Duct Design & Air Distribution

Room-by-Room Airflow Calculation · Duct Sizing · Static Pressure · Diffuser Selection · Smart Zoning

A high-performance ducted HVAC system requires more than selecting an air conditioner and connecting ductwork.

Room cooling and heating loads, required airflow, duct dimensions, air velocity, pressure loss, supply and return-air distribution, diffuser selection and HVAC equipment performance must be considered together as one complete system.

YUJU provides project-based duct design and air-distribution engineering support for villas, residences, hotels, offices, schools, commercial buildings and other ducted HVAC applications.

From Architectural Plans to Air Distribution Design

Every room has different HVAC requirements. Floor area alone does not determine the final cooling capacity or airflow.

Building orientation, glazing, roof exposure, insulation, room function, occupancy, internal heat gains, outdoor climate and indoor design conditions can all influence the actual cooling and heating requirements.

YUJU can review available architectural drawings and project information to establish a room-by-room design basis before determining equipment capacity, airflow and duct dimensions.

• Room area and ceiling height
• Room volume
• Building orientation
• Window and glazing conditions
• External wall and roof exposure
• Building insulation conditions
• Room function and occupancy
• Indoor design temperature
• Local outdoor climate
• Fresh-air requirements where applicable

YUJU engineering workflow connects architectural information, room-load evaluation, airflow calculation, duct sizing, static pressure and HVAC equipment selection into one coordinated design process.

Room-by-Room HVAC Load & Airflow Calculation

Instead of dividing the total HVAC airflow equally between rooms, YUJU determines the design airflow according to the actual requirement of each space.

Different rooms within the same building can have very different loads because of orientation, glazing, room size, occupancy and usage patterns.

This approach helps reduce common problems such as insufficient airflow in high-load rooms, excessive airflow in small rooms, temperature imbalance and unnecessary fan energy consumption.

YUJU AIRFORM Multi-Room HVAC Design Tool

To improve the speed and consistency of preliminary HVAC engineering, YUJU has developed AIRFORM, a browser-based multi-room design tool for ducted and all-air HVAC systems.

AIRFORM helps convert building and room information into practical engineering data for HVAC capacity evaluation, room airflow calculation, duct planning, static-pressure review and air-distribution design.

According to the available project information, AIRFORM can generate or assist with:

• Room-by-room cooling and heating requirements
• Required airflow for each room
• Total system airflow
• Main and branch duct sizing
• Air velocity verification
• Supply diffuser sizing
• Return-air requirements
• Preliminary static pressure evaluation
• HVAC equipment capacity matching

YUJU AIRFORM helps engineers organize multi-room HVAC design information and convert room requirements into practical airflow, duct and equipment-selection data.

Duct Sizing Based on Actual Airflow

Duct dimensions should be determined according to the airflow carried by each section rather than selected only from experience.

For every main or branch duct section, airflow volume, duct cross-sectional area, air velocity, pressure loss and acoustic requirements should be considered together.

Air velocity targets are selected according to duct location, airflow volume, available static pressure and project noise requirements.

This is particularly important in residential and luxury-villa applications where excessive duct velocity can increase airflow noise and system resistance.

Main Duct & Branch Duct Design

As supply air is distributed to individual rooms, the airflow remaining in the main duct gradually decreases.

The duct system should therefore be divided into sections, with each section sized according to the airflow it actually carries.

The same principle applies to return-air design. Return paths must provide sufficient airflow without creating excessive resistance, pressure imbalance or noise.

Static Pressure & Critical Air Path Evaluation

Airflow alone is not enough to select a ducted indoor unit or AHU. The fan must also provide sufficient external static pressure to overcome the resistance of the complete air-distribution system.

YUJU evaluates the most critical airflow path and considers the resistance created by relevant external components.

• Main and branch ductwork
• Elbows and transitions
• Tees and fittings
• Balancing dampers
• Motorized zoning dampers
• Supply diffusers
• Return-air grilles
• External filters and accessories where applicable

The calculated requirement can then be compared with the available fan performance of the selected AHU or ducted indoor unit.

