EXPAND YOUR BUSINESS Optimizing wall performance Using rainscreen metal walls for high-performance walls
For high-performance walls that manage moisture movement, consider exterior met- al-framed walls designed using rainscreen principles. With the DOW-KNIGHT CI-System from Midland, Mich.-based Dow Building Solu- tions, contractors can easily build rainscreen metal framed walls, while designers benefi t from the ad- ditional value of continuous insulation for improved energy effi ciency, fl ashing and an air barrier in a four-in-one solution. In rainscreen design, the exterior cladding
sits away from the backup wall, creating an air cavity to help protect the building’s important weather-resistant barrier. By design, any mois- ture that does migrate through the cladding will easily drain down the cavity, away from the building. Air that fl ows between the cladding and the wall accelerates evaporation of any residual moisture (Figure 1). A properly designed rainscreen accommo-
dates water penetration; it should not be confused with a weather-resistant barrier, which is just one component of a rainscreen and whose primary function is to provide barrier protection against water penetration. Instead, a rainscreen limits the amount of water that could potentially come into contact with the primary building envelope mois- ture barrier, to reduce the chance of water fi nding a way into the wall assembly.
Four-in-One Solution The DOW-KNIGHT CI-System delivers a systematic approach to achieving effi ciency at every level: simpli- fi ed design, streamlined construction and reduced energy consumption. The award-winning system addresses one of the biggest challenges facing designers: how to obtain continuous insulation (ci), especially with thick insulation, when attaching clad- ding without creating a thermal bridge. (Figure 2). To maintain the required air space, the DOW-KNIGHT CI-System uses the CI-GIRT.
This all-in-one cladding attachment, support and rainscreen cavity system lets a wide range of claddings be installed without thermal bridging. In addition, fasteners that penetrate the insula- tion are also isolated to further increase effi cien- cy. The unique design acts as a brace, working with the rigid insulation and fasteners for wind and cladding load resistance. This approach eliminates the need for a separate furring system that penetrates the insulation and may create a thermal bridge. The result is a wall system that delivers true continuous insulation. Because the claddings mount on the same sub-frame, mul- tiple claddings can be used on the same building without altering the sub-frame or the primary building envelope. The layer of rigid continuous insulation uses
high R-value THERMAX (ci) Exterior Insulation to moderate the temperature of the wall cavity, and help reduce the potential for dew point condensa- tion, mold and mildew. An integral, durable acrylic- coated aluminum facer provides a drainage plane and water-resistive barrier, eliminating the need for an extra step to install a membrane or building wrap. Up to 3 inches* of insulation (depending on the exterior veneer) can be used. To further protect the wall from possible
moisture entry, WEATHERMATE Flashing is used at through-wall penetrations, including over the insulation ship-lapped joints to help direct water drainage to the outside of the wall assembly. The butyl rubber adhesive fl ashing tape is self-sealing and self-healing to make installation quick. Finally, to meet any air barrier requirements in-
creasingly required by energy codes, STYROFOAM Brand Spray Polyurethane Foam (SPF) Insulation (CM Series) is applied in the steel stud wall cavity to effectively block air infi ltration by fi lling gaps, cracks and penetrations. With this insulation—as well as the rigid insulation—there is no need for batt insulation in the cavity.
Streamlined Construction Contractors appreciate the ease of installation as no expensive tools are required to assemble the system, including the cladding attachment framing. Backed by two well-respected industry leaders, a complete package of installation videos and guides are avail- able, as well as other free support tools such as CAD details, guide specifi cations and project profi les. Here’s a quick snapshot of how the DOW-
KNIGHT CI-System is installed: • Install the structural steel and exterior wall steel studs.
• Install and appropriately fasten each THERMAX (ci) Exterior Insulation board.
• Seal all end and edge joints and through-wall penetrations with WEATHERMATE Flashing.
• Install the STYROFOAM Brand Spray Polyurethane Foam Insulation (CM Series). NOTE: Only trained and qualifi ed personnel should install the spray foam insulation.
• When the spraying job is completed, install the cladding attachment system with any of the approved veneers including terra cotta, stucco, metal composite metal, cladding, metal panel and fi ber cement siding. Construction can be streamlined. For example,
once a portion of the rigid insulation is correctly installed and fl ashed, the rainscreen cladding attach- ment system can be installed. Once closed in, the insulated and weatherized envelope allows work to progress quickly on the building interior, speeding up the work of other trades beyond the exterior walls.
Doug Todd is the market manager of commercial construction for Midland, Mich.-based Dow Build- ing Solutions, North America. For more informa- tion, visit
www.building.dow.com. For more information, including installation instructional videos, see
building.dow.com/na/en/dowk- nightsolutions.
By Doug Todd
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5 4
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WEATHERMATE Flashing over board joints and penetrations
5 Exterior claddings Figure 1: Components of an effective rainscreen. Figure 2: Four-in-One Solution
* Exact insulation thickness depends on specifi c cladding and wall assembly details per NFPA 285 fi re approval ®™* Trademark of The Dow Chemical Company ("Dow") or an affi liated company of Dow
40 METAL CONSTRUCTION NEWS December 2012
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Continuous layer of THERMAX (ci) Exterior Insulation
CI-GIRT Attachment System to maintain air space
STYROFOAM Brand Spray Polyurethane Foam (SPF) Insulation (CM Series) in cavity to meet air barrier requirements
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