Leaky, inefficient buildings have plenty of uncontrolled air exchange through gaps, cracks and openings that provide pathways for air infiltration and air exfiltration. But in an energy-efficient home that has a tightly sealed “building envelope,” indoor air can easily become stale and unpleasant. Opening a window can make your air feel less stuffy, but this isn’t practical during the hotter and colder months of the year. An open window also invites pollen and other allergens into your home. Installing a HRV (Heat Recovery Ventilator) or an ERV (Energy Recovery Ventilator) can improve indoor air quality, boost HVAC efficiency, and help with odor control. HRVs and ERVs address these issues by exchanging stale indoor air for fresh outdoor air. Both ventilation aids are designed to work with forced-air heating and cooling systems. An ERV can also help retain the relative humidity levels in your home.
How does a HRV or ERV Work?
HRVs and ERVs are equipped with two fans, one that draws fresh outside air into your home and one that pulls stale air out. The HRV has a heat exchanger inside, usually made of aluminum, which allows indoor and outdoor air to pass through without actually touching each other. This helps to prevent cross-contamination between the stale indoor air and fresh outdoor air. The heat exchange occurs through conduction. In the winter, the warm indoor exhaust air is used to heat the incoming fresh cooler outside air. In the summer, the reverse occurs. The cool indoor exhaust air is used to cool the incoming fresh warmer outside air. Small channels in the heat exchanger allow the air to spread across a large surface area, this quickens the temperature transfer. Filters ensure you are not introducing any unwanted contaminants from outdoors. HRVs have a Sensible Recovery Efficiency rate generally between 70% and 80%.
ERV systems are designed not only to maintain temperature, like a HRV, but also humidity levels. An ERV heat exchanger is usually made of a different material, often paper, so that moisture can transfer between incoming and outgoing air while still preventing cross-contamination of air streams. A high efficiency of humidity transfer would be around 70% but this value depends on the actual humidity inside and outside.
The type of buildings that need a mechanical ventilation system the most, are well sealed and well insulated, built from the early energy-conscious era of the late 1970s through today.
How to Choose
The best option between a HRV or an ERV depends on your climate and specific needs. Due to our low humidity in Colorado, particularly in the winter, an ERV might seem like the better choice. However, a number of factors, including air leaks in the home envelope, the number of square feet measured against the number of occupants, and even the personal habits of people in your home may impact the decision. There are certain applications where a HRV makes more sense, such as specifically for a locker/shower room. In this case, the indoor humidity always is much higher than the outdoor humidity and it is desirable to remove that moisture from the space at all times of the year. Determining whether or not your home will benefit most from a HRV or ERV will vary on a case-to-case basis.
Benefits of HRVs
HRVs come with a host of advantages for homeowners. Whether you’re thinking about having one installed in a new build or added to an existing home, you’ll enjoy several benefits after installation.
Improved Indoor Air Quality
When a HRV flushes stale air out of your home, it also flushes out the pollutants contained in it. Additionally, the HRV filters the incoming outside air, capturing contaminants such as pollen, dust, and other pollutants before they can get inside your house. This leads to improved indoor air quality. Good indoor air quality is associated with improved sleep, better concentration, and fewer respiratory issues.
Better HVAC Efficiency
When a HRV transfers heat energy between incoming and outgoing airstreams, it effectively pre-cools or pre-heats (depending on the season) the air entering your home. This decreases the amount of work your HVAC system has to do, boosting its efficiency, decreasing energy usage, and lowering utility bills.
Improved Odor Control
By removing airborne contaminants from your home and filtering the incoming air, a HRV will help with odor control. Odors from pets, cooking ingredients, and other sources are greatly decreased, helping the air in your home smell fresh, crisp, and clean.
Improved Moisture Control
When an ERV transfers heat energy between two streams of air, it also transfers the moisture that’s contained in them. So, when the two airstreams enter the ERV, the system takes some of the moisture from the more humid airstream and applies it to the less humid airstream. This helps keep some of the humidity out of your home during warm, humid months and helps some humidity to stay inside during the cool, dry months.
That said, ERVs aren’t humidifiers or dehumidifiers. They simply help with moisture control. If you want better humidity control you should consider having a whole-home system installed as well.
ERVs and HRVs are easy to maintain. We can clean and inspect it during your annual maintenance visits. All you need to do is change the filter every few months. Other than that, they require very little intervention from you.
Increased Comfort Levels
With improved air quality, controlled ventilation, and moisture control, an ERV can vastly improve the comfort levels of your home in an energy-efficient manner. These capabilities go a long way in helping to make sure your home environment is clean, pleasant, and healthy.
We would be happy to make a visit to evaluate your home for a HRV or ERV system. Simply give us a call to learn more.