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Appropriate Whole House Ventilation Strategies for WNC Homes
By: Cindy Meehan-Patton, Shelter Ecology, Inc.
Human beings sometimes need ventilators to breathe. Our homes do as well. Mechanical ventilation (rather than reliance on natural ventilation) began in northern, colder climates. HRV’s (or air to air heat exchangers) bring a controlled amount of outdoor air in, it travels through a core that heats the air up while stale indoor air is exhausted out. Because homes in northern climates have a tendency to be very tightly built so that heat can be held in the home more efficiently, these ventilators or what I call "breathing machines" are vital to balancing the oxygen levels in the home. Without these, suffocation would occur, and reliance on natural ventilation is not an option when it is 20 below outside! So, these machines quickly became the lungs of the home.
Today, all homes, in all climates, have tightened up their envelopes due to the energy crisis’s we continually endure. So, naturally the use of mechanical ventilation has moved south. However, the climatic issues in the south are very different. The greatest breathing challenge that homes in WNC face is chronic high humidity levels resulting in chronic moisture and mold issues. Soil gases, like Radon and combustion gases from fuel powered mechanical equipment and appliances are also high on the list, but are more of an exhaust issue or a exhalation issue for the home rather than an inhalation issue like moist air. High humidity levels coming against our homes requires a system of building that is set apart from traditional construction techniques, which I will cover in future articles.
HRV’s (Heat Recovery Ventilators) and ERV’s (Energy Recovery Ventilators) are in a category called Balanced Ventilation because their job is to balance exhausted/ stale or indoor air (negative pressure) with outside air (positive pressure). The core in the middle that each air stream passes through can enhance energy use by providing a limited level of dehumidification or heat for the incoming air stream. Unless the installation is done correctly, this system is rarely balanced, which can actually create indoor air quality problems rather than correct them. Pressurization balance with this system is key, or else you end up with a lot of "spikes" of high humidity and air temperature indoors.
10 years of personal experience using even balanced HRV’s and ERV’s has left me with the following conclusion: The technology needs further development for humid climates. The core does not provide sufficient dehumidification for mixed to high humid climates, resulting in high humidity spikes in indoor air and difficulty maintaining indoor humidity levels below 58%. Therefore, if you currently have one of these units or are planning on installing one in a new home, whole house dehumidification will be essential (along with air conditioning, heating and air filtration). Air filtration methods used today are very controversial, which is cause for yet another article! Coming soon!
Supply Ventilation offers a better opportunity for constant pressurization (positive) in our homes. It supplies controlled amounts of outdoor air, but does not exhaust mechanically like balanced ventilation does. Instead, reliance on natural pressure balancing takes place. As positive pressure is brought in, stale air in the home is automatically, naturally pushed out through "weep" holes in the structure, which most homes have. If your home is extremely tight, then strategically creating small through the wall vents may be necessary for exhaustion.
Supply Ventilation Plus, gets my vote for the most appropriate ventilation strategy for WNC homes. The plus factor that is offered on one particular Supply Ventilation unit available today is whole house dehumidification and air filtration. Now you are really getting "fresh" air. Supply (outside) air being brought in without these 2 steps is not really giving you fresh air. Why go to all the trouble to get outside air in, if it is full of moisture and contaminants like formaldehyde, mercury, benzene and pesticides- most of which are cancer causing. The other advantage to constant pressurization of your indoor air is that soil gases like Radon do not stand a chance at hanging around. They have no choice but to exit out of those weep holes.
We live in a high potential radon belt. This means that many of our homes have unsafe levels of radon and we need to take preventative measures to keep it out of our air. It to is cancer causing. All these cancer-causing issues brings me to my next article titled Environmental Illness: Cause and Effect. Coming soon!
Cindy Meehan-Patton, Co-Founder and Past President of the WNCGBC Green Building Council, began Shelter Ecology, Inc. in 1992 as Healthy Home Consultant/ Interior Designer. In 1997 it expanded into a retail store after designing and building her own healthy / green home which houses the offices and store as well. www.shelterecology.com
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By: Cindy Meehan-Patton, Shelter Ecology, Inc.
