Suggested MERV rating for filters?

[Jadnashua]

I have allergies, and have been using MERV 12 filters in my HVAC system. They help. Any suggestions on whether that is a reasonable value or not? I've not had any issues with the coils freezing up or lack of response (unless I forget to replace the thing, and then maybe slightly!).

I usually buy them by the dozen, and it's time for a new batch.

 

[WorthFlorida]

I use MERV 8 as to me they are cost effective. If MERV 12 works for you stay with it. I've read that above MEER 12 there can be too much flow restrictions though I never tried any. After I finish with my batch of MERV 8 filters I'm going to try them for my wife. She doesn't have bad allergies but sometimes complains about her sinuses.

If you suffer from bad allergies and can't get enough relief, the best is an electronic air filter. We had one installed in our Illinois home for my kid. During the heating season he would cough 24/7 and in his sleep. It made a huge difference and the dust it collected was amazing. I had to wash the grid once a week for a month or two before the house would clean up a bit. Here in Florida for my granddaughter, when she was a baby, we bought stand alone HONEYWELL HEPA filters. For my wife I have a Therapure HEPA filter with a UV light. I seems to help her. It does reduce the amount of dust that will accumulate on the ceiling fan blades. In Florida, just about every house in every room has ceiling fans.

 

[Sponsor]

 

[Dana]

MERV 4 is "good enough" for removing pollen, MERV 8 will take care of mold spores. At MERV 12 almost all dust, and even bacteria-sized pathgens will be filtered out. (At duct velocities <300 feet per minute even some of the PM2.5 would be handled by MERV 12 filters.)

So, if the air flow isn't too restricted, sticking with the MERV 12s is fine. With 1" thick MERV 12s you're more likely to run into air flow issues than with oversized thicker pleated filters.

With 4-6" deep pleated filters there is usually no need to swap out the filter media more than once per year, unless you live in an ultra-high pollen zone or some soot-belching industrial hell. In my home I have an hydronic air-handler + AC coil zone fitted with an AprilAire 2400 (16" x 28" x 6" deep) filter, and I've even forgotten to swap it out for 18 months or more without exhibiting air flow issues such as coil icing up on the AC or in ability to deliver design-day heat, even when using MERV 11 or MERV 12 filter media.