When we think about being comfortable in our homes, we often focus on our heating and air conditioning systems. But, they are not the only factors to consider in your home. Another key component to your indoor climate is your indoor air quality.

When looking at your indoor air quality, air filtration and purification systems are key.

Air filters work by having air pass through a filter that will remove particles from the air. They act as a sieve, capturing particles you don’t want flowing through your home.

Air filters will help remove airborne contaminants from your home’s air supply, which can include:

  • Dust

  • Dirt

  • Mold

  • Animal Fur

  • Bacteria or Other Microorganisms

Understanding MERV Ratings

Have you ever taken a close look at your HVAC filters when replacing them? If so, you may have noticed that each filter has a MERV rating -- and this number has important implications.

MERV stands for “minimum efficiency reporting value” and the MERV rating is a measure of how effectively a filter removes particles from the air that passes through it. The higher the MERV rating, the more particles the filter will catch.

There’s a flip side to this, though. Filters with higher MERV ratings generally feature denser filtration material, which means more force is required to push air through the filter. It takes exceptionally powerful HVAC fans to effectively push air through the filters at the high end of the MERV rating scale.

Find Your Number

If you use a filter with a too-high MERV rating in your home HVAC system, it could have the effect of using a dust-clogged filter -- air struggles to push through, which puts accelerated wear on your system’s fan and other components. This leads to more frequent service and repairs.

To make more thoughtful decisions about what type of filter to use in your home HVAC system, start by checking your system’s documentation for a maximum MERV limit. Using filters above the MERV limit will hurt your energy efficiency immediately and will likely cause more expensive problems down the line.

Once you know your available range of MERV ratings, consider whether there are signs you might need more filtration than you currently enjoy. Are there allergy or asthma sufferers at home? Do you have a shedding pet? Does your home seem abnormally dusty? If the answer to any of these questions is yes, you may be able to find some relief by upgrading to a filter with a higher MERV rating.

By The Numbers

MERV ratings range from 1 to 20. In residential HVAC systems, filters in the 1-4 range are most common, but it’s not unheard of for homeowners to use filters with MERV ratings as high as 8 in typical household systems.

Here’s a quick rundown of what filters of various MERV ranges are capable of filtering out of the air:

  • MERV 1-4: These filters catch large particles: dust, dust mites, pollen, carpet fibers, insects, and some of their waste. They’re primarily used in residential HVAC systems.

  • MERV 5-8: These filters are used in some homes and in most commercial and industrial settings. They can catch finer dust particles, mold spores, aerosol spray particles, and pet dander.

  • MERV 9-12: Rarely used in residences, these filters are common in certain commercial buildings and in some hospital laboratories. They can capture automotive emissions, welding fumes, lead dust and larger bacteria.

  • MERV 13-16: These heavy-duty filters are typical in hospital surgical centers and other areas where heavy filtration is paramount, such as smoking lounges. They collect a larger range of bacteria, smoke particles, oil droplets and fine particles from sneezing.

  • MERV 17-20: At the top of the scale, these filters are used in cleanrooms where pharmaceuticals and sensitive electronics are produced. They can catch viruses, carbon dust and the smallest smoke particles.

Why Does Your HVAC Filter Get Dirty So Quickly?

Responsible homeowners know to replace their HVAC system filters on schedule. But sometimes, “on schedule” just isn’t good enough. If you check your filter at replacement time and find that it’s completely covered in dust, hair and other particles, you might start wondering what causes it to clog up prematurely.

There are a few common causes of this, as well as a few things you can do to correct the problem:

  • Pet hair - If you have one or more shedding pets in the home, this is almost certainly contributing to your fuzzy filter. Daily vacuuming and weekly pet brushing can go a long way toward reducing this problem.

  • Your fan is set to “on” - There should be two fan settings on your thermostat -- “on” and “auto”. When the fan is set to “auto”, it only blows when your system is actively heating or cooling your home. But when it’s set to “on”, it runs continuously, which means air is passing through that filter 24/7. Switching to the other setting will help you get more life out of your filters.

  • Extreme temperatures - Even if your fan is set to “auto”, extreme hot or cold weather will keep your system running almost continuously. You may need to shorten your replacement intervals until the seasons change.

  • Your filter has a high MERV rating - The higher this rating is, the smaller the particles your filter can trap. An inexpensive fiberglass filter will let smaller particles pass through, so it won’t clog up as quickly as a thick, pleated filter that will catch those particles. Thicker isn’t always better -- it will make your home’s air cleaner and fresher, but it accelerates the wear on your HVAC fan and may lower your system’s energy efficiency. The filters themselves are also more expensive, and you may have to replace them more often. Your HVAC technician can help you weigh your options and choose the best filter for your system and situation.

  • Dusty home - Whether it’s from a recent home construction project or just accumulated dust in seldom-used rooms, anything you don’t vacuum up has a chance of ending up in the filter. If you need help, you can always call our friends at The Cleaning Authority.

A New Lease on Life

If your filter seems to fill up after just a couple of weeks, one step you can take is to vacuum off the surface of the filter. This doesn’t make the filter clean -- there are still plenty of particles trapped deep within the filtration media -- but it can remove a significant amount of hair and larger particles. It’s an easy step that can help stretch your filter for a few more days.

A more effective solution is to supplement your HVAC system with an air purification system. This system will remove any particles on its own before they can reach your HVAC filter. You should consider air purification if someone in your home has severe allergies or a respiratory condition, or if you have multiple pets. You can also switch to a reusable filter that can be cleaned regularly with a vacuum attachment or garden hose.

Let Us Help With Your Indoor Air Quality Needs

At One Hour Heating & Air Conditioning, we love helping our neighbors maintain healthy indoor air quality in their homes. Our local, experienced technicians are highly knowledgeable and skilled. We maintain a strict code of ethics, including high-level services, respecting our clients, and offering honest prices.

Contact us today to discuss your indoor air quality needs. We’ll ensure your family will breathe cleaner and healthier air.