What Are Custom Air Filters And Why Would I Need Them?

If your HVAC system needs a non-standard air filter size or thickness, or you need to precisely control the air quality in your business due to environmental factors, a custom-designed air filter is the best solution. When a standard air filter doesn’t fit the slot in your HVAC unit, a custom-made alternative can be created that will outperform standard air filters, producing better airflow and filtration.

Are Custom AC Filters As Effective As Standard Filters?

When created with effective, high-grade materials, custom AC filters can match or exceed the quality levels of standard air filters. Custom AC filters meet compatibility requirements and can exceed industry standards for HVAC systems when properly constructed. When they decide to purchase custom air filters with appropriate MERV ratings, customers can use a custom filter to achieve superior performance and filtration.

Can Custom Furnace Filters Improve Air Quality In My Home?

Upgrading to a custom furnace filter can allow you to have a furnace filter that is made with materials like HEPA-grade fibers or activated carbon. By customizing the air filter you use, you can decrease the chance of airborne pollutants from circulating and benefit from the increased amount of clean air in your living space.

How Do I Measure For A Custom HVAC Filter?

To determine the size of the custom AC filter your system needs, measure its length and width. The smaller measurement should be listed first. Then measure the depth of your existing filter from front to back to assess its thickness. Combine all of these measurements in this format, L x W x D, or the proper filter size for your HVAC system.

How Often Should I Replace A Custom Air Filter?

Ensuring you replace your custom air filter every 1 to 3 months will maintain optimal indoor air quality and make sure your HVAC system operates smoothly. If your custom air filter clogs up or gets dirty, or discolored, replace it immediately so it won’t strain or damage your HVAC equipment. Commercial and industrial buildings or homes with pets may need to change their custom air filters more often.

What Types Of Materials Are Used In Custom Air Filters?

Custom air filters are made of a variety of materials that are strong and durable. Pleated filters have synthetic polypropylene and polyester fibers to capture airborne particles effectively. Lightweight fiberglass filters are a cost-effective solution for capturing larger contaminants, but don't provide a high rate of filtration compared to filters with high MERV ratings. If you want to neutralize odors, filters made with activated carbon can eliminate VOCs (volatile organic compounds) and smoke. Electrostatic filters attract microscopic organisms to keep your airspace healthier. Filters created with HEPA materials filter out 99% of bacteria, harmful pollutants, and allergens.

Are Custom Filters Available For Commercial HVAC Systems?

Commercial HVAC systems can use custom air filters to improve air purification and make their HVAC system more efficient. They can be engineered to fit when a company needs a filter with exact dimensions, a specific MERV rating, medical grade filtering, special applications that include odor control, reducing allergens, or for use in large-scale HVAC systems. Another advantage of custom air filters is that they can be created to comply with air quality standards.

How Does MERV Rating Affect Custom Filter Performance?

The MERV rating of a custom air filter can affect its ability to capture airborne particles. Custom filters with higher ratings act as a barrier to stop the spread of finer contaminants like dust, bacteria, pollen, and mold from circulating. While higher MERV ratings offer better air purification, when not correctly matched to the specific HVAC system, they can impede airflow, especially if they aren’t able to handle the resistance.

Can I Wash And Reuse My Custom Air Filter?

Some custom air filters are created to be reused and can be washed regularly to maintain their filtration capabilities, improving indoor air quality while ensuring better HVAC performance. If your filter is designed to be used repeatedly, following the instructions when you wash it will preserve its effectiveness. Not every filter is intended to be washed—cleaning a disposable or non-washable filter can damage fibers, reduce airflow, and affect filtration efficiency. Check your custom filter’s specifications before you attempt to wash it to verify if it's washable, reusable, or disposable.

Do Custom AC Filters Help Reduce Energy Costs?

Custom AC filters allow homeowners to select a MERV-rated filter that is best suited for their environment. Whether they want to eliminate odors, dust, allergens, or other pollutants, custom filters can be designed to address specific filtration needs. Using the right design, custom AC filters protect HVAC parts from accumulating large amounts of dust that can affect your HVAC equipment's longevity. Installing a custom AC filter is a good way to improve air quality and breathe healthier air.

Build Custom Air Filters for Commercial and Institutional Systems

Facility HVAC systems vary. We make filter to match.

