Wind regions, regional wind speeds and the panel-to-roof load path under AS/NZS 1170.2.
A New Zealand solar wind assessment needs two decisions at the start: the engineering edition and the Building Code compliance pathway. The regional map and wind-speed table then establish the starting wind input. Site exposure, array geometry and the supporting structure determine what that input means for a particular installation.
This guide helps EPCs, installers and project engineers review a mounting proposal. A useful proposal connects the site wind assessment to panel pressures, fixing reactions and verified roof or foundation capacity. A product statement such as “rated to 60 m/s” cannot establish that connection on its own.
The short answer
- Decide the engineering edition and the Building Code compliance pathway first. B1/VM1 Second Edition cites AS/NZS 1170.2:2011 with Amendments 1 to 5; the 2021 edition with Amendments 1 and 2 is a separate design basis, not an interchangeable label.
- Read the map and the wind-speed table with the same edition label: A6, A7 and W on the 2011 basis, NZ1 to NZ4 on the 2021 basis. Old labels do not prove the new allocation.
- A council’s residential wind-zone label and an AS/NZS 1170.2 regional classification serve different purposes. “High wind zone” is not a substitute for the regional and site assessment required for specific engineering design.
- The building-consent exemptions (28D and 48A) are screening criteria. They do not supply mounting capacities or release the work from Building Code requirements.
- Lee-zone effects and local hill effects are separate checks. A site behind a mountain range can still experience severe wind.
- Convert panel loads into support reactions and assess the roof under the applicable combined load cases. Uniform fixing spacing can be valid when calculations demonstrate that it satisfies all relevant zones and load cases.
1. Confirm the edition before selecting the wind region
The engineering publication set discussed here is AS/NZS 1170.2:2021 with Amendment 1:2023 and Amendment 2:2024. New Zealand’s B1/VM1 Second Edition, however, cites AS/NZS 1170.2:2011, including Amendments 1 to 5, with the verification method’s own modifications. These are separate design bases, not interchangeable labels. B1/VM1, Appendix A
Record the edition and amendments separately from the compliance pathway. A project specification calling for the 2021 edition does not, by itself, demonstrate Building Code compliance. A departure from the cited verification method needs an explicit compliance justification, including any alternative-solution assessment and acceptance required for the project. MBIE: Alternative solutions
New Zealand wind regions by edition
| Publication basis | Regional labels | How to use the classification |
|---|---|---|
| 2011 regional scheme | A6, A7 and W | Use the 2011 map for a 2011-based assessment. |
| 2021 regional scheme | NZ1, NZ2, NZ3 and NZ4 | Use the 2021 map. Recheck boundaries and local provisions; old labels do not prove the new allocation. |
NZ1 covers the northern North Island; NZ2 covers the central North Island and much of the South Island; NZ3 is the defined Cook Strait region; NZ4 covers the far south and includes Chatham and Auckland Islands. On the Standard’s 2021 map, Blenheim falls in NZ2. Sites around Cook Strait, the NZ1/NZ2 transition and Invercargill need particular care with boundary interpretation. AS/NZS 1170.2:2021, Figure 3.1(B)
Read the selected map with the wind-speed table bearing the same edition label. Record the site coordinates, regional classification and any boundary interpretation. A national overview supports initial orientation; the project calculation must check the exact location against the applicable licensed Standard, including special regional and local provisions.
A council’s residential wind-zone label and an AS/NZS 1170.2 regional classification serve different purposes. “High wind zone” is not a substitute for the regional and site assessment required for specific engineering design. Conversely, a regional label alone says little about the pressure on an exposed roof corner.
Keep the map, regional-speed relationship, direction multipliers, terrain provisions and aerodynamic coefficients on a documented basis. Where information from another edition is introduced, identify and justify that departure instead of silently combining the two.
2. Select regional wind speed for the required probability
Table 1. Selected 2021 regional wind speeds in m/s
Reference basis: AS/NZS 1170.2:2021, including Amendments 1:2023 and 2:2024; Table 3.1(B). This is the 2021 engineering framework, not the regional table of the 2011 standard cited by B1/VM1.
| R (years) | Annual probability | NZ1 and NZ2 | NZ3 | NZ4 |
|---|---|---|---|---|
| 25 | 1/25 | 39 | 46 | 45 |
| 50 | 1/50 | 41 | 48 | 46 |
| 100 | 1/100 | 42 | 50 | 47 |
| 200 | 1/200 | 43 | 51 | 48 |
| 500 | 1/500 | 45 | 53 | 50 |
| 1000 | 1/1000 | 46 | 54 | 50 |
| 2000 | 1/2000 | 47 | 55 | 51 |
Source: AS/NZS 1170.2:2021, Table 3.1(B), printed page 26. Selected rows. NZ1 and NZ2 share regional speeds but remain separate regions for the directional provisions. The 2021 speeds use peak gusts with an equivalent moving-average time of approximately 0.2 seconds. They precede direction, terrain, height, shielding and topographic effects; Mc is 1.0 for NZ1 to NZ4. A regional value such as 44 m/s is not the B1/VM1 design wind speed used in consent screening.
