Swisspearl Windstopper Basic

Swisspearl Windstopper Basic is a wind and weather barrier board installed behind exterior cladding. It is a build board, not a finished façade panel, and it is placed behind the final cladding of a ventilated wall rather than left as the outer screen. In the US listing it is a commercial rainscreen substrate. It sits behind the insulated wall and rainscreen systems that carry the visible Swisspearl panels.

The datasheet for the board is dated May 2023 and is titled Datasheet - Build Boards.

The board consists of gray cement and limestone filler, reinforced with a specially selected fiber material. The fiber absorbs and releases moisture without affecting the durability, strength or performance of the board. The manufacturing process does not include compression, which leaves a natural rough surface. The surface is uncoated and is one natural color.

The board resists rot and fungal growth and withstands considerable fluctuations in weather and climate conditions. It is non-combustible.

Windstopper Basic has a very low vapor transmission resistance, so moisture from inside the building can pass through it. Insulation can therefore be placed directly against the inner side of the board.

• Vapor transmission resistance, Z-value: 1.7 GPa m² s/kg.
• Vapor transmission resistance: 12453 s/m.
• Vapor diffusion equivalent air layer thickness, Sd: 0.33 m.
• Vapor resistivity: 176 MN s/(g m); resistance factor μ: 34.2.
• Water vapor transmission: 10.3 USPerm.

Air permeability (EN 12114) is 0.004 m³/m² h Pa. Water impermeability (EN 12467) is recorded as no drop.

• Thickness: 9 mm.
• Standard width: 1200 mm (47.24 in). Standard lengths: 2400, 2700 and 3000 mm (94.49 in for the 2400 mm board).
• Project sales sizes reach a maximum of 3050 mm in length and 1250 mm in width.
• Tolerances (EN 12467, Level 1): thickness +/- 0.9 mm, width +/- 3.6 mm, length +/- 5 mm.
• Dry density: 1300 kg/m³ minimum, 1450 kg/m³ average (EN 12467).
• Average weight including 5 percent moisture: 13.7 kg/m².
• Moisture content on dispatch ex works: 3 to 7 percent.

• Bending modulus of elasticity: 2 GPa along the grain and 3 GPa across the grain at ambient conditions.
• Bending strength, ambient: 9 MPa along the grain and 11 MPa across the grain.
• Bending strength, wet: 4 MPa along the grain and 6 MPa across the grain.
• Coefficient of thermal expansion: 0.01 mm/m °C.
• Thermal conductivity, λ10 (ISO 8301, EN 12667): 0.34 W/(mK).
• Frost resistance: 25 cycles (RL greater than 0.75, EN 12467).

Water absorption (24 hours at 105 °C, 24 hours in water, EN 12467) is 21.0 percent. Moisture movement at 30/90 percent RH is 1.07 mm/m, and wet-dry-wet movement is 3.1 mm/m.

Sound reduction under ISO 717-1:2013 is Rw 32 dB, Rw + C 30 dB and Rw + Ctr 29 dB.

• Reaction to fire (EN 13501): A2-s1, d0.
• Fire protection classification (EN 13501-2): K1 10 and K2 10.
• ASTM E136: Pass.
• Category and class: NT D2 I.

Installed to the Swisspearl installation instructions, Windstopper Basic can function as a temporary façade for up to 6 months.

The US product page gives attachment information for steel and wood framing. On steel the screw is the SCR-S 4.2 by 30 millimeter universal screw. On wood it is the SCR-W 3.9 by 38 millimeter universal screw, with no predrilling required in the listed application.

The companion board Windstopper Extreme has a different size range, a longer temporary-exposure period and an A1 fire classification.