# HVAC Filter Guide: Types, Ratings, and When to Change
Your HVAC filter is the first line of defense for your system and your indoor air quality. Understanding filter options helps you make the best choice for your home.
Understanding MERV Ratings
MERV (Minimum Efficiency Reporting Value) rates a filter's ability to capture particles:
| MERV Rating | Captures | Best For |
|---|---|---|
| 1-4 | Large particles | Basic protection |
| 5-8 | Dust, mold spores | Most homes |
| 9-12 | Fine dust, pet dander | Allergy sufferers |
| 13-16 | Bacteria, smoke | Superior filtration |
| 17-20 | Viruses | Hospitals, clean rooms |
For most Bay Area homes, MERV 8-11 provides the best balance of filtration and airflow.
Filter Types
Fiberglass Filters (MERV 1-4) - Cheapest option - Protects equipment only - Replace monthly - Not for allergy sufferers
Pleated Filters (MERV 5-13) - Good particle capture - 90-day lifespan typical - Best value for most homes - Various MERV ratings available
HEPA Filters (MERV 17-20) - Hospital-grade filtration - May require system modification - Higher cost and more airflow restriction - Ideal for severe allergies
Washable/Reusable Filters - Higher upfront cost - Lower ongoing cost - Requires regular cleaning - Often lower MERV ratings
When to Change Your Filter
Standard Guidelines: - Fiberglass: Every 30 days - Pleated (1"): Every 90 days - Pleated (4-5"): Every 6-12 months - Washable: Clean every 30 days
Change more frequently if you have: - Pets (especially multiple pets) - Allergies or asthma - Recent home renovation - Wildfire smoke in the area - Dusty location or construction nearby
Bay Area Filter Considerations
Wildfire Season During fire season, consider: - Upgrading to MERV 13 temporarily - Checking filters weekly - Running system on fan mode for continuous filtration
Coastal Humidity Higher humidity can cause filters to deteriorate faster. Check monthly even if normally you'd wait longer.
Multi-Pet Homes Bay Area's pet-friendly culture means many homes need filter changes every 30-45 days.
Signs Your Filter Needs Changing
- Visible dirt buildup
- Reduced airflow from vents
- Increased dust in home
- Higher energy bills
- System running longer cycles
- Unusual odors
Choosing the Right Filter
Consider: - System compatibility (check size and type) - MERV rating appropriate for your needs - Replacement frequency you can maintain - Budget for ongoing replacement
Pro tip: Buy filters in bulk to save money and ensure you always have a replacement ready.
The Bottom Line
The right filter, changed regularly, protects your HVAC system and improves indoor air quality. For most Bay Area homes, a MERV 8-11 pleated filter changed every 60-90 days is ideal. Upgrade to MERV 13 during wildfire season for additional protection.