Jackson Systems

ERV vs HRV: What’s the Difference?

We all strive to have a well ventilated space to come home to. It’s a sign that air flow is circulating throughout the home, forcing the unwanted stale air from collecting in pockets. Stale air runs a risk of allowing toxins and chemicals to collect. In serious scenarios heavy concentrations of bacteria, mold, or fungi can lead to higher risks of asthma in young adults or potentially a serious type of pneumonia known as Legionnaires disease. Fortunately there’s a variety of ways to stimulate better air flow in the home and allow fresh air to properly circulate.

ERV’s and HRV’s are great options for repurposing and “recovering” indoor air. Both utilize a similar process but share some key differences that mainly apply to your geographic location. Let’s break down those differences and get into which one is right for you.

ERV's: Energy Recovery Ventilators

The easiest place to start is the abbreviations. ERV stands for Energy Recovery Ventilator. They are described as a “balanced ventilation mechanical systems” or, in simpler terms a fresh air machine.

The device works by drawing in fresh air from outside to replace stale indoor air. During that process, it transfers heat or chill from outdoors to the new air supply. This happens as a cross stream of air within the device. ERV’s also retain relative humidity within the home and in some climates improve humidity conditions.

HRV's: Heat Recovery Ventilators

Like the ERV’s, Heat Recovery Ventilators draw in fresh air from outside, but can recover indoor heating from your furnace to warm fresh incoming air. In the summer HRV goes through a similar process but instead works to “recover” outgoing air chill from your A/C to cool incoming air. Unlike the ERV, HRV’s do not recover humidity levels, it’s strictly about assisting with heat/chill recovery.

How Do They Work?

Both the ERV and HRV utilize two fans that assist in the input and output of airflow from the house and outdoors. These airflows are passing through a rectangular “core” designed to maximize airflow and filter any unwanted toxins from the air. The core is usually constructed from polypropylene material that allows latent heating and chilling between airstreams.

The efficiency rating of an HRV unit determines the amount of energy that will be saved using the device. This requires a consistent operation of the fan. The energy recovered from indoor air is much larger than the energy required for the fan. Typical HRV efficiencies range from 55% to 75% but you can find extremely efficient models that touch the low 90s. 

ERV’s take it a step further by maintaining humidity levels during the process of cycling air in and out of the home. This extraction of humidity happens in the entropy energy core.

In the center of the core, there’s a very thin membrane responsible for preventing cross-contamination of airstreams while increasing the air flow efficiency. Airstreams do not cross during this process inside the core. They pass through separate channels of the core allowing the exchange of heat through conduction. 

Which one is right for you?

This question is mainly dependent on the size of your space and the climate you’re located in. Since HRV’s don’t maintain or improve your humidity conditions, they are recommended in areas where humidity levels rise in the summertime. ERV’s are recommended in most southern states in the U.S. because they allow for a constant retention of humidity from outdoor air. 

A separate factor to consider is the age of the home or building. ERV’s are generally recommended for homes built prior to 1970. This is due to construction methods that allow humidity to escape easier throughout the home. HRV’s make more sense for well insulated, air tight homes you see in newer buildings.

Always consider your home’s natural humidity levels when evaluating the right device for you. There’s no right choice for everyone but when factoring in your climate, lifestyle, and your home’s humidity levels it should make the decision easier to make.

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