In Japan, the number of external insulation renovations has been increased because it is expected not only that the living environment will be improved, but also that the cost of heat and electricity will be cut and the life span of the building will get longer. While there are many researches about saving energy after construction, there are few researches during construction. This research deals with the work efficiency and man-day survey about external insulation renovation of an existing apartment. Each processes was subdivided from preparation to cleaning up, and we measured how long it took to complete these steps. In the man-day survey, the number of worker who engaged in each kind of construction process was calculated and the relation between some features of the building and the number of worker was also revealed.
