The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
Being narrow, mountainous, islands lying in the path of strong prevailing winds, New Zealand is subject to high rainfall and high humidity. Compared to much of the world — where 70% relative humidity is considered the threshold of corrosion and health problems — New Zealand has very high humidity, particularly in northern regions, where the mean annual humidity levels are often around 80% or more. This means the dew point (temperature at which condensation begins to form) is also higher than in colder but drier climates.
The design requirements to deal with this environment are specific to New Zealand, which is reflected in our building practices. It is not advisable to use design or installation practices from countries with different environmental conditions without a comprehensive assessment of the management of internal moisture under NZ conditions.