When examining the economic optimization model, building green becomes even more cost effective. The clauses for the economic alternative were chosen in the following manner: first,according to the minimum demands of the Standard (for each category and for specific categories). Then, in accordance with the Standard’s constraints, clauses with high construction costs were removed. Items, with a very long payback period were also removed.The main difference between the economic and the optimum alternative lies in the energy chapter: under the economic alter-native, no additional investment in air conditioning and heating systems is required. Furthermore, the investment in IS 5282 Energy Rating of Buildings (on which energy calculations for IS 5281 are based) was made for economic optimization, not energetic optimization, hence was smaller. The optimum alternative for IS 5282 points to the largest energy saving, without taking cost consid-erations into account. The economic optimization is set by theminimization of the life cycle cost (life cycle of buildings assumedto be 50 years) and the energy cost. In this case energetically prefer-able solutions might not be the ones selected).We see that under the economic alternative, the invest-ment on constructing a low standard building is significantlysmaller, involving an additional cost of 0.11% (large building,medium standard) to 1.33% (small building, medium standard).Furthermore, the difference in cost stems mostly from the lowerinvestment on energy saving, which required no extra cost undereconomic optimization. These data show that energy efficientdesign has a major effect on construction costs. The economic opti-mization of other chapters only had minor effects.