The house is so peaceful that Michael and Susan Mullendore had to install microphones to hear the outside brook trickling through the yard.
"It's wonderfully quiet; still and quiet," Susan said of her Ellicott City home.
Indeed, the strength of the Mullendore home fosters a comforting inner silence. Why? Well, the answer is fairly concrete.
The Mullendore home is made of a concrete-polystyrene combination, or ICF, for "insulated concrete form." The Mullendores chose it because of its anticipated energy savings, quality and strength.
"We expect it to go nowhere," she said. "It's solid and wonderful."
They took concrete about as far as it goes -- even choosing concrete counters and splashboards for the kitchen.
Television meteorologist Bob Turk and his wife, Tina, picked an ICF system for their new home in Phoenix. During a hurricane conference in Florida, Bob Turk learned about the systems, researched the varieties, and chose the ECO-Block brand.
The Turks were impressed with the strength of the material, its energy efficiency and the idea that the system -- since it's not wood -- doesn't involve chopping down trees.
"All things considered, it just made sense," said Tina Turk. "This is a strong house. It's energy-efficient. We had to downsize our [current] heating system three times."
Now the Turks recommend the system to everyone -- even for home additions.
Concrete converts Bob and Deb Bollinger estimate that they will pay only $40 to $60 per month in propane gas bills -- even in winter -- for their 3,100-square-foot, concrete-polystyrene home nearing completion in Reisterstown.
"It's like using cast iron vs. plastic piping in plumbing," Bob Bollinger said. "Cast-iron pipe is a dinosaur now. The plastic is better. And it's better to have this [concrete] construction."
ICF construction is gaining popularity. Questions remain and research results are still coming in, but many builders have been won over by its benefits. ICF is also becoming a competitive industry with more than 20 brands on the market.
The Illinois-based Insulating Concrete Form Association says 20,000 homes across the country have been built using ICF, in terms of above-grade walls. Though particularly popular in states with rough weather such as Florida and Texas, the construction is spread fairly evenly across the country.
ICF President Dick Whitaker predicts that half the new homes in the United States will have ICF framing within 10 years.
Building with ICF construction is fairly simple, though it takes crews two to three projects to really get the hang of it, various builders say.
Individual, hollow polystyrene blocks are stacked to form the skin of the walls. They're reinforced with steel rods and linked together with plastic studs. Steel used in the foundation extends into the wall system to form an interlocking bond, anchoring the home to the ground. When the wall is ready, concrete is poured through a big hose from the top of the wall -- filling the wall cavity from bottom to top.
Somewhat like Lego blocks
Many ICF systems look like foam Lego blocks when they're being assembled. The process still shocks some building inspectors -- and getting approvals can take a little longer than normal.
"They said we couldn't build out of foam," said Bob Bollinger. "My wife told them it was concrete. They got another inspector out and he OK'd it."
"Anyone who sees it is pretty impressed -- through common sense," said Bruce McIntosh, spokesman for the Portland Cement Association, based in Skokie, Ill. "The process eliminates a lot of steps. There's no sheathing, no [fiberglass] insulation -- and there's a lot of stability. It's a monolithic pour."
After it's poured, the concrete makes a "phenomenally strong" wall, said Lee Yost, president of Advanced Building Systems of Monkton, which markets the ECO-Block and resulting "superhomes." Yost was in charge of the ICF system in the Turks' home.
The idea is that the concrete provides the strength and silence as well as better fire and storm resistance.
The polystyrene provides the insulation and moisture protection. No other insulation is required. Competing systems are similar, though they may have variations on the type of polystyrene and type or shape of the blocks.
"It's like wrapping your home in a cooler," Yost said.
After the walls are poured, drywall and siding can be screwed into indentations in the polystyrene, and attached to the concrete. The concrete actually cures as it sits in the blocks. Siding can be anything from stone to vinyl.
Horizontal tubing is run through the walls so that electric wires can be channeled to the outside of the house. Inside wiring is run through channels cut in the polystyrene. Contractors can even run drainpipe to the basement.
