To answer the question concisely, a 4-inch filter is usually the better choice. These thicker filters are proven to provide better air quality and will last longer. 

Now that we have established that, there are several factors that may determine which size filter is actually better for you

Some things to consider include the type of system you have, your maintenance preferences, air quality requirements, and budget. Below, we’ll discuss each of these aspects to help you decide if a 4-inch or 1-inch HVAC filter is the right choice for your home. 

HVAC System Requirements 

Your system is either set up for a 1-inch or a 4-inch filter. They are not interchangeable. This primarily dictates what size filter you should use. 

You cannot force a 4-inch filter into a system designed for a 1-inch filter. It could damage your HVAC system, and it will not provide the efficiency you would normally get from a 4-inch filter. 

Also, a 1-inch filter shouldn’t be used in a system that requires 4-inch filters. It won’t fill up the space, leaving gaps where impurities can get through. 

We should note, though, that you can have a professional come in and modify your system so that it will be compatible with 4-inch filters. If you are able to afford this added cost, we suggest that you make the switch so you can use 4-inch filters for even better air purifying capabilities. 

Maintenance Preferences 

4-inch filters don’t need to be changed as often, so if this is chore you don’t enjoy, you’ll have to do it less often with a 4-inch filter. 

Here’s why… 

Thicker filters have larger pleats. The result of this is more surface area in the same 2-dimensional space. These pleats can catch up to 5 times as many particles as a 1-inch filter. 

A 1-inch air filter needs to be changed every 30 days or so, while a 4-inch filter may last 3-6 months. Some are even rated for up to 12-months of use. 

The amount of time between your filter changes will be determined by the air quality in your home. Pets, high traffic, and low outdoor air quality can all affect the frequency of your filter replacements. 

Air Quality Needs 

If someone in your home has allergies or asthma, you need to pay close attention to the air quality inside your home. Your HVAC system air filters are a key factor in maintaining high air quality. 

How MERV Rating Impacts Air Quality

Not only will the thickness of your air filter matter, but the MERV rating of the filter will be very important as well. MERV is an acronym that stands for the minimum efficiency reporting value of an air filter. This measures how effective the filter is for small particles. 

A higher MERV rating means that the filter traps smaller particles (which is preferable, since these particles are often responsible for allergy and asthma flare-ups). 

A MERV rating of 16 or below is good. These filters are for general use in homes and businesses. Filters with a rating of 17-20 are usually reserved for operating rooms and anywhere else extreme measures need to be taken. 

How Air Filter Thickness Affects Air Quality 

An air filter with a high MERV rating will clog faster because it is trapping more particles. Therefore, a 1-inch air filter with a high MERV rating will clog very quickly. 

For this reason, you may want to opt for a 4-inch filter if a high MERV rating is important to you and your family. 

As a general rule, 4-inch filters have higher MERV ratings than 1-inch filters. They generally range between 8-16, while 1-inch filters start at a MERV rating of 1 and the highest you’ll find is around 13. 

The lowest rated 4-inch filter (MERV 8) would still be good enough to remove dust mites and most varieties of pollen, but if you have someone with respiratory issues in your home, you need an air filter with a rating of at least 13. 

This would remove smaller particles responsible for poor air quality, including the following: 

  • Pet dander
  • Some viruses 
  • Smog and outdoor smoke
  • Tobacco smoke
  • Bacteria
  • Mold and other fungi 

Budget Restrictions 

We recommend buying the best air filter you can afford once you have sorted through all the other factors. 

Again, MERV rating is going to affect cost more than the depth of the filter. To illustrate this point, the average high MERV filter (rated 8-16) will cost anywhere from $25-55, while you can purchase a low MERV filter (rated 1-7) for $5-20. 

That said, the depth of the filter will affect cost over time. 

Remember we said that 1-inch filters need to be replaced more frequently? So over the course of a year, you could end up paying more for less expensive 1-inch filters because you will need more of them. Meanwhile, the upfront cost of a 4-inch filter may be more, but you would potentially replace it just one time over the course of the same year. 

Unsure About the Air Filter You Need? 

If you still have questions about the right air filter for your home, we can help! Give Pure Air Mold Remediation a call and we can help you decide which size is right for you.