Time lag constant that is response time period from environment temperature to air-conditioner electricity consumption and Q-value that is the index expressing heat penetrating rate per unit floor area, are estimated for a campus building in Daido University. In diagnosis of the building in view of energy saving, the building total energy consumption and peak energy consumption are both very important issue. The total energy consumption is closely related to building insulation performance. The insulation ability is expressed by Q-value. On the other hand, the peak energy consumption related to time lag of the heat transfer from the environment to the interior space. These data is obtained by autumn-winter data. By these data, the building model is constructed and should be examined by spring-winter data.