What does MERV rating mean?
A MERV rating tells you, on a scale of 1-16, how effectively your filter traps the small particles you don’t want circulating through your home. The higher a MERV rating, the higher the amount of particles the filter traps.
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) established the ratings system in 1987. Each filter’s rating represents its lowest possible performance, meaning every MERV rating answers the question, “worst case scenario, how many particles will this filter trap?”
MERV 8 pleated filters are made with synthetic media. They catch small particles and allergens, between 3-10 microns in size. They are a decent upgrade from cheaper disposable products.
MERV 11 pleated filters are also made with synthetic media and are step up from Merv 8, without a significant price increase. A very good upgrade, providing good indoor air quality.
MERV 13 pleated filters are also constructed with synthetic media. Excellent filtration however, not suitable for most hvac systems due to air flow resistance. Check with your furnace manufacturer to ensure that your system is designed for this type of filter.
So should I buy filters with high MERV ratings?
You’d prefer a 5-star hotel to a 2-star hotel but should you prefer a filter with a MERV rating of 16 to one with a rating of 9? Probably not.
If your filter has a high MERV rating, you know it’s highly effective in preventing things like pollen, bacteria and pet dander from circulating throughout your home; however, it may be overly effective in preventing air itself from circulating, which is a bad thing. The end result of less air circulation may be poorer overall air quality in your home. Furthermore, more resistance means more work for your HVAC system. If you’re using a filter with a MERV rating that’s not compatible with your system, inefficiency and high energy costs may be the result. Over the long-term if your HVAC system becomes overworked, you may be faced with costly repairs.
What MERV rating should my filter have?
The answer to this question will vary based on your HVAC system, but generally aiming for a MERV rating between 8 and 13 is ideal for the typical home. Remember, you should make sure your filter and your system work in harmony. Filters with high MERV ratings may remove more harmful contaminates from your home, but they may actually reduce the quality of the air you breath if you select a filter with a MERV rating that’s too high for your HVAC system. You’ll also have to change these filters more frequently than filters with a lower MERV rating.
HVAC system aside, you may be thinking 8 to 13 is a pretty wide range. If three families had identical HVAC systems in their homes that were compatible with filters that have a variety of MERV ratings, should they all be using the same type of filter? Once again, it depends.
Is this your Household?
Perhaps one household is comprised of two newlyweds who are working hard to jumpstart their careers. They have no time for pets, neither of them smoke and they rarely have guests over. They select an air filter with a MERV rating of 8. There are only two of them, they have no allergies, they don’t smoke and don’t often have guests over to bring in dust and dirt.
A family of five resides in the second household. The children are between the ages of 8 and 15. They’re all healthy kids who are into sports, and their parents enjoy hosting team dinners for each of their chilren, who have friends over often either way. They also have a young lab. They select an air filter with a MERV rating of 11.
No one in this family suffers from a breathing condition that would warrant buying a filter with a higher MERV rating, but more dirt, dust and other contaminants find their way into this home every time they have guests over. Lucy the lab joins the guests and family members themselves in churning up these contaminants within their home, and she leaves behind pet dander. They need an air filter that traps a few more particles than our first household, but they don’t need the highest level of protection.
Finally, a family of six lives in the third household. Everyone chips in to take care of Grandma, who lives with them, and has emphysema. They don’t have any pets because the children seem to have the same allergies that their mother does, but occasionally host friends and family. They select an air filter with a MERV rating of 13. Because most of the family have allergies and the grandmother has a severe breathing problem, and because there are six people bringing contaminants in as opposed to one or two, a relatively high MERV rating is in their best interest.
Do some research about your system to find out what MERV rating is ideal for you. And, don’t forget to change your filters, otherwise the MERV rating will be the least of your worries!