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a b s t r a c tTo make roofs energy efficient, typically two types of techniques are followed: surface treatments (cool roofs, radiant barriers) and thermal property modifications (roof insulation). The interplay between these two techniques has been studied using energy simulations. A single storey, daytime operational, office building of 200 m 2 area has been simulated for five climatic zones in India. A total of 88 different roof combinations have been studied for each climatic zone. An economic analysis using Internal Rate of Return has been performed to identify a suitable roof insulation thickness for a roof with high albedo, and radiant barrier combination. The incremental benefits in energy savings reduces by adding insulation after a limit. For a roof with albedo of 0.6 and radiant barrier emittance of 0.2, the optimized roof R-value is 0.49 m 2 K/W in hot and dry and composite climates, 0.31 m 2 K/W in warm and humid and temperate climates, and 1.02 m 2 K/W for cold climates.