Piedmont Filter Co.(704) 237-0572
Fig. 01
What your filter is up against, by sizeA logarithmic scale of airborne particle size from 0.3 to 100 microns, showing PM2.5 combustion particles at roughly 0.3–2.5 µm; pet dander at roughly 0.5–10 µm; mold spores at roughly 3–40 µm; household dust at roughly 1–100 µm; pollen grains at roughly 10–100 µm; human hair (for reference) at roughly 50–70 µm. Capture ranges are marked above the scale: MERV 8 addresses particles down to about 3 µm, MERV 11 addresses particles down to about 1 µm, MERV 13 addresses particles down to about 0.3 µm. Sizes are approximate and describe the range each type spans, not a single value.MERV 8down to 3 µmMERV 11down to 1 µmMERV 13down to 0.3 µm0.312.51050100particle diameter, microns (µm), logarithmicPM2.5 combustion particles0.3–2.5 µmPet dander0.5–10 µmMold spores3–40 µmHousehold dust1–100 µmPollen grains10–100 µmHuman hair (for reference)50–70 µm
A logarithmic scale of airborne particle size from 0.3 to 100 microns, showing PM2.5 combustion particles at roughly 0.3–2.5 µm; pet dander at roughly 0.5–10 µm; mold spores at roughly 3–40 µm; household dust at roughly 1–100 µm; pollen grains at roughly 10–100 µm; human hair (for reference) at roughly 50–70 µm. Capture ranges are marked above the scale: MERV 8 addresses particles down to about 3 µm, MERV 11 addresses particles down to about 1 µm, MERV 13 addresses particles down to about 0.3 µm. Sizes are approximate and describe the range each type spans, not a single value.
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Charlotte, NC

The right filter, the right size, on the month it is actually due.

Filters are cheap, easy, and almost universally forgotten. Piedmont Filter Co. delivers the exact size your system takes, on a schedule built around the Charlotte pollen and cooling seasons rather than a generic 90 days.

Delivery across Charlotte, Matthews, Mint Hill, Pineville, Huntersville, Cornelius, Davidson, Concord, Indian Trail, Waxhaw, and Belmont.

Find your sizeSee all sizes

Not open for orders yet. Each size page has a notify link.

01

How it works

  1. 01

    Find your size

    Read it off the frame of the filter in your system, or measure the opening and use the size finder.

  2. 02

    Pick a MERV rating

    MERV 11 is the right default for a 1 inch slot. MERV 13 if you have a 4 or 5 inch media cabinet.

  3. 03

    Choose a cadence

    Every 1, 2, or 3 months, or a single one-time order. Change or cancel by email or phone, any time.

More on subscriptions, delivery, and cancellation

02

The sizes most Charlotte houses take

If you are guessing, start with 20x25x1 or 16x25x1. Both are extremely common. Then go check the frame.

  • 20x25x1

    The most common size in American homes overall. Standard on a great many gas furnaces.

  • 16x25x1

    One of the two most common residential sizes in the country. Check here first if you are guessing.

  • 20x20x1

    The other extremely common size. Square wall and ceiling returns in almost every era of house.

  • 16x20x1

    Compact systems and secondary zones. Shows up in condos, townhomes, and bonus-room units.

  • 20x25x4

    The most common 4" media cabinet size. Sits directly against the air handler in the return plenum.

  • 20x25x5

    A 5" cabinet, typically installed with the system rather than added later. Deeper pleat, longer service interval.

All 16 sizes, grouped by depth

03

From the guide

What actually gets pulled into your HVAC system in Charlotte?

Your return vent pulls in whatever is already floating around inside the house — tree and grass pollen that came in on clothes and through doorways, dust from carpet and drywall, pet dander and hair, fibers shed by bedding and upholstery, and fine particles from cooking and traffic.

It helps to know which way the air is going. The vents that blow cold or warm air at you are supplies. Somewhere else in the house — usually a large grille in a hallway wall or ceiling, or a slot at the furnace itself — is the return, and the return is an intake. Every cubic foot of air your system moves gets sucked through that opening, pushed through the filter behind it, run across the coil, and blown back out into the rooms. The same air goes around that loop again and again all day.

That loop is why the filter matters more than its price suggests. It is the one point in the circuit where a particle can be removed rather than just relocated. A vacuum moves dust that has already landed. The filter takes it while it is still in the air.

Read the full guide: charlotte air quality and your air filter