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

Same R-value, different jobs: batt must be packed void-free, dense-pack flows around wires and boxes, spray foam also air-seals, and rigid board goes continuous over the studs to break the thermal bridge.

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. — Source: Building-science practice (DOE / BSC); air-sealing & continuous-insulation principles

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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.

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