The external convective heat transfer coefficient (CHTC) of building horizontal roof is an indispensable parameter for accurately calculating heat transfer through the roof and simulating airflow around the building. A novel method, namely naphthalene sublimation method, was developed for measuring external CHTC and was compared with heat balance method in this study. The comparative field measurements were carried out on the roof of a nine-story building using both methods simultaneously. The measured CHTCs on the roof of building show an approximate linear relation with representative wind velocities. The magnitude of results using the two methods was very close to each other, though the slope of the linear function using the naphthalene sublimation method was a little larger than that using the heat balance method. The difference can be considered as the slow response of heat flux meter used in heat balance method. In addition, the variance of temperature on test specimen's surfaces was not found to have significant effect on measurement results. (C) 2009 Elsevier B.V. All rights reserved.