Rain Control / Weather Tightness

Uncontrolled rain water penetration remains the most fundamental threat to the structural integrity and performance of the building enclosure. The essential 4D’s of weather protection are Deflection, Drainage, Drying and Durability and all of these issues need to be considered when specifying the building envelope. Claddings do the job of deflection, but how good are the layers in behind the cladding at dealing with the other 3D’s?

Why is the ARIDON® SMART WALL a superior weather protection layer?

The ARIDON® SMART WALL comprises rigid interlocking panels which form a continuous weather resistant shell around the building wall frame before the claddings are installed. The SMART WALL system includes all the flashings required to provide peace of mind from external moisture problems no matter how complex the building is.

Key features include:

  • Superior jointing – ARIDON® SMART WALL’s interlocking self-sealing joints mean that each panel interlocks with its neighbour forming a continuous shell that is not reliant on tape at every joint.
  • Homogeneous weatherproofing - ARIDON® SMART WALL panels are made of extremely high density water resistant EPS. The moisture resistance is consistent through the entire thickness of the panels ensuring water is kept out of the framing cavity. The SMART WALL panels are not reliant on a thin skin of water-proofing which can easily be damaged and/or lock moisture in.
  • Built in drainage cavity - ARIDON® SMART WALL ribbed panels incorporate an in-built drainage cavity via its moulded ribs in the front face to provide drainage and drying capability behind the cladding. Water that does penetrate the cladding will not penetrate the wall framing cavity; thereby reducing material degradation and extending the service life of the building.
  • Moves the Risk Zone – ARIDON® SMART WALL moves the ‘risk zone’ of water penetrating the wall frame at least 60mm further away from the structure
    Good design – the ARIDON® SMART WALL system has been thought through to create a reliable secondary water-proofing layer. Every project, however, is unique and the ARIDON® team are there to provide specialist knowledge and detailing advice specific to your project.
  • Temporary weather protection – The ARIDON® SMART WALL system has been BRANZ Appraised as a 60 day temporary cladding meaning that inside trades can start work as soon as the ARIDON® Smart Wall system is installed and the windows are in – saving significant time on the build.

Figure 1: SMART WALL – PANEL TOP: Rain is deflected down the panel and out the base. Compressible V rib air and moisture seals prevent moisture moving into the framing cavity.

Figure 2: SMART WALL – PANEL Base: Rain is deflected down the panel and out the base. Compressible V rib air and moisture seal.

What exactly is the ARIDON® SMART WALL jointing system?

The secret to the SMART WALL system is in the jointing. All panels have a moulded interlocking detail around the outside enabling panels to fit into the neighbouring panel creating a waterproof seal without the need for any tapes or sealants. This incorporates a factory moulded shiplap joint with a 6mm capillary groove plus 2 compressible V rib air and moisture seals. What this means is that the waterproofing between panels can be assured regardless of how cold, windy or dusty the site may be during construction. EPS is a stable material that doesn’t degrade and there is no reliance on adhesion for sealing and so there is no concern around things “coming unstuck” in the wall cavity.

Figure 3: SMART WALL – Interlocking Panels: Moulded interlocking joint with capillary groove and compressible V rib air & moisture seals

Separating the Wet and Dry Zones in the Building Envelope

Wall constructions should be separated into the “wet zone” and the dry zone” within the envelope.
The wet zone is intended to be exposed to short and long term effects of rain water penetration and/or moisture ingress.

Think of the wet zone as two layers of defense – the cladding is like an umbrella and it blocks the majority of rain – however sometimes driving rain can get past your umbrella. This is where we need a strong second line of waterproof defense that can not only block the rain and ensure it is drained away from the frame (the dry zone) but also block the wind - as wind can drive moisture into the dry zone.

Weathertightness in New Zealand

Source: BRANZ

Weathertightness1 has become an important issue in New Zealand. The Claddings Institute of New Zealand has been making its members aware of these problems and, in 2000, undertook a study tour to the USA and Canada.

Source 1: http://www.cinz.org.nz/newsweathermay02.htm

  • Key Findings:
  • All buildings leak - More rain means more rain control is needed.
  • Moisture penetration is deceptive in its apparent simplicity.
  • The building envelope must have drying potential.
  • Greater building complexity leads to lower building performance.
  • The envelope is a climate transition zone that can provide ideal micro-ecological niches for destructive organisms.
  • The creation of energy efficient buildings has resulted in tight, cold and unforgiving claddings.
  • Scientific research is needed to better understand the building envelope and its role with moisture - Such understanding will eventually lead to a rational approach for the development and design of exterior wall systems.

It has taken 14 years – but finally a supplier has developed an exterior wall system which suits any cladding type and provides superior protection for the frame against rain. The SMART WALL is the solution the NZ building industry has been looking for.


Do I need a building wrap?

No building wrap is required on either side of the ARIDON® SMART WALL panels as the SMART WALL system provides a far superior level of water resistance than any flexible wrap. Building wraps may be required for other reasons for a specific project and we recommend Aridon Ltd is contacted to discuss this during design.

How does the ARIDON® SMART WALL perform if exposed to moisture?

Typically when insulation gets wet it needs to be replaced as mould and mildew forms and the material has degraded in terms of performance. EPS is one of the most resistant products to the adverse effects of moisture.

Moisture spreading within the installation or after accidental leakage will only marginally influence the thermal performance of EPS. This results in lifetime durability.

Interesting Fact: After almost 30 years in the ground, samples of EPS retrieved from locations as little as 200 mm above the groundwater level all showed less than 1% water content by volume, whilst blocks which are periodically entirely submerged show less than 4% water content - performance notably superior to other foamed plastic materials. EPS is used for floating decks as a base for river buildings and sea pontoons so moist coastal air is no problem for EPS.

What is temporary weather protection?

The ARIDON® SMART WALL system has been BRANZ Appraised as a temporary cladding and so provides temporary weather protection to the build. Whether it is a re-clad or a new build, it is important that ‘dry’ areas of the building dry out as soon as possible and remain weathertight during construction. Specifying temporary weather protection speeds up the project and provides certainty around programming of internal and external trades since internal tradesmen such as plumbers, electricians and GIB fixers can be working prior to the external wall claddings being installed. This can take 2-4 weeks out of the build process for a single residential dwelling.

Does the SMART WALL shrink when it gets wet?

EPS is one of the most resistant products to the adverse effects of moisture. Other board type systems can suffer from shrinkage which means that gaps might open up between the boards. The stable qualities of the EPS material in the ARIDON SMART WALL system combined with the unique overlapping jointing system means that long term weather tight performance is assured.

Can the SMART WALL be installed when it rains?

Absolutely!! EPS is one of the most resistant products to the adverse effects of moisture; there is no risk of degradation due to moisture ingress. Tip - Other foam boards cannot be installed in the rain and require replacement if wet –so it’s always important to read the material installation instructions when researching products. The moisture run-off from SMART WALL panels is not acidic and so there is no elevated risk of rusting of screws and/or structure.

Why are there no weatherproof facings on the ARIDON® SMART WALL panels?

They are not required and facings do more harm than good. We have selected a specific type of EPS bead, production process and panel thickness to ensure the SMART WALL panels are water resistant. Any moisture that might find its way into the ARIDON® layer through damage or a services penetration migrates naturally to the closest surface. Most leaks occur from the outside and so that moisture is able to migrate to the drainage cavity behind the cladding and drain outside. The key advantage of this is that there is no risk of moisture being trapped between water resistant layers to eventually find its way into the wall frame. In addition, a thin skin of weatherproofing is always more vulnerable to leaks through penetrations and mechanical damage.