Section 1: Product Overview

The Rooftop Ventilation Exhaust Fan addresses one of the most fundamental requirements in building ventilation system design — the need to move large volumes of air from the interior of a building to the outdoor environment through the most direct available pathway, which in most building types is vertically upward through the roof structure. By positioning the fan at the roof level discharge point rather than at floor level or in a mechanical room with ductwork connecting to a roof penetration, the rooftop exhaust fan eliminates the pressure losses and installation complexity associated with long vertical duct runs, reduces the space consumed by mechanical systems within the building envelope, and places the exhaust point where natural buoyancy and wind effects can assist rather than oppose the mechanical exhaust function.

The product family encompasses three fundamentally different operating types that share the rooftop installation format while addressing different performance requirements and application contexts. The axial impeller type delivers high air volume at low static pressure, suited to open building spaces where the ductwork resistance between the building interior and the fan inlet is low. The centrifugal impeller type generates higher static pressure, enabling it to overcome the resistance of ductwork connections that extend below the roof level to serve lower building areas. The motorless turbine type requires no electrical power, using the combination of wind-induced pressure differentials and thermal buoyancy from warm interior air to drive continuous ventilation without any operating energy cost.

Understanding which type is appropriate for a specific application requires matching the fan performance capability to the building ventilation system design requirements — the correct selection produces reliable, energy-efficient ventilation; an incorrect selection results in either insufficient airflow, excessive energy consumption, or premature equipment failure from operation outside the intended performance range.

Dezhou Pengkai Air Conditioning Equipment Co., Ltd. is a comprehensive HVAC manufacturer based in Dezhou, Shandong Province, integrating research and development, production, sales, installation, and after-sales service. We supply rooftop ventilation fan products to building contractors, HVAC engineers, facility operators, and equipment distributors across Southeast Asia and global markets.

Section 2: Product Types and Configuration Guide

DWT-I Type — Axial Impeller Rooftop Fan The axial impeller configuration uses a wide-blade space-twisted axial impeller for high-volume, low-pressure exhaust from large open building spaces directly through roof-level exhaust openings. The axial design is the highest-volume option within the rooftop fan range, capable of handling extremely high airflow rates at minimal static pressure. Some models in this type offer reversible rotation for bidirectional operation — the same unit can switch between exhaust and supply modes depending on ventilation strategy requirements. For larger machine numbers, blade angle adjustment allows airflow optimization without replacing the unit. Dual-speed and variable frequency motor options are available within this type for energy-saving operation during partial-load periods.

DWT-II and DWT-III Types — Centrifugal Impeller Rooftop Fan The centrifugal impeller configuration uses an optimized centrifugal impeller to generate significantly higher static pressure than the axial type, enabling the unit to serve building exhaust systems where ductwork extends below the roof level to collect exhaust from lower building areas. The centrifugal type is the appropriate selection when the total system resistance from the building interior to the fan discharge exceeds the low static pressure capability of the axial type. DWT-II and DWT-III represent different centrifugal impeller design variants within this configuration category.

DWT-IV Type — Motorless Turbine Rooftop Ventilator The motorless turbine type operates entirely without electrical power, using the aerodynamic effect of wind flowing across the turbine head to create a low-pressure zone at the exhaust outlet, and the thermal buoyancy of warm interior air to assist upward airflow through the ventilator body. This type requires zero operating energy cost and zero electrical installation, produces no operating noise, has no spark risk making it inherently safe for use above spaces containing flammable vapors, and requires virtually no maintenance. Limitations include dependency on wind availability and thermal conditions — performance is lower in calm weather and when interior-exterior temperature differentials are small.

Section 3: Product Structure and Key Components

Weatherproof Housing and Rain Cap The housing enclosure and integral rain cap are the elements that distinguish the rooftop fan from its indoor counterpart and make outdoor continuous operation possible. The rain cap is positioned above the discharge outlet, shaped to allow free upward air discharge while deflecting rain and snow away from the opening regardless of wind direction. The cap geometry also creates a low-pressure zone at the exhaust outlet under cross-wind conditions, using the Venturi effect of wind across the cap profile to assist exhaust discharge rather than opposing it. Anti-bird mesh and insect screen are standard fittings within the discharge opening to prevent wildlife entry.

