Common types of insulation materials used in HVAC systems include fiberglass, foam, rock wool, and reflective insulation. Each type of insulation has its own characteristics, such as R-value, density, and moisture resistance, which affect its performance and suitability for specific applications. For example, fiberglass is a popular choice for duct insulation due to its low cost and ease of installation, while foam insulation is often used for pipe insulation due to its high R-value and durability.