Increasing insulation thickness affects conduction through a wall in what way?

Increasing insulation thickness affects conduction through a wall in what way?

• A. It increases heat transfer.
• B. It has no effect on conduction.
• C. It only affects convection, not conduction.
• D. It increases thermal resistance, reducing heat transfer.

Answer: (D)

Increasing insulation thickness raises the resistance to heat flow. In conduction through a plane wall, the heat transfer rate decreases as the thickness increases, because q = (kAΔT)/L and also R_th = L/(kA). So when you make the insulation layer thicker (larger L), the thermal resistance goes up and the amount of heat that can pass through the wall for a given temperature difference goes down. This is why adding insulation slows heat transfer. The other options don’t fit because thicker insulation does affect conduction by adding resistance, it does not increase heat transfer, and it isn’t limited to convection only.

Increasing insulation thickness raises the resistance to heat flow. In conduction through a plane wall, the heat transfer rate decreases as the thickness increases, because q = (kAΔT)/L and also R_th = L/(kA). So when you make the insulation layer thicker (larger L), the thermal resistance goes up and the amount of heat that can pass through the wall for a given temperature difference goes down. This is why adding insulation slows heat transfer. The other options don’t fit because thicker insulation does affect conduction by adding resistance, it does not increase heat transfer, and it isn’t limited to convection only.