Article No: 84

2006-05-02 06:58:26
Open House Perspectives
By: Carole McMichael

The chamaeleon nature of concrete systems is an advantage to developers, builders and homeowners because they can have all the benefits of a concrete-built home and still choose any style they desire. However, other people can't tell a concrete-built house just by looking at it. The difference begins to come through when people go to an open house or parade of homes.

"You can feel the difference," said Jon Rufty of Rufty Homes Inc., located in Cary, N.C. Rufty has just finished a 12,000-square-foot European style home built using Wall-Ties and Forms concrete systems. There is 10,000 square feet of living space and 2,000 square feet of conditioned space (the mechanical room and walk-up attic), which is inside the heated envelope.

Photo by Ray Barbour

The house offers the usual rooms plus a four-car garage, six bedrooms and baths and two half-baths. Special amenities include an elevator that goes to all floors except the attic, a home theater, a wine cellar and tasting room, a game room, a covered terrace and a sun porch.

"We plastered directly on the raw concrete wall," Rufty said, "so, if you knock on the walls, you can feel the solidness. Every floor in the house is concrete. On the lower level, the floors use stained concrete as the finish; on the main level, which includes the kitchen and master suite, the floors use two-foot squares of limestone over the concrete. Even the attic floor is concrete."

"The fancy ceiling design in the living room consists of 700 pieces of molded plaster that we put together like a puzzle," Rufty said. "The finishing of the joints was complicated. All together, it took 120 man hours to install. The curved ceiling in one of the bathrooms has a barrel vault done with framing and sheetrock. If you cut a hole in that ceiling, you would find the concrete ceiling above it."

Some of the other concrete work includes: the driveway pavers, the walkway, the terrace and the low walls by the front entrance. The walls were added to the plan after the pour so they were done in masonry. The chimney on the right is masonry with a stucco finish. The one on the left, a false chimney added as a balancing design feature, was built out of framing with stucco. The roofing is not concrete, but a composite slate with a class A fire rating made of a recycled product. A closed-cell foam that expands into all the nooks and crannies was sprayed on the roof rafters in the attic to create a moisture barrier on both sides.

The system
Visitors who want to see the bones of the Rufty project can look in the mechanical room where an area of the wall is cut away to show what the raw wall looks like. The Cary house, which took 12 months to complete, was Rufty's first one constructed from Wall-Ties. About 5 years ago, he started searching for a higher quality construction method. A lot of his clients had either owned homes overseas or traveled abroad extensively and wanted to know why homes in the United States were not as high a quality as those in Europe. He found most high-end houses around the world used concrete. After investigating various systems, he decided to go with Wall-Ties and Forms.

One of the things Rufty likes about Wall-Ties is the monolithic pour--walls and floors. "We use a special mix of concrete with a high flow rate and then use vibrators," Rufty said. "The advantage of doing it this way is that the entire structure is a reinforced concrete cube. It is absolutely superior. We use 2 inches of rigid insulation on the outside of the concrete walls. The advantage of this is that the interior walls can use the thermal mass to absorb the heat or cooling effects."
Maximizing the system

The house is heated by gas, solar panels and hydronic radiant heat on the first and main levels. The radiant system was designed for this house and installed by a specialist. Before a pour, the contractor puts pressure on the line. The pressure is then kept on during construction, using a gauge to indicate that the lines are holding. In the future, if there were a failure, it would be easy to identify which segment failed and just turn it off. Because of the way heat transfers through the concrete mass, losing one little loop would not really affect the whole system.

"In summertime, we run cool water through the hydronic tubing to cool the concrete," Rufty said. "We cool the water by running it through the tubing underneath the basement. It circulates down below grade and back up, so we actually are not doing anything to chill the water. Radiant cooling has never been technically proven, so we are pioneering. If the cooling system can be proven in the field, it will probably be accepted.

"We used a redundant forced air system because we are still required to have AC. The duct work goes through soffit drops or through ceilings heights that might have been lowered. The kitchen soffit is visible in the room. In some cases, the duct goes through the hallway, or above in the attic or below in the mechanical rooms. The dining room gets its air from the floor; the top floor rooms from the attic.

"One problem we have to deal with is in controlling humidity; so we put in two ultra-high efficient whole-house dehumidifiers, which are much more cost-efficient than an AC system. We just introduce fresh air, filter it, dehumidify it and pump it into the house under a pressurization so slight that it is nothing you can feel or tell."

Monitoring energy
The energy monitoring system was installed a few months ago. Working with N.C. Power and Light Co., Rufty chose not to use a conventional system, where homeowners pay so much per kilowatt hour no matter when they use the electricity. Instead, the Cary house uses an energy-management time-use system. With time-use rates, if the homeowner can push power usage into non-peak times, it brings costs down about 50 percent. Through the N.C. Power and Light Co., the house is monitored every 15 minutes. An outside contractor sat down with them to identify major consumption units and what needs to be controlled. Then Rufty set the threshold. If he exceeds it, the system will shut the power off to selected items.

"We have used such a system for five years, saving about $1,500 a year," Rufty said. "Not once have we experienced an inconvenience. If a house is built of concrete, the owners will not have to worry about exceeding usage. Concrete houses are ideal for this approach to energy. When I heat the house at night, using lower energy rates, the house absorbs the heat and releases it in the day so I need to do very little heating when rates are higher. The environmentalists love this because you can control the use of peak power."

Choosing concrete
Rufty noted that the learning curve on the first project inevitably involves time and money, but by the third house, they were all pretty much through the learning curve. Also, preplanning and working with subcontractors is a particularly important part of the process. So far, Rufty has done only spec houses. He advises builders new to concrete systems to start with a spec house. It allows them to learn at their own pace. "When a client does get involved, you are more comfortable and you have the answers," he said.

Although Rufty is building high-end custom houses, he is very interested in concrete housing for first-time average buyers.

"They are the buyers who can benefit the most from savings on energy bills and insurance premiums," Rufty said, "and they are the ones who can least afford the cost of damage from natural disasters. So concrete makes a lot of sense in that market."

The Cary house has been leased to the developer for three years to use as an office and model.