Six inch insulation with conductivity of .48 BTUH per hour, square foot – F is replaced by insulation with conductivity of .32 BTU-inch per hour-ft2-F. What thickness is required to provide equal insulating value?

Six inch insulation with conductivity of .48 BTUH per hour, square foot – F is replaced by insulation with conductivity of .32 BTU-inch per hour-ft2-F. What thickness is required to provide equal insulating value?