Table 2. 2011 regional baseline for edition comparison in m/s
| R (years) | Annual probability | A6 and A7 | W |
|---|---|---|---|
| 25 | 1/25 | 37 | 43 |
| 50 | 1/50 | 39 | 45 |
| 100 | 1/100 | 41 | 47 |
| 500 | 1/500 | 45 | 51 |
| 1000 | 1/1000 | 46 | 53 |
Source: Climate Futures primary research report, Table 1, which attributes these baseline values to AS/NZS 1170.2:2011 Table 3.1. This limited comparison does not reproduce the complete amended B1/VM1 design procedure.
For B1/VM1 verification, use the cited 2011 edition with Amendments 1 to 5 and all verification-method modifications. More onerous local wind information published and required by the territorial authority takes precedence under B1/VM1 Section 2.4.1.1. Verify those local requirements before adopting a regional baseline. B1/VM1 Second Edition, Section 2.4
Regional wind speed, VR, is selected using the site’s wind region and the required annual probability of exceedance, commonly expressed as 1/R. The table is the beginning of the wind calculation. Its values do not yet include the site’s terrain, topography or the aerodynamic behaviour of the array.
The required probability depends on the project’s structural design basis, importance level and limit state. A 1-in-500 annual probability means a 0.2% chance of exceedance in any particular year. It does not mean the event happens once on a 500-year timetable, or that the mounting has a 500-year service life. Under a simple independent-year illustration, that annual probability produces about a 9.5% chance of at least one exceedance over 50 years. This is probability arithmetic, not a rule for selecting a project’s return period.
Design working life, importance level and return period should therefore appear as separate entries in the design brief. Attaching a shorter-life PV system to an existing building does not by itself justify reducing the wind demand on the building or its connections. The responsible designer needs to establish the applicable requirements.
Before accepting a table value, check three items together: the edition, the region and the annual probability. Then confirm whether any special provisions apply to the location. A number copied from a city example cannot settle a boundary site, a mountain-range exposure or the wind basis of an existing roof.
3. Screen consent separately from structural adequacy
New Zealand provides building-consent exemptions for qualifying roof-mounted solar work. The area and wind conditions are screening criteria; they do not supply mounting capacities or release the work from applicable Building Code requirements. MBIE consent-exemption guidance, sections 14.3 to 14.4
| Initial screening case | What to check |
|---|---|
| Total array area ≤40 m² on the relevant roof | Assess Exemption 28D, including all supporting-frame and structural-fixing conditions. Its wind criterion uses design wind speed ≤44 m/s calculated using B1/VM1, or a wind zone no greater than High under B1/AS1. |
| Area more than 40 m², or outside the 28D wind criterion | Assess Exemption 48A and the applicable Part 3 engineer-design or review conditions. Do not conclude that consent is automatically required from these two numbers alone. |
| Incomplete site, roof or design information | Resolve the missing facts before declaring the work exempt. A product’s rated wind speed cannot replace the specified assessment. |
The operative 28D area condition includes exactly 40 m², despite the shorter wording used in its heading. Multiple arrays must be assessed using the applicable total-area condition; splitting an installation into smaller arrays does not create separate allowances on the same relevant roof. Statutory conditions: Exemptions 28D and 48A
For the engineer-designed or reviewed route, the design must cover the actual installation and construction must follow that design. Where a pre-engineered kit is used, check that its signed design scope covers the site, roof, substrate and array arrangement. A certificate with no demonstrated connection to those conditions is insufficient evidence for the project. MBIE guidance, section 14.4
4. Carry terrain, direction and lee effects into site wind speed
A site behind a mountain range can still experience severe wind. In New Zealand, the assessment must consider nominated lee-zone effects as well as acceleration over local hills, ridges and escarpments. A survey limited to the property boundary may miss the terrain feature that controls the design.
