Most newer buildings will require some sort of mechanical ventilation system in order to replenish the oxygen and fresh air inside the structure. Both HRV and ERV ventilation systems are designed for this task. However, the two systems work differently and provide different benefits. Therefore, it is important to understand how they work and what the differences are in order to decide which system is best.

Why Is Ventilation Necessary?

Before getting into the specifics of HRV (heat recovery ventilation) and ERV (energy recovery ventilation) systems, it’s first important to understand why ventilation is necessary. All buildings require some type of passive or mechanical ventilation to ensure that there is enough fresh air inside the structure. Ventilation is also important as it works to prevent problems with excess humidity that could lead to mold growth and potentially damage the building’s underlying structure.

Modern building technologies mean that today’s newer buildings are far better insulated and sealed up than they used to be. This has the benefit of ensuring that energy waste is drastically reduced in modern buildings compared to older construction by preventing air leaks. While this is obviously a good thing, it does mean that these buildings require a ventilation system in order to replenish the fresh air inside the structure.

Mechanical ventilation was never really necessary with older buildings as they tended to allow enough fresh air to get inside the building for it not to be an issue. However, without the use of some type of mechanical ventilation system, many newer buildings would never be able to replenish the fresh air inside. Of course, opening a window can easily overcome this problem. Nonetheless, this really isn’t a practical solution during the hottest and coldest months of the year since it would cause your HVAC system to have to work overtime. Not only that but it can also quickly fill the home with pollen, dust and other allergens and pollutants and decrease indoor air quality.

Essentially, older buildings have passive ventilation as they let enough air leak inside to prevent most humidity issues. This also ensures that a steady flow of fresh air comes into the building and that pollutants and other airborne contaminants inside the building can escape. This steady flow of fresh air into the building isn’t bad, but it does contribute to a huge increase in energy use. During the winter, all that cold air makes it much harder to keep the building warm and forces the heating system to work much harder. Similarly, it allows the hot, moist summer air inside the building, which can both make it difficult to keep the building cool and to regulate the humidity level.

How HRV and ERV Ventilation Systems Work

HRV and ERV are the two most common types of mechanical ventilation systems. These systems work by venting stale air from the interior to outside the building and drawing fresh air in from outside. However, these systems don’t just allow the cold air from outside to get in as this would again lead to the same problems as with passive ventilation. Instead, HRV and ERV ventilation systems work to heat up the air coming into the structure so that it is the same ambient temperature as the interior of the building. This helps to lower utility costs by reducing the amount of energy it takes to heat up the incoming air.

An HRV ventilation system works by drawing heat out of the outgoing exhaust air and transferring this warmth to the incoming fresh air. The incoming and outgoing air never mix though. Instead, the heat is transferred from the outgoing air in one chamber to the incoming air in a separate chamber by means of a heat exchanger. As you might expect, this process does still result in some heat loss as the heat exchanger is incapable of capturing and transferring 100% of the heat from the outgoing air.

Most HRV units have an efficiency rating somewhere between 55% and 80%, and this directly corresponds to the maximum percentage of heat that the unit can transfer from the outgoing to the incoming air. However, you can find some units that have an efficiency rating of 90% or more. The more efficient the unit is, the more it will cost. Nonetheless, the added energy savings a more efficient unit provides may still make spending the extra money on a higher quality unit well worth it.

ERV ventilation systems work using the same basic principle as HRV by capturing some of the heat from the outgoing air and transferring to the incoming air. However, this type of system also captures some of the humidity from either the incoming or outgoing air. During the cold, dry winter months, the system captures humidity from the outgoing air to prevent the air inside of the structure from becoming overly dry.

The system then reverses during the hot, humid summer months to capture excess moisture from the incoming air to help maintain relatively normal, steady humidity levels inside the building. This can contribute to even greater energy savings during the summer months by ensuring that your air conditioner and dehumidifier don’t have to work as hard to cool the air and prevent excess humidity. A highly efficient ERV system may be able to transfer up to 70% of the humidity from ingoing to outgoing air or vice versa. However, this is wholly dependent on the actual interior and exterior humidity levels.

HRV or ERV: Which Is Best for My Home?

Both HRV and ERV systems can be a good choice, but it depends on your specific needs and the local climate in your area. People who live in drier climates are probably best off going with an HRV system since excess humidity usually isn’t a problem in these areas. HRV systems are also generally the better choice for areas or homes where the humidity level gets above 60% during the winter. In these situations, an ERV system can actually trap excess humidity inside the building during the winter.

However, people who live in areas that frequently experience high humidity during the summer may be better off going with an ERV system. An ERV system will usually cost a few hundred dollars more than a comparable HRV system. However, the fact that an ERV system can eliminate the need for a dehumidifier and reduce the load on your air conditioner means that it may be a more cost-effective solution for anyone living in an area with high humidity.

HVAC Experts You Can Count On

Whether you’re in the market for an HRV system or ERV system, the team at Shines Energy is always on hand to help. Dartmouth residents can also take advantage of our wide range of other HVAC services including furnace and air conditioner maintenance, repair and installation. Boilers, radiant heating, mini-split systems, hot water heaters are just a few of the other services and systems that we specialize in. We can also offer you a variety of options to improve your indoor air quality including humidifiers, dehumidifiers, air scrubbers and purifiers, UV lights and more. No matter what your HVAC needs are, give Shines Energy a call today to see how we can help.

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