Which of the following is a characteristic of good insulation?

Good insulation materials are primarily characterized by their ability to resist moisture. This is crucial because moisture can lead to a host of problems such as mold growth, degradation of the insulation material, and reduced thermal performance. Insulation that absorbs moisture can lose its effectiveness, leading to higher energy costs and potential damage to the structure itself. Therefore, a resistance to moisture is critical for ensuring both the longevity and effectiveness of insulation materials in various environments, especially in areas prone to humidity or water exposure.

While other characteristics such as cost, appearance, and disposability are relevant in certain contexts, they do not pinpoint the essential functional properties that insulation must possess to effectively maintain temperature and protect the integrity of a building. A focus on moisture resistance ensures that insulation performs as intended over time, making it the most critical characteristic among the options provided.