Why We Recommend MERV 8 for Most Homes
For most homes, a MERV 8 furnace filter is the right choice. It’s tempting to buy the highest-rated filter on the shelf, but filters above MERV 8 (like MERV 11 or MERV 13) are thicker and can choke the airflow through your furnace. That makes it work harder, raises your energy bills and can shorten its life. Here’s why higher isn’t always better.
What Is MERV?
The MERV rating measures a filter’s ability to trap airborne particles. Filters rated MERV 1–4 capture larger particles like dust and lint. A MERV 8 filter effectively traps pet dander, mold spores, and dust mites, making it a popular choice for residential use. Filters with ratings above MERV 8, such as MERV 11 or MERV 13, are designed for environments requiring stricter air quality control, like hospitals.
The Drawbacks of High-MERV Filters
- Increased Airflow Resistance
High-MERV filters are denser because they are designed to trap smaller particles. This density restricts airflow through your furnace, forcing the system to work harder to circulate air. Over time, this can strain the motor and other components, leading to increased wear and potentially costly repairs. - Reduced Energy Efficiency
When your furnace works harder to overcome the resistance caused by a high-MERV filter, it consumes more energy. This reduces the overall efficiency of your HVAC system, leading to higher energy bills. - Shorter Lifespan for Your HVAC System
Excessive strain on the furnace can shorten its lifespan. The harder your system has to work to move air, the faster critical components may wear out, leading to premature replacement costs. - Overkill for Most Homes
Most homes do not need the level of air filtration provided by filters with ratings above MERV 8. Unless someone in your household has severe allergies, asthma, or a medical condition requiring ultra-clean air, a MERV 8 filter provides sufficient protection against common pollutants without compromising system performance.
Balancing Air Quality and System Performance
For most residential settings, a MERV 8 filter strikes the perfect balance between air quality and HVAC efficiency. It traps the majority of harmful particles without causing undue strain on your system. If you’re concerned about indoor air quality but want to avoid the pitfalls of a high-MERV filter, consider the following:
- Regular Maintenance: Clean or replace filters according to the manufacturer’s recommendations (see how often to change your furnace filter). A clean MERV 8 filter will outperform a clogged higher-rated filter.
- Supplemental Air Filtration: If additional air filtration is needed, bypass style HEPA filters will improve indoor air quality further, without overburdening your furnace.
Your filter is also checked during your annual furnace maintenance.
- 99.97% efficient at .3 microns
- A human hair is 100 microns wide
- Spores and pollen are all larger than 8 microns
- A micron is 1/1000 of a millimeter, or less than 1/2 of 1/10,000 of an inch
Furnace Filters: Frequently Asked Questions
For most homes, MERV 8. It traps pet dander, mould spores and dust mites without restricting the airflow your furnace needs.
It can be. Higher-rated filters are denser, so your furnace has to work harder to push air through them. That can mean higher energy bills and more wear on the motor and other parts.
Minimum Efficiency Reporting Value. It’s a scale that shows how well a filter traps airborne particles. The higher the number, the smaller the particles it catches, and the denser the filter.
Check a 1″ filter about every 6 weeks and change it at least twice in the heating season and twice in the cooling season. A 4″ pleated filter should be changed at least once a year. Busy households with kids or pets may need to change it more often. More in Changing Furnace Filters.
Instead of a denser furnace filter, a bypass-style HEPA air cleaner can clean the air further without overworking your furnace. Call us at (519) 451-8910 to talk about the options.
