Welcome to the Energy Efficiency Myths series from Direct Energy! As many myths arise from incomplete knowledge, they can create seemingly possible answers that many people accept as fact. Each month, we will examine common misunderstandings about energy efficiency — whether it’s in your home or about the energy industry — and deliver real facts behind the myth (and how they they might be costing you money).
Air filters are all the same. If it fits, it’s fine.
Air filters remove different sizes of particulates from the air before the air flows through the blower and into the the rest of your home. Not only do filters remove dust allergens, mold spores, and other contaminates from the air your family breathes, they also filter out fine dirt particles that can degrade the performance of the HVAC system itself.
Fine dust and dirt particles collect in the furnace’s heat exchangers and cooling coils, blocking air flow. If the air flow is choked off, the system will run longer to bring the home to the set temperature. Longer run times use more energy, cost you more money, and even worse — reduce the blower motor’s lifespan eventually leaving you an expensive repair bill. By using the manufacturer’s recommended Minimum Efficiency Reporting Value (MERV) filter, your HVAC system will be better protected from dust, dirt, wear and give longer lasting reliable performance.
Home HVAC air filters are graded by their MERV rating with most home filters falling between 1 and 13 (13+ are for HEPA filters).
- Spun fiberglass filters are the cheapest, minimum protection for HVAC equipment: 1-4 MERV.
- Disposable pleated paper or polyester filters: 5 to 7 MERV.
- Electrostatic self-charging cotton or paper fiber filters: 2 to 10 MERV.
- Pleated residential filters —specifically designed for their housing, 2 to 5 inches thick: 11 to 13 MERV.
- High-efficiency particulate arrestance (HEPA) more filtering out fine 0.3 micron particles: 13+ MERV.
All systems, homes, and air quality needs are going to be different. While cost is an important factor to consider, the goal is to find the right balance between air filtration for your family’s health, effective air flow, and energy efficiency.
High-rated air filters use more energy than lower-rated varieties.
At first blush, this sounds right. A higher MERV rated air filter can pick up finer bits of dirt from the air than lower rated ones so these high rated filters must be denser and thicker and thus harder to push air through. Blower motors will have to run longer to circulate the same volume of air as they would with a lower MERV rated filter. Sound legit, right?
Not exactly. A little over 10 years ago, manufacturers began putting in more pleats (or folds) into air filters and increasing their surface area. So, while the pleats offer thicker filter media, the increased surface area allowed more more free space for air to pass through. So, if you have two filters of equal length and width but the lower rated filter has 3 pleats per inch and the high rate filter has 9 pleats per inch, comparing airflow between the two might come up as a draw or even better for the higher rated filter.
Higher-rated air filters must be replaced more frequently
Not really. Because higher-rated air filters are constructed with pleats, they have more surface area per square inch than plain flat air filters. The higher the surface area, the longer the air filter can continue working. Some high rated air filters that are 2 to 5 inches thick have an operational life span of one year. Flat filters should be replaced every 3 months, or monthly if there are allergies, pets, or someone smokes.
Of course, as filters fill up with dirt, their airflow will drop and blower performance will decline. Over time, a blower fan might not have the power to work well with a higher rated filter, especially if it was designed only to use a medium rated filter. That’s why it’s important to only use air filters with the MERV rating recommended by your HVAC system’s manufacturer.
Do you know of any Energy Efficiency Myths you’d like us to dispel? Share with us in the comments!