Four basic systems encompass the whole-house industry. These are energy recovery, balanced, supply, and exhaust.
The 4 Types of Whole-House Ventilation System
An exhaust ventilation system is designed to depressurize the home. Air is exhausted from the house, while more air infiltrates through leaks found in the building shell along with vents.
Exhaust ventilation systems work best for people in cold climates. When a climate has a warm and humid summer, depressurizing the air can cause the moistness to be drawn into wall cavities. From there, it can cause water damage, rot, and mold.
As ventilation systems go, an exhaust system is relatively simple. It’s also not particularly expensive to install. The system includes a single fan that has been connected to a single point of exhaust within the house. Another helpful design involves attaching the fan to ducts from multiple rooms, so the air circulates faster.
There is one pressing concern with exhaust systems. They might attract pollutants when they bring in fresh air. Potential pollutants include:
- Mold and radon found in a crawlspace
- Dust from the attic
- Fumes from the garage
- Gases from a fireplace
These types of pollutants cause particular concern when bath fans and clothes dryers are run simultaneously with an exhaust system.
A supply ventilation system uses a fan to pressurize the home. It forces outside air to enter the building, while the indoor air leaks outside through holes and ducts. Supply systems are similar to exhaust systems in their ease of installment.
Typically, a supply system will consist of a duct and fan system that provides fresh air to at least one room. When wired to several ducts, it can provide fresh air to several rooms. It makes the most sense to have the fresh air go to rooms most occupied by people, like the living room and bedrooms.
Supply systems give better control over the air coming into the house than an exhaust system. Pressurizing the house is a good way for supply systems to minimize outdoor pollutants from being introduced. Supply ventilation has the added bonus of allowing outdoor air to be filtered before it circulates through the home.
These systems are best optimized for hot or mixed weather climates. Due to their pressurization, they might cause problems with moisture in a cold climate. In the winter, the system makes warm internal air leak through random openings. This could cause moisture to condense on the exterior wall or in the attic, which would then lead to decay and mold.
A balanced system, when it’s correctly installed and designed, doesn’t make any change to the pressure in your home. Instead, they filter out and introduce equivalent quantities of polluted inside air and fresh outside air.
Balanced systems typically consist of two great fans and two distinct duct systems. You can install vents for exhaust and fresh air supply in each room in the house, but typically the system is only designed to provide fresh air to highly occupied rooms. In addition, it exhausts more air from areas that generate a lot of pollutants and moisture, like the bathrooms and kitchen.
Depending on the design, you might have a single-point exhaust that supplies outside air directly. A balanced system can use filters to remove pollen and dust from the outdoor air before it’s introduced to your house.
A balanced ventilation system will be appropriate for any climate. However, since they require two separate systems, they tend to be more expensive to operate and install than the previous two options.
The goal of energy recovery systems is to ventilate your home in a controlled manner, while also minimizing the loss of energy. They reduce wintertime heating costs by transferring the heat from the exhaust air into the fresh supply air. In summer, the inside air cools down the hotter supply air to reduce summertime cooling costs.
Two main types of energy recovery systems are on the market today. HRV, or heat recovery ventilators, is one of the systems. ERV, or energy recovery ventilators, is the second system.
Both types come with a heat exchanger, at least one fan that pushes air through the system, and user controls. Some small models are mounted on the window or wall, but the majority of these systems are central ventilation that use their own duct work.
The biggest difference between HRV and ERV systems is the design of the heat exchanger. In ERV systems, the exchanger transfers some water vapor with the energy. In HRV systems, only heat is transferred.
Because ERV ventilators transfer moisture from exhaust air into the less-humid winter air, the house has a more constant-feeling humidity. This also allows the core to stay warmer, so issues with freezing are minimized.
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During the summer, an ERV system might help with humidity control by transferring some of the incoming air’s water vapor to the drier outgoing air. If you use air conditioners, an ERV system tends to give better humidity control than heat-recovery. With that said, there’s a bit of controversy regarding the use of ventilation systems during mild, humid summer weather.
There are some experts who believe it’s better to turn your system off entirely during humid weather so your indoor humidity levels stay low. The system can also be set up to run only when the air conditioning system is running.
The majority of ERV systems are capable of recovering between 70 and 80 percent of the energy in the air that’s exiting. They then deliver this energy to the air incoming. With that said, they have the most cost-effective use when installed in climates that have extreme summers or winters. With mild climates, additional electricity might exceed energy savings.
So Which Is Best?
- For cold climates, use the exhaust.
- For hot climates, use the supply.
- If you have a little extra money to spend, try a balanced version.
- If you live in places with extreme weather, try an ERV system.
Image Credit: Pixabay
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