Human beings sometimes need ventilators to breathe. Our homes do as well. Mechanical ventilation (rather than reliance on natural ventilation) began in northern, colder climates. HRV’s (or air to air heat exchangers) bring a controlled amount of outdoor air in, it travels through a core that heats the air up while stale indoor air is exhausted out. Because homes in northern climates have a tendency to be very tightly built so that heat can be held in the home more efficiently, these ventilators or what I call "breathing machines" are vital to balancing the oxygen levels in the home. Without these, suffocation would occur, and reliance on natural ventilation is not an option when it is 20 below outside! So, these machines quickly became the lungs of the home.
Today, all homes, in all climates, have tightened up their envelopes due to the energy crisis’s we continually endure. So, naturally the use of mechanical ventilation has moved south. However, the climatic issues in the south are very different. The greatest breathing challenge that homes in WNC face is chronic high humidity levels resulting in chronic moisture and mold issues. Soil gases, like Radon and combustion gases from fuel powered mechanical equipment and appliances are also high on the list, but are more of an exhaust issue or a exhalation issue for the home rather than an inhalation issue like moist air. High humidity levels coming against our homes requires a system of building that is set apart from traditional construction techniques, which I will cover in future articles.
HRV’s (Heat Recovery Ventilators) and ERV’s (Energy Recovery Ventilators) are in a category called Balanced Ventilation because their job is to balance exhausted/ stale or indoor air (negative pressure) with outside air (positive pressure). The core in the middle that each air stream passes through can enhance energy use by providing a limited level of dehumidification or heat for the incoming air stream. Unless the installation is done correctly, this system is rarely balanced, which can actually create indoor air quality problems rather than correct them. Pressurization balance with this system is key, or else you end up with a lot of "spikes" of high humidity and air temperature indoors.
10 years of personal experience using even balanced HRV’s and ERV’s has left me with the following conclusion: The technology needs further development for humid climates. The core does not provide sufficient dehumidification for mixed to high humid climates, resulting in high humidity spikes in indoor air and difficulty maintaining indoor humidity levels below 58%. Therefore, if you currently have one of these units or are planning on installing one in a new home, whole house dehumidification will be essential (along with air conditioning, heating and air filtration). Air filtration methods used today are very controversial, which is cause for yet another article! Coming soon!
Supply Ventilation offers a better opportunity for constant pressurization (positive) in our homes. It supplies controlled amounts of outdoor air, but does not exhaust mechanically like balanced ventilation does. Instead, reliance on natural pressure balancing takes place. As positive pressure is brought in, stale air in the home is automatically, naturally pushed out through "weep" holes in the structure, which most homes have. If your home is extremely tight, then strategically creating small through the wall vents may be necessary for exhaustion.
Supply Ventilation Plus, gets my vote for the most appropriate ventilation strategy for WNC homes. The plus factor that is offered on one particular Supply Ventilation unit available today is whole house dehumidification and air filtration. Now you are really getting "fresh" air. Supply (outside) air being brought in without these 2 steps is not really giving you fresh air. Why go to all the trouble to get outside air in, if it is full of moisture and contaminants like formaldehyde, mercury, benzene and pesticides- most of which are cancer causing. The other advantage to constant pressurization of your indoor air is that soil gases like Radon do not stand a chance at hanging around. They have no choice but to exit out of those weep holes.
We live in a high potential radon belt. This means that many of our homes have unsafe levels of radon and we need to take preventative measures to keep it out of our air. It to is cancer causing. All these cancer-causing issues brings me to my next article titled Environmental Illness: Cause and Effect. Coming soon!
Cindy Meehan-Patton, Co-Founder and Past President of the WNCGBC Green Building Council, began Shelter Ecology, Inc. in 1992 as Healthy Home Consultant/ Interior Designer. In 1997 it expanded into a retail store after designing and building her own healthy / green home which houses the offices and store as well. www.shelterecology.com
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