How should flexible (batts) insulation placed in floor joists above an unheated crawl space be supported?

Flexible batts insulation installed in floor joists above an unheated crawl space should be well supported between the joists to ensure optimal thermal performance and stability. Proper support helps prevent the insulation from sagging and losing its effectiveness. If the insulation is not adequately supported, it may create gaps where heat can escape, reducing the overall energy efficiency of the building.

When insulation is loosely placed or left to hang freely, it can shift over time due to air movement, vibrations, or settling, leading to gaps and spaces that diminish its insulating properties. Permanent attachment is not ideal because it may complicate future access for repairs or modifications to the structure, while well-supported insulation allows for easy adjustments if necessary while maintaining its intended insulation value. Thus, providing ample support between the joists is critical for ensuring that the insulation performs effectively throughout its lifespan.