By Valerie Stakes
To further improve the home's IAQ, the owners removed wall-to-wall carpets and painted the home with low-VOC paint.
(Left to right): Jim Satterfield and Richard Barksdale teamed up to design and install an awardwinning system.
Lush greenery and the warm humid climate of Richmond, VA can make breathing a challenge. Gilman Mechanical's HVAC system prevents too much of the outdoors from getting in.
The Harlow's home is divided into four zones, each with its own dedicated supply trunk, temperature sensor, and motorized damper.
All the ductwork and equipment had to be carefully installed in the garage, away from the floor in the event of flooding.
For Laura Harlow, proper indoor air quality isn't a luxury; it's a health-mandated necessity. "I have had environmental and seasonal allergies all my life. Although my allergist does an excellent job with controlling my symptoms, there are still buildings I can't enter because of mildew and dust. Pet stores are also out of the question," she says. In fact, she can even sense dust from 10 ft. away.
While Mrs. Harlow can't change the environments she encounters, she knew she could improve her own home's indoor air quality.
Initially, she and her husband Mike sought to build a new "Healthy Home" in the Richmond, VA area, according to the building requirements of the American Lung Association.
However, when this didn't come to pass, they opted to renovate their own home and mechanical system.
To tackle this project, the Harlows hired Gilman Mechanical, an 88-year service and repair contractor in Ashland, VA. The company had recently started a new construction division, which was headed by none other than healthy homes expert and multiple-QHCA and Design/Build award winner Jim Satterfield, formerly with Southern Comfort.
"My experience is primarily in new construction, so I was a bit wary about taking on this project," says Satterfield. "Because Richard Barksdale, who manages Gilman's installation department, had the expertise in retrofit construction, we decided to collaborate together on this project."
CUSTOMER IAQ EXPERTISE
Before Barksdale and Satterfield had even met with the Harlows, the couple had become quite knowledgeable about healthy home construction and IAQ products. They also had begun making several improvements to their home.
For example, they removed the insulation from the floor joist cavities and removed the wallto-wall carpets The foundation walls were also sealed to prevent hot, damp outside air from entering the space.
"The floor of the crawl space has a moisture barrier to keep any moisture, radon, or termite poisons from migrating into the area. Conditioning a crawl spaces turns it into a mini-basement," says Satterfield. "A small amount of supply air keeps the crawl space under a slight positive pressure. So when it becomes part of the conditioned house, there's no longer a home where mold or mildew can grow."
While Gilman's team was working, the Harlows continued the improvements on their home by:
- Replacing the original windows with doublepane, low-e, low-infiltration windows
- Painting the house with low VOC paint
- Removing unused low sidewall supply registers and filling the holes with sheet rock.
TOP-NOTCH SYSTEM DESIGN
After several consultations with the Harlows, Satterfield and Barksdale calculated the load requirements for the house and took Mrs. Harlow's need for superior indoor air quality and control into account for the system's design.
The team started by removing the home's existing heating and air conditioning equipment, along with any ductwork they could access. "Their original air distribution system was designed for fuel-fired hot air, without air conditioning," says Barksdale. "In addition, all of the supply outlets were low, sidewall with 4-in. supply ducts."
Gilman's team removed as many as possible of the supply outlets and replaced them with 5-in., 6-in. and/or 7-in. round, flex runouts and with floor diffusers. They also had to reuse several of the existing outlets that went through concrete and added new supply runouts where needed.
Because the house had undergone a number of expansions, the equipment retrofit faced some challenges.
The house originally had two central return grilles, both low side sidewall, which were located in the front and back hallways. For increased comfort, the team installed returns in the ceilings of two bedrooms and the den, and in the floor of the room over the garage. They also added new supply ducts for this room.
Satterfield adds, "Because of the different construction methods used in the home, we decided that the only means to ensure the Harlow's comfort throughout the entire house was zoning."
The Harlow's home is divided into four zones: bedrooms, living front area, living rear area, and the room over the garage. Each zone has its own dedicated supply trunk, temperature sensor, and motorized damper. When zoning the home, Gilman's team took factors such as usage and solar orientation into account.
