Rooftop Unit (RTU) Air Filters
Rooftop units typically use 2" or 4" pleated filters in standard sizes like 20x20x2, 20x25x2, 16x25x2, and 24x24x2. Specify MERV 8–11 for equipment protection or MERV 13 for occupant air quality, and confirm the unit's static pressure budget before going higher.
Common RTU filter sizes
- 20x20x2, 20x25x2, 16x25x2, 24x24x2 (2" pleated)
- 20x20x4, 20x25x4, 24x24x4 (4" pleated for longer life)
- Multiple filters per unit are common — count every slot when ordering
Choosing the right RTU filter
RTUs see harsh outdoor conditions — wind-blown dust, pollen, and debris. A 4" pleated filter lasts longer and resists airflow less than a 1" at the same efficiency, reducing rooftop maintenance trips. For occupied spaces, MERV 13 is the target where the unit's fan can handle it.
Frequently Asked Questions
What size filter does a rooftop unit use?
Most RTUs use 2" or 4" pleated filters in standard sizes such as 20x20, 20x25, 16x25, and 24x24. Many units hold multiple filters, so check the size printed on the existing filters and count the slots.
How often should RTU filters be changed?
Typically every 1–3 months for 2" filters and up to 6 months for 4" filters, depending on rooftop dust load. Pressure-drop monitoring gives the most accurate schedule.
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Need help choosing the right filter?
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