NZ wind zones, window test pressures and automated openings
How New Zealand wind-zone pressures guide the selection of windows, glass louvres, chain drives, locking and weather performance.
For buildings using the NZS 3604 wind-zone pathway, the wind-zone label nominates the minimum SLS and ULS structural test pressures and the corresponding static water-test pressure. Those pressure requirements provide the basis for comparing a proposed window or louvre configuration with its test evidence.
Where the façade is specifically engineered, the project engineer supplies the positive and negative SLS and ULS pressures instead. EBSA then reviews the applicable product evidence together with the opening size, glass, supporting structure, hardware, actuator and operating requirements.
Wind zone becomes product requirements
SLS establishes the required stiffness and serviceability performance.
ULS establishes the structural wind load and informs sash locking requirements.
Water pressure establishes the minimum weather-performance test level.
EBSA uses these values with the opening size and system geometry to select and coordinate the solution.
Use the pressures behind the wind-zone label
SNZ TS 4211:2022 connects New Zealand exposure ratings with structural, air and water-performance testing for windows and exterior doors. The practical value is the pressure data behind the label: it gives the project team measurable requirements that can be compared with product evidence.
For automated windows
The nominated pressure and sash area establish the wind force acting on the closed opening. EBSA uses that force with the sash geometry to select the chain drive, closing force, locking arrangement and number and position of operating points.
For architectural glass louvres
The SLS, ULS and water requirements allow the proposed louvre size and configuration to be matched with independently tested performance. This creates a clear selection pathway for the architect, façade consultant and engineer.
EBSA louvre performance: the tested 1540 × 2840 mm BT90 exceeds the SNZ TS 4211 Extra High SLS, ULS and static water-pressure requirements. LF550 has independently tested large-format configurations exceeding the same numerical benchmarks, and MP2 SGI evidence covers both tall and wide insulated-glass arrangements so the appropriate result can be selected for the proposed geometry.
SNZ TS 4211 is the New Zealand classification pathway for discrete windows and exterior doors. Each EBSA louvre page identifies the test basis applying to that system.
SNZ TS 4211 pressure values for NZS 3604 wind zones
The table below summarises the minimum structural test pressures in the standard’s exposure table and the corresponding minimum static water-test pressure. Positive and negative signs represent pressure acting in opposite directions on the test specimen.
| NZS 3604 exposure | Structural test pressures | Static water-test pressure |
|---|---|---|
| Low (L) | SLS ±510 Pa ULS ±720 Pa |
155 Pa |
| Medium (M) | SLS ±680 Pa ULS ±960 Pa |
205 Pa |
| High (H) | SLS ±970 Pa ULS ±1360 Pa |
290 Pa |
| Very High (VH) | SLS ±1250 Pa ULS ±1760 Pa |
375 Pa |
| Extra High (EH) | SLS ±1515 Pa ULS ±2130 Pa |
455 Pa |
Source: SNZ TS 4211:2022, exposure rating and static water-test tables. This is a practical summary, not a substitute for the complete standard, the current Building Product Specifications or project engineering.
EM7 and specific engineering design
EM7 exposure
SNZ TS 4211:2022 gives EM7 structural test pressures of +2250/−2750 Pa at SLS and +3200/−3950 Pa at ULS, with a 675 Pa static water test. These directional values should remain visible rather than being reduced to one larger number.
SED — specific engineering design
For SED classification, the positive and negative SLS and ULS test parameters are the net cladding pressures acting on the window, including relevant local pressure coefficients, derived for the project. The standard sets the static water-test pressure at 30% of the SLS test pressure.
What SLS, ULS and water pressure tell the project team
SLS — Serviceability Limit State
SLS confirms that the window or louvre remains sufficiently stiff and serviceable at the nominated wind pressure. It is the key comparison for deflection, frame and blade stiffness and everyday façade performance.
ULS — Ultimate Limit State
ULS establishes the ultimate structural wind load. For an awning sash, the ULS pressure multiplied by the sash area gives the total wind force that the closed window and its locking points must resist. That force is an important input to actuator and locking selection.
Water penetration
The wind-zone or SED pathway nominates the water-test pressure. Testing with water spray and positive air pressure then demonstrates the closed system’s resistance to wind-driven rain at that performance level.
