Thermal Seal Experts

HEALTHIER

• Asthma Letter
• Indoor Air Quality (IAQ)
• Review on Icynene
• Envirodesic Certificate
• Health House ALA Guidelines

Health House ALA Guidelines

Minneapolis architect Chuck Knight got more than he bargained for when he signed on with the American Lung Association two years ago to help develop design guidelines for healthier office buildings. As he plunged into the project. he realized the lung association's ongoing Health House program for residential construction was an appealing design template for the house he wanted to build for himself in suburban Woodbury. Minn. What resulted was a 5,400 sq.ft. house he finished last fall. The first in the country to be built under updated Health House guidelines and a national showcase for construction detailing and products aimed at improving both health and comfort.

The ALA launched its Health House program in 1993 to combat polluted indoor air that has become more worrisome as building envelopes get tighter. There are now some 120 demonstration houses in thirty srates. Building techniques and material choices are intended to benefit the 26 million Americans who have been diagnosed with asthma and the millions more who suffer from allergies. Both conditions. the association says, are linked to indoor air that can be five times as polluted as outdoor air. Knight knows of the problem firsthand: one of his children has mild asthma.

Knight says he WJS especiJlly affected by association statistics on poor indoor air quality that is leading to an increase in health problems. "It hit my heart strings right away," Knight says. "We have a mold epidemic, and we have an asthma epidemic." Robert Moffitt. communications manager for the program. says Knight "dug a little deeper into the literature and very quickly became a convert. As he has on the office side, he started to think. 'Well, if I'm going to be putting all this effort into creating a healthy building for people I don't even know, why don't I at least do the same for my own family?" Among potential problems with conventionally built houses are moisture, which promotes the growth of mold, and floor surfaces that trap allergens and dust. To eliminate as many potenrial sources of these problems as possible, the Health House program covers everything from heating and cooling equipment to roof pitches and overhangs, windows, insulation. finishes, and even carpets.

Mechanical systems are a key part of the package. A forced-air heating system was the original choice for Knight's new house, but the builder's HVAC subcontractor suggested radiant-floor hear in rhe basement where a home theater was planned. Before the project was finished, the system had grown until it served about eighty percent of the house.

IN-FLOOR HEATING
Knight says a big plus for radiant floor heating, in which hot water is circulated through plastic tubing buried in 1-1/2 inches of lightweight concrete, is that it eliminates mold-producing moisture on floor surfaces almost right away, In carpeted houses, he says, rain or snow tracked in from the outside works its way into floor surfaces where it helps produce mold and mildew. "People just aren't aware of it until they replace the carpet and then they say. 'Oh my God, what is all this stuff?'.

Knight covered the entire first floor with slate and heated it with a three-zone system. Upstairs, other zones heat hard flooring surfiJces in the children's bathroom. The master bath, and the laundry room. There are two radiant zones in The basement. The combination forced-air and radiant floor heating system. CompleteHeat by Lennox, contains a 30-gallon domestic hot water tank supplemented by a 40-gallon storage tank next to it in the basement.

Upstairs. the radiant floor heating is controlled with slab-sensing thermostats embedded in the lightweight concrete substrate. According to donor Roger Conrad, project estimator for Apollo Heating and Ventilating, the slab temperature should be controlled separately from the forced-air system, as an air-sensing thermostat would prevent the radiant floor from being turned on.

The home's ductwork for air conditioning and heat is attached to an array of equipment. including two Honeywell ultraviolet lights that kill microbes, electronic air cleaners, an energy-recovery ventilator (ERV) for the kitchen and bathrooms, humidification equipment, and HEPA filters that cleanse air pulled from reTurn ducts. A Beam central vacuum cleaner, four times more powerful than a conventional upright or canister model, removes dust and dirt from living areas.

In addition. Honeywell donated thermostats that allow telephone communications. Knight might be called with an alert that the heating system is not functioning properly, or simply reminded to change the HEPA filters.

Altholtgh forced-air heating was originally foreseen for the entire house, in the end it became a "backup." as Knight puts it. The system that took its place keeps rooms comfortible and draft-free, and also makes for a noticeable drop in the amount of dust found the house. He says the radiant floor system cost about $12,000 for every 2,000 square feet of floor space. More expensive than conventional heat, Knight says the system is less costly to operate and has a payback period of eleven years.

MOISTURE CONTROL
Protecting the house from the intrusion of unwanted moisture extends to virtually every part of interior and exterior detailing. Roof overhangs, for example, are three and four feet wide. That's much wider than usual, but the design keeps water from beating against exterior walls. Wide overhangs also keep rain water and snow melt well away from concrete foundation walls so mold-spawning dampness on interior surfaces is reduced. A granular fill beneath the foundation slab prevents water from moving into floors and walls.

Another potential source of moisture in conventional construction is the migration of water vapor through exterior walls. Warm, moisture-laden air can find its way through even tiny holes or gaps In the building envelope. When it strikes a cold surface. such as the back side of an exterior wall, water will condense. In heating climates, polyethylene sheeting is often used as a barrier on the warm side of the wall to head off the problem, but the film is susceptible to damage during construction and extremely careful installation is essential.

In Knight's house, a layer of Icynene foam insulation coupled with properly installed Tyvek housewrap prevents air and water from getting into wall cavities where moisture could encourage the growth of mold. A thin layer of the insulation sprayed into walls and ceilings expands 100 times in volume in only a few seconds and cures quickly to form a leakfree barrier. Unlike fiberglass-batt insulation, the foam fills all crevices and potential air leaks. Interior partitions also were filled with the foam to make the house quieter.

So effective is the insulation as an air block that Knight won permission from local building inspectors to reduce ceiling insulation toa total of R-19, far below whiat codes typically require.

Knight also planned the home's interior spaces to promote comfort for his family of six. For example, he oriented the house to make the most of natural light in the living room, a space he says often is relegated to a shady part of the house in conventional construction. Sunlight and warm floors encouroges the family to use the space. The kitchen, he says, was designed as a huge space because it's the hub of family life. Three sealed, gas fire places scattered around the house create comfort zones that might otherwise see less use.

"Our social activity has changed a lot just because of how we put the rooms together." Knight says.

Moffitt estimates that building a Health House to Lung Association recommendations typically adds three to five percent onto the cost of construction. Because Knight's house was relatively expensive, however, the added costs were only about one percent - the added features being proportionally less. Including the $110,000 cost of the lot, Knight spent $975,000 on the house, or about $170 per square foot.

Knight is a managing principal of Perkins & Will, the 1999 AIA firm of the year. The 770 employee firm is known for its work on public schools. classrooms. and labs for higher education facilities. As well as corporate architecrure and interiors, but not houses. Knight says that although the firm does virtually no residential architecture, the project has sparked an interest. "I'd love the opportunity to do more of them." he says.