How should flexible insulation be installed in floor joists above an unheated crawl space?

The recommended method for installing flexible insulation in floor joists above an unheated crawl space is to ensure that it is well supported between the joists. This approach is essential for a number of reasons.

First, proper support helps to maintain the insulation's effectiveness. Loose or unsupported insulation can sag or shift over time, which can create gaps that allow for air movement. These gaps can significantly reduce the insulation's thermal performance, leading to energy loss and increased heating costs.

Moreover, well-supported insulation prevents it from becoming compressed. The insulating properties of flexible insulation rely on the air trapped within its fibers. If the insulation becomes compressed, its R-value (a measure of thermal resistance) decreases, making it less effective at keeping the space warm.

Additionally, by installing the insulation correctly, it can help to mitigate moisture issues. In an unheated crawl space, moisture can be a concern, and properly installed insulation can act as a barrier to moisture, reducing the risk of mold and rot in the building structure.

In summary, securing flexible insulation properly between the joists ensures its performance and longevity, maintains energy efficiency, and protects the overall integrity of the building.