To prevent dew condensation by applying a finish to the surface of a heating element which is produced by covering the surface of a linear or filmy resistor with an insulating film thereby restricting the transmission of low temperature by outside air to the inside of a building and by warming up the frame by applying electric power for heating.

A heat build-up composite sheet for an architectural finish member is constituted by a heating element sheet 14 covered with insulation film on both the surfaces of a thin resistor 13 attached to the surface of a window frame 12, and a finish 15 laminated on that sheet. An insulating layer 16 made of a resin sheet or the like in which foamed resin sheet or hollow particles are scattered between the heating element sheet 14 and a finish 15 can be laminated as required. The heating element sheet 14 is fixed to the window frame 12 and thus power is applied to the resistor 13 for generating heat which is transmitted to the window frame 12. Power is applied by using a battery charged by transparent solar cells laminated on the surface of glass. By applying power for generating heat, the window frame 12 is warmed up and dew condensation is prevented. Also, they don't give any unusual appearance since the finish 15 is applied.