Homeowners need to know about the issues that can arise when using a high MERV air filter. Oftentimes, the HVAC tech will install a system but will not necessarily coach the homeowner on how to properly maintain it. Proper maintenance is key to having a system that will operate properly and last for years to come.
What is MERV rating?
The MERV rating(Minimum Efficiency Reporting Value) measures how well a filter traps particles. These particles range from 0.3 to 10 microns. The typical MERV rating for residential HVAC systems is usually on a 1-13 scale. MERV 1 traps the least, while MERV 13 offers the highest filtration.
Isn’t high filtration better?
Filtering the indoor air is always a good idea. Typical indoor air can have pollutants such as mold spores, dust, pet dander & emissions. However, it’s not recommended to use your HVAC system for this because you will need a high-MERV air filter to capture most of these particles, which can put strain on the system. A system that is under strain will not perform well and definitely will not last!
Why does it strain the system?
Most HVAC systems installed in a home are single stage units. This means that the blower will run at one speed always. There are 2 stage systems and Variable Speed systems, but this article will focus on the more common single stage. A typical air handler(furnace) will have a rating at which the blower is listed for. This rating indicates the amount of total static pressure the system is designed to encounter. Many of these high merv air filters exceed this rating for pressure drop. This can add strain to the blower and even effect the refrigerant cycle which will put strain on the outside condenser.
Are all high merv air filters bad?
If you want to use a high-MERV air filter, you should consider having an oversized air filter installed. These filters come in thicker sizes, which range from 2″ to 5″. Increasing the filter thickness gives it more surface area. More surface area means better airflow, and better airflow means less of a pressure drop. These thicker air filters do come with a cost though as most filters will be 2-3x the price of your standard 1″ filter.
Other filter options
If you do not wish to use a high merv air filter in your hvac system you can still have clean air by running stand alone HEPA filters in your home. These stand alone units will let you place them in rooms that get the most use like a living room, bedroom or office.
If you or anyone you know is in need of a home inspection please feel free to call our office at 407-633-1661 or visit our online booking tool.