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If you have walked into a hardware store looking for a furnace filter and found nothing that matched, this is why: the common mobile home furnace filter size is a quarter-inch-thick foam panel — typically 16 × 26, 19 × 36 or 19 × 54 inches — and almost no home center stocks them.
Your furnace does not take the 1-inch pleated panel everybody else buys. Here is the full list of sizes, where the filter actually lives, and how to measure yours.
Where your filter actually is
Before the size, the location. In a site-built house the filter usually sits in a slot at the air handler or behind a return grille in a hallway ceiling.
In a manufactured home — built to the federal standard summarized in HUD’s own homeowner resources — the furnace is normally a downflow unit in a closet, and the filter is usually mounted inside the furnace door itself — a thin foam sheet held in place by wire retainer clips. Open the closet, open the furnace door, and look at the back of the door panel.
That is why it is thin. It has to fit inside a door panel, not in a slot.
Some homes instead use a hoghair filter — a coarse, springy fiber pad, often grey or green — sitting flat in a return opening. Same idea, different material.
The common mobile home furnace filter sizes
These are real part sizes sold by manufactured housing suppliers. Thickness is a quarter inch on all the foam ones.
| Type | Size | Typical part no. | Fits |
|---|---|---|---|
| Foam door filter | 1/4″ × 16″ × 26″ | F-10 | Many Miller, Nordyne, Nortek, Intertherm, Broan and Maytag furnaces |
| Foam door filter | 1/4″ × 19″ × 36″ | F-20 | Coleman Evcon and many Intertherm units |
| Foam door filter | 1/4″ × 19″ × 54″ | F-30 | Larger Miller / Intertherm units |
| Foam roll | 1/4″ × 24″ × 25 ft | F-25 | Cut to size for anything non-standard |
| Hoghair pad | 14″ × 20″ | P-1420 | Return-opening installations |
| Hoghair pad | 16″ × 20″ | P-1620 | Return-opening installations |
| Hoghair pad | 19½” × 21¾” | P-2022 | Return-opening installations |
| Hoghair pad | 19½” × 28″ | P-2028 | Return-opening installations |
Prices run from about four dollars for a small hoghair pad to sixteen or so for the largest foam panel. Filter-and-retainer kits, which include the wire clips that hold the foam in place, cost roughly twice the filter alone.
If nothing on that list matches, buy the 24-inch roll and cut your own. That is what it exists for, and it is the cheapest way to keep a non-standard furnace filtered.
How to measure yours
Do this rather than guessing from your furnace model, because the same model was built over many years with running changes. Your data plate lists the furnace that was fitted at the factory, which is a better starting point than the label on the unit.
- Kill the power at the breaker before opening anything.
- Open the furnace closet, then the furnace door. If the unit in there is not one listed for manufactured housing, that is a separate and more serious problem.
- Take out the old filter. If there isn’t one, measure the inside of the door frame or the retainer clips, not the outside of the door.
- Measure height × width, then the thickness.
- Round to the nearest common size from the table. Foam filters are meant to be a snug friction fit, so a quarter-inch under is fine; a quarter-inch over is not.
Write the size on the inside of the closet door with a marker. You will thank yourself in six months.
Can you use a regular pleated filter instead?
Short answer: no, and it is not just a fit problem.
A one-inch pleated filter is far denser than a quarter-inch foam panel. Mobile home furnaces are compact downflow units with blowers sized for a low-resistance filter. Put a high-MERV pleated filter in front of one and you restrict airflow, which at best makes the furnace work harder and at worst trips the limit switch and short-cycles the unit.
If you want better filtration than plain foam gives you:
- Use an electrostatic washable panel cut to your size, which filters better than plain foam without the pressure drop of a pleated panel.
- Or address air quality with a standalone room air purifier rather than by choking the furnace.
Do not stack two foam filters. Same problem, less obvious.
How often to change it
Foam and hoghair filters are washable, which is the point of them. Rinse in warm water, let dry completely — completely — and reinstall.
- Heating season: check monthly, wash when it looks grey rather than white.
- With pets or a smoker in the home: check every two to three weeks.
- Replace outright once the foam starts to crumble or tear at the edges, usually after a couple of seasons.
A collapsed or torn filter is worse than none, because the gap lets debris straight onto the blower wheel and the heat exchanger.
Common questions
My furnace has no filter at all. Is that normal?
It is common in older homes where the original fell apart and was never replaced. It is not fine. Measure the retainer clips and fit one.
Is the mobile home furnace filter size different between a single-wide and a double-wide?
Not by width class — it follows the furnace, not the home. A double-wide is more likely to have a larger unit and therefore the 19 × 54, but measure.
Can I buy these locally?
Rarely at a general home center. Manufactured housing parts suppliers stock them, and most sell online.