Why Are Some HRVs / ERVs So Noisy?

Heat Recovery Ventilators (HRV) or Energy Recovery Ventilators (ERV) have been commonly used in Canada for years and have become increasingly common in high-performance homes in the US.  Though there is an increasing awareness of the importance of an HRV or ERV in an energy-efficient home, across the US and Canada we’ve heard complaints about the noise levels of the first generation HRV or ERV units.  Due to the noise level, often the HRV or ERV units are only used intermittently or turned off altogether.  This is a major issue because these ventilation systems are supposed to provide the required fresh air ventilation for these homes.  Without proper ventilation health and comfort issues arise.  Home indoor air quality issues have soared since increased energy-efficient construction gained ground in the late 1970’s.

HRV/ERV systems don’t have to be noisy resulting in intermittent use and IAQ issues associated with improper ventilation.  Often we find that customers are surprised by how quiet a Zehnder ventilation system is in comparison to the previous generation of HRVs/ERVs. If you have a quiet HRV/ERV with designed and matched system components, noise is minimal and your energy-efficient home will have the combined benefits of a continuous supply of fresh air ventilation and reduced heating/cooling loads.

What causes an HRV system to be noisy?           

The HRV/ERV unit itself could be causing a lot of noise, and even a perfect design and installation is not going to cover up a loud central unit.  More often though sound issues arise from improper design and installation.  Often the issue is from incorrect design work where the HRV/ERV is located too close to bedrooms and/or there isn’t suitable acoustical isolation for the HRV or ERV unit.  In other cases, noise is significantly amplified by improper mounting and duct sizing.

What is the solution?

It’s important to do your research and choose an HRV/ERV unit known to be very quiet.  One important aspect of quiet HRVs or ERVs is their size. Larger relative units tend to produce less noise, as they are better insulated and provide for air moving at lower velocity through the heat exchanger. Next, look for manufacturers that offer design, installation and commissioning support of the whole HRV/ERV ventilation system. When you have a system that is designed with properly matched system components, it will minimize the noise and often provide a smoother installation.  Some HRV/ERV systems, such as Zehnder’s, are built in with sound attenuators (or silencers) to minimize noise.

On the opposite end, choosing an HRV/ERV unit and piecing together unspecified ductwork and air distribution components sometimes leads to noise issues and decreased heat recovery efficiency of the system.  As a result of inappropriate components and ductwork sizing, homeowners tend to use the system intermittently or turn off the unit altogether, which presents potential IAQ issues. This is the reason we recommend having a complete system designed and then after the system is installed, have it commissioned to ensure the system is working properly.

In related upcoming posts, we’ll discuss in more detail how a proper HRV/ERV design and installation ensures maximum thermal and electrical efficiency of the HRV system.