Sensitive Precautions on Residential Project
January 11, 2010
On one level, contractors are facing increasing challenges when it comes to new refrigerants and new regulations. And they face new demands regarding energy efficiency and ever-changing technologies to achieve that efficiency.
But it does not end there, at least in the case of a residential project in Hanover, Wis. There, one of the homeowners has acute chemical sensitivity, meaning special precautions needed to be taken concerning the HVAC equipment chosen and how it was installed.
Kevin and Kathy Christopherson set about building a home that is a two-story Cape Cod with a guesthouse and a loft bedroom with the dwellings connected by a breezeway.
While several construction challenges arose, consultant Marilee Nelson, president of The House Doctors (Hunt, Texas), directed the chemical sensitivity aspects of the project.
Nelson required that the home be constructed with minimal use of fossil fuel systems in the building. She also was concerned about electromagnetic fields. Nelson instructed contractors and subcontractors to empty their work trucks of all unapproved materials and tools prior to entering the jobsite to prevent their accidental introduction to the home. Also, all sheet metal used in the home had to be scrubbed to remove any oils on it.
The homeowners didn’t want to use drywall, and initially considered using a clay-based product for plaster, but it didn’t provide the necessary thickness. They ended up specifying a magnesium oxide wallboard that’s fireproof, moldproof, and waterproof.
CHEMICAL-FREE HVACWith regard to the HVAC system, the challenges were faced by a team including mechanical contractor Don-Martin Heating, Cooling & Geothermal (Janesville, Wis.); Radiant Cooling Corp. (Chicago); and the engineering firm DS Design Consultants Inc. (Watertown, Wis.). The general contractor was Zimwood Custom Homes of Janesville.
Don-Martin was contracted to handle the home’s HVAC needs from the start of construction through its completion seven months later. Initially Don-Martin’s owner, Don Kohlhagen, suggested radiation heating, with forced-air cooling for the job. But Nelson did not like the idea of forced-air cooling. So the mechanical design team selected a dedicated outside air system (DOAS) for fresh-air introduction, and a water-to-water unit to heat and cool the home. A unit with a desuperheater was selected. It was connected to a 50-gallon electric tank for domestic hot-water heating. The pumps selected to run the system had to be bronze in order to handle condensation issues with the chilled water.
Additionally, the team sought a chemical- and flame-free piping option to connect all the home’s radiant cooling and radiant heating by microcapillary tube radiant mats. These 1/8-inch, inside diameter plastic polypropylene capillary tubes were installed close to the wall, floor, or ceiling surface and were designed to provide silent and healthy heating and air conditioning without dryness.
For the home, the mats were installed in the ceiling and then plastered in after leak checking. Wally Shah, president of Radiant Cooling, specified radiant mats, a control system, and polypropylene-random (PP-R) piping for HVAC applications.
The piping product, which was designed specifically for HVAC applications, requires no flames, chemicals, or mechanical connections. Once fused, the pipes and fittings have the same physical properties, thus eliminating systematic weaknesses, according to Aquatherm, the manufacturer.
Shah purchased the welding irons and equipment to be used by the installing contractor and explained the welding technique in the field. “We found the product easy to install since we are a geothermal company, and it is similar to joining pipe for a ground loop,” Kohlhagen said. He added that the natural R-value allowed them to run cooler water through the system without serious sweat issues.
Daniel Schlicher, designer of engineering systems for DS Design Consultants, drew up the system’s schematics and also handled pipe sizing along with the help of Radiant Cooling.
The installation proceeded without any real glitches, Kohlhagen said. He recalled that roughly 1,000 linear feet of 1/2-inch, 3/4-inch, and 1-inch pipe sizes and 400 fittings were installed. “The only real challenge was how to connect the pipe to the Caleffi manifolds,” he said. They ended up using a meter socket adapter for the connections.
THE RESTIn order to meet the other infrastructure demands, purification units with HEPA and charcoal filters, a photocatalytic oxidation system, and air-to-air exchangers were used. Electric duct heaters were installed to temper the air entering the air-to-air exchangers when the outdoor temperature drops below 30°F.
Additionally, the owner directed Don-Martin to install an adjustable control on the exterior of the two heaters so he could fine-tune when to preheat the air. A dehumidifier was also installed in each home to run independently of the other air handler to prevent the humidity level from exceeding 45 percent. A wall-mounted dehumidistat controls the rh.
After the system was up and running, it had to be balanced to provide the designed air delivery, which required getting the space under slight positive pressure to prevent infiltration into the space. “This was a challenge since the homeowners wanted to be able to operate the system at different speeds because the home is out in the country and there are occasionally farm chemicals in the air and grass burning in the spring,” Kohlhagen said.
The homeowners wanted to be able to shut off the outside air and just recirculate the air through the filters, which required the installation of a bypass switch and damper system. “We instructed them that the design was to provide positive pressure, but they insisted that they needed to adjust it at their own discretion; this was understandable considering the circumstances,” Kohlhagen added.
Kohlhagen also said they experienced a challenge in providing a simple changeover from heating to cooling mode since the thermostats need to know how they control temperature. “By using a double-pole-double-throw switch and shunting the connection on each thermostat, we could allow for this,” he said. However, the owner still has to go into the basement and select heating or cooling on the equipment.
Regarding the project, Kohlhagen said, “I liked doing this job, but product selection was tough. It was a time and materials job, and keeping costs down was also a challenge, but in the end, we provided what the homeowner wanted.”
For more information, visit Aquatherm’s Website at www.aquatherm.com.
Publication date: 01/11/2010