The better insulation is the one with the __________ K-Factor.

• A. Highest
• B. Lowest
• C. Medium
• D. Zero

Answer: (B)

Insulation that keeps heat from moving through a material best does so when the material resists heat flow as much as possible. This resistance is quantified by its thermal conductivity, the K-factor. A lower K-factor means heat flows more slowly through the material, so you lose less heat for the same temperature difference and thickness. In the conduction equation q = k A (ΔT/Δx), reducing k directly lowers the heat transfer rate. So the better insulation is the one with the lowest K-Factor. Higher K-factors would let more heat through, and a zero K-factor isn’t realistic for real materials.