The design of buildings is a multi-criterion optimization problem, there always being a trade- off to be made between capital expenditure, operating cost, and occupant thermal comfort. This paper investigates the application of a multi-objective genetic algorithm (MOGA) search method in the identification of the optimum pay- off characteristic between the elements of the building design problem. Results are presented for the pay-off characteris- tics between daily energy cost and zone thermal comfort, and for building capital cost and energy cost. It was concluded that the MOGA was able to find the optimum pay-off characteristic between the daily energy cost and zone thermal comfort, but that the characteristic between the capital cost and energy cost was sub-optimal. However, it can be concluded that multi-criterion genetic al- gorithm search methods offer great potential for the identification of the pay-off between the ele- ments of building thermal design, and as such can help inform the building design process.