Role of WRB in Open-Joint Cladding Design

Open-joint cladding systems are unique. While enhancing the visual aesthetics of a building, they expose structural components within the wall to wind, water, and sun, ultimately jeopardizing building performance if not properly protected.

Applying a barrier will provide extreme water and UV protection. If the water-resistive barrier (WRB) selected is not designed to withstand all weather climates, or stable when exposed to prolonged periods of UV light, the wall system will prematurely fail.

In a recent issue of Construction Specifier, Dörken’s Peter Barrett explains the important role of WRBs in open-joint cladding, diving deep into proper installation, UV stability, and the value of industry testing. Peter’s experience with the design community and building materials spans more than 25 years, and he is currently a board member of the Air Barrier Association of America (ABAA).


Building Protection

A WRB, specifically manufactured for open-joint cladding systems, is designed as a part of the primary cladding to channel bulk water from wind-driven rain and snow to the outside of the structure – keeping the wall dry and protecting the insulation from the effects of wind-washing.

As Peter outlines in the April Issue of Construction Specifier, if wind, rain, and snow can get through the open joints, so too can UV light. This accelerates the aging process of the wall system, having a significant impact on the performance of the exterior wall assembly. Using a UV-stable membrane, along with best practices in understanding and preventing excessive UV exposure, will help protect components of the wall system.


The High-performance Solution

Designed for permanent UV exposure in open-joint cladding systems, DELTA®-FASSADE S may be installed in all back-vented cladding systems featuring open joints up to 2” (50 mm) wide and open-joint areas of up to 40% of the entire surface. Its acrylic coating ensures weatherproof performance that won’t break down, no matter the environment. The product’s advanced ability to reduce wind-washing of insulation also provides enhanced energy efficiency, helping maintain R-values and reducing heat loss.

With DELTA®-FASSADE S there is no need to ever leave insulation exposed, subjecting it to the elements that break it down over time. It means building the best wall, both structurally and aesthetically, for the best protection.

As the first water-resistive barrier of its kind, DELTA®-FASSADE S was developed based on the philosophy of “no compromise.” At a time when building professionals were left deciding between design integrity and protection, the new advancement of DELTA®-FASSADE S provided a solution that allowed for architects to be innovative with open-joint cladding while knowing their buildings were set up for success.

Extensive research, trialing, and testing went into the development of DELTA®-FASSADE S to ensure the product’s effectiveness and longevity. DELTA®-FASSADE S is now well known in the industry for its superior ability to protect buildings, resist UV rays, maintain the integrity of the insulation underneath, and complement any open-joint cladding design.

It is for this reason that DELTA®-FASSADE S is still the only UV-resistant barrier solution for open-joint cladding available on the market that has been tested to and passed ICC-AC38.


Effective Installation

The right water-resistive membrane will also be highly vapor permeable, allowing moisture within the wall cavity to move through diffusion, while protecting the insulation from possible damage by moisture infiltration. To ensure the selected WRB performs accurately in an open-joint cladding system, it must be installed in a way that seals all potential leakage points, including:

  • Wall connections to the roof’s air barrier and the building foundation;
  • Seismic and expansion joints;
  • Piping, conduit, duct, screws, bolts, and similar penetrations;
  • Changes in plane; and
  • All other potential pathways for air and water leakage in the building enclosure.


The Collaborative Life Sciences Building (CLSB) in Portland, Oregon is made up of prefinished perforated panels of aluminum, fabricated in a corrugated profile. With unique features, the design required a durable building envelope that could withstand Oregon’s notoriously high wind and wet weather – DELTA®-FASSADE S was specified for the project as it is designed to channel water from wind-driven rain and snow to the outside of a structure.


Protecting buildings with open joint claddings from water, wind, and sun is extremely important since, unlike other cladding designs, open joints could expose the inner parts of the wall to all weather conditions. The featured case study outlines the importance of installing a membrane that is water and wind resistant in open-joint cladding systems. With DELTA®-FASSADE S, building professionals deliver a product clients and occupants will appreciate – for both look and feel.