Air Quality: Proud Green Home of Louisville
Zehnder ComfoAir ERV in the Proud Green Home of Louisville
The Proud Green Home of Louisville was designed and constructed with healthy living in mind. Because it will be a very energy-efficient home, there will be little naturalairflow, unlike many older homes that leak air around doors and windows and other openings.
Sy Safi of UberGreen Spaces & Homes, the builder of Su Verde, or About Green in Italian, incorporated a range of strategies to ensure fresh, healthy air fills the home, including an energy recovery ventilator and low and zero VOC paints, finishes and other materials.
The high performance home in the Norton Commons development in Louisville is seeking certifications from multiple organizations, including DOE Zero Energy Ready Home, LEED, Passive House, National Green Building Standard, Living Building Challenge Petal Certification and the LBC Net Zero Certification.
While much of the high performance design takes place behind the walls and inside the components of the home, the proof is in the way the home feels.
"When you live in or visit a healthy home or a credible green home, you can feel the difference, although people who are not in the industry may not be able to understand why it feels different, but it does feel different," said Clive Pohl, architect of the home. "It’s largely because we’re not aware of air movement. We’re not feeling the propulsion of air being blown into the room. We’re not aware that we’re not breathing toxins. These are all subconscious experiences."
Energy Recovery Ventilation
One of the most common misconceptions is that a building has to breathe, which is not necessarily true.
"You do want moisture to be able to move back and forth through a building, but you don’t want air leaks, so when you tighten up a building, which is the right thing to do, then you need to be in control of the mechanical ventilation," Pohl said.
The home uses a Zehnder ComfoAir energy recovery ventilation system that continuously extracts moist, stale air from wet rooms (kitchens, bathrooms and utility rooms) and supplies fresh, filtered air to habitable rooms (bedrooms, living rooms and dining rooms). Up to 90 percent of the heat in the extract air is recovered by the heat exchanger in the unit and used to heat the incoming fresh air.
The ERV recovers most of the comfortable room temperature and uses it to pre-cool the incoming air. Therefore, the incoming air to the home is already close to room temperature when it is distributed to living spaces. The air conditioning needs to be run far less for cooling. By distributing the pre-cooled air evenly through rooms, hot spots in the home are reduced, and it’s a lot more comfortable for inhabitants.
The home will have eight air changes per day, all managed by the ERV rather than air leaking through cracks and crevices in the home.
"People have actually commented on the air flow and comfort in the home and described it as a positive energy," Pohl said.
The ERV runs in the background, without any intervention from the homeowner. There's no thermostat or other control.
"The good thing is that the homeowner doesn’t need to know how it works, what they want to know is that it’s a comfortable home," Pohl said. "They just can lie in bed and feel great. You’re not hot, you’re not cold."
Low & Zero VOC Products
It does no good to bring fresh air into the house if it will become contaminated once it's there.
The builder and architect worked with Sandra Perry, an interior designer with Honest Homes to use low and zero VOC products in the home. These products emit low or zero levels of volatile organic compounds, substances that can cause discomfort and lead health problems, especially in people with chemical sensitivities.
"The number one choice was making sure that everything was zero VOCs, toxic-free. That’s across the board, hands down everything that we pegged and selected," Perry said.
Zero VOC products included floor and cabinet finishes formulated using whey as well as zero VOC paints. The whey is a cheese-based poly-whey, that is as durable as a traditional finish, "but you don’t have to worry about how it’s going to affect your health," Perry said.
Sourcing the right products can help improve the homeowner’s health.
"We have customers that have chemical sensitivities or sensitive to smells and we work with new moms who are educating themselves and want products that’s are going to be safer for the family,” she said.
The building products where chosen to have zero impact on the air, and some even improve the air in the home.
The walls were painted with Sherwin Williams Zero VOC paints, and construction components included ECOBOND Zero VOC adhesives, Purebond FSC Certified plywood with no added formaldehyde by Columbia Wood Products.
VOC and Fire Retardant-free furniture and built-ins and furniture were made from reclaimed KY barn lumber and sealed with Vermont Coatings Zero VOC wood sealers.
The Certainteed AirRenew drywall acts like trees do in the environment by capturing VOC’s that may have been brought into the home and rendering them inert, actually making the air cleaner in the room where it's used. Certainteed’s M2Tech drywall that resists mold growth in wet areas was used in the home's bathrooms.
To help keep the home clean, built-in shoe shelves at both entrance doors encourage removal of shoes at the door to avoid tracking toxins inside the home.
During construction and showing the build team used Norwex non-toxic cleaning supplies to clean and disinfect using only water.
Geothermal HVAC & Filtration
The home uses an energy-efficient geothermal heat pump system, and the builder and HVAC contractor paid close attention to getting the details right, including duct sealing and air filtration.
Ron Neal, a comfort designer with Allgeier Air, designed the duct system slightly oversized to accommodate the variable speed of the ground source heat pump. That boosts energy efficiency and comfort so air flows through the filter most of the time. The filtrations system incorporates a 2-inch MERV-11 rated filter, which is highly efficient, Neal said.
The Zehnder energy recovery ventilator, which supplies fresh air and exhausts all stale air in the home from all wet/odor rooms, incorporates a HEPA filter to trap dust and allergens for a low-maintenance fresh air solution.
Finally, the forced air duct system for the geothermal HVAC system was sealed with Aeroseal to reduce air leaks and dust infiltration. Aeroseal is a patented breakthrough technology that tackles duct leaks from the inside out.
"Aeroseal not only saves energy by delivering air to the proper place, but there is also the possibility that you could be pulling in contaminants wherever the ductwork is located - basement, attic, even the walls, but with Aeroseal that’s all sealed up so you’re not pulling in potential dust or contaminants like bacteria, fungus, and mold," Neal said.
The Aeroseal process puts escaping air under pressure and causes polymer particles to stick first to the edges of a leak, then to each other until the leak is completely sealed.
"A typical ductwork systems will leak up to 50 percent, so a home is waisting that heated or cooled air," Neal said. "The Aeroseal system will take that down to 5 percent or less leakage."
Research shows that typical indoor air can be as much as five times more polluted than outdoor air. But that may be a different story with the Proud Green Home of Louisville.
"All these measures were put in place to improve the homeowner's respiratory health, immune health and protect from potential future health risks," Safi said.
Topics: Building Green, Certification / LEED, Dehumidifiers and Air Purifiers, Energy Recovery & Heat Recovery, Geothermal Heating & Cooling, Going Green, Heating & Cooling, Home Design & Plans, Indoor Air Quality, Proud Green Home of Louisville, Thermal Envelope, Ventilation