Cush a Therm
Cush-A-Therm is a patented, pre-insulated pipe clamping support system manufactured by ZSi-Foster and Unistrut, engineered to secure chilled water, refrigeration, and HVAC piping directly to standard metal strut channel without crushing insulation or compromising vapor barriers. By integrating high-density polyurethane foam cores with durable elastomeric insulation sleeves, Cush-A-Therm eliminates thermal bridging, stops condensation drip, and prevents corrosion under insulation (CUI) across commercial mechanical installations.
Engineering Principles and Thermal Bridging Prevention
In commercial chilled water systems operating at 38°F to 45°F or low-temperature ammonia refrigeration lines running sub-zero, traditional uninsulated pipe clamps create severe thermal bridges. Heat from ambient building air rapidly conducts through steel strut clamps into the chilled pipe wall, causing atmospheric moisture to condense uncontrollably into water droplets that damage ceiling tiles and foster mold growth.
Cush-A-Therm solves this critical building envelope failure by encasing the piping within an airtight thermal barrier. Its structural core consists of high-density rigid polyurethane foam capable of supporting full pipe fluid operating weights, surrounded by closed-cell elastomeric rubber foam that seamlessly tapes into surrounding pipe insulation runs, preserving an unbroken vapor retarder barrier.
Review technical performance parameters, temperature ratings, and compliance standards for Cush-A-Therm clamps:
| Engineering Metric | Performance Specification | Test Standard | Mechanical Application Impact |
|---|---|---|---|
| Operating Temperature Range | -50°F to +225°F (-45°C to +107°C) | ASTM C-534 | Supports cold refrigeration and hot hydronics |
| Insulation Core Material | High-density polyurethane foam | ASTM D-1621 | Resists crushing under filled pipe weight |
| Outer Vapor Barrier | Closed-cell flexible elastomeric | ASTM E-96 | Zero vapor permeance stops condensation drips |
| Flame & Smoke Spread Rating | Class 1 (25 Flame / 50 Smoke) | ASTM E-84 / UL 723 | Approved for return air plenums and high-rises |
| Clamp Hardware Material | Electro-galvanized or stainless steel | ASTM B-633 | Superior corrosion resistance in humid plant rooms |
Sizing Configurations and Strut Channel Integration
Cush-A-Therm assemblies are precision-manufactured to match standard copper tubing (CTS) and iron pipe sizes (IPS) ranging from 1/4-inch outside diameter up to 6 inches, with insulation wall thicknesses of 1/2-inch, 3/4-inch, 1-inch, and 1-1/2-inch. Each unit incorporates an integrated steel wrap clamp that locks securely into 1-5/8-inch Unistrut channels.
Unlike makeshift field solutions where mechanical contractors carve wood blocks or slide PVC shields under regular conduit clamps, Cush-A-Therm features self-adhesive closure seams. Mechanical insulators simply peel the protective backing strip, press the elastomeric lap seal tightly around the copper line, and tighten the outer channel clamp to specified torque values without compressing the insulation core.
Compare Cush-A-Therm against legacy field-assembled pipe support methods:
| Pipe Support Method | Vapor Barrier Continuity | Crush Resistance | Plenum Safety Rating | Installation Labor Speed |
|---|---|---|---|---|
| Cush-A-Therm Clamp | 100% airtight self-sealing lap | High (Rigid core holds weight) | ASTM E-84 25/50 compliant | Under 2 minutes per hanger |
| Wood Block & Metal Clevis | Prone to seam tears and air leaks | Moderate (Wood degrades if damp) | Combustible (Fails strict plenums) | 8 to 12 minutes field fabrication |
| Calcium Silicate Shields | Requires mastic paste wrap | Very High (Rigid mineral) | Non-combustible | 6 to 10 minutes multi-step assembly |
| Uninsulated Metal Strut Clamp | Zero (Direct metal-to-metal contact) | High pipe support | Not applicable | Fast but causes severe dripping |
Installation Protocols, Plenums, and Vapor Sealing Standards
Installing Cush-A-Therm pipe supports requires careful alignment along overhead strut trapezes. Mechanical crews must verify that the pipe surface is clean, dry, and free of oxidation before wrapping the clamp around the copper or steel pipe. The self-adhesive vapor-barrier tab is pressed firmly with a bone tool to ensure complete mechanical adhesion without air bubbles.
