Article No: 197

2006-11-30 13:21:15
Squaring off against mold
By: Carole McMichael



Photography courtesy of Polar ICF 
With the best of intentions, Minnesota’s residential building code tackles the state’s frigid, energy-devouring winters. To do this, it applies vigorous specifications that make the envelope wall system so tight that there is practically no air loss. This should be good, but to maintain the specification for air infiltration, the wall assembly is wrapped and sealed so tightly that moisture can be trapped inside.

“The weather in Minnesota ranges from 95 degrees with 95 percent humidity in the summer to 30 below zero in the winter,” says Kyle Smith, owner of Polar ICF, which builds in the Minneapolis–St. Paul metro region and the western Wisconsin area. “There is a lot of confusion as to which side of the wall is going to be the cold side—should you insulate to keep the cold in or out? You have to be able to pass vapor one way or the other. It depends on which side of the wall is cold or warm.”

Smith says that it only takes a pinprick-size hole in the exterior wall to allow warm, moist air to penetrate. “If it comes in through the wall assembly and hits the cold sheetrock, it begins to condense, form moisture—and that leads to mold. If that is going on in a number of places in the house for three or four years, it literally starts to eat the house from the inside out. Large pieces of stucco start falling off. The house is actually rotting.

“There are a large number of wood-frame home owners in this area that are undergoing litigation because of the moisture problems in wood construction. It has become a forefront issue. People are literally tearing down brand-new, million-dollar homes as little as three years old because they are not fixable and the insurer is not willing to pick up the remediation costs.”

The ICF solution
The most obvious answer to the energy and mold dilemma is to build homes using concrete systems, such as insulating concrete forms (ICFs). Smith, whose building background and technical expertise were in commercial concrete construction, knew that poured concrete wouldn’t harbor mold or moisture, so it would be the perfect fit in a residential market in need of mold-resistant wall assemblies. Also, when he was looking for a faster and more reliable footing and foundation for slab-on-grade for his commercial work, he discovered the outstanding insulating properties of ICFs. From there, the transition from commercial to residential building was easy, according to Smith.

Polar ICF is a design and turnkey builder exclusively of concrete homes. When Smith decided to make that transition, he looked at all the wall systems for what they offered from a builder’s standpoint.

“Each system has desirable features,” Smith says. “It is not uncommon for us to use three different blocks on one structure. We choose on the basis of form size, cost and availability. Right now availability is much better than it used to be because there are more plants producing these blocks in the Midwest.”

Getting started
Generally clients that come to Polar ICF are already savvy about concrete and are looking for quality in a structure. Most of them have sought him out or have met him at home shows. They say they’ve seen concrete houses and want something similar.

Smith has a staff that will guide the client through the design process. The architect, who handles the structural design and drafting, and the project manager assigned to the project are responsible for moving the process along; but all aspects of the final plan are designed to meet the budget.

“We employ all of the staff that builds the house,” Smith said, “which allows us to build the house from the ground up. We have our own concrete crews, framing crews and interior-finishing crews that do trim, flooring and tile. Providing a lot more understanding and consolidation of the building process goes a lot further with the client. The more people the client gets handed off to for different parts of the project, the less likely he would be to follow through.

Smith says potential clients often are confronted with a barrage of products at home shows. “We have chosen the ICF shell, the wood truss system, Icynene insulation and geothermal for the mechanical systems. Those components have consolidated things so the client knows what they are buying. And it is easy for them to understand.”

Smith also has developed a subcontracting team, so he doesn’t have to put out his projects for bid. Polar ICF works with the same plumbers, electricians and mechanical specialists. That way, he doesn’t have to run up labor costs going through the learning curve over and over with contractors who are new to concrete wall systems. 

Extreme weather
Minnesotans have very challenging weather. Besides tornados and straight-line winds of hurricane strength, the state experiences hail, heavy rains—3 or 4 inches at a shot—and extremely high humidity. ICFs offer huge advantages in dealing with all of these, including the energy demands of extreme temperatures. ICFs are especially effective when coupled with the geothermal systems that resource stable ground temperature (60 degrees) to heat and cool concrete structures.

“We drill vertical wells in the backyard or underneath the driveway,” Smith says. “We either add heat or take it out of the house. Compared to a regular air exchanger, this system uses a more complicated approach that includes air monitoring and moving the air at a more constant rate, but at a lower volume. That means concrete homes inherently stay cooler in summer and warmer in winter with less energy input. Once they get to a temperature, it doesn’t take much energy to keep them there.

