Discussion on difference of cooling degree days between island and inland buildings at similar latitude in different sea areas

 Selects island and inland cities at similar latitude to form five sea-land comparison groups from north to south, analyses the difference of cooling degree days (CDD26) relative size among the sea-land comparison groups, and seeks the reason for the difference. The results indicate that the CDD26 of island cities in northern and eastern sea areas is less than that of inland comparison cities, and it is opposite for southern sea area. The CDD26 distinction between island and inland cities is mainly caused by different underlying surface property. The difference of CDD26 relative size between island and inland cities in different sea areas is closely related to annual mean temperature, distribution range of daily average temperature above 26 ℃ and marine heat storage. If the indoor design temperature is increased under the condition of satisfying indoor comfort, the energy saving effect for island and inland cities in the south would be significantly better than that in the north.