How Does Insulation Performance Change Based on Airflow?

Airflow and Down-Filled Insulation

Down-filled insulation, such as that found in high-quality sleeping bags and jackets, is highly susceptible to airflow. When air penetrates the insulation, it can disrupt the loft of the down, causing it to compress and reducing the insulation’s effectiveness. For example, a study by the US Army Natick Soldier Systems Center found that a 100 mph wind can compromise the loft of down-filled insulation by as much as 50%. This can result in a significant reduction in the insulation’s R-value, making it less effective at retaining body heat.

Synthetic Insulation and Airflow

Synthetic insulation, such as polarguard or holofill, is more resistant to airflow than down-filled insulation. This is because synthetic insulation is typically made up of small, uniform fibers that retain their loft even in wet conditions and when exposed to air. In fact, a study by the manufacturer of one popular synthetic insulation found that its R-value remained relatively constant even in winds of up to 50 mph. This makes synthetic insulation a good choice for applications where airflow is a concern, such as in extreme weather conditions or for users who expect to be exposed to wind.

Designing for Airflow Resistance

To mitigate the effects of airflow on insulation performance, designers often use techniques such as baffling, draft tubes, and wind-blocking fabrics. Baffling involves inserting a thin, wind-resistant material, such as a membrane or a mesh, into the insulation layer to prevent air from penetrating. Draft tubes are tubes or channels that direct airflow away from the insulation, while wind-blocking fabrics are designed to resist wind penetration and keep the insulation layer intact. By incorporating these design elements, manufacturers can create products that remain effective even in windy conditions.