We all strive to have a well-ventilated space to come home to. It’s a sign that air is circulating throughout the home and preventing unwanted stale air from collecting in pockets.
Stale air creates a risk of toxins and chemicals accumulating indoors. In serious situations, high concentrations of bacteria, mold, or fungi can contribute to asthma and other respiratory illnesses. Fortunately, there are several ways to improve airflow and allow fresh air to circulate properly throughout the home.
ERVs and HRVs are excellent options for replacing stale indoor air while recovering energy from the outgoing air. Both use a similar process, but they have several important differences that can affect which system is best for your geographic location.
Let’s break down those differences and determine which option may be right for you.
ERVs: Energy Recovery Ventilators
ERV stands for Energy Recovery Ventilator. ERVs are described as balanced mechanical ventilation systems or, in simpler terms, fresh-air machines.
An ERV works by drawing fresh outdoor air into the home while exhausting stale indoor air. During this process, the unit transfers heat between the two airstreams, reducing the amount of energy needed to heat or cool the incoming air.
ERVs also transfer a portion of the moisture between the incoming and outgoing airstreams. Depending on the climate and season, this can help moderate indoor humidity levels.
HRVs: Heat Recovery Ventilators
Like ERVs, Heat Recovery Ventilators draw fresh air into the home while exhausting stale indoor air.
During the winter, an HRV recovers heat from the outgoing indoor air and transfers it to the cooler incoming air. During the summer, it can transfer some heat from the incoming outdoor air to the cooler outgoing indoor air, reducing the load on the air-conditioning system.
Unlike an ERV, an HRV does not transfer moisture between the two airstreams. Its primary purpose is heat recovery.
How Do They Work?
Both ERVs and HRVs use two fans to control the movement of air into and out of the home. The incoming and outgoing airstreams pass through a rectangular core designed to transfer energy while keeping the two air sources separated.
The core is commonly constructed from materials that allow heat to transfer between the airstreams. Filters inside the unit also help prevent dust and debris from entering the core and being distributed throughout the home.
The efficiency rating of an HRV indicates how much heat the unit can recover from the outgoing air. Although the fans require electricity to operate, the recovered heating or cooling energy can be greater than the energy used by the fans.
Typical HRV efficiency ratings range from approximately 55% to 75%, although some high-efficiency models can exceed 90% under certain testing conditions.
ERVs take the process a step further by transferring a portion of the moisture between the incoming and outgoing airstreams. This moisture transfer occurs through an enthalpy core.
A thin membrane inside the core separates the two airstreams while allowing heat and moisture to transfer. The airstreams do not mix. Instead, they travel through separate channels while energy moves through the core material.
Which One Is Right for You?
The best option depends largely on the size and construction of your home, your local climate, and your indoor humidity levels.
HRVs are commonly used in colder climates and in homes where excess winter humidity needs to be removed. Because an HRV transfers heat without transferring moisture, it can help exhaust humid indoor air and replace it with drier outdoor air.
ERVs are often beneficial in hot, humid climates because they can reduce the amount of outdoor moisture entering with the fresh air. They may also be helpful in dry winter climates by retaining some indoor moisture that would otherwise be exhausted.
The age and construction of the home are also important considerations. Older homes are often less airtight and may already allow significant amounts of outdoor air and moisture to enter naturally. Newer, well-insulated homes are generally more airtight and may benefit more from a properly designed mechanical ventilation system.
Always consider your home’s natural humidity levels when choosing between an ERV and an HRV. There is no single correct choice for every property, but evaluating your climate, lifestyle, building construction, and indoor moisture levels can make the decision easier.
