A woman standing in front of an oscillating fan unbuttons her blouse to cope with high humidity levels

All modern homes need a mechanical ventilation system. 

This requirement is because modern residences tend to be much more airtight than in previous decades to conserve energy and increase the efficiency of the HVAC system.

The Importance of Mechanical Ventilation

Ventilation is when stale indoor air is removed from your home, and fresh outdoor air is brought in, thus improving the indoor air quality. And when natural ventilation is no longer a viable option, a reliable mechanical ventilation system, like HRVs or an ERV, must take its place. 

Such a system will help maintain optimal humidity in your home—preventing too much moisture from building up in the indoor air and keeping your interiors from becoming too dry and arid. (Click here to learn about the best home ventilation methods.)

Furthermore, a mechanical ventilation system can provide homeowners with some other significant benefits:

  • Helping keep the indoor air fresh and clean.
  • Keeping pollutants and allergens out of your home. 
  • Preventing excessive condensation in your living space.
  • Balancing heat distribution throughout the house.
  • Finally, helping reduce the cost of residential heating.  

When installing a mechanical ventilation system in your airtight home, you have two main options—Heat Recovery Ventilation (HRV) or Energy Recovery Ventilation (ERV). 

An HRV system extracts heat from the stale indoor air and uses it to preheat the fresh, outdoor air being brought into your home. An ERV system also does this and also captures some of the moisture from the outgoing air to keep your home at an optimal humidity level. 

Therefore, the primary difference between the two is that an HRV system transfers heat between outgoing, stale air, and incoming fresh air, while an ERV system transfers both heat and moisture. 

This article will inform you about ERVs and HRVs—their benefits, features, and impact on indoor humidity. 

Someone using the interface to adjust the settings of an HRV system

Mechanical Ventilation and Humidity

Too much humidity in the indoor air can lead to the growth of mold and mildew, which might then cause allergic reactions in the residents of the house.

Conversely, too little humidity might lead to dry air in the home’s interiors, which would make the residents more vulnerable to sore throats, dry skin, and other such health conditions.

Hence, a good ventilation system should optimize the humidity level present in the indoor air. During the hot and humid summers, it should extract some humidity from the indoor air while infusing it with more humidity during the cold and dry winters. 

This management will help keep the home comfortable throughout the year. 

If you want a ventilation system that actively monitors and modulates the level of humidity in your home, then you should opt for an ERV. 

The Dehumidification Process

When the weather is cold and dry, the fresh, outdoor air will likely be quite arid, while the indoor air will be more humid due to all the moisture collected from cooking, hot showers, and other day-to-day activities. 

During such times, the ERV system works to extract moisture from the stale, indoor air being expelled from the house. It then transfers this moisture to the fresh, outdoor air brought into the home through the process of ventilation. 

This process is reversed in summer when the outdoor air is hot and humid. Excess moisture is extracted from the fresh, incoming air and inserted into the stale, outgoing air, preventing the home from becoming too sticky, which would cause sweating and encourage mold growth. 

An ERV system keeps the internal ambient humidity comfortable throughout the year. As a result, indoor air can be retained between 40 to 50 percent moisture at all times, for instance, with no significant fluctuations, regardless of the season or weather conditions outside. 

ERVs also help reduce the load on the dehumidifier (if you have one), which in turn saves some energy and lowers utility bills. Depending on humidity levels on either side of the building envelope, an efficient ERV system could transfer as much as 70 percent of the moisture. 

An HRVs exchange component and vents on a home's exterior

Heat Transfer through Ventilation

The HRV system also helps save energy and reduce utility bills, but without having as much of an impact on humidity levels. 

In winter, the indoor air is warm and comfortable (from the heat generated by the furnace, water heater, cooking stove, etc.), while the outdoor air is exceptionally chilly.

An HRV system will extract the heat from the stale indoor air before removing it from your home. It will then transfer this heat to the fresh, cold, outdoor air brought into the house. This process ensures the incoming air has been pre-warmed to a comfortable level before it is circulated throughout the house.

HRVs also reduce the load on your furnace and help minimize the energy bills. (Click here to learn more about energy-saving home upgrades.)

In the summer, the stale indoor air is cold (due to air conditioning), while the fresh, outdoor air is much hotter due to the nature of the season. 

During this season, the HRV extracts some of the chill from the cold, outgoing air and transfers it to the hot, incoming air, keeping the interiors cool while minimizing the load on the air conditioner. 

You can install an HRV system in your home if you live in an area that doesn’t have very humid summers or dry winters. In that case, installing a dehumidifier (along with the HRV system) should be enough to keep your home comfortable throughout the year. 

Which One Should You Choose? 

Whether you should choose an HRV or an ERV ventilation system depends mainly on your location, the size of your home, the climate in your area, and some other factors. 

Listed below are some things to consider when deciding on the right ventilation system for your home.

The Usual Climate in Your Area

If the local climate has relatively moderate temperatures throughout the year, without significant fluctuations in humidity levels, then an HRV system would be ideal. 

However, if you live in a place with long, dry winters and hot, sweltering summers, then an ERV system is a must for maintaining consistent humidity levels. 

Size of Your Household

The size of your house – and the number of residents – can help determine which type of ventilation system would be the most suitable. 

Many people living in a small home would generate a lot of moisture—from cooking, showering, or even just breathing. On the other hand, a large house with fewer inhabitants would tend to be dryer. 

Therefore, if you live in a small house with lots of people, you can opt for the HRV system even if you live in a relatively cold and dry place. 

On the other hand, an ERV system would be best for a larger house with fewer inhabitants, even if it is located in the same area. 

Age of Your Residence

If you live in an older house (one built before 1970), you should opt for an ERV system. This is because older homes were prone to air leakage, meaning that humidity could escape outdoors during the winter, and the moist outdoor air could infiltrate the house during the summer. In such homes, a ventilation system that can monitor and modulate the humidity levels is essential. 

However, newer homes (especially those constructed in the 21st century) are built to be much more airtight. They can retain humidity when needed and do not allow much infiltration of outdoor air. For such homes, an HRV system, along with a dehumidifier, might be sufficient.  

Personal Health Issues

Too much humidity in the air can exacerbate certain health conditions, such as asthma and allergies. On the other hand, the extremely low moisture content in the air can cause dry skin, nosebleeds, and other issues. 

Therefore before choosing a ventilation system, you should consider if you (or any of your family members) suffer from a health condition that might be affected by fluctuations in the humidity level. 

If so, you should choose an ERV system, as it is better at controlling the level of humidity in the indoor air. 

Concluding Note

The selection and proper installation of a suitable ventilation system are essential for building a comfortable and durable home. So be sure to do some independent research (and consult an experienced HVAC technician) before choosing either an ERV or HRV system.

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