HVAC Filters Explained: Types, MERV Ratings, and Selection
Your HVAC filter is your home's first line of defense against airborne particles. Understanding filter types, ratings, and maintenance requirements helps you maintain good air quality and protect your HVAC system.
Types of HVAC Filters
1. Fiberglass Filters
- Description: Flat, disposable panels
- Pros:
- Very affordable
- Good airflow
- Widely available
- Cons:
- Basic filtration only
- Short lifespan
- Limited particle capture
- MERV Rating: 1-4
2. Pleated Filters
- Description: Folded material design
- Pros:
- Better filtration
- Longer lifespan
- More surface area
- Cons:
- Higher cost
- More air resistance
- MERV Rating: 5-13
3. Washable Filters
- Description: Reusable mesh design
- Pros:
- Cost-effective long-term
- Environmentally friendly
- Durable construction
- Cons:
- Regular cleaning required
- Limited filtration
- Higher initial cost
- MERV Rating: 1-4
4. High-Efficiency Filters
- Description: Dense media filters
- Pros:
- Superior filtration
- Captures small particles
- Better air quality
- Cons:
- Highest cost
- May restrict airflow
- Not suitable for all systems
- MERV Rating: 14-16
Understanding MERV Ratings
MERV Rating Scale
| MERV Rating | Particle Size | Typical Use |
|---|---|---|
| 1-4 | ≥ 10.0 μm | Basic residential |
| 5-8 | 3.0-10.0 μm | Better residential |
| 9-12 | 1.0-3.0 μm | Superior residential |
| 13-16 | 0.3-1.0 μm | Hospital/Healthcare |
What MERV Ratings Filter
- MERV 1-4:
- Pollen
- Dust mites
- Carpet fibers
- MERV 5-8:
- Mold spores
- Hair spray
- Cement dust
- MERV 9-12:
- Lead dust
- Auto emissions
- Welding fumes
- MERV 13-16:
- Bacteria
- Tobacco smoke
- Sneeze droplets
Choosing the Right Filter
System Considerations
- Check System Specifications:
- Maximum MERV rating
- Filter size requirements
- Airflow requirements
- Consider Your Needs:
- Allergies/asthma concerns
- Pets in home
- Local air quality
- Budget constraints
Size and Fit
- Measuring Guide:
- Length x Width x Depth
- Check actual vs nominal size
- Consider thickness limitations
- Common Sizes:
- 16x20x1 inches
- 20x20x1 inches
- 16x25x1 inches
- 20x25x1 inches
Filter Maintenance
Replacement Schedule
- 1-inch Filters:
- Every 1-3 months
- Monthly if pets present
- Check monthly during peak seasons
- Thicker Filters:
- 3-6 months for 2-inch
- 6-12 months for 4-inch
- Monitor condition regularly
Signs of Filter Replacement
- Visible dirt accumulation
- Reduced airflow
- Increased energy bills
- More dust in home
- System running longer
Filter Installation Tips
Proper Installation
- Direction:
- Follow airflow arrows
- Arrow points toward unit
- Check proper orientation
- Secure Fit:
- No air gaps
- Proper frame contact
- Secure filter cover
Common Mistakes
- Wrong size selection
- Incorrect orientation
- Skipping replacement
- Using damaged filters
- Improper sealing
Improving Air Quality
- Beyond Filtration:
- Regular cleaning
- Proper ventilation
- Humidity control
- Source control
- Additional Solutions:
- Air purifiers
- UV-C lights
- Whole-house filtration
- Regular duct cleaning