ATTENTION TO IAQ DETAIL
When it came to the Harlow's goals for their mechanical system retrofit, nothing was more important than improved IAQ.
One of the key points of Gilman's design was moisture control. To ensure that the relative humidity (RH) was neither too high nor too low, they chose to use Carrier's dual-capacity heat pump, a variable speed fancoil, and a Thermidistat.
"This system is ideal because of its increased run times and ability to go into enhanced dehumidification when needed," says Satterfield. "Longer run times also mean that the filters and energy recovery ventilator (ERV) have more time to improve the air."
To handle the outside air and combat Mrs. Harlow's sensitivity to volatile organic componds (VOCs), mold, and pollen, the team installed an ERV. In the summer, the ERV removes unwanted moisture from the incoming humid air. During the winter, the ERV also preheats cold, dry air, preventing the desired moisture in the air from escaping.
"By adjusting the two opposing airflows, we can give the home a slight positive pressure, which helps decrease the infiltration of hot, humid, and pollen-ridden outside air," says Barksdale.
To treat the inside air, Satterfield and Barksdale decided to use two devices. The first is a HEPA filter, which is 99.9% effective on airborne particles .3 microns in size and larger. The second is a photocatalytic oxidation (PCO) filtering device from Lennox. This device has a MERV 9 pleated pre-filter, a bank of ultraviolet lamps, and a plate coated with titanium dioxide catalyst.
Satterfield explains, "The prefilter captures the large particulate matter. Then, the light chemically reacts with the coating. This generates hydroxyl radicals that attack the mold, VOCs, etc. not affected by the prefilter, destroying them by changing their state and producing hydrogen and water vapor, which are both harmless."
CHALLENGES & LESSONS LEARNED
For most contractors, each project presents its own set of unique challenges. With the Harlow's home, one of those challenges was having sufficient space for the mechanical equipment.
"All of the equipment, except for the outdoor unit, had to be installed in a small, attached garage because Mrs. Harlow was concerned installing equipment in her crawlspace or attic could cause moisture," says Barksdale. "Because the garage is subject to flooding during heavy rains, we had to put the equipment and ductwork on stands tall enough to keep them away from any water."
Satterfield adds that duct leakage was also an issue. "Sealing the ductwork turned out to be more difficult than we anticipated. Because of the age of the home, the ductwork wasn't easily accessible," he says. "As a result, we had to return a few times before we were able to achieve the American Lung Association's standards for duct sealing."
Finally, when asked what they learned most from this project, both Satterfield and Barksdale point to whole-house dehumidification.
"Spring and fall are challenging seasons. The temperature may be cool, yet the relative humidity can be extremely high," Barksdale adds. "Air conditioning only removes moisture as a secondary process to cooling. If the system comes on whenever dehumidification is needed, it will drive the temperature below the setpoint, making the home too cold and uncomfortable."
In addition, running the fan constantly can take moisture in the drain pan or on the coil and circulate it back into the house.
To ensure the needed 'year-round control, they installed a Thermastor 150H dehumidifier, which has more than enough capacity to keep humidity level at Mrs. Harlow's desired 45% RH.
A FINAL TEST AND BALANCE
Once the Harlow's new HVAC system was installed, the Gilman team tested it for required airflow, temperature rise, and refrigerant levels. "Because of the variable airflows resulting from the zoning system, we had to rely on digital thermometers to set temperatures in each room and/or zone. Currently, all zones are within a 0.5F of each other," says Satterfield.
They also used temperature/humidity recorders to measure temperature settings in problem areas. The airflow for the ERV was set up using a manometer in order to have slightly more air entering the house than leaving it. According to Satterfield, this slightly positive pressure helps keep outside air from infiltrating the home.
Finally, to test for duct leakage, the team used a duct blaster.
A SATISFIED CUSTOMER
Once the work was complete, the Harlows noticed an immediate difference in their home.
"We're very pleased with Gilman Mechanical's work," says Mrs. Harlow. "I no longer need a filter in every room. And most important, my home is the easiest place to breathe."