Impeller and Motor Assembly For DWT-I axial type units, the impeller uses aerofoil-section blades of the space-twisted profile characteristic of high-efficiency axial fan design. For DWT-II/III centrifugal type units, an optimized centrifugal impeller with backward-curved or aerofoil-section blades provides the higher pressure capability. Motors are specified as outdoor-rated units with insulation class F or above and protection grade IP54 or IP55, appropriate to continuous outdoor temperature and humidity exposure. Direct-drive motor mounting is the standard configuration for compact, reliable operation.

Base Plate and Weatherproof Sealing The base plate connects the fan housing to the roof structure and is the critical waterproofing interface between the fan installation and the building envelope. The base plate perimeter is designed to integrate with standard roofing materials — both metal deck and membrane roofing systems — with sealant application points and overlap profiles that prevent water ingress at the roof penetration boundary. The base plate material and finish are specified to provide long-term corrosion resistance at this critical interface.

Gravity Check Damper A gravity-operated check damper is available as a standard fitting within the fan housing, preventing backdraft through the fan when it is stopped and preventing cold air, rain-driven moisture, or wind pressure from entering the building through the exhaust opening during shutdown periods. The damper opens automatically under airflow pressure when the fan operates and closes under gravity when the fan stops.

Turbine Assembly — DWT-IV Type The motorless turbine assembly consists of a multi-blade turbine rotor mounted on a sealed bearing assembly within the turbine head housing. The turbine blade geometry is designed to extract energy from wind flowing across the turbine head from any direction — omnidirectional wind response means the unit generates exhaust suction under wind conditions regardless of wind direction. The sealed bearing assembly requires no maintenance lubrication and provides long service life in outdoor weather conditions.

Section 4: Technical Specifications

DWT-II Centrifugal Type — Representative Performance Data:

Complete data for DWT-I axial and DWT-III types available upon request. Contact our sales team with your roof exhaust airflow and static pressure requirements for model and type selection guidance.

Section 5: Type Selection Guide — Matching Performance to Application

Correct type selection is the most important factor in rooftop fan performance and reliability. The following framework guides the selection between DWT-I axial, DWT-II/III centrifugal, and DWT-IV turbine types based on application characteristics.

When to Select DWT-I Axial Type The axial type is appropriate when the building space to be ventilated is directly below the roof level with minimal duct resistance between the space and the fan inlet, and when the primary requirement is maximum air volume movement at low resistance. Large open factory halls, warehouse buildings, agricultural production buildings, and sports arenas with high roof-level exhaust openings are the primary applications for the axial type. The high volume-to-pressure ratio of the axial impeller maximizes ventilation effectiveness in these low-resistance installations.

When to Select DWT-II/III Centrifugal Type The Low Noise Centrifugal Roof Fan is appropriate when exhaust ductwork extends below the roof level to collect air from spaces on lower floors, when the total duct system resistance exceeds 150 to 200 Pa, or when the exhaust requirement involves concentrated extraction from specific sources such as kitchen hoods, laboratory fume cupboards, or process exhaust connections. The higher static pressure capability of the centrifugal type maintains required exhaust airflow against these higher resistance conditions.

When to Select DWT-IV Turbine Type The motorless turbine type is appropriate for supplementary natural ventilation in spaces where continuous low-level airflow is beneficial, where electrical installation is impractical or undesired, and where performance variability with wind conditions is acceptable. Agricultural buildings, simple storage facilities, and building types where the primary ventilation strategy is natural rather than mechanical are the appropriate contexts for turbine type selection.

Section 6: How It Works — Operating Principle by Type

DWT-I Axial Type Operation The motor starts and drives the axial impeller at operating speed. The impeller blades generate axial thrust force on the airstream, drawing building interior air upward through the fan base opening and discharging it through the rain cap to the outdoor environment. The rain cap geometry assists discharge under cross-wind conditions by creating a low-pressure zone above the cap that supplements the mechanical exhaust pressure. When the fan stops, the gravity check damper closes within seconds, sealing the roof opening against backdraft and wind ingress.

DWT-II/III Centrifugal Type Operation The motor drives the centrifugal impeller, which draws air axially into the impeller eye and accelerates it radially outward into the scroll housing, generating static pressure that overcomes the resistance of the connected ductwork and discharges air through the rain cap. The higher static pressure of the centrifugal type maintains design airflow against duct system resistance conditions that would cause airflow collapse in axial type units. The Rooftop Ventilation Exhaust Fan of centrifugal type is therefore the correct selection for duct-connected rooftop exhaust systems.

