This paper attempts to formulate Overall Thermal Transfer Value (OTTV) coefficients for Composite, Hot-Dry and Warm-Humid climates, the three main tropical climates in India. Four existing air-conditioned office buildings - two mid-rise and two high-rise were modeled as case studies using eQuest v.3.6, which is a DoE2.2, based building energy simulation tool. Based on the study of building envelope, loads, operation and HVAC system characteristics of these case study buildings, a hypothetical high-rise, 16 storey office building, octagonal in plan was created for parametric studies. 98 types of opaque exterior wall constructions and 93 types of glass constructions were varied sequentially in parametric runs to obtain results for hourly wall conduction, glass conduction and glass radiation heat flow in eight orientations for each of the climate type. These hourly results were processed to obtain annual heat gain intensities for each parametric case for all three modes of heat transfer. Regression analysis was used to obtain the OTTV coefficients - TDeq, DT and SF for the three climates. A new OTTV equation is obtained and presented. The set of coefficients obtained were verified by calculating the OTTV for the four case study buildings, for various parametric runs. The computed OTTV for the four case study buildings exhibits good linear correlation with the annual space cooling plus heating energy use in three climates. (C) 2010 Elsevier B.V. All rights reserved.