Box vs. Header Style Filters: What's the Difference?

Rigid filters are a go-to choice for commercial and industrial HVAC systems due to their strength, durability, and high dust-holding capacity. But when it comes time to choose one, you'll often see options like Box Style, Single Header, and Double Header. What’s the difference, and why does it matter?

Let’s break it down.

Box vs. Single Header vs. Double Header

Rigid filters may all serve the same core purpose, capturing particulates and protecting HVAC systems, but how they’re framed can have a major impact on installation and performance.

The three most common styles are Box, Single Header, and Double Header. These terms refer to how the filter is constructed on the ends that face the direction of airflow.

Here’s a quick breakdown of each configuration:

• Box Style: A simple frame with no header on either side.
• Single Header: A filter with a header on one side - typically the air entering side.
• Double Header: A filter with a header on both the air entering and air leaving sides.

These headers aren’t just cosmetic. They affect how the filter is installed and secured in the system. So choosing the right style depends largely on how your system is designed and which types of air filters work best for your setup.

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Box Style Filters

Box style filters are rigid filters built with no header on either side, just a durable frame enclosing the filter media.

This headerless design makes them a popular choice for face-loading systems, where filters are installed directly into the frame or housing from the front, allowing air to flow through the face of the filter.

These systems don’t use a track to guide the filter in from the side, so the filter must be manually positioned and secured. Because box filters lack the extra structure provided by a header, they rely on external hardware to stay in place.

Most commonly, installers use filter clips or retaining brackets to lock the filter securely into the housing. These clips grip the edges of the filter frame, preventing it from shifting or rattling during system operation.

In addition to clips, some systems may also use gaskets or foam seals around the edges of the filter to ensure a tight fit and prevent air bypass. When installed correctly, box filters can deliver excellent performance and efficiency, even in high-velocity systems.

Advantages of box-style filters include:

• Simple, economical design
• Compatible with most face-loading housings
• No need for side rails or tracks

Box-style filters are widely used in commercial and industrial environments, especially where simplicity, versatility, and cost-effectiveness are priorities. However, because they require manual placement and securing hardware, proper installation is critical to ensuring optimal filtration and system performance.

Single Header Style Filters

Single header filters include a header on one end, typically the air-exiting side, while the opposite end remains a simple frame.

The header adds structural support and provides a standardized edge that slides into side rails or tracks within the filter housing. This makes single header filters ideal for side-access systems, where filters are loaded horizontally or vertically along a rail system.

In these systems, the header helps ensure consistent alignment and a tight seal against the gasketed surface inside the housing. This reduces the chance of air bypass and improves overall system efficiency, especially in high-performance HVAC units.

Single header filters are easier to install and replace than box filters in track-based systems because the header guides the filter into position. Once inserted, the header end forms a stable, secure seal while the open frame side fits snugly within the housing.

Advantages of single header filters include:

• Improved stability and sealing
• Easy installation in track systems
• Reduced risk of air bypass
• Standardized fit for common housing styles

Single header filters strike a balance between structural rigidity and installation convenience, making them a go-to option for commercial HVAC systems designed around rail-guided filter banks.

Double Header Style Filters

Double header filters feature a header on both the air-entering and air-leaving sides, creating a fully enclosed, reinforced design.

This dual-header construction provides maximum structural integrity and sealing surface, making double header filters well-suited for demanding environments with high airflow velocity or pressure fluctuations.

Thanks to their robust design, double header filters are compatible with both face-loading and side-access systems. In face-loading applications, the dual headers help center and stabilize the filter within the housing. In track systems, the headers on both ends glide smoothly into place and form a reliable seal on either side.

The extra rigidity also reduces flexing or bowing over time, which helps maintain consistent filter performance and minimizes the risk of air bypass.

Advantages of double header filters include:

• Enhanced strength and durability
• Tight seals on both ends
• Versatile use in various system types
• Ideal for high-pressure applications

While double header filters are often more expensive than single header or box styles, their added durability and flexibility make them a smart choice for critical systems where performance and longevity are top priorities.

Which Is Right for You?

Choosing the right rigid filter style depends entirely on the design of your HVAC system, not personal preference. Selecting the proper style plays a direct role in improving indoor air quality.

Side-access system? You’ll likely need a Single or Double Header filter.

Face-loading system? A Box or Double Header filter might be best.

Ultimately, the safest and most cost-effective choice is to have an HVAC professional evaluate your system. They’ll know what your equipment was built to accommodate and can recommend the best filter style for performance, fit, and longevity.

Need help navigating your options? Our team has decades of experience helping businesses and facility managers choose the right filtration solutions. Reach out anytime, we’re here to help.