There are a few extras involved. Fresh-air exchangers are required because the homes are so dense and air-tight. This keeps radon levels safe, too, Yost said.
Yost also installed rubber sheeting over the Turks' ground-level polystyrene blocks to further protect the basement against the moisture of the grade.
Yost also uses protective material against the walls to prevent penetration when backfilling.
Costs and savings
Various studies show ICF homes costing 3 percent to 8 percent more than traditional, wood-frame design.
When planning a new home, a buyer can estimate that using ICFs for the walls -- above and below grade -- will add $1 to $4 per square foot to the overall building cost. Construction costs for a new stick-built, wood-frame home typically can run $60 to $100 per square foot, excluding land and financing.
Therefore, on a 5,000-square-foot home at $100 per foot, you might expect to pay up to $520,000 for ICF instead of $500,000 for a traditional system.
Yost added that a wall system on a 1,500-square-foot rancher with a 1,500-square-foot basement would cost from $23,000 to $25,000 total with his ECO-Blocks. That compares with $18,000 to $22,000 for traditional construction.
Of course, the complexity of the project figures into the bottom line as well, Yost said.
Partly because of the cost, the appeal has been mostly to luxury, custom buyers, though Yost thinks it will eventually spread into the mass market. He's built seven custom homes in Maryland and a few others in Virginia and the Washington area.
"There is more focus on amenities now," Yost said. "There should be a focus on structure.
"The frame is the most important part of the house."
While front-end costs are higher, energy savings are actually a chief selling point of ICF. Builders say the expense of the system is quickly made up by energy savings.
The Portland Cement Association estimates savings of $200 to $300 per year on energy bills, in addition to reducing the initial cost of heating and cooling equipment because less capacity is needed.
According to the PCA, energy efficiency can be one-third to 40 percent better than in a standard, stick-built home.
Insulation is another plus for ICF walls.
Energy efficiency of material is measured by an R-value rating, which correlates to the material's ability to maintain the internal temperature of a container or structure. While wood-framed walls offer insulations around R-9 to R-15 (R-0 equals no insulation at all), ICF insulations usually range from R-17 to R-26.
Bollinger says he's projecting an R-47 value. Susan Mullendore remains a little more skeptical.
"I think it'll probably take a long time to repay it through our energy bills," Mullendore said, adding that her system ("Poly- Steel") was about 30 to 35 percent more expensive than standard cost would have been.
Just how these homes save energy is still being debated and studied by researchers -- and studies are being conducted by organizations such as the National Association of Home Builders.
NAHB researchers say ICF homes can conserve energy, but the amount depends not only upon the materials, but also upon the climate, the energy habits of the family members and even the number of people in the family.
"Some manufacturers claim up to 44 to 50 percent savings in energy bills. Each family is different. Your neighbor may not have as many people -- or may have different habits," said Andrea Vrankar, researcher at the NAHB Research Center near Washington.
NAHB recently built three test homes in Chestertown and monitored them for energy use, among other factors. One house was a standard home with wood construction. The other two were ICF variations. Preliminary results suggest about 20 percent energy savings with ICF. NAHB studies have not shown 50 percent savings, Vrankar said.
Jim Dorr, an executive vice president for Eco, which produces the Eco-Block, built his own ICF house in New York state, installing a propane boiler and radiant floor heat. His total heating and air-conditioning bill came to $1,100 last year. And that's on 6,000 square feet.
"It was 60 percent less than the fuel man thought it would be here if it were of wood," Dorr said.
Strength and endurance
Strength is another selling point. The homes are heavy. The Turks' concrete weighs about 800,000 pounds. If built with wood, the weight would total some 220,000 pounds, Yost said. For unusual loads, such as a heavy deck or floor, more steel reinforcement can be added.
ICF walls are also tough because of the steel and concrete.
Various ICF and wood-framed walls were recently tested by the Wind Engineering Research Center at Texas Tech University.
