Merv 8 is a great choice, the most anyone should go is Merv 11. These two help remove dust and whatever else they can pick up. I try to get 8's but sometimes stuck with 11. If I only had one return grill I would stick with 8.
HVAC Systems are not meant to be whole house air cleaning systems.
The main purpose of any filter was to keep the evaporator coils clean and that can be done with a cheap Merv 5 or less filter, such as flat panel fiberglass filters Merv 2 that can be bought at Home Depot or any dollar type store for $2 or so.
Most people will want to step it up and Merv 8 is a good compromise and if you must Merv 11 Other than that buy a real air cleaner made for the purpose of cleaning the air for your home. I actually think this is sound thinking as I do believe it will also keep your ductwork cleaner.
Most dont realize that even a merv 8 becomes more efficient as it's used, meaning it starts to accumulate dust and dander making the pore sizes smaller as it clogs.
If you're concerned with energy efficiency the lower the merv rating = less air restriction = better system efficiency.
True there are some very good high merv rated filters with low or even lower air restriction but good luck finding out which ones other than marketing. Even so, with that said, they will quickly pick up dust and dander and become more restricted.
GM mentioned the air grill return filters, they are a great choice, I had 4 in my last home, 2 - 14x14 and 2- 20 x 20.
Return grill filters can be bought in advertised sizes of up to 5 inches think if you have the room behind the grill. They arent cheap but if you only want to change twice a year good choice and the shear size means lower restriction.
I used a bunch of different manufacturers as I found the Honeywell pricey and not over all impressed with the quality feel compared to some others. With that said they arent easy to find in all sizes sometimes so take what you can get.
A good hard search on the internet you will be able to find different manufacturers by searching the filter size such as this (your filter size) x (your filter size) X 5 and as you search you can lower that "5" to "4" than "3"
Example = "return grill filter 20x20x5"
No filters are their actual size in depth, meaning a 5 inch deep will be 4.5, some even 3.5 I think Honeywell has been marketing one at 3ish inches saying it's as efficient as a 5 inch.
One thing to keep in mind is like anything now a days, your mind is being controlled by corporations and most dont even know it. Dress up a product that has been made for 70 years that used to cost less then 50 cents and build it up, specialize it, make it sound great, even if its not great for your HVAC system and sell it for $15 at a 500% markup when you can buy one still to this day for $2.50
Im not saying go out and put in $2.50 filters but I am saying your system will be more happy with the $2.50 filter than that of some more restrictive filters.
I personally think Merv 8 changed every three months is a great choice. I buy them at the best prices I can find on the Internet.
Just bought two 6 packs of standard 1 inch for our new home as we have two different sizes. I haven't decided if I will go to the larger 4 to 5 inch in this home or just change the current 1 inch ones at 3 months max.
Im not an Amazon fan and I order from all kinds of places by doing internet searches. With that said my last order was from Amazon and I am happy with the price/quality of these filters. I have the Merv 8s I have two sizes and ordered 6 packs. Happy with both but come next year when I order more I am loyal to no one if I find what I think maybe better but these have impressed me favorably.
https://www.amazon.com/stores/page/844037A4-CAC3-4DD4-8274-1E7E1801FE98?
Another company that I used frequently was called "Filterbuy" can be bought on Amazon or direct at filterbuy.com just to stress I am loyal to no one but kind of into the filter thing and have used a lot of different brands except the store brands like filtrete and such. Im not someone sold on those department store prices and products and marketing. Not to say some products dont shave merit.