DWT-IV Turbine Type Operation Wind flowing across the turbine head creates a velocity-induced low-pressure zone at the turbine blade tips by the Bernoulli effect. This low-pressure zone is communicated to the building interior air column through the turbine body, reducing the pressure at the top of the air column and allowing atmospheric pressure at lower building openings to push interior air upward and out through the turbine. Simultaneously, warm interior air — which is less dense than cooler exterior air — rises naturally toward the roof level, adding thermal buoyancy to the wind-induced suction. The combined wind and thermal driving forces create continuous low-level ventilation without any electrical energy input.

Section 7: Manufacturing Process and Quality Control

Dezhou Pengkai Air Conditioning Equipment Co., Ltd. applies systematic quality management to all Rooftop Ventilation Exhaust Fan production:

Material Incoming Inspection Galvanized steel sheet, glass fiber reinforced plastic components, stainless steel sheet, motor units, bearing assemblies for turbine type, rain cap components, and base plate materials are all inspected against specification on receipt. Motor units receive electrical testing before assembly. Material certification records are retained.

Rain Cap and Housing Fabrication Rain cap components are formed using tooling that produces the specified aerodynamic profile, verified against dimensional drawings after forming. The rain cap geometry is critical to weatherproofing performance and wind-assisted exhaust effectiveness — dimensional consistency between production units ensures consistent field performance. Base plate penetration profiles are formed to standard roofing material overlap dimensions.

Impeller Fabrication and Dynamic Balancing Axial and centrifugal impellers are fabricated, assembled, and dynamically balanced to the precision grade appropriate to the operating speed. The outdoor installation environment, with potential for uneven dust or moisture accumulation on impeller surfaces over time, makes initial balance quality particularly important for long-term vibration performance.

Weatherproofing Verification Completed units are inspected for weatherproofing integrity at all rain cap joints, motor cable entry points, base plate sealing surfaces, and motor housing interfaces. Any gaps or insufficient sealing at these locations would result in water ingress during field operation.

Final Running Test Each completed motorized unit undergoes a running test verifying correct rotation direction, smooth operation, correct current draw, and correct gravity damper function. Turbine type units are tested for free rotation of the turbine assembly without binding or drag.

Section 8: Product Features and Advantages

Rooftop Installation Eliminates Long Vertical Duct Runs Installing the Industrial Roof Mounted Exhaust Fan at the roof discharge point removes the need for long vertical ductwork connecting a floor-level fan to a roof penetration, eliminating the pressure losses, installation space, and material cost associated with extended vertical duct runs.

Weatherproof Rain Cap for Continuous Outdoor Operation The integrated rain cap allows the Rooftop Ventilation Exhaust Fan to operate continuously in all weather conditions — rain, wind, snow, and high humidity — without water ingress into the fan housing, motor, or connected ductwork. The cap geometry also uses cross-wind energy to assist rather than oppose exhaust discharge under windy conditions.

Three-Type Range Covers All Roof Exhaust Requirements The axial, centrifugal, and motorless turbine configurations within the product range cover every building roof exhaust requirement from simple agricultural building natural ventilation augmentation to high-pressure duct-connected commercial building exhaust systems, within a consistent product family with compatible installation interfaces.

Multiple Material Options for Corrosive Environments Standard galvanized steel, glass fiber reinforced plastic, stainless steel, and full aluminum construction options address the full range of installation environment corrosion challenges from standard commercial buildings to coastal marine environments, chemical plant rooftops, and agricultural facility rooftops with high ammonia exposure.

Explosion-Proof Configuration for Hazardous Areas Explosion-proof motor configurations are available for the Low Noise Centrifugal Roof Fan and axial type, enabling safe installation above spaces containing flammable vapors or explosive dust atmospheres. The motorless turbine type is inherently spark-free and suitable for hazardous areas without special motor specifications.

Variable Speed Options for Energy Efficiency Dual-speed and variable frequency motor options allow the Industrial Roof Mounted Exhaust Fan to operate at reduced speed during partial-load periods, providing meaningful energy savings over the operating year in buildings with variable occupancy or variable heat generation profiles.

CAD Optimized Aerodynamic Design Both axial and centrifugal impeller types use CAD aerodynamic optimization to achieve the lowest noise level consistent with the required airflow performance. The noise levels of ≤57 to ≤72 dB(A) across the centrifugal type range are achieved through impeller design that minimizes aerodynamic noise generation at the design operating point.

