costsWhen examining the economic optimization model, buildinggreen becomes even more cost effective. The clauses for the eco-nomic alternative were chosen in the following manner: first,according to the minimum demands of the Standard (for eachcategory and for specific categories). Then, in accordance withthe Standard’s constraints, clauses with high construction costswere removed. Items, with a very long payback period were alsoremoved.The main difference between the economic and the optimumalternative lies in the energy chapter: under the economic alter-native, no additional investment in air conditioning and heatingsystems is required. Furthermore, the investment in IS 5282 EnergyRating of Buildings (on which energy calculations for IS 5281 arebased) was made for economic optimization, not energetic opti-mization, hence was smaller. The optimum alternative for IS 5282points 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.