Reduction of energy consumption in buildings is one of the main concerns worldwide and it is a serious challenge particularly in desert regions. In India there are many regions where desert conditions prevail. In this study the effect of some of the parameters such as (i) insulating material on the external walls and roof and (ii) the orientation of the building on indoor thermal environment has been simulated using commercial software – ‘Design Builder’. The insulating material was selected from the Design Builder’s material library and four different orientations of the building i.e. 0o, 30o, 60o and 90o were selected. The building adopted for the simulation is cuboid in shape has 12 flats – four flats on each floor. The building is located at Jaipur in India. From the simulation study, it was found that maximum temperature of indoor air during summer, averaged over all the flats, drops by 3.82 oC when insulation is used; the existing orientation of the building (0o orientation) gives lowest maximum temperature of indoor air during summer and of the twelve flats, flats on the ground floor are most comfortable during summer.