Type of Filters

    20″x20″x1″ or 20″x20″x2″ MERV 13 filters are recommended. MERV 13-A filters are available here.  Why 13-A? Because they are top of the line.

    If MERV 13-A filters are not available, the next filters recommended are MERV 13 filters from 3M .  Specifically, 3M 1900 filters are excellent (the people on the thread are IAQ experts) .

    These can gotten at:

    • Lowe’s
    • Home Depot
    • Walmart
    • Ace Hardware
    • etc.

    What is not recommended?

    FilterBuy’s filters sourced from Amazon. There have been knock-offs sold on Amazon, and so it is recommended to avoid those.

    Last tip – if you are making the 4 or 5 filter box, you could make the sides out of 20″x30“x1 filters – and get a huge gain in filter area. You can find 20″x30” filters at Walmart. Tip courtesy of ocnj of Twitter.

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