Researchers, simulating tornado-like conditions, shot wood studs traveling up to 100 mph at the walls.
The wood-frame walls couldn't stop penetration of the studs, but ICF walls sustained damage only to the outer foam.
Yost said "superhome" walls can withstand 2 million pounds of downward force, compared with 10,000 to 15,000 pounds for the same surface area in a wood wall. Simply, that would be the equivalent of parking a couple of Union Pacific "Big Boy" locomotives or 1,000 pickup trucks on top of an ICF wall.
The Federal Emergency Management Agency has also launched a program in Oklahoma to build and encourage the building of ICF "safe rooms."
These rooms are projected to keep residents safer during natural catastrophes, such as a tornado.
The NAHB's Vrankar noted that a wood home can also be designed to withstand a hurricane, though it does take stronger fortifications and often comes down to cost.
As for day-to-day wear and tear, ICF systems help avoid problems that often plague wood frames such as nail-pops, ridging, buckling and waving and even shrinking floor-joist systems, said Ron Friedenberg, the Turks' project manager and president of Builders & Homeowners Consultants of Maryland Inc.
Concrete's strength does have its downside, however. Some builders complain that changes to the home after the pour can be difficult and expensive, while others such as Yost say they're not much different than in standard homes.
"You'll spend more time planning the home," Yost said.
ICF homes also have a three- to four-hour fire rating -- and, because of the concrete, allow about one-sixth of the sound to get through, compared with an ordinary frame wall, according to the PCA. And the surrounding foam burns with no more toxicity than standard construction.
Because of America's tradition in wood, research and questions still remain on ICF systems.
Perhaps the biggest debate sparks over labor and learning curves.
"We feel that the ICF systems are much better for custom homes," said Ryan Houck, spokesman for the Ryland Group Inc., one of Maryland's largest residential builders. "Some of our fears are that there aren't enough crews experienced in the job."
"It could be hard to find a builder," Vrankar said. "They can be reluctant to do new things. Most builders I've spoken with like using it. Some have converted from light frame. Some do both. We've found it's a two-to-three-home learning curve."
"You work with what you know best," said Pat Hagan, president of Hagan & Hamilton, Timonium-based custom home builders. "Wood has been around a very long time. It's the typical way residential construction has been, and it's comfortable. There's not a lot of new engineering involved. Wood will continue for a long time. The risk factor goes up with using new materials."
"The bottom line is that it's very early. It's not institutionalized," Houck said. "That's part of the problem for a high-volume builder. Our goal is to provide the best product to the customer."
Ryland's Houck added that the company doesn't condemn ICF, but feels that it's better suited to areas of more severe weather, such as Chicago.
Try something different
Hagan adds that there is also a trend to explore different building products, such as steel framing and concrete construction.
"Lumber is a very dynamic market. There are fluctuations in price. In 10 years, I can't say," Hagan said.
PCA authorities say that "stacking blocks is intuitive for most people, and the cutting and leveling involved draw on standard carpentry skills." Even so, building officials recommend getting an experienced, knowledgeable contractor.
"Don't do it yourself. You can't stack them and call the ready-mix truck," Whitaker said.
"Homebuilders are slower to change; everyone is conservative about it," said Bruce McIntosh, the Portland Cement Association's spokesman. "The upper-end homes are a good point of entry into the market. Plus the initial expense is easier to bear. It's like introducing Jacuzzis into that market -- and then it spread."
"I don't know what's going to happen with it," said builder Dwight Griffith, past president of the Home Builders Association of Maryland. "The majority of homes are wood. I don't see where it'll take over. Wood is easier to work with. In a concrete house, how easy is it to change things?"
Information
For more ICF information, call:
Insulating Concrete Form Association, 847-657-9730
Portland Cement Association Hot Line, 888-333-4840
NAHB Research Center, 301-249-4400
Post-Tensioning Institute, 602-870-7540
Precast/Prestressed Concrete Institute, 312-786-0300
American Portland Cement Alliance, 202-408-0877