This report deals with the guarded hot plate apparatus of round shape and one side heat flow type which has been developed in B.R.I.The errors caused by various effects are discussed and the total error in determining the thermal conductivity is derived by the theoretical analysis using the experimental data.

* This paper was reproduced from the manuscript prepared for the Fourth International Symposium on the Use of Computers for Environmental Engineering Related to Buildings, 1983, Tokyo.
^*1 Principal Research Director.