The MERV scale runs from 1 to 20 with the bigger numbers for scientific clean rooms and hospitals and the lower values for residential use, usually a value between 4 plus 12
I’m 1 of those people who get intimidated at stores like Ace Hardware or Home Depot. It doesn’t help that I use a Phillips screwdriver to open beer bottles and that is about it. I’m simply clueless about all things mechanical. Everyone, though, needs to know a few basic things and knowing how to change your Heating and A/C filters is 1 of them. Even I can remove a respected size filter and take it with me to the hardware store. I then tell them I want this exact HVAC filter and they hand it over. But if you don’t have a model to supply the worker wearing the blue apron, then you need to be prepared with some information. The first thing to know is the difference between the nominal size plus larger size. And that difference is usually a half on the width plus length dimensions to allow for clearance around the perimeter. So, if the filter packaging gives a nominal size the thickness remains unchanged. Most people are happy with the respected cheap Heating and A/C filter, but some people will need or desire a better filter. And at this point, you will want to be acquainted with MERV ratings. Not your cousin Merv who consistently needs a loan, but the Minimum Efficiency Reporting Value. The MERV scale runs from 1 to 20 with the bigger numbers for scientific clean rooms and hospitals and the lower values for residential use, usually a value between 4 plus 12. Higher MERV ratings cost more money but the added benefits for those with respiratory problems and smokers make it worth the extra cost.