Understanding MERV Ratings: Why MERV 8 Is Often the Smart Choice for Austin Homes

Back to Post 1: Breathe Easier This Spring in Austin: Why Indoor Air Quality Matters More Than You Think in our March Post Series

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​March in Austin means one thing: oak pollen everywhere. When allergies flare up, many homeowners think the solution is simple: "Let’s buy the strongest air filter possible." But when it comes to HVAC filtration, higher isn’t always better.
 
In this post, we’ll explain the term you see printed on every air filter: MERV. We’ll cover what it means, how it affects your HVAC system, and why MERV 8 is often the right choice for many Austin homes. We’ll also explain why installing a higher-rated filter without the right system setup can sometimes create new problems.
 
If you’re interested in upgrading your filtration system, we’ll cover that in Post 3: Upgrading Filtration in Older Austin Homes: The Right Way to Increase MERV. And we can still help you out before Post 3. Just give Bluebonnet A/C Services call at 512-470-6240! Or book online.

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Filter Maintenance Basics

​We all know the basics of HVAC filters. Changing filters regularly is critical.

For a typical Austin home, the guidelines for filter changes are:
1-2 inch filters: replace about every month
4-6 inch filters: replace about every 4-6 months

​Depending on what happens in your home or during heavy pollen seasons, you might need to change your filters more often. But what about that number on the side of just about every filter you buy? What does MERV mean?

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What Is MERV?

MERV stands for Minimum Efficiency Reporting Value. It’s a rating system developed by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) to measure how effectively an air filter captures particles.
 
MERV ratings range from 1 to 16 (or higher for more specialized systems). Higher numbers mean the filter captures smaller particles, but they also restrict airflow more. Here’s a simplified breakdown:

For years, MERV 8 has been the industry standard for residential air filtration. But you’ll commonly see MERV 11 and even as high as MERV 13 filters in your local hardware store. You might also hear these higher MERV ratings referred to as “air cleaners” instead of “air filters.
 
When we talk about filtration for this article, we’re focusing on filters installed in your HVAC system, not standalone air purifiers. For additional background, the U.S. EPA has helpful guidance on residential filtration.

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Why We Often Recommend MERV 8

​For many Austin homes, MERV 8 strikes the right balance between filtration and airflow. MERV 8 filters:

• Capture most pollen
• Capture most mold spores
• Protect equipment from these particles
• Maintain airflow by not being too restrictive

 
A MERV 8 filter captures about 70-85% of particles sized between 3 and 10 microns, which includes the particle sizes most commonly found in our area’s pollen and mold. Just as importantly, MERV 8 usually allows your system to maintain proper airflow. And airflow is critical for HVAC performance.

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Why Airflow Matters

We know that air filtration is important. The American Lung Association emphasizes consistent filter maintenance as critical to a healthy home. But airflow is an important partner to filtration. NIOSH (National Institute for Occupational Safety and Health) emphasizes that filtration effectiveness depends on proper airflow conditions.
 
Remember from Post 1 that your home is a system? Your HVAC system is designed to move a certain volume of air through the ductwork and into your rooms. The air must pass through:

• The air filter and return ducts,
• The blower (indoor fan) and indoor coil,
• The supply ducts,
• And finally into your rooms.

​To move air, the blower motor creates pressure inside the duct system. This resistance to airflow is called static pressure. An easy way to think about static pressure is like blood pressure for your HVAC system.

• Too low → not enough air moves through the house
• Too high → the system has to work much harder

When static pressure is in the right range, your system can move air efficiently and operate the way it was designed.

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What Happens When Static Pressure Is Too High?

Typically in Austin, TX, we see more systems that have problems with high static pressure than low static pressure, so we’re going to focus on high static pressure issues here. The most common reasons we see for high static pressure are:

• Dirty filter.
• Dirty evaporator coil or blower wheel.
• Fan speed was never optimized and is too high.
• Ductwork is undersized.
• Not enough return area or a filter that is too restrictive for the existing return area.

 
High static pressure can lead to:

• More wear and tear on your system. Motors work harder and wear down faster.
• Lower energy efficiency. Your system uses more electricity to move air.
• More duct leakage.  If your supply ducts are leaky, more conditioned air will be pushed into your attic where it doesn’t help cool your home.
• Potentially worse indoor air quality. If your return ducts leak, dusty attic air may get pulled into the system without ever going through the filter.

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The Takeaway

If your system was designed for higher MERV filtration – by all means, use it! Better filtration in this case means better indoor air quality.
 
But if you’re unsure, MERV 8 is usually a safe and effective choice for many Austin homes. It captures most of the particles that matter locally without creating unnecessary airflow restrictions.
 
If you’re considering higher-MERV filtration but want to make sure your system can handle it, Bluebonnet AC Services can help evaluate your setup and recommend the right approach for your home.
 
And next week in Post 3, we’ll walk through the right way to upgrade filtration in older Austin homes.

​Call 512-470-6240 or book online to schedule an evaluation.