Heat recovery ventilators (HRV) started showing up in new homes since about 2008. HRVs bring fresh air into the house and reclaim or recover about 80 percent of the heat from the stale air that is being drawn out of the house. The need for these systems started when building codes began requiring homes be built tighter and more energy efficient. Homes in the past leaked enough fresh air into the home that a special ventilation system was not needed.
These systems have air filters that need cleaning regularly depending on how much they run. I have not yet found a single HRV that had been serviced and cleaned during a home inspection. On average, they need cleaning at least twice per year. The cleaning task is not difficult when the instructions are followed in the owner’s manual. People are just not told what the systems do and they need regular cleaning. HRVs are about a foot tall and two feet long and are found mounted close to the furnace and hung from the ceiling. Now that you are aware they need cleaning, it is time to find that manual and get started cleaning your unit.
Here is a good HRV YouTube video to get you started on cleaning your system: https://www.youtube.com/watch?v=pxjwM_P_J14
Chuck retired from an engineering management career to start a home inspection business