Section 9: Application Scenarios

Industrial Factories and Warehouses Large factory production halls, assembly workshops, and warehouse buildings require high-volume roof exhaust to remove heat buildup under metal roofs during warm weather, to dilute process fumes and particulates from production operations, and to maintain acceptable working temperature and air quality for building occupants. Axial type units in larger machine numbers provide the volume flow required for large industrial building footprints.

Commercial Kitchens and Food Processing Facilities Commercial kitchen roof exhaust systems require fans capable of handling hot, grease-laden air discharged from kitchen hood exhaust ducts through roof penetrations. The Low Noise Centrifugal Roof Fan in stainless steel configuration is the appropriate specification for kitchen exhaust rooftop positions, combining the higher static pressure capability required for duct-connected kitchen exhaust with material resistance to grease and cleaning agent exposure.

Cold Storage and Refrigerated Warehouses Cold storage facility ante-room ventilation, refrigerated warehouse loading dock exhaust, and frozen food processing plant ventilation require fans reliable in low ambient temperatures. The standard operating temperature range of the motorized types covers cold storage environments without special low-temperature specifications.

Chemical Plants and Process Facilities Chemical production facilities, pharmaceutical manufacturing plants, and industrial process buildings require roof exhaust fans resistant to chemical fume exposure. Glass fiber reinforced plastic housing and impeller configurations provide the chemical resistance required for aggressive process exhaust environments. Explosion-proof motor configurations serve locations above classified hazardous areas.

Agricultural Buildings and Livestock Facilities Poultry houses, pig farms, greenhouse growing facilities, and feed storage buildings require high-volume ventilation for temperature, humidity, and ammonia management. The Rooftop Ventilation Exhaust Fan in axial type provides the volume flow required for agricultural building roof exhaust, with construction materials and motor protection specifications appropriate to the humid, ammonia-rich environment of livestock buildings.

Schools, Sports Facilities, and Public Buildings School gymnasium exhaust, sports hall roof ventilation, swimming pool hall exhaust, and public assembly building heat exhaust applications require reliable, low-noise roof exhaust fans appropriate to occupied building environments. The Low Noise Centrifugal Roof Fan noise levels of ≤57 to ≤65 dB(A) in smaller machine numbers are compatible with occupied educational and recreational building environments.

Data Centers and Equipment Buildings Data center roof exhaust systems, generator building exhaust, and electrical switchroom roof ventilation require reliable, energy-efficient fans with consistent performance. Variable frequency motor options allow precise airflow matching to real-time heat rejection requirements.

Section 10: Customer Application Feedback

Our rooftop ventilation fan products have been supplied to commercial, industrial, and agricultural projects across Southeast Asia and international markets:

"We installed Pengkai centrifugal rooftop fans for the kitchen exhaust systems of a large hotel complex. The stainless steel construction has held up well against the grease and cleaning agent exposure at the rooftop discharge points, and the weatherproof rain cap has performed correctly through several monsoon seasons without water ingress issues." — Building Services Contractor, Southeast Asia

"For a warehouse complex ventilation project, we used Pengkai axial rooftop fans across multiple large warehouse buildings. The installation was straightforward — the base plate design integrated well with the metal deck roofing system, and the units delivered the required air change rates at commissioning measurements. After two years of operation, no maintenance issues have been reported." — HVAC Engineering Company, Regional Project

"We specified Pengkai Industrial Roof Mounted Exhaust Fan products for a poultry production facility expansion. The IP55 motor protection and hot-dip galvanized housing have proven appropriate for the ammonia and high humidity environment. The after-sales team has been helpful with technical queries about maintenance intervals and replacement parts availability." — Agricultural Facility Developer

Section 11: Installation Guidelines

Pre-Installation Preparation Verify that the fan type, machine number, motor configuration, housing material, and base plate dimensions match the project design. Prepare the roof base opening to the dimensions specified for the selected model, with structural reinforcement of the opening perimeter if required by the roof structure design. Verify that the roof structure load capacity is adequate for the fan weight at the installation position.

