk-in closet. Adjacent to the master suite is a safe room with separate heating and cooling controls, built for the client's collection of artifacts and artifact restoration and research. This level also has two guest bedrooms, a guest bath and the laundry.

"When you enter the upper level, you go right into a large foyer with barrel vaults," Vogstrom said. "The foyer leads into a barrel-vaulted gallery. The kitchen and dining area have a full bank of windows with views designed to look out over the lake below. Separated by a large stone fireplace, there is a great room, a bathroom and the three-car garage with separate storage. There is also a screened-in porch and a den off of the great room. All three levels are connected by a hydraulic elevator and have their own mechanical rooms.

"A good portion of the floors were ceramic tile, but on the lower level, we put in acid-etched concrete flooring. The fireplaces used a cultured concrete stone. Interior walls were sheet-rocked and the exterior was finished in synthetic stucco. Generally, the house had an Old World style with a witches hat feature at the entrance and stone around the arch-topped windows. The back of the house, which goes up three stories, is softened by cantilevered decks in wood."

One of the more remarkable features of this hilltop house is the landscaping, designed to blend in with the neighboring lots. Large boulders, one weighing as much as 8,000 pounds, were placed on each side of the house. These boulders and the house itself help act as a retaining wall.

Taking on the hill
In collaboration with engineers, the Vogstroms had the soils tested to determine how far they would have to go to get good soil for footage and what to do to hold back the hill. They then designed the house and selected materials that would do precisely that.

"We put in a number of 90-degree bends, because they would help retain the hill," Vogstrom said. "Every story went up about 12 feet, so we used prestressed, precast concrete planks between the floors to push against the outside wall. This also allowed us to use less thick walls. As it was, the walls' thickness turned out to be 18 inches of concrete, plus the foam on each side, adding up to 23 inches total. It would have had to have been much thicker without the planks.

"To handle water seepage, at 32 feet in the ground we installed Form-a-Drain (a square piece of plastic with perforated holes about 12 inches high) and poured concrete for footage to hold it in place. There are drain tiles inside and outside of the footing. Every 5 feet up, we added gravel and drain tile with fabric over it, directed toward the lake. We also used waterproofing and a fiberglass drape designed to direct moisture away. We have a sump in the lower level, but because the house is built on a hill, gravity helps the flow."

Fighting Minnesota cold
The floors on all the levels and in the garage are heated with a hydronic radiant heat system. Vogstrom backfilled with gravel under the concrete slab about 6 to 8 inches. Next, he sprayed a closed-cell polyurethane foam over the rock to create a thermal break and attached the radiant heat tubes to that. He then poured 1.5 inches of chip Spancrete, a self-leveling liquid concrete made for radiant heat. The process was repeated on the remaining two levels. The house is divided into various control zones; for example, the master bedroom can be kept cooler than the master bath. There are also thermostats in both garages.

"We power that hydronic system with geothermal technology," Vogstrom said. "Geothermal heat uses the ground temperature to assist in heating and cooling the house. The ground temperature will stay at 58 degrees year-round below the frost line. There are a number of ways of doing it, but what worked best for this site, because it was very steep, was not to dig horizontal trenches, but to dig instead vertical wells just underneath the driveway and backfill them. Each well has 1.25-inch pipe that goes down, makes a 180-degree bend and comes back up that same hole. We could not use a casing like regular wells, but just drilled the holes. They are all tied together in a closed-loop system to use the same water over and over again.

"In winter, the 58-degree water is stepped up to 110 degrees. We take that and run it through the heat pump for the radiant system. In summer, the 58-degree water is chilled to 45 degrees and then passed through a water coil, which we pass air through, and that becomes the central AC. We used an air handler, as well. The big advantage of this system is that it is 300 percent more efficient than a traditional system. We can heat and cool this house for about $500 a year. Another 20 percent efficiency can be added because of the ICF walls, making the house 60 to 70 percent more efficient than stick-built for a 7,200-square-foot house."

Building with ICFs
Walls for this hilltop house run longer and deeper than normal. Around the sides, the dimensions return to normal. Bracing was placed every 12 feet up rather than 24 feet because of the prestressed concrete floors. The basement floor, 5.5 inches thick, used a network of rebar, designed to help keep the inside footing from kicking out.

Reward Wall's eForms were placed over rebar protruding vertically from the footing. The recessed polyethylene inner ties cut out temperature transference that can come with systems that use exposed plastic or wire tires. Those ties are 1.5 inches wide and embedded a quarter-inch below the outside of the foam, functioning as a continuous nailing stud running the full height of the wall. The forms are connected in a ship-lap design that delivers a cleaner connection than tongue-and-groove. There is a choice of core thickness and a smooth flow of concrete through the inner webbing. The form size corresponds to dimensional lumber, ensuring stick-built plans can easily be translated into eForms.

"We pour one story at a time," Vogstrom said, "high enough to put our floor package in and then go up to the next floor. Minnesota's temperature extremes are not a problem. We build all year long, no matter how cold it gets. The day after we pour, we take the bracing off and put in the floor package. A day or so after that, we start stacking the next course. We do courses all the way around - a floor every week, if not faster. The pour itself usually takes three or four hours. On this house, true building time was five months and four days. An equivalent stick-built house would take about eight months.

"There is no better house you can build than an ICF house. It will stand for 200 years. The cost is only about 3 percent more than stick-built, and that is easily offset by savings on fuel, insurance and the mortgage."

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