With each passing year, mechanical ventilation systems are becoming more and more common in American homes. Two of the most common types of mechanical ventilation systems are heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs).
Together, both can be defined as balanced ventilation mechanical systems or ‘fresh air machines’ in layman’s terms.
The primary purpose of such a machine is to bring fresh, outdoor air into your house and help draw the stale indoor air out, along with all the excess moisture, dust, and pollutants that the indoor air typically carries.
Both ERVs and HRVs filter the outdoor air before introducing it into your living space. The external air is brought in in a measured way and is circulated throughout the house so that every room feels fresh and well-ventilated.
Furthermore, both ERVs and HRVs have a unique ‘heat-exchanger core’ which extracts heat from one airstream and uses it to warm up the other during the ventilation process.
In winter, the heat-exchanger core will extract heat from the furnace-warmed indoor air and use it to warm up the fresh, outdoor air coming into the home.
The opposite process occurs during summer—heat is extracted from the hot outdoor air and absorbed by the conditioned indoor air on its way out.
So, how do you choose between the two systems if they’re so similar?
What is the Main Difference Between HRVs and ERVs?
The primary difference between ERVs and HRV is that the former regulates moisture and heat while the latter only regulates heat. In other words, an ERV transfers both humidity and heat from one airstream to the other, whereas HRVs only transfer heat and have minimal impact on the moisture in the air.
Therefore, whether you choose to install an ERV or an HRV system in your home will depend mainly on your local climate, as well as the average humidity level in your living space.
To try and make the decision-making process a bit easier, we will discuss the major differences between ERVs and HRVs at great length in the next section of this article.
Other Distinctions Between ERVs and HRVs
HRVs and ERVs are mechanical ventilation systems that primarily serve the same function. Therefore, it’s pretty easy to become confused about what exactly sets the two apart.
Listed below are just some differences that should be considered when deciding on the right ventilation system for your home.
A heat recovery ventilation system aims to provide thermal comfort to your living space.
In winter, the outdoor air is much colder than the indoor air that has been warmed by the furnace, gas stove, boiler, or water heater. So, the HRV extracts heat from the indoor air before expelling it from the house.
It then uses this heat to warm up the cold outdoor air coming into the house. In this way, the temperature in your living space remains constant and comfortable. (Click here to learn more about how an HRV works.)
An energy recovery ventilator also provides thermal comfort, but it performs an additional function on top of that. It helps with controlling the moisture content of your indoor air.
Suppose the relative humidity of the indoor air is significantly different from that of the outdoor air. In that case, the ERV core will remove the excess moisture from one airstream and infuse it into the dryer one.
For instance, if the relative humidity outside is at 80 percent, but you want to keep your home at a comfortable 45 percent relative humidity, you would need an ERV to help you with this.
As the humid outdoor air crosses the relatively dry indoor air inside the ERV core, the ERV will extract the moisture from the more humid air stream and move it to the less humid one, just like it does with heat.
As a result, the fresh air brought into your home will lose much of its excess moisture before being introduced into your living space, which will prevent excess humidity in the indoor air.
Too much humidity can lead to mold, mildew, and fungus. It can also cause health issues like allergies, asthma, and more. So preventing excess moisture from entering your living space can benefit both the house and its occupants.
The cost of an HRV or an ERV system can vary widely, depending on a variety of factors. Variables include:
- The brand and model of the device
- Whether it is a whole-home ventilation system or a single-room unit
- Whether you’re installing it in a new home or an old one
- The size and location of your home
- The amount of existing ductwork in the house
However, if all other factors are equal, an ERV will almost always cost more than an HRV. This figure includes the cost of the unit itself and its installation. On average, an ERV might cost anywhere between $150–$250 more than an HRV.
Depending on your circumstances, an HRV can cost anywhere between $1,150–$2,250 at most. On the other hand, installing an ERV can set you back by as much as $4,500, although that would be an exception. Usually, ERVs cost about $2,000, including installation.
The climatic conditions in your area will impact your choice of a ventilation system. For instance, if you live where the climate is frigid (and relatively dry), an HRV would be the best option. This is why HRVs are popular in the northern states of Minnesota, North Dakota, and Maine.
However, if you live in any southern state where the climate is hotter and more humid, you will want to install an ERV.
States like Texas, Florida, and Louisiana can get extremely humid, particularly during the swing seasons (spring and fall). Not only does this lead to an uncomfortable living situation, but it can also cause moisture damage to your home.
Another reason ERVs are preferable in hot and humid climates is that moist air is more challenging to cool than dry air. As a result, your air conditioner has to work extra hard to cool down the hot and humid summer air.
