What type of insulation should be used on a cold vessel?

• A. Cellular glass (like foamglass)
• B. Fiberglass
• C. Rigid polyurethane
• D. Asphalt

Answer: (A)

Insulation for a cold vessel needs to minimize heat gain while staying dry and stable at very low temperatures. Cellular glass fits this role because it is a rigid, closed-cell material that resists water absorption and vapor diffusion. Its moisture resistance means the insulation value stays consistent even in damp or condensating conditions, which is crucial on cold vessels where any moisture can freeze and raise heat transfer. It is also noncombustible and dimensionally stable across a wide temperature range, including cryogenic temperatures, making it reliable for long-term cold-service performance.

Fiberglass relies on trapped air in its structure, but it can absorb water if moisture penetrates the jacket. When wet, its insulating value drops, compromising performance and potentially leading to frost or ice buildup. Rigid polyurethane offers high insulation value per inch, but moisture ingress and compatibility concerns at very low temperatures can degrade its performance, and it often requires careful moisture barriers and coatings. Asphalt is not suitable as primary insulation for cold vessels; it’s mainly used as a waterproofing coating and does not provide the durable, moisture-resistant thermal barrier needed for cryogenic or very cold service.

So, the best choice for insulating a cold vessel is cellular glass due to its combination of low moisture uptake, stability at low temperatures, and noncombustibility.