Which of the following can negatively affect insulation effectiveness over time?

Moisture intrusion and physical damage are significant factors that can negatively impact the effectiveness of insulation over time. When moisture penetrates insulation materials, it can lead to a reduction in thermal resistance. This occurs because wet insulation loses its ability to trap air, which is essential for insulating properties. Additionally, moisture can promote mold growth and deterioration of the materials, further compromising the insulation's performance.

Physical damage, such as tears, compression, or exposure to harsh environmental conditions, can also hinder insulation effectiveness. Damaged insulation may not provide the intended thermal barrier, leading to energy loss and increased heating or cooling costs.

In contrast, increased thermal resistance would typically improve insulation effectiveness, while regular maintenance and inspection help to identify issues before they worsen. The use of high-quality materials generally contributes to better durability and performance over time. Therefore, moisture intrusion and physical damage stand out as key factors negatively affecting insulation performance.