Case studies2 min read

How Often Should You Replace Your Furnace Filter?

A clean filter protects your blower, keeps air flowing, and helps your furnace run efficiently. Here is a practical schedule for Vancouver-area homes.

Clean furnace filter next to HVAC equipment — Sub Zero Temp Control

Your furnace filter is the first line of defense against dust, pet hair, and debris. When it clogs, airflow drops, the system works harder, and you risk overheating or frozen coils on paired heat-pump setups.

General rule of thumb

  • 1 inch disposable filters: check monthly; replace every 30–60 days with pets or carpet.
  • Thicker pleated filters (4–5"): often 6–12 months, but still verify monthly.
  • High-MERV filters: capture more particles but restrict airflow more — follow the manufacturer max and your technician’s guidance.

Pacific Northwest considerations

Wet winters mean more indoor time and tighter homes. If you run the fan continuously or have allergies, shorten the replacement interval.

Quick test

Hold the filter up to a bright light. If you cannot see light through the pleats, it is time to swap it.

Not sure which filter fits your system? Our techs note the correct size during maintenance visits so you always have the right match.

Need an honest second opinion?

Every option, not just the expensive one.

If you’ve been told your AC or furnace needs replacement and want a thorough, no-pressure diagnosis, give us a call. We serve Vancouver, WA and all of Clark County. We’ll tell you exactly what’s wrong, show you the numbers, and give you every option.

What neighbors say

Neighbors, in their words.

5.0Google rating · 460 reviews
★★★★★

I highly recommend this honest business! Our hallway control panel went completely dark, and the repairman quickly found a loose wire behind the drywall, restoring our heat in minutes.

WWilliam P.Google · Oct 2026
★★★★★

My central air completely froze over with ice during a humid weekend, but the tech from Sub Zero came out fast to thaw and fix the refrigerant leak. Everything is running perfectly now, and the house is finally comfortable again!

OOwen P.Google · Oct 2026
★★★★★

Our air stopped working completely and we panicked. The repair guy came over quickly and figured out the wall thermostat just needed new batteries. He swapped them out, checked the rest of the system to be safe, and didn't overcharge us. Very honest and simple service. Highly recommend!

IIan U.Google · Oct 2026

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