The Dow THERMAX™ Wall System is designed for commercial applications, providing continuous insulation and a drainage plane for exterior walls. Installation involves adhering THERMAX™ insulation boards to steel stud framing, with specific recommendations for joint closure to maximize efficiency and minimize air and moisture infiltration. The system allows for scheduling overlaps, enabling multiple contractors to work concurrently on finishing the exterior wall. Several joint closure systems are available, utilizing components such as foil tapes, clip strips, interlocking systems, J-channels, and flashing, along with appropriate sealants and adhesives.
System Overview and Sequencing
Installation of the THERMAX™ Wall System can commence after the structural steel and exterior wall steel studs are installed and braced. The system’s design allows for immediate installation of THERMAX™ (ci) Exterior Insulation boards, which can remain exposed for up to 180 days. As boards are applied, WEATHERMATE™ Flashing is adhered to adjoining board joints and around thru-wall penetrations. Windows and other openings are flashed after removing excess insulation in those areas. This process creates an insulated and weatherized building envelope. The system is applicable to walls only; THERMAX™ Heavy Duty Plus Insulation is not designed for other applications. Specialized considerations apply to parking garage ceilings, requiring direct consultation with Dow representatives.
THERMAX™ (ci) Exterior Insulation Installation
Specific installation recommendations exist for THERMAX™ (ci) Exterior Insulation. Boards should be installed horizontally with the printed side facing exteriorly and the shiplap edge oriented upwards when contacting steel studs. Maximizing board lengths minimizes the number of joints. Edge joints should be aligned parallel to and on the framing flange, with end joints centered over supports and staggered in each course.
The insulation boards are secured to the exterior face of the exterior metal stud wall framing using appropriate fasteners. Fasteners should be spaced 12 inches on center at the perimeter and 16 inches on center in the field. Dow specifies the Wind-Lock ci-LOCK fastener/washer system, as it was used during ASTM E330 wind load testing. However, other fasteners specifically designed for rigid foam sheathing may be used, as detailed in Tech Solutions 513.0.
Joint Closure Systems and Components
Properly finished joints are crucial for maximizing the efficiency of THERMAX™ Polyisocyanurate Insulation, particularly in metal buildings and alternative applications like tilt-up concrete wall panels. Finished joints reduce air leakage and moisture infiltration, and contribute to a professional appearance in interior applications. Dow recommends several joint closure systems applicable to various THERMAX™ products, including:
- THERMAX™ Sheathing
- THERMAX™ Metal Building Board
- THERMAX™ Heavy Duty
- THERMAX™ Heavy Duty Plus
- THERMAX™ Light Duty
- THERMAX™ White Finish
Each joint closure system utilizes one or more of the following components:
- THERMAX™ white foil tape (for THERMAX™ Heavy Duty, THERMAX™ Heavy Duty Plus, THERMAX™ Light Duty, or THERMAX™ White Finish)
- THERMAX™ aluminum foil tape (for THERMAX™ Sheathing and THERMAX™ Metal Building Board)
- Clip Strip
- Interlocking System
- J-Channel
- WEATHERMATE™ Straight Flashing
- Construction-grade sealant and adhesive
- Shiplap board joint
All accessories required for these systems are available for purchase in conjunction with the insulation products. Specific product installation guidelines should be consulted for detailed board attachment procedures.
Detailed Joint Closure Option: Foil Tape Application
One specific joint closure option involves the application of THERMAX™ foil tape. This method is suitable for square-edged boards. The procedure involves centering the appropriate foil tape (white for certain THERMAX™ products, aluminum for THERMAX™ Sheathing and Metal Building Board) over a dry, clean edge joint and applying it firmly. A squeegee or stiff bristle brush should be used to ensure complete adhesion. The tape should be cut with a knife rather than torn to maintain its integrity.
Sealant and Adhesive Recommendations
To achieve a continuous air- and moisture-resistant seal, the documentation recommends using Vulkem 116, Sikaflex 201, or Dow Corning 790, or an equivalent sealant. Dow representatives can provide recommendations for appropriate sealants and adhesives based on the specific application. Construction-grade sealant and adhesive are also listed as components of the joint closure systems.
Repair Procedures
Minor repairs to the THERMAX™ Wall System can involve applying a strip of flashing over small holes. Larger holes may require filling with a piece of THERMAX™ insulation board, followed by appropriate flashing and sealant application.
Conclusion
The Dow THERMAX™ Wall System offers a comprehensive solution for continuous insulation and weatherization in commercial building applications. Proper installation, particularly regarding joint closure, is critical for maximizing performance and ensuring long-term durability. The system’s modular design and compatibility with various accessories allow for flexibility and efficient construction scheduling. Adherence to the manufacturer’s recommendations regarding fastener spacing, sealant selection, and joint closure procedures is essential for achieving optimal results.