Base Plate Installation and Waterproofing Position the fan base plate on the roof surface with the opening centered over the prepared roof penetration. For metal deck roofing, apply a bead of weatherproof sealant around the base plate perimeter before fixing, and secure the base plate to the roof deck using the specified self-tapping fasteners at the required intervals. Seal all fastener penetrations with appropriate sealant. For membrane roofing systems, integrate the base plate with the membrane upstand per the roofing system manufacturer's requirements. Waterproofing integrity at the base plate perimeter is critical — any gaps will result in water ingress during rainfall.

Fan Body Installation Position the fan body onto the base plate mounting interface and secure with the specified fasteners. Verify that the fan body is level and that the mounting interface is fully seated without gaps. Install the anti-bird mesh and gravity check damper if supplied as separate components. For larger heavy units, use appropriate lifting equipment and ensure the unit is stabilized before completing fastening.

Ductwork Connection — Centrifugal Type Connect the ductwork from the building exhaust system to the fan inlet connection using a flexible soft connector. The flexible connector prevents structural vibration transmission between the fan and the ductwork and accommodates any minor positional offset between the duct and fan inlet. Ductwork must be independently supported and must not apply weight or bending stress to the fan inlet connection.

Electrical Connection Electrical connection must be performed by a qualified electrician using weatherproof cable gland fittings and conduit appropriate to outdoor installation. Verify supply voltage, phase configuration, and motor rotation direction before completing the installation. For three-phase units, confirm correct rotation direction with a brief test start before final installation of rain cap or any temporary protection removed for rotation check.

Post-Installation Commissioning Run the fan for a minimum of 30 minutes at initial start, monitoring for abnormal noise, vibration, water ingress, or excessive current draw. Verify that the gravity damper opens correctly during operation and closes on shutdown. Measure delivered airflow where practical and compare to design specification.

Section 12: Maintenance Schedule

Monthly Inspection Visually inspect the rain cap, anti-bird mesh, motor cable entry points, and base plate perimeter sealing for physical damage, debris accumulation, or sealant deterioration. Confirm gravity damper operation. For kitchen exhaust installations, monthly cleaning of rain cap and impeller grease accumulation is recommended.

Quarterly Cleaning Clean impeller blades, rain cap interior, and gravity damper of accumulated dust, debris, or process deposits using soft brush or low-pressure compressed air with power isolated. Inspect base plate sealant condition and reapply to any areas showing cracking or detachment.

Annual Inspection Check motor bearing condition by listening for unusual noise and measuring current draw. Verify all structural fasteners — base plate fixings, body-to-base plate fixings, and rain cap fixings — for tightness and corrosion. For motors with grease nipples, apply specified grease per motor manufacturer recommendation. Inspect impeller for corrosion, erosion, or mechanical damage. For turbine type units, check turbine bearing assembly for smooth rotation and absence of rust or contamination.

Section 13: Packaging, Shipping, and Lead Time

Packaging Each Rooftop Ventilation Exhaust Fan unit is packaged in protective carton packaging for smaller machine numbers and wooden crate packaging for larger and heavier units, with foam padding and structural blocking appropriate to unit dimensions and weight. Rain cap components are typically packed separately within the crate to prevent damage. Export-grade packaging is standard for all international shipments.

Minimum Order Quantity We accept single-unit project orders and multi-unit supply contracts. Please contact our sales team to discuss specific machine numbers, types, and configurations.

Lead Time Standard machine numbers in common single-speed configurations are available with short lead times. Stainless steel, FRP, explosion-proof, and dual-speed configurations are produced to order with lead times confirmed at order placement.

Shipping We ship from Dezhou, Shandong Province. Sea freight is the standard mode for international orders. Air freight is available for smaller urgent units. We work with established freight forwarding partners serving Southeast Asia, the Middle East, and global destinations.

Sample Policy Product samples for pre-order technical evaluation are available by arrangement. Sample costs and shipping fees are agreed prior to dispatch.

Payment Terms We support T/T bank transfer and other payment arrangements as mutually agreed. Please contact our sales team for terms appropriate to your project order requirements.

Section 14: Certifications and Quality Assurance

Dezhou Pengkai Air Conditioning Equipment Co., Ltd. manufactures rooftop ventilation fan products in compliance with applicable national standards for outdoor-rated mechanical ventilation equipment. Production quality management covers incoming material inspection, impeller dynamic balance testing, weatherproofing integrity verification of completed units, and running tests before dispatch. Quality documentation for each production batch is available on request. Pre-shipment inspection by buyer-nominated agencies is welcomed for project orders.