Batt vs. dense-pack vs. spray foam vs. rigid board — what each insulation type does

What this diagram shows

Four matched plan sections of one stud bay compare how four insulation types fill a wall. Batt is friction-fit and must fill the cavity completely, because gaps and voids around wires and electrical boxes cut its real R-value. Dense-pack blown insulation flows around obstructions and leaves no voids. Spray foam expands to insulate and air-seal the cavity in one step. Rigid foam board is installed continuous across the outside of the studs, so it covers the framing and breaks the thermal bridge instead of only filling the cavity. All four can reach the same R-value; they differ in air-sealing, filling around obstructions, and whether they interrupt thermal bridging through the studs.