For a basement ceiling, fiberglass batt insulation is commonly recommended due to its effectiveness in preventing heat transfer and its ability to absorb sound. This type of insulation is available in pre-cut panels that fit easily between ceiling joists, making it relatively simple to install.
The 3.5 inch thick R-15 insulation offers 36% more R-value compared to the standard R-11 fiberglass insulation. It features a kraft facing that must not be exposed as it can burn. Ensure the facing is in substantial contact with the finishing material and protect it from open flames or other heat sources.
Batt insulation consists of pre-cut, flat pieces that resemble small blankets. This type of insulation is one of the most common forms and is available in various materials, including fiberglass, mineral wool, and sheep's wool.