Exterior terminations represent a frequent failure point in high-performance ventilation systems. Standard stamped metal or molded plastic hoods regularly introduce excessive resistance, altering fan performance curves, increasing noise levels, and escalating mechanical wear. For commercial projects and high-efficiency residential systems, mitigating pressure drop at the building envelope requires precision geometry and durable materials.
Seiho’s product lines are engineered to maintain low system static pressure while ensuring robust weather defense and long-term durability.
Aerodynamic Architecture and Static Pressure Metrics
Standard commercial architectural specifications demand precise performance metrics to safeguard fan motors and maintain targeted volumetric airflow (CFM). Seiho wall terminations resolve this by maximizing free area and optimizing air velocity pathways.
Versatile Applications
Seiho engineered terminations are tailored for distinct mechanical applications, offering specialized configurations for general exhaust/intake (standard vent caps) and lint-safe configurations for dedicated dryer exhaust. Models are available in multiple dimensions to match system requirements (values in parentheses indicate Net Free Area)
Vent Caps
Seiho vent caps are perfect for any venting applications such as storage rooms, attics, basements, and bathroom / kitchen exhausts.
SFX-S / SX-S Series: The polished stainless steel versions of the immensely popular SFX and SX Series. Available in 4″ (0.04 sq. ft.) or 6″ (0.08 sq. ft.) duct sizes.
SFX-S Product Page | SX-S Product Page | SFX-S Dimensions | SX-S Dimensions
KX / KXU Series: The clean anodized aluminum square design is a perfect match for contemporary and classic buildings alike. Available in 3″ (0.12 sq. ft.), 4″ (0.14 sq. ft.), 5″ (0.21 sq. ft.), and 6″ (0.21 sq. ft.) duct sizes.
KX Product Page | KXU Product Page | KX Dimensions | KXU Dimensions
SFX / SX Series: The beautiful anodized aluminum design fits many decorating schemes. The hooded vent cap is excellent for exteriors where protection from the elements is necessary and not already carried out by the building design. Available in SX 3″ (0.02 sq. ft.) to 8″ (0.14 sq. ft.) duct sizes, SFX available in 3″ (0.02 sq. ft.) to 12″ (0.31 sq. ft.) duct sizes.
SFX Product Page | SX Product Page | SFX Dimensions | SX Dimensions
CFX / CFX-P Series: The CFX features a louver plate that can be easily opened for regular cleaning. The CFX-P series features a heavy-duty 8 1/2″ long aluminum pipe ideal for through-the-wall mounting. The CFX is available in 3″ (0.03 sq. ft.) to 12″ (0.26 sq. ft.) duct sizes while the CFX-P is available in 4″ (0.03 sq. ft.) or 6″ (0.08 sq. ft.) duct sizes.
CFX Product Page | CFX-P Product Page | CFX Dimensions | CFX-P Dimensions
RCA-S Series: This polished stainless steel series provides one of the largest free area for the based on duct size with weather and corrosion resistance. Available in 4″ (0.08 sq. ft.) and 6″ (0.18 sq. ft.) duct sizes.
Dryer Vents
Seiho dryer vents feature larger openings to reduce clogging, or backdraft / backdraft flapper dampers that prevent outside air from back-drafting into the house through the dryer. While designed for dryer exhaust, they also work great for bathroom or kitchen exhaust venting.
SB / SFB Series: Easy to install and designed for exterior applications, the SB and SFB series comes standard with a flapper damper. Available in 4″ (SB: 0.059 sq. ft. SFB: 0.054 sq. ft.) and 6″ (SB: 0.14 sq. ft. SFB: 0.13 sq. ft.) duct sizes.
SB Product Page | SFB Product Page | SB Dimensions | SFB Dimensions
SB-P / SFB-P Series: These feature a rigid, heavy-duty 8 1/2″ long aluminum pipe ideal for through-the-wall mounting. Available in 4″ (0.59 sq. ft.) and 6″ (0.14 sq. ft.) duct sizes.
SB-P Product Page | SFB-P Product Page | SB-P Dimensions | SFB-P Dimensions
SFZ / SFZC Series: The SFZ and SFZC series is a louvered dryer vent that features larger openings that allow lint to flow easily past it. The SFZC series features a backdraft damper. Available in 4″ (0.04 sq. ft.) and 6″ (0.11 sq. ft.) duct sizes.