Surrounding elastomeric tube insulation (such as Armaflex or K-Flex) must be glued directly to the Cush-A-Therm elastomeric shoulders using approved contact adhesive. This step prevents ambient humid air from migrating beneath the insulation jacket, where moisture could generate unseen corrosion under insulation (CUI) along expensive copper piping.
Meeting international building codes (IBC) and mechanical codes (IMC), Cush-A-Therm maintains a 25/50 flame spread and smoke development rating, permitting its unrestricted installation within concealed return-air ceilings, commercial computer server rooms, and medical cleanroom environments.
How to Install a Cush-A-Therm Pipe Clamp in 5 Steps
Follow these five mechanical installation steps to secure insulated piping to strut channels while preserving vapor barrier integrity.
Clean Pipe and Position on Strut Channel
Wipe down the copper or steel piping surface, ensuring it is dry and aligned over the structural Unistrut channel.
Fit the Cush-A-Therm Insulated Core Around Pipe
Open the flexible foam collar and seat the high-density polyurethane core snugly around the pipe circumference.
Peel and Seal the Self-Adhesive Overlap Tab
Remove the protective backing film from the factory adhesive tab and press the elastomeric seam firmly to seal the vapor barrier.
Position Steel Clamp and Tighten to Strut
Slide the outer electro-galvanized steel clamp over the assembly and tighten the fastener into the strut channel nut.
Adhere Adjoining Pipe Insulation with Contact Cement
Apply approved elastomeric contact adhesive to the mating edges of adjoining pipe insulation tubes for a hermetic seal.
Frequently Asked Questions (8 Questions Answered)
Q1: What is Cush-A-Therm used for in HVAC installations?
Cush-A-Therm is an insulated clamp used to secure chilled water, refrigerant, and hydronic lines to strut channel without crushing pipe insulation or causing condensation leaks.
Q2: How does Cush-A-Therm prevent condensation drips?
By combining an inner high-density polyurethane foam core with a closed-cell elastomeric vapor barrier, it eliminates thermal bridging that causes moisture condensation on cold pipes.
Q3: What temperature range can Cush-A-Therm handle?
Cush-A-Therm operates across a wide temperature spectrum from -50°F up to +225°F (-45°C to +107°C), making it suitable for deep freezing lines and hot hydronic systems.
Q4: Is Cush-A-Therm approved for installation in return air plenums?
Yes, it meets ASTM E-84 and UL 723 standards with a 25 flame spread and 50 smoke development rating, qualifying it for installation within commercial air plenums.
Q5: What sizes of Cush-A-Therm clamps are available?
Units are manufactured to accommodate pipe outer diameters from 1/4 inch to 6 inches, with standard insulation wall thicknesses of 1/2 inch, 3/4 inch, 1 inch, and 1.5 inches.
Q6: Who manufactures the Cush-A-Therm system?
Cush-A-Therm is manufactured by ZSi-Foster and distributed widely through Unistrut and commercial plumbing supply houses.
Q7: Can Cush-A-Therm replace wooden blocks and clevis hangers?
Yes, Cush-A-Therm replaces traditional labor-intensive wooden blocks and metal shields, providing a faster, code-compliant, and airtight factory-engineered solution.
Q8: Do you need special adhesive to connect adjacent insulation?
Yes, mechanical contractors use elastomeric contact cement to weld the ends of surrounding tube insulation directly to the Cush-A-Therm collar for vapor-tight seals.
Final Thoughts & Key Takeaways
In conclusion, understanding cush a therm provides essential clarity, practical strategies, and actionable advice. By incorporating these foundational insights, adhering to verified safety guidelines, and following structured best practices, you ensure reliable, long-term outcomes while preventing common mistakes. Stay informed, consult certified professionals when needed, and maintain consistent quality care.