Recently, the condensation of floor slab often occurring in data centers is an important problem because IT equipments are particularly sensitive to high humidity levels. This work aims to study the indoor environment conditions favourable for surface condensation of high-density data centers. The risk for occurrence of surface condensation depends mainly on the surface energy balance and on the moisture content of the ambient air. This paper describes an evaluation tool for assessing condensation risk and the effect of remedial measures, and presents a method to solve these problems by using IES4D VE energy model. This measure of condensation risk is calculated for two zones (between IT server rooms and office areas) from air temperatures, moisture generation and ventilation rates. Because of different environment conditions and air conditioning period of time, the risk of surface condensation between two zones will be high. We analyzed insulation factors and cooling conditions of IT server room, and predicted the change of indoor temperature to find the cause of the condensation state. The results show that the application of floor slab insulation can substantially increase the lowest inside surface temperature, temperature difference ratio and inside air humidity for preventing surface condensation.