Supply Diffuser & Return Grille Design

A diffuser should not be selected only by appearance.

Its size and configuration should correspond to airflow volume, effective outlet area, acceptable outlet velocity, throw distance, room geometry and acoustic requirements.

According to project requirements, YUJU can assist with:

• Room airflow allocation
• Supply outlet dimensions
• Linear slot diffuser sizing
• Ceiling diffuser selection
• Wall supply-air grille selection
• Return-air grille sizing
• Plenum and transition requirements

Supply Air, Return Air & Fresh Air

A complete air-distribution system must consider supply air, return air and, where required, outdoor fresh air.

Depending on the architectural layout, return air can be designed individually by room, through common return-air plenums, or through centralized return locations such as corridors.

Outdoor ventilation can also be incorporated according to the project ventilation strategy, indoor air-quality requirements and HVAC equipment configuration.

Duct Design for Smart Zoning Systems

Smart room-by-room zoning creates additional requirements for duct design because system airflow changes continuously as individual zones increase, reduce or stop their airflow demand.

YUJU Air Basic™ combines individual room demand, proportional damper control, static-pressure management and HVAC operating logic to provide intelligent room-level airflow control.

A typical system can integrate:

• Individual room thermostats or controllers
• Temperature and humidity sensors
• Motorized proportional dampers
• 0–10V airflow regulation
• PLC-based central control
• Modbus / RS485 communication
• Static-pressure monitoring
• Bypass control where required
• Variable-speed fan coordination where available
• HVAC capacity coordination

YUJU Air Basic™ connects room demand, proportional dampers, duct pressure and compatible HVAC equipment to create coordinated room-by-room airflow control.

Why Zoning Changes Duct Design

When several rooms reduce airflow at the same time, duct static pressure can increase.

Simply closing multiple dampers without considering minimum system airflow may create excessive duct pressure, airflow noise and unstable HVAC operation.

For this reason, YUJU zoning design can consider:

• Minimum equipment airflow
• Minimum zone airflow
• Proportional damper positions
• Duct static pressure
• Fan-speed control where available
• Bypass strategy where required
• Compatible inverter HVAC capacity coordination

Integration with Inverter HVAC Equipment

For compatible inverter or variable-capacity HVAC systems, room demand and airflow requirements can also be considered as part of the equipment-control strategy.

The exact integration method depends on the selected HVAC equipment and the communication or control interfaces provided by the manufacturer.

Depending on the equipment platform, integration may use Modbus, RS485, 0–10V signals, dry contacts, thermostat interfaces, manufacturer gateways or other supported methods.

Ductwork Materials & Project Supply

According to project requirements and local installation practices, different duct materials and air-distribution accessories can be selected.

Where suitable for the project, YUJU can coordinate HVAC equipment, controls, dampers, diffusers and related air-distribution components as part of one integrated project package.

Installation & Commissioning Support

For international projects, physical duct installation is normally completed by the customer's local HVAC contractor according to project drawings and local construction requirements.

YUJU can provide engineering documentation and remote technical assistance to support the local team during installation and commissioning.

• Duct layout information
• Room airflow requirements
• Equipment connection requirements
• Damper and controller configuration
• Installation guidance
• Airflow-balancing guidance
• System commissioning support
• Remote troubleshooting

Typical Applications

YUJU Engineering Workflow

Why YUJU

YUJU does not treat ductwork as an isolated accessory to HVAC equipment.

Our engineering approach considers the relationship between building load, room airflow, duct resistance, diffuser performance, fan capability, HVAC capacity and intelligent controls.

AIRFORM further supports this process by giving project teams a practical browser-based tool for organizing room and duct design information.

This allows distributors, contractors and project developers to source HVAC equipment while receiving coordinated air-distribution and control-system engineering support from one project partner.