Lee effects and hill-shape effects answer different questions. The former concern specified downwind exposure from mountain ranges; the latter concern local terrain geometry. Applicable elevation provisions add another input. Site elevation above datum is also different from the building reference height above local ground. Both need a clear value and source. The 2021 framework and Amendment 1’s lee-zone changes should be read together. AS/NZS 1170.2 publication text
Illustrative site-speed equation, 2021 engineering framework:
Vsit,β = VR × Mc × Md × Mz,cat × Ms × Mt
| Input | Record in the calculation |
|---|---|
| VR | Regional speed, wind region and annual probability. |
| Mc | Climate-change multiplier: 1.0 for all New Zealand regions in the 2021 framework. |
| Md | Wind-direction multiplier and the direction being assessed. |
| Mz,cat | Terrain category and reference height, with the required upwind-fetch assessment. |
| Ms | Shielding determined using the applicable New Zealand procedure and qualifying surroundings. |
| Mt | Local hill-shape, applicable lee-zone and elevation treatment. |
Here, β identifies the wind direction used for the site assessment. Each factor must follow the definitions and direction rules in the selected edition. Do not import Australian shielding assumptions or credit trees as qualifying building shielding. B1/VM1 calculations using the cited 2011 edition must follow that edition and the verification method’s modifications, rather than copying this 2021 equation unchanged. AS/NZS 1170.2 publication text, Section 2 site wind speed
Show true north, building axes, roof ridges and array rows on one plan. This lets the reviewer follow a terrain exposure through to the roof or array edge it loads. Collapsing everything into one speed too early can hide why a particular connection governs.
5. Match the solar method to the actual geometry
The 2021 publication set contains solar-specific provisions with defined scopes. Confirm the New Zealand compliance basis before using them, then check the complete geometry against the selected clause. A sales description such as “flush mount” or “commercial flat roof” is not an applicability check. AS/NZS 1170.2, Appendix B
Keep two reviews distinct. Clause applicability establishes whether the aerodynamic method covers the building and array. Structural verification checks the resulting reactions against the actual mounting, roof or foundation. Substrate thickness, purlin condition and fastening capacity are essential project checks even when the aerodynamic geometry qualifies.
B.6.3 belongs to the 2021 publication set with Amendment 2. Its use cannot be described as unmodified verification under a B1/VM1 basis that cites the 2011 edition. Tilted panels also generate horizontal and vertical reaction components; an uplift-only check can miss connection shear or frame demand. AS/NZS 1170.2, Appendix B and Amendment 2
6. Turn pressure into a complete load-path check
Velocity pressure follows the square of design wind speed. With all other terms unchanged, increasing speed from 40 m/s to 44 m/s increases velocity pressure by 21%. This illustrates the sensitivity of pressure to wind inputs.
For the 2021 engineering framework, a general pressure relationship is:
p = 0.5 × ρair × Vdes,θ2 × Cshp × Cdyn
Here, ρair is air density; Vdes,θ is the design wind speed for the relevant structural direction after the required site-to-design-speed procedure; Cshp represents the applicable aerodynamic shape treatment; and Cdyn accounts for dynamic response where required. In SI units, pressure is obtained in Pa. The calculation must state whether that pressure is a panel net pressure or a building-surface pressure. AS/NZS 1170.2 publication text
Panel net pressure and pressure across the building envelope are different quantities. Convert panel loads into support reactions, then assess the supporting roof under the applicable combined load cases. State the pressure sign, loaded area, coefficient basis and wind direction so that pressures or local factors are not counted twice.
For illustration, 1.5 kPa uniform net pressure over 2.0 m² produces a 3.0 kN resultant normal to that surface. It does not mean each roof foot receives 3.0 kN, or that four feet each receive exactly one quarter. Span, cantilever, eccentricity, load distribution and structural stiffness determine the individual reactions. This example explains units and load transfer; it provides no product capacity.
Trace the resulting forces through the module, clamps, rails, roof attachments, cladding or deck, purlins or battens, and primary framing. Check pull-out, pull-over, local deformation and member or connection capacity against the actual substrate and condition. Existing roofs need particular attention to corrosion, moisture damage, previous repairs and fastening details.
Research illustrates why the roof cannot simply be assumed unchanged. Tests of flush-mounted PV on 15° gable and flat roofs reported increases of about 10% and 40%, respectively, in critical batten-to-truss connection demand beneath leading-edge panels. Those results apply to the tested configurations and are not general design multipliers. They demonstrate the need to examine the supporting connection as well as the mounting above it. Ingham and colleagues, AWES 2024
Provide a pressure and reaction schedule covering every applicable roof and array zone. Uniform fixing spacing can be valid when calculations demonstrate that it satisfies all relevant zones and load cases. The concern is missing verification of the controlling demand, not uniformity itself. Installation drawings should make that verified arrangement unambiguous.