SFZ Product Page | SFZC Product Page | SFZ Dimensions | SFZC Dimensions
CFXC / CFXF-P Series: The CFXC features a backdraft damper while the CFXF-P features a backdraft flapper damper and a rigid, heavy-duty 8 1/2″ long aluminum pipe ideal for through-the-wall mounting. The louver plate can be easily opened for regular cleaning. Available in 4″ (0.03 sq. ft.) or 6″ (0.08 sq. ft.) duct sizes.
CFXC Product Page | CFXF-P Product Page | CFXC Dimensions | CFXF-P Dimensions
RCC-S Series: This polished stainless steel series provides the largest free area of dryer vents while featuring a backdraft damper. Available in 4″ (0.07 sq. ft.) and 6″ (0.16 sq. ft.) duct sizes.
Vent Selection with Free Area Velocity and Pressure Drop Calculations
The Seiho SFX series is engineered to operate efficiently up to a maximum recommended free area velocity of 750 FPM. At this threshold, the static pressure drop is limited to just 0.09 in. w.g., preventing the system choking common with standard hardware. To determine the minimum required size for your exhaust or intake line, apply the standard manufacturer-approved formula:
For instance, an inline fan delivering 125 CFM requires a termination with at least 0.16 sq. ft. of free area. A review of the Seiho dimensional tables shows that an 8-inch SFX unit (providing 0.14 sq. ft. of free area) would be near the margin, but not over the 0.16 sq. ft. minimum requirement whereas a 10-inch SFX unit provides 0.24 sq. ft. of free area. Reverse engineering the equation using using the free area of an SFX-10 brings the free area velocity to 521 FPM. Cross referencing with the pressure drop graph, that would mean the system has a static pressure of approximately 0.045 in. w.g.
Material Durability and Mechanical Features
The longevity of a building’s envelope depends heavily on the materials anchoring its terminations. Inferior exterior caps suffer from UV degradation, environmental stress cracking, and atmospheric oxidation.
Seiho assemblies are manufactured using heavy-gauge anodized aluminum or premium polished 304 stainless steel (such as the SFX-S series). These alloys are designed to be corrosion-resistant for durability. For products with aluminum housings, custom powder-coating is available.
Functional Engineering Elements
- Integrated Moisture Mitigation: Each louvered assembly includes a built-in water condensation drain channel. This feature forces moisture outward, keeping it out of the ductwork.
- Pest Control: The SFX-N and SFX-SN sub-models can be configured with integrated stainless steel insect screens, blocking pest entry without creating an excessive restriction in the airflow path.
- Low-Mass Flapper Dampers: The SFZC and SFB lines implement low-resistance backdraft flapper dampers. These dampers open fully under active static pressure from bathroom fans or dryers, yet close tightly when the system is idle to halt wind penetration or cold air infiltration.
Friction-Fit Mechanical Mounting
Seiho terminations utilize a fastener-free installation system. The rear neck of the assembly features heavy-duty, factory-mounted friction-fit spring clips. The installation sequence requires only four steps:
- Verify the round rigid ducting or wall sleeve is cut flush with the exterior substrate.
- Apply a sufficient amount of high-grade silicone caulk around the neck of the vent.
- Align the termination and press firmly to compress the caulk for a good seal at the duct.
- Apply caulk around the outside edge of the vent to create a weather-tight seal against the building facade. Wipe off any excess. The vent openings must be positioned at the bottom.
Because the unit is retained via spring clip friction and caulking, the vent caps can be easily pulled completely out of the duct for line inspection and lint clearing.
Engineering Meets Logistics
Ultimately, optimizing a mechanical system requires matching premium components with a reliable supply chain. Seiho provides the precision geometry needed to protect fan performance. By maximizing Net Free Area and utilizing architectural-grade materials, these terminations eliminate the excessive resistance common in standard hardware. To ensure these solutions reach the job site without delay, HVACquick maintains deep stock across the entire Seiho lineup alongside matching fans, louvers, and dampers to complete any commercial or residential venting array.
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