Koch Duo-Cube 3-Ply MERV 8 Cube Filters are high medium efficiency extended-surface synthetic cube filters built on a three-ply blend of progressively dense polyester media with anti-microbial treatment and integral steel wire support. The 3-Ply tier sits at the high-efficiency end of the Duo-Cube line — substantially better capture than 1-Ply or 2-Ply at the cost of marginally higher pressure drop, with the anti-microbial treatment as a meaningful upgrade for installations where biological loading on the filter media matters.
What a cube filter is (and where it goes)
Cube filters are extended-surface filters — the media is folded or pleated into a deep three-dimensional cube that increases the effective filtering surface area dramatically compared to a flat panel filter of the same face dimensions. A 24x24x12 cube has the same face footprint as a 24x24x12 panel, but several times more media area packed into that depth. This means longer service life, lower pressure drop at equivalent capture, and significantly better dust holding capacity.
Cube filters drop into side-load cube baskets, top-load racks, or front-load holding frames commonly found in commercial AHUs, packaged rooftop units, and larger industrial air handlers. Typically deployed as a final filter stage behind a panel prefilter, capturing what makes it past the prefilter while the deep pleated geometry extends service life.
What "3-Ply" means and why it matters
The Duo-Cube 3-Ply uses three layers of progressively dense polyester media stacked together — coarser media on the upstream side, finer media on the downstream side. This staged capture extends service life by distributing particle loading across all three layers rather than overloading the first layer the way a single-density filter does. The downstream-most layer captures the finest particles that make MERV 8 capture possible.
The integral wire frame creates a self-sealing design — the filter expands against the rack perimeter and seals the gap on its own, eliminating bypass that happens when filters shift in their racks. Fits standard holding frames without clips or fasteners.
Anti-microbial treatment
The 3-Ply Duo-Cube media is treated with an anti-microbial agent that inhibits the growth of bacteria, fungi, and other microorganisms on captured organic matter (dust, skin cells, pollen, etc.). This protects the filter media itself from becoming a substrate for microbial growth over the filter’s service life — particularly relevant in healthcare environments, food processing, hospitality, and high-occupancy commercial buildings where captured biological material would otherwise grow on standard untreated media.
The anti-microbial treatment protects the filter; it does not actively kill airborne pathogens passing through the filter.
Design and construction
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Construction: Extended-surface synthetic cube filter, 3-ply progressively dense media
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Media: 100% synthetic polyester (3-ply, anti-microbial treated)
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Moisture resistance: Suitable for high-moisture air handling applications
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Frame: Integral 9-gauge steel wire (self-sealing, fits standard holding frames without clips or fasteners)
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Anti-microbial: Yes (media-side treatment)
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Efficiency rating: MERV 8 per ASHRAE Test Standard 52.2-2007
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Reference bulletin: Koch K111C
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Sold by the case. Carton quantity varies by depth: 8″ and 11″ depths ship 10 per case; 15″ depths ship 7 per case; 20″ depths ship 5 per case (with one exception: 12x24x20 ships 5 per case). The variant price is the case price.
When the 3-Ply Duo-Cube is specified
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High-IAQ commercial HVAC — office buildings, schools, retail, hospitality where MERV 8 is the design target
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Healthcare facilities — clinics, dental offices, medical buildings where anti-microbial protection on the filter media is a meaningful upgrade
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Food processing and hospitality — environments with elevated organic loading where standard untreated media would support microbial growth
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Final filtration in industrial systems — manufacturing, warehousing, process environments needing MERV 8 with extended service life
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Easy upgrade from conventional panel filters — when an existing system uses MERV 8 panel filters and the maintenance team wants longer changeout intervals at similar capture efficiency
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Variable-air-volume systems where the deep pleated geometry handles airflow swings better than flat panels
What MERV 8 captures
MERV 8 captures dust mite debris, pollen, mold spores, pet dander, and most household and office airborne dust. The standard high-efficiency target for commercial buildings and high-IAQ residential applications, balancing capture performance with airflow.
Choosing across the Duo-Cube line
Koch offers four media tiers in the Duo-Cube cube filter family:
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Duo-Cube 1-Ply (MERV 6): Economical entry point, single-density poly media. Equipment protection and basic filtration.
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Duo-Cube 2-Ply (MERV 7): Dual-ply gradient density, dry or tackified. Step up from 1-Ply for marginally better capture.
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Duo-Cube 3-Ply (this product) (MERV 8): Three-ply blend with anti-microbial treatment. High medium efficiency for healthcare, food processing, and commercial HVAC.
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Duo-Cube 4-Ply (MERV 8 max): Four-ply blend for the highest performance in the Duo-Cube series. Anti-microbial, highest dust holding capacity.
Step down to 1-Ply if your application doesn’t require MERV 8 capture and pressure drop is the limiting factor. Step up to 4-Ply for maximum performance in critical applications. For most commercial MERV 8 applications, 3-Ply is the right choice — the anti-microbial treatment alone justifies the upgrade in most occupied buildings.
Sizing and ordering notes
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Specify both face dimensions and depth. Cube filters are sized as Width x Height x Depth (e.g., 24x24x15). Match all three dimensions to your filter rack — cube filters cannot be cut or trimmed in the field.
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Header frame option available. The 3-Ply Duo-Cube can be ordered with an integrated header frame for installations that require it — request a quote if you need the header-frame configuration.
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Sold by the case. Variant price is for the full case. 8″-11″ depths typically ship 10 per case; 15″ depths ship 7 per case; 20″ depths ship 5 per case.
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"Call for Quote" sizes: Some sizes are catalog items but require direct quoting due to lower order volume or build-to-order production. These appear unavailable in the dropdown — request a quote for these sizes or for facility-scale orders.
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Carton quantities are approximations. Per Koch policy, please state the exact number of filters required when ordering — we can adjust for partial cases on quoted orders.