From wind pressure to actuator and locking selection
Electric chain drives are routinely used in place of manual handles, stays and similar operating hardware. The selection process translates the window’s pressure and geometry into the force, stroke and locking performance required from the automated system.
1. Calculate the wind force
Wind pressure is measured in pascals, or newtons per square metre. Multiplying the nominated pressure by the sash area gives the total wind force acting on the opening.
2. Resolve the force through the sash
The hinge position, sash proportions and actuator location determine how that total force is shared between hinges, actuators and locking points.
3. Select actuation and locking
EBSA uses the calculated reactions to select the actuator closing force and holding performance, or dedicated locking drives where required, together with the number and position of operating points.
4. Confirm the operating duty
Stroke, opening angle, sash weight, seals, friction, daily ventilation duty and any nominated wind condition for movement complete the actuator selection.
Awning-window example: the ULS pressure is used with the sash area and geometry to calculate the force trying to pull or push the closed sash away from its seals. EBSA then selects and positions the chain actuators and, where required, supplementary locking drives to provide the necessary closing and holding performance.
- Window type, width, height, weight and opening geometry
- Positive and negative project pressures and any operational wind limit
- Hinge, seal and hardware resistance
- Required stroke, opening angle and free area
- Chain position, bracket geometry and available fixing structure
- Closing and locking requirements
- Daily ventilation, BMS, rain, wind and fire-system control sequences
- Access for installation, testing, adjustment and maintenance
Why controlled air leakage matters
Low air leakage supports occupant comfort, reduces unwanted draughts and conditioned-air loss, and helps the closed façade maintain predictable pressure and weather performance. It is particularly valuable where operable elements form part of an insulated external envelope.
SNZ TS 4211 uses four air-permeability classes, with Class 4 representing the highest performance band. The tested BT90 recorded area leakage of 0.61–0.65 L/s·m² at 75 Pa and 0.99–1.02 L/s·m² at 150 Pa. These area-based results sit inside the Class 4 thresholds of 0.685 L/s·m² and 1.10 L/s·m² respectively.
What this means in practice: BT90 combines large operable insulated-glass blades with area-based air leakage in the standard’s highest performance band—a strong result for naturally ventilated façades that still need a well-controlled closed condition.
Use tested performance to select the right louvre
EBSA’s tested range gives designers clear pathways across thermally broken framed louvres, large-format single-glazed louvres and structurally glazed insulated-glass louvres. The wind-zone or project pressures allow EBSA to match the proposed size and façade intent with the most relevant tested configuration.
BT90 provides the clearest SNZ TS 4211 pathway and exceeds Extra High requirements at its tested size. LF550 offers strong large-format performance across several tested sizes and glass arrangements. MP2 SGI combines insulated glazing and a frameless external appearance, with tall and wide test configurations available to guide selection.
Frequently asked questions
What are the New Zealand wind zones?
The NZS 3604 exposure sequence is Low, Medium, High, Very High and Extra High. SNZ TS 4211:2022 assigns minimum window structural and water-test pressures to those exposure categories. Buildings outside that simplified pathway require project-specific pressure inputs.
Can I convert a wind zone directly into a façade pressure?
Not for every building or component. Commercial and specifically designed façades use net project pressures that account for the actual building, location and local pressure effects. Use the engineer’s positive and negative SLS and ULS values.
Does SLS mean the window will not leak?
No. SLS assesses serviceability and deflection. Water penetration is assessed in a separate spray test at its own nominated positive pressure.
How does ULS pressure help select a chain drive?
ULS pressure multiplied by sash area establishes the total wind force acting on the closed window. EBSA resolves that load through the sash geometry to determine the required actuator holding and closing performance, locking arrangement and operating-point positions.
Can electric chain drives replace manual window hardware?
Yes. Electric chain drives routinely replace manual handles, stays and similar operating hardware. EBSA selects the actuator, brackets, stroke and locking arrangement to suit the window type, size, geometry, calculated loads and control function.
Read the complete standard
This EBSA resource is an application guide. Refer to the complete current SNZ TS 4211:2022 document and the current New Zealand Building Code compliance documents for specification and consent work.
Coordinate the window, louvre, drive and controls as one system
Send EBSA NZ the proposed opening sizes, glass, structure, positive and negative design pressures, operational wind requirements, control sequence and access strategy. We will identify the product evidence and coordination inputs required for the project.
