What is one common type of insulation used in boiler systems?

Fiberglass is commonly used as insulation in boiler systems primarily due to its excellent thermal resistance properties and lightweight nature. Its effectiveness in preventing heat loss and maintaining temperature within the systems is crucial for efficiency and safety. Fiberglass insulation is also resistant to moisture and mold, making it suitable for high-temperature applications typical in boiler systems.

The other materials listed do not serve the same purpose effectively. Wood, while it may provide some level of insulation, is not used in high-temperature areas due to its combustibility and lower thermal resistance. Plastic generally does not provide adequate insulation for high-heat applications like boiler systems, and concrete, while strong and durable, is not an effective insulator due to its density and thermal mass. Hence, fiberglass stands out as the most suitable choice for insulating boiler systems.