7. Prepare a reviewable mounting package
A useful engineering handover makes the assumptions inspectable and the installation repeatable. It should contain enough information for the project team to connect the site basis, mounting layout and supporting structure without guessing.
| Project information | Minimum useful content |
|---|---|
| Site and design basis | Coordinates, elevation, region, edition and amendments, compliance pathway, importance level, limit states and required probabilities. |
| Building and roof | Dimensions, roof pitch and orientation, openings, parapets, drawings, existing design basis and condition observations. |
| Supporting construction | Roof profile and thickness, support spacing, member details and grades where available, fastening arrangement and relevant capacity evidence. |
| Array and mounting | Module dimensions, layout, tilt, gaps, setbacks, rail direction, spans, cantilevers and attachment or ballast arrangement. |
| Design outputs | Applicable clause and scope check, pressure zones, reaction schedule, capacity checks and installation requirements. |
Wind is one part of the structural assessment. Address dead load, serviceability and, where applicable, snow, seismic restraint, sliding, overturning and foundation behaviour. Roof penetrations must preserve weathertightness, while materials and corrosion protection must suit the exposure. Record unresolved information before a layout is accepted for construction.
Planning a New Zealand solar mounting project?
Send Solaracks the site location, roof drawings, proposed module layout and available wind-design basis. Include roof profile, substrate thickness and support spacing where known, and identify information still to be confirmed. For New Zealand projects, state the engineering edition and compliance pathway separately. Product pages: standing-seam mount SR-R3, L-foot rail mount SR-R5, tile-roof rail mount SR-R8 and ground screw pile SR-G5.
Frequently asked questions
Should a New Zealand solar project be designed to the 2021 or the 2011 edition of AS/NZS 1170.2?
B1/VM1 Second Edition cites AS/NZS 1170.2:2011 with Amendments 1 to 5 and the verification method’s own modifications. The 2021 publication set with Amendments 1 and 2 is a separate design basis. A specification calling for the 2021 edition does not by itself demonstrate Building Code compliance; a departure from the cited verification method needs an explicit compliance justification. Settle the edition and the compliance pathway before the calculation is run.
Does a regional value such as 44 m/s mean the site’s design wind speed is 44 m/s?
No. A regional value is selected by wind region and annual probability, and it precedes direction, terrain, height, shielding and topographic effects. It is not the B1/VM1 design wind speed used in consent screening.
Can the council’s “High wind zone” label be used to select a mounting system?
No. A council’s residential wind-zone label and an AS/NZS 1170.2 regional classification serve different purposes. “High wind zone” is not a substitute for the regional and site assessment required for specific engineering design. Conversely, a regional label alone says little about the pressure on an exposed roof corner.
Is a roof-mounted array of 40 m² or less exempt from building consent?
Not automatically. Exemption 28D covers a total array area of 40 m² or less on the relevant roof (exactly 40 m² is included), with a wind criterion of design wind speed of 44 m/s or less calculated using B1/VM1, or a wind zone no greater than High under B1/AS1, plus its supporting-frame and structural-fixing conditions. Larger or non-qualifying arrays are assessed under Exemption 48A and the applicable engineer-design or review conditions. The exemptions are screening criteria and do not supply mounting capacities.
Does the existing roof need checking, or just the mounting?
Both. Panel net pressure and pressure across the building envelope are different quantities: convert panel loads into support reactions, then assess the roof under the applicable combined load cases. Tests of flush-mounted PV on 15° gable and flat roofs reported increases of about 10% and 40%, respectively, in critical batten-to-truss connection demand beneath leading-edge panels. Those results apply to the tested configurations and are not general design multipliers.
Does a site behind a mountain range get shelter from the wind?
Not necessarily. Nominated lee-zone effects and acceleration over local hills, ridges and escarpments are separate checks, and a survey limited to the property boundary may miss the terrain feature that controls the design.
For Australian projects, see Solar mounting wind design in Australia. For design wind speeds across other markets, see Global design wind speeds for solar mounting systems. For a general checklist, see Solar PV design in high wind areas.
This article explains the review process. Project design requires the applicable licensed standards, current compliance requirements and assessment by appropriately qualified professionals.
Be Supported.