Building codes and standards

Cavityrock® Black: the future of open-joint rainscreen application design

January 1, 1

Simplify your wall assembly by combining the insulation installation and masking in one step

Rainscreen cladding systems continue to gain traction in the market, mainly for the benefits offered in terms of rainwater management.

While traditional the joints of these systems have been sealed to minimize the potential for water intrusion into the drainage cavity, today architects and designs are increasingly moving toward open-jointed rainscreen options.

What is an open-joint rainscreen?

In new construction, particularly in climate zones where rain or snow is a regular part of the annual weather patterns, the enhanced moisture management properties of rainscreen cladding systems have helped them become the norm.

The move toward open-joint rainscreens means that the joints between the cladding elements are intentionally left open, principally to increase the aesthetic appeal of the structure’s exterior. While it may seem those aesthetics come at the expense of the system’s performance, that’s not necessarily the case. While closed joints provide optimum protection against the impact of water, open joints are perfectly acceptable when the system is designed with proper ventilation.

The role of insulation within the exterior wall assembly

Hydrophobic in nature, ROCKWOOL stone wool repels water. If some water does enter the insulation from snow or wind-driven rain, it can dry out due to the higher drying potential of stone wool – making it an ideal choice for open-joint rainscreens.

Once added to the external cavity, the insulation offers superior long-term thermal efficiency with a stable R-value, fire resilience given its non-combustible characteristics, and added acoustic performance. Stone wool is also easy to install within framing systems and helps to protect the WRB from exposure to UV, variability in heating and cooling cycles, oxidation and the elements to lengthen the lifespan of the wall assembly.

Learn more about the future of high-performance rainscreen systems in our brochure.

Introducing the next phase of open-joint rainscreen design with Cavityrock® Black

This new insulation board is specially designed to mask the insulation layer in open-joint rainscreen application designs with a bonded black mat fleece facing that leaves you with crisp, black lines.

By using a technology unlike any other in the North American mineral wool market, ROCKWOOL applies the fleece used on Cavityrock® Black before the product has been cured, bonding the two materials into one and offering improved mechanical properties and superior long-term performance. Not only that, the black mat fleece has been purposely designed for exposure to the elements (weather, heat, and UV).

Following in the footsteps of the performance you’ve come to know and expect from ROCKWOOL Cavityrock® stone wool insulation, Cavityrock® Black maintains the thermal performance of R4.3 per inch and achieves a flame spread and smoke development index lower than commonly used black scrim materials.

For open-joint cladding solutions where your goal is to improve aesthetic, this product delivers that while saving time on the job site. When many open-joint cladding solutions are using a combination of materials such as a secondary weather-resistive barrier (WRB) to mask the insulation layer, Cavityrock® Black simplifies the system by combining the insulation installation and masking all in one step. This reduces the installation time and material cost to achieve the clean, distinguishable aesthetic along the façade.

Available in a variety of dimensions to meet the requirements of your project, Cavityrock® Black features a dual-density design in thicknesses greater than 2”. More information about the product including performance against industry test standards is available by downloading a copy of the product datasheet.


R-value (4.3/inch)

2” x 16” x 48”


2” x 24” x 48”


3” x 16” x 48”


3” x 24” x 48”


4” x 16” x 48”


4” x 24” x 48”


5” x 24” x 48”


6” x 24” x 48”




Cavityrock® Black

Unrivaled open-joint rainscreen façade aesthetic. Efficient job-site installation. Same great Cavityrock® performance.


20200309 RWNA PROD 1574