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Guide

New home / move-in furnace filter checklist

When you move in, replace the return filter before trusting the old one. Read the printed size on the frame; if the print is gone, measure and round up to the nominal. Pick a MERV your system can handle (MERV 8 vs 11 vs 13), then stock a spare so you are not stuck with a filthy prior-owner panel on day two.

Why change it on day one

You did not load that filter. Prior owners, vacant periods, renovation dust, and pets can leave a packed or collapsed panel in the slot. Central heat and AC usually share the same return — so a clogged filter hurts airflow whether you are cooling or heating. Carrier-style residential guidance puts thin 1-inch filters in a roughly 30–90 day band and thicker media cabinets around 6–12 months; a move-in check still beats waiting for the calendar. CNET’s year-round advice is to replace typical thin filters at least every three months, including summer — a fresh start when keys change hands is the same idea.

This page is equipment and fit care, not medical advice or health cures.

Move-in checklist

1. Find the filter slot — usually a wall or ceiling return grille, a furnace / air-handler cabinet door, or a deeper media cabinet beside the unit. Turn the system off before you pull the panel.
2. Read the printed W×H×T on the cardboard frame (e.g. 16x25x1). That rounded label is the size you order — not a custom cut of the tape reading.
3. Measure if there is no print — length, width, and thickness, then round face dimensions up to the nearest whole inch. Step-by-step: how to measure. Brand cuts differ for the same label — see the 1-inch actual-size chart.
4. Note thickness vs how often — 1-inch fiberglass / cheap flat often ~30–60 days; 1–2 inch pleats commonly ~60–90 days; 4–5 inch media cabinets often ~6–12 months. Details: how often to change a furnace filter.
5. Pick MERV your system can handle — overview of capture bands: MERV 8 vs 11 vs 13. Pets or common household allergens: pets / allergies. Do not assume MERV 13 on an unknown older blower without a tech check.
6. Match the household — seasonal spring/fall anchors: seasonal change reminder. Wildfire / smoky outdoor air: change sooner than the thickness band — wildfire smoke guide.
7. Odd printed size? — not 16x25, 20x20, or 20x25? Start at odd sizes.
8. Cabinet media (not a 1-inch grille filter) — deeper cartridges use model numbers. Common OEM pages: Honeywell FC100A1037 · AprilAire 210 / 213.
9. Install airflow arrows correctly — arrows on the frame point toward the blower / away from the return. Close the grille or door snugly.
10. Stock a spare of the same printed size and thickness so the next change is not a hardware-store scramble.

If the manufacturer sticker or equipment manual gives a different interval or MERV limit, follow that. Visual check (gray, packed, collapsing pleats) beats any calendar.

What NOT to do

• Do not guess size from tape alone without rounding up to the nominal shopping size. Ordering 15.75×24.75 as a custom cut is usually wrong — retail SKUs are sold as 16x25x1. Measure guide: /measure/.
• Do not assume MERV 13 on an unknown older system without checking what the blower and filter slot will tolerate. EPA’s upgrade language is MERV 13 or as high as the system can handle — ask a technician when unsure. Overview: /merv/.
• Do not leave a filthy prior-owner filter in place “until next season.” You inherit their dust load; swap it when you take possession, then set your own thickness-band schedule.
• Do not force the wrong thickness — a 1-inch pleat does not replace a 4- or 5-inch media cartridge (and vice versa).

What to buy next

This guide does not list pack prices — those move daily. Use your printed size and thickness, then open a money page for current merchant rows:

• Top 1-inch sizes — 16x25x1 · 20x20x1 · 20x25x1 · 16x20x1
• MERV 13 comparisons — 16x25x1 MERV 13 · 20x20x1 MERV 13 · 20x25x1 MERV 13 · rating overview: MERV 8 vs 11 vs 13
• Thicker media / brands — 16x25x4 · 20x25x4 · Honeywell FC100A1037 · AprilAire 210 / 213
• Related guides — How to measure · How often (thickness bands) · Seasonal change · Wildfire smoke · Pets / allergies · Odd sizes · All sizes

Full policy: disclosure.