Natural Ventilation Systems

Natural ventilation in New Zealand buildings

Ventilation is an important part of New Zealand building design. For occupied spaces, the New Zealand Building Code requires adequate ventilation for the intended use and expected occupancy of the space. Natural ventilation is one method that may be used by the project design team as part of a compliant ventilation strategy, where the building layout, opening areas, airflow paths, weather exposure, occupancy and operating conditions support that approach.

EBSA NZ does not determine Building Code compliance for the whole building ventilation design. Our role is to design, supply and support the automated opening system that may form part of that wider compliant solution. This can include the window drives, control panels, sensors, switching, interfaces and control logic required to operate suitable windows, skylights, façade openings or operable louvres.

Natural ventilation may be used to support outdoor air supply, indoor air quality, occupant comfort, passive cooling, night purge strategies or reduced reliance on mechanical cooling where the project design and operating conditions allow. It is often considered alongside façade design, room depth, opening position, internal airflow paths, weather protection, user control and mechanical services strategy.

Common natural ventilation strategies

What an automated natural ventilation system includes

An automated natural ventilation system normally combines operable façade elements with electric drives, control panels, sensors and project-specific operating logic. The final system arrangement depends on the opening type, required control function, number of ventilation zones, power supply, sensor strategy, user override requirements and interface requirements.

Basic natural ventilation control arrangement

The simplified schematic below shows a basic natural ventilation control arrangement using a wall switch, GVL 8301-K ventilation controller, VRS10 rain sensor and window drive. Final system design, wiring and product selection are project-specific.

Natural ventilation functionality

Natural ventilation systems can range from simple manually switched window groups through to multi-zone systems with sensors, weather response and BMS integration. The available functionality depends on the selected drives, control panel, sensors, wiring arrangement and programmed control strategy.

Mixed-mode ventilation

Many commercial buildings do not rely on natural ventilation alone. A mixed-mode ventilation strategy combines automated natural ventilation openings with mechanical ventilation, heating, cooling or building control systems. This allows the building to use outdoor air when conditions are suitable, while retaining mechanical systems for periods where temperature, air quality, weather, noise, security or occupancy requirements make natural ventilation unsuitable.

In a mixed-mode building, automated windows or louvres may need to coordinate with the mechanical services strategy. This can include temperature set points, CO2 inputs, time schedules, rain and wind response, façade zoning, mechanical plant interlocks and user override requirements.

Where a project-specific CPS-M control panel is used, some mixed-mode control functions can be managed directly within the CPS-M system rather than relying on a separate standalone BMS for that part of the building operation. Depending on the project requirements, inputs, outputs and programmed logic, a CPS-M panel may be configured to control or coordinate automated windows, fans, heating, cooling and other connected systems as part of the natural ventilation strategy.

This approach can be useful where the required control logic is specific to the ventilation system, façade zones or room conditions. For larger buildings, central plant, whole-building monitoring, energy reporting or broader facilities management requirements, the CPS-M system may still need to interface with a BMS or mechanical services control system.

Correct mixed-mode operation depends on clear control logic and early coordination. EBSA NZ can assist with the automated opening system, CPS-M control panel configuration and interface coordination, while the overall mixed-mode strategy should be confirmed by the project design team.

Project-specific control logic

The value of an automated natural ventilation system is often in the control logic, not just the hardware. A simple natural ventilation controller may provide basic open, close and weather response functionality. A project-specific CPS-M control panel can support more advanced sequencing, grouping, feedback and integration requirements.

For example, a CPS-M control panel can be configured to respond to wind-driven rain by closing only the windows on the affected elevation, rather than closing every window in the building. In some project-specific natural ventilation strategies, windows may also be programmed to partially close where the conditions, awning geometry and agreed control logic allow a protected ventilation position to remain open.

These control strategies should be reviewed during design and confirmed during commissioning so the system response matches the building’s ventilation intent, user expectations, weather exposure and maintenance requirements.

Night purge ventilation

Night purge ventilation uses controlled opening outside normal occupied hours to help release warm internal air and support passive cooling strategies. It is typically considered for buildings where the design, climate, security approach, weather response and operating schedule make overnight ventilation practical.

Night purge strategies need careful coordination. The system may need to consider external temperature, internal temperature, rain, wind, security, time schedules, BMS inputs and manual override requirements. EBSA NZ can assist with selecting suitable drives, control panels and sensor inputs for the intended control strategy.

Rain, wind and weather response

Weather response is a key part of most automated natural ventilation systems. The required response may be simple, such as closing all windows when rain is detected, or more advanced, such as responding differently by elevation, zone, wind direction or control mode.

The correct strategy depends on the building design, window type, awning protection, exposure, sensor location and control panel capability. Weather response should be treated as part of the complete system design rather than as an isolated sensor selection.

Where natural ventilation systems are used

• Schools and education buildings.
• Commercial offices.
• Aged care and community facilities.
• Apartment common areas and shared spaces.
• High-level windows and skylights.
• Operable façade openings.
• Glass louvre and façade ventilation systems.
• Mixed-mode buildings using both natural and mechanical ventilation.
• Buildings requiring sensor-based ventilation control.

Coordination considerations

Natural ventilation should be coordinated early in the project. The type of window, sash weight, required opening distance, bracket arrangement, cable route, panel location, sensor location and control interface requirements can all affect the final system selection.

For commercial projects, EBSA NZ can assist with reviewing:

• window type, sash size, sash weight and opening geometry;
• drive force, stroke, speed and bracket requirements;
• control panel selection and actuator load;
• ventilation zones and grouping strategy;
• switching, override and user control requirements;
• rain, wind, temperature and CO2 sensor requirements;
• BMS or mechanical services interfaces;
• field cabling, access for installation and future maintenance;
• commissioning requirements and project-specific control logic;
• project specification content, including EBSA NZ’s Masterspec work section/code where applicable.

Related product groups

Natural ventilation and smoke control

Some buildings use automated openings for both day-to-day natural ventilation and smoke control-related functions. These systems require careful review because normal ventilation operation and fire-mode operation may require different control priorities, interfaces, power supplies, commissioning checks and approval pathways.

Where natural ventilation and smoke control functions overlap, EBSA NZ can assist with the automated opening system selection and control panel coordination. Final suitability must be reviewed against the project fire strategy, mechanical services design, control interfaces, installation requirements and approval process.

Talk to EBSA NZ about natural ventilation

Natural ventilation system selection depends on the building design, opening type, required functionality, weather exposure, user control requirements and integration strategy. EBSA NZ can assist with reviewing the system arrangement before products are selected, specified or ordered.

Discuss a Natural Ventilation Project