Factory Filters Direct builds custom size air filters for labs, schools, hospitals, rental properties, and large facilities that require precise airflow control and dependable indoor air quality.

How to measure your filter

StepEnter your filter dimensions (actual) Length x Width x Depth

StepSelect your performance rating

MERV 8 CLEAN

Traps: lint, dust, mold spores

MERV 11 ALLERGY

Traps: pollen, pet dander, smoke, auto emissions

MERV 13 HEALTH

Traps: bacteria and virus carriers

Additional Info

Nominal Depth 1”

Actual Depth 3/4”

Nominal Depth 2”

Actual Depth 1 3/4”

Minimum Size

5” x 5”

Maximum Size

40” x 40”

Please Note: Due material limitations used to build a custom filter, we construct a double filter (two filters fused together) when any filter dimension is larger than 24.75” on both sides and or larger than 29.75” on one side. Please allow up to an additional five (5) business days for processing your custom filter order.

Custom filters are not eligible for return or refund.

How to Measure Your Filter

Steps 1 & 2

Measuring Length and Width (L x W). (If your filter is not a square, the smallest measurement goes first).

Step 3

Measure the thickness (Depth) of your filter from front to back.

Step 4

Put Your measurements together (L x W x D).

Actual Size

A filter’s true dimensions.

Example: 19.75” x 19.75” x 1”

Nominal Size

Rounded numbers used by manufacturers.

Example 20” x 20” x 1”

View Detailed Instructions

What’s the difference between actual and nominal size?

Actual Size

A filter’s true dimensions.

Example: 19.75” x 19.75” x 1”

Nominal Size

Rounded numbers used by manufacturers.

Example 20” x 20” x 1”

Learn More

Why Facilities Choose Factory Filters Direct

Engineered for Performance

Made to fit non-standard and legacy HVAC units
High-efficiency pleated media and rigid frames
Consistent performance you can plan maintenance around

Wholesale Value

Factory-direct pricing on case quantities
Streamlined reordering for maintenance teams
Reliable lead times and nationwide shipping

Trusted by: laboratories, hospitals & clinics, schools & universities, rental property owners, commercial and municipal facilities.

How to Order a Custom Filter

Measure the filter slot: record exact length, width, and depth.

Select MERV rating: match filtration to your environment (see guide below).

Choose case quantity: standard packs of 6 filters per case.

Place your order: built to spec and shipped from our U.S. facility.

Example	Nominal	Actual (Approx.)
Standard 1″ filter	20×20×1	19.75×19.75×0.75
Standard 2″ filter	20×20×2	19.75×19.75×1.75

Example

Nominal

Actual (Approx.)

Standard 1″ filter

20×20×1

19.75×19.75×0.75

Standard 2″ filter

20×20×2

19.75×19.75×1.75

MERV Ratings for Facility Environments

MERV	Recommended Use	Filtration Capability
MERV 8	General offices, schools	Dust, lint, pollen
MERV 11	Healthcare, education, mid-level particle control	Bacteria, mold spores, fine dust
MERV 13	Labs, high-sensitivity areas	Smoke, fine particles, allergens

MERV

Recommended Use

Filtration Capability

MERV 8

General offices, schools

Dust, lint, pollen

MERV 11

Healthcare, education, mid-level particle control

Bacteria, mold spores, fine dust

MERV 13

Labs, high-sensitivity areas

Smoke, fine particles, allergens

Specifications & Ordering Details

Sizes: From 5″×5″ up to 40″×40″

Depths: 1″ and 2″ (actual ~0.75″ and ~1.75″)

Oversize builds: Very large formats may be constructed as fused filters (adds 2–3 business days)

Case quantity: Sold in cases of 6

Lead time: Typical 5–7 business days; oversized add 2–3 days

Returns: Custom filters are made-to-order and not returnable

Build Custom Air Filters for Commercial and Institutional Systems

Facility HVAC systems vary. We make filter to match.

Additional Info

How to Measure Your Filter

Steps 1 & 2

Step 3

Step 4

Actual Size

Nominal Size

What’s the difference between actual and nominal size?

Actual Size

Nominal Size

Why Facilities Choose Factory Filters Direct

Engineered for Performance

Wholesale Value

How to Order a Custom Filter

Nominal vs. Actual Size (Use Actual Measurements)

MERV Ratings for Facility Environments

Specifications & Ordering Details

FAQs