HRVs and ERVs: How These Ventilating Options Impact Your Home ComfortPublished on: December 2, 2013
Being comfortable in your home takes more than having it set to the right temperature. The quality of the air you breath can also have a huge impact on how you feel while at home and on your overall health. Ventilation systems can help you maintain good indoor air quality to make sure being at home actually feels good.
Why You Need Ventilation
After the energy crises of the 1970s, one of the biggest points of emphasis in new home construction was on energy efficiency. A large part of this involved making homes as airtight as possible to stop drafts and other leaks from letting in cold outside air or letting out freshly heated air. What wasn’t realized in a lot of cases was that these leaks inadvertently served the purpose of ventilating a home and keep its air fresh.
A tightly sealed home can hold air that’s more polluted than what’s just outside the door. Building materials, cleaning sprays, gas stoves and food preparation all give off chemicals that can be toxic in large quantities. Additionally, showers, doing dishes and even just breathing allows humidity to build up in a home.
To avoid negative health effects and mold growth, experts recommend that a home’s air be changed roughly once every three hours. In an old, drafty home, this rate was often exceeded. In a modern home, the rate is much lower and ventilation systems are needed to help cycle the air. Two very effective types of systems are heat recovery ventilators (HRVs) and energy recovery ventilators(ERVs).
HRVs are designed to solve the ventilation problem without relinquishing the energy-saving gains of tighter construction techniques. When drafts are present, cold air comes into the house during the winter and forces the heater to work longer to keep the house at the same temperature. HRVs control the incoming airflow so that the temperature difference isn’t as great.
HRVs feature a blower along with incoming and outgoing vents. In the middle of the ventilator, the incoming and outgoing air runs through a series of small passages in close proximity to each other. This allows heat to transfer between the incoming and outgoing air without mixing stale air and fresh air.
The end result is that the incoming air is much closer to room temperature when it’s sent into the house. This is because heat likes to balance itself, so as the air passes through HRVs, it will always adjust to roughly the average of the incoming and outgoing temperatures before it leaves.
ERVs work essentially the same way as HRVs with one added feature. In addition to transferring heat, they transfer humidity. As the air passes through ERVs, water is forced out of either the incoming or outgoing air depending on which is more humid, and then is sent back in the opposite direction. This helps keep a home from becoming too humid in the summer or too dry in the winter.
Which is Better?
ERVs are typically recommended over HRVs. In the past, it was thought that they were uneconomical outside of humid, tropical climates. A recent study proved this wrong, as even in a dry part of western Canada, dehumidifying costs were 20 percent lower and cooling costs were reduced by 12 percent when ERVs were used instead of HRVs. Because some type of dehumidification will always be needed to prevent mold growth, ERVs are almost always worth the increased price over HRVs.
Can’t You Just Open a Window?
If you live in a climate with mild temperatures for most of the year, you might be tempted to just open your windows to air out your house for a few hours. This is still a good thing to do every once in a while, but it doesn’t replace ventilators. Remember, the target is to completely cycle the air in your home about once every three hours. Even if you achieve great circulation with the windows open with the aid of a strong breeze or fans, there will still be long periods of time when they are closed, especially in the middle of the summer and winter. For the best indoor air quality, a ventilator will be needed.
If you’d like more information on having a ventilation system installed in your home, click here to find a contractor near you. We have experts throughout the Southeast helping customers in Florida, Georgia, Mississippi, South Carolina and Alabama.