Roxul ComfortBoard IS - Manual (Page 19)

INSULATING SHEATHING FOR RESIDENTIAL CONSTRUCTION APPLICATION GUIDE 17
Cladding attachment through Continuous Insulation
Cladding attachment is a common question when assemblies with exterior continuous insulation (“ ci “)
are proposed. Although solutions for semi-rigid stonewool insulation boards are not currently widely
used in all parts of North America, they are simple, straightforward, and time tested in Europe and other
parts of the world. Two methods of cladding attachment are considered here:

a “Thin ci” approach for ROXUL COMFORTBOARD IS thicknesses of 1.5” (38 mm) and less,
where light-weight cladding systems are attached directly to the wall structure through the
insulation, and

a “Thick ci” approach for ROXUL COMFORTBOARD IS thicknesses greater than 1.5” (38 mm),
where light-weight or mid-weight cladding systems are attached to furring that is itself
fastened to the structure through one or more layers of insulation
1.5” represents a practical limitation to the “Thin ci” approach because this is the maximum thickness
that commonly available fasteners can span to reach the wall structure. In addition, insulating sheathing
of all types has long been used by the industry at thicknesses of up to 1.5” or 38 mm and hence there is
experience with its installation and detailing.
For light-weight cladding systems, such as vinyl siding, wood siding, and fiber cement siding or panels,
on low rise buildings that are not in a high wind design area, the “Thin ci” cladding attachment approach
is appropriate. This approach takes advantage of the compressive strength of the insulation to support
the cladding (see Figure 7
below).
Figure 7: A "strut-and-tie" model can be used to explain the remarkable strength and stiffness that is achieved
through the use of standard furring strips screw fastened through insulating sheathing. This low-cost and high-
performance approach can be used to support gravity loads for most lightweight claddings.
For ROXUL COMFORTBOARD IS thicknesses greater than 1.5” (38 mm), light-weight and mid-weight
(stucco, manufactured stone veneer) cladding, systems must be attached using the “Thick ci” approach.
This approach requires that furring or “strapping” first be attached through the insulation, often with
long fasteners, directly to the wall structure. The cladding is then attached to the furring (see Figure 8
below).