Zehnder ERV meets the indoor air quality challenge for the Proud Green Home
One of the key elements of the indoor air quality strategy for the Proud Green Home of St. Louis is an energy recovery ventilator that will ensure a continuous flow of fresh air.
Nestled in a rural subdivision in a St. Louis suburb, the Proud Green Home of St. Louis is a 3,700 square-foot, Prairie-style home that will serve as a demonstration home for a variety of green building systems and technologies.
|Proud Green Home of St. Louis Rendering|
Green from the Ground Up
Curtiss Byrne, the architect, and Kim Hibbs, president of Hibbs Homes, the builder, worked with the clients Michael and Emily Kuentz to design a home that would meet their family's needs for years to come.
Indoor air quality is one of the top goals of the new home, because one of the children that will be living there has environmental sensitivities due to asthma and allergies. The Kuentzes wanted a home that will not cause adverse respiratory issues for their child.
Starting with the architectural design, the entire home will reflect the desire for a high level of indoor air quality, as well as energy efficiency, and an inviting refuge for the family. That means from the foundation to the roof, all the aspects of the house work together.
"It's a bunch of systems that make up the big system called the house," said Matt Belcher, principal with Verdatek Solutions LLC, a green building consultant to Hibbs Homes.
Leading Edge Green Technology
To ensure a steady supply of fresh, filtered air, the home will incorporate an energy recovery ventilator (ERV). An ERV is a ventilation system separate from the home's heating and cooling system. Zehnder America is supplying a Comfoair 550 ERV for the home.
The ERV brings in fresh outside air, through a series of filters, and delivers it to the living areas of the house. The ERV system transfers heat and humidity
"As part of keeping the systems separate, the system is designed to pull exhaust continually from the bathrooms, eliminating the noisy, ineffective bath fans," said Kevin Rapp, Midwest technical sales representative for Zehnder America. "The fresh, filtered outside air is delivered to the bedrooms and living spaces."
To move the air through the home, the project will use UL-approved ComfoFlex ducting as well as be the first project to use the air distribution boxes that are made in the U.S., Rapp added.
Watch an explantion of the ERV/HRV ventilation system
An ERV system works continuously to extract moist, stale air from wet rooms (kitchens, bathrooms and utility rooms) and supply 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 HRV/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.
A Heat Recovery Ventilator, or HRV, only exchanges heat in the air. An ERV also exchanges transfers humidity from one airstream to the other. The Zehnder ERV transfers the humidity as water vapor by diffusion from the high to the low partial vapor pressure side. As this process occurs, it also prevents cross contamination of the air streams, so that the exhaust air (gases, odors, etc.) is not recirculated into the fresh air stream. The ERV exchanger pores are just large enough for a small water vapor molecule to fit through but too small for larger air constituents or VOC molecules to fit through.
Energy recovery ventilators help maintain a comfortable and healthy home by reducing the temperature and humidity of the fresh incoming air during the hot, humid summer time. This is an important energy saving method. It’s a healthier and more comfortable alternative to excessively running air conditioning to combat high humidity and temperature infiltrating a home through cracks and openings in the building.
The ERV is designed to run quietly in the background, with a very low sound level so the homeowners won't even know it's there.
"You don't want to know it's running, that defeats the purpose," Rapp said. "You can set it and forget it."
Zehnder hopes to use the Proud Green Home of St. Louis project to educate builders and contractors about the best way to install an ERV/HRV system. Rapp has found that contractors are routing the exhaust flow into the home's HVAC forced air system.
Themanufacturers recommend that contractors install the ERV duct system separately from the HVAC system.
"Ducting the ERV into the central forced air system is a bad idea because it ruins the efficiency equipment," Rapp said. "It causes an imbalance of air brought in so you're not getting proper heat transfer. And with the individual ducts we're able to put the fresh air where it's supposed to go."
Companies: Zehnder America