An ERV system will reduce the load on your air conditioner (and lower your energy bills) by extracting some of the moisture from the outdoor air before introducing it into your living space.
The number of occupants living in your home and the size can help determine whether you need an ERV or HRV.
Large houses with fewer occupants tend to be less humid than smaller houses with many occupants. The behavior of those occupants will also affect the moisture level because inhabitants generate a certain amount of humidity through their daily activities.
For example, cooking, taking a shower, or even just breathing can increase the amount of moisture in the indoor air. Likewise, your home will also be more humid if you have a lot of pets.
So, if you have a small, airtight house occupied by many people or animals, you should opt for an HRV system.
The HRV will regularly expel the stale and humid indoor air and bring in fresh, dry outdoor air without transferring moisture from one airstream to the other. Since the house’s occupants already generate a lot of humidity, you do not need to retain moisture.
On the other hand, large homes with few occupants will be relatively dry since the little humidity generated is soon dissipated within the vast indoor space. Such homes will need to retain moisture to keep the occupants comfortable. Therefore, you should invest in an ERV system if you live in a big house and have a small family.
The Differences at a Glance
|Heat Recovery Ventilator||Energy Recovery Ventilator|
|Moves heat from one airstream to the other.||Moves both heat and moisture from one airstream to the other.|
|Relatively cheaper, costing up to $2,250.||More expensive and usually cost about $2,500.|
|Best suited to cold and dry climates.||Ideal for hot and humid climates.|
|Suitable for small, airtight homes with many occupants.||Ideal for large, leaky homes with few occupants. |
Common Myths and Misconceptions
There are many myths and misconceptions about what an ERV or HRV does and how they are different. This section will discuss and try to clear some of them up.
Myth #1: The ERV Core Will Freeze in a Cold Climate
The first misconception is that ERVs can’t be used in a cold climate, as their cores will freeze up.
This myth is not totally baseless since this was a problem with ERVs about 15-20 years ago. However, HVAC manufacturers solved that issue years ago, making it no longer a concern.
So if you’re living in a state with a mixed climate, such as Vermont or Pennsylvania, you can install an ERV system in your home without having to worry about it freezing up in the winter.
In places that experience hot summers and cold winters, an ERV is the better choice since it can also act as an HRV if needed. An HRV system, on the other hand, cannot do the work of an ERV.
Therefore, if your home has moisture issues during the summer or winter, you should choose an ERV system. (Click here to learn more about the ERV installation process.)
Myth #2: An HRV System Will Increase Your Electricity Consumption
There is a persistent myth that installing an HRV system at home will lead to higher energy bills. However, an HRV indeed uses some energy to operate its fans, which expel stale air while drawing in fresh air from outside.
Still, a high-quality HRV system will reduce energy consumption and lower electricity bills over the long run—an HRV can effectively reduce the load on your air conditioner during summer while also reducing the load on your furnace in winter.
The HRV passes heat from the furnace-warmed indoor air to the chilly outdoor air during the winter before circulating it in your home. Since the outdoor air is already warmed up before being introduced indoors, the furnace doesn’t have to work as hard to heat the fresh air.
In the summer, the HRV extracts heat from the incoming outdoor air and passes it to the air-conditioned indoor air. As a result, the hot outdoor air is cooled down significantly before being introduced inside, ensuring your air conditioner doesn’t have to work extra hard to cool down the fresh summer air.
Thus, it is easy to see how installing an HRV will help you save a ton of energy on heating and cooling your home. The little bit of extra energy needed to operate the HRV fans will be far outweighed by the energy being saved.
Myth #3: An ERV Can Dehumidify Your Home
Many people believe that because an ERV system can control the humidity level in a house, it must work as a dehumidifier. However, this is a fallacy.
An ERV has no impact on the moisture level of the air that is already inside the house. It can only extract excess moisture from outdoor air before drawing it into the indoor space.
Hence, if you install an ERV system at home, you can be sure that the fresh, outdoor air coming in through ventilation is less humid than it would have been otherwise. But this is only because the ERV transfers the moisture from the incoming air stream to the outgoing one.
If the indoor humidity increases due to cooking, hot showers, or any other activity, the ERV won’t help dehumidify this air. It will simply cycle it out after a while (through ventilation) and bring in the fresh air that is relatively less humid.
You should install a separate dehumidifier in addition to the ERV if you want to ventilate and dry your home simultaneously.
By now, you should know precisely how HRV and ERV systems differ, as well as the types of misconceptions people often have about both.
This insight will help you make an informed decision about which type of ventilation system is right for your home, taking into account the local climate, the number of occupants, as well as your budget.