A wood ceiling with thermal resistance ?R?1 is covered with a layer of insulation with thermal resistance ?R?2. Prove that the effective thermal resistance of the combination is ?R = ?R?1+ ?? .

Solution 108P Step 1: We know that Q is directly proportional to temperature difference and area,inversely proportional to thickness. Q = (T 2 T )/1L/k A)* Where Q rate of heat per second T outer temperature 2 T inner temperature 2 A effective area k thermal conductivity L thickness