K&N and possibly others make dense washable filters - much better than the green or blue style you see at big box stores. You can spray simple green (or another safe cleanser like that) on the back, and then quickly hit it with hot tap water and let it soak.
20"x20" is ~$30 iirc. for people interested in this style of filter the fans don't last very long, maybe a year or two. They are ~$20+ each. I was buying the highest MERV without carbon for a long time, then i switched to carbon and fiber washable ones, then K&N.
Not an endorsement of K&N in particular, i just know the brand and use them.
20"x20" is ~$30 iirc. for people interested in this style of filter the fans don't last very long, maybe a year or two. They are ~$20+ each. I was buying the highest MERV without carbon for a long time, then i switched to carbon and fiber washable ones, then K&N.
Not an endorsement of K&N in particular, i just know the brand and use them.