“Geothermal is a very good system, especially in combination with radiant heat in the slab. We have homes in the 6,000 to 8,000 square-foot range that are heating for as little as $90 to $100 a month. The annual heating and cooling audit on the 13,400-square-foot Orono, Minnesota, house is less than $1,500.”

The Orono home
Built for a professional basketball player, the Orono house is a luxurious, 13,400-square-foot, two-story French Country manor with a stucco and stone exterior. The centerpiece of its spacious layout is a great room with a dramatic curved stairway and a 22-foot ceiling. The Old World look of the vaulted entrance lets visitors feel like they’re on the set of The Sound of Music when they walk in the front door.

Formal dining and living rooms, a light-filled sunroom and a well-appointed kitchen with Brazilian cherry cabinetry and stone countertops continue the French Country styling. The four spacious bedroom suites include full baths and walk-in closets. One bedroom is on the main level, the other three, including the master, are on the second level where there is also a laundry facility, an office, a workout room and a large entertainment room with a theater seating capacity. As one might expect for a basketball player, the doorknobs and countertops were set high and there were custom 8-foot doors. Appropriate to the size of the home and the owner’s interests, the garages, which have stained concrete floors, have room for six cars.

Another impressive style feature of the Orono house is its great use of windows. “When you have a lot of windows, you want as much passive solar heat as you can get,” Smith says. “The house inherently wants to store that heat, so we positioned it in such a way that it could. The geothermal system also comes into play by offsetting the potential heat loss from windows.”

The interior wall finishes all use VOC paint. When not made of dark cherry, the millwork, the columns and the staircase were finished in enamel. Smith encourages as much natural fiber coverings as possible in his homes to add to the healthy air atmosphere that ICFs and concrete construction create. He goes through a lot of steps to put materials into the house that won’t off-gas, and cabinetry is allowed to cure offsite before it is installed.

The building process
The first step before Smith’s company even begins to design is testing the soil at the site. There is a line item or two within the structure of Polar ICF’s pricing that includes soil modification. With the Orono house, Smith did a lot of soil modification, and brought in a variety of rock that was compacted. The house was erected on top of the modified soil.
“We used PolySteel ICF for all the above-grade walls,” Smith says, “because we had a lot of stone hanging on the wall and it has a steel-tie block. This house is slab on grade, but there is a 4-foot frost footing that runs the entire perimeter of the house. The frequency of rebar in the walls could be anything from single No. 4 every 4 feet vertically to a piece of No. 6 vertically every foot. It depends on the backfill height and the soil makeup of the backfill material. The ceilings ranged from 11 feet to 12 1/2 feet. 

“We use a 4,000-psi ICF mix, and poured lifts of 14 feet at a time. The mix has to be pump-able by a 3-inch hose. As long as we keep the concrete moving through the hose fast enough, we can pump in very inclement weather, even down to 0 degrees. The same is true for working on a 100-degree day, using a 6-inch slump. We can also pour in the rain unless we have lightning. It took 2 1/2 months to do the entire shell.”
The tours
The Orono house’s first tour exposure had an international flavor. Smith was approached three months into the job by the U.S. Department of Commerce to entertain a number of people from this department, as well as the from U.S. Department of Energy and a large group from Eastern Europe who were here looking at energy-efficient housing. Smith’s project was chosen as an example of an ICF construction site in progress. “They were impressed with both the site and the system,” Smith says.

The second tour was a Luxury Home tour. Smith, who had about 1,000 visitors, was amazed at how many people came to see not just a high-end home, but the technology as well. The house was not completely finished, but he showed it anyway. People were still saying “wow!” all the way through, he says.

Down the road
“Right now, Minnesota is one of the leading states in the ICF market,” Smith says. And for the future, I see ICFs exploding in the residential home market. Because of the green building requirements in a lot of commercial structures, I see this as an eventual co-compliant within 10 years.

“The future ICF builders are most likely to come out of concrete commercial construction rather than out of stick-builders making the switch. It is so easy for the commercial builders to make the move. There is plenty of opportunity for crossover. A lot of guys who do our carpentry have made the transition to erecting the wall systems. They have a very good sense of plumb and straight and we get good results. We just have to teach them to pour concrete.”
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