The aim of this part is to discuss advantages of energy efficient building design in high-rise buildings by a project designed for Istanbul Municipality Headquarters. The building has 42 storeys and oriented to south. The proposed project is ecologically, economically and aesthetically considered.

It is based on natural energy use for heating and cooling systems as a main part of ecological architecture approach. In a high-rise office building one of the biggest energy consumption is cooling load. Energy cost can be reduced by intelligent design: e. g. correct orientation and location, use of solar energy collected in attached greenhouses, intelligent facades etc.

In this study, orientation difference for main surface and greenhouse effect for heat gain are analyzed by SUNCODE program, which is personal computer version of SERI/RES thermal analysis program. The analysis is realized for four different cases, which are, attached greenhouse, without greenhouse, oriented to south and west. For these cases solar gains and heat losses are analyzed and the results are discussed.

The program calculates heat losses and solar gains from building and different building elements for each indoor space for different periods (hourly, daily, monthly, seasonal, yearly etc.) according to user preference.

In addition, heating and ventilating equipments loads and heat losses and solar gains from windows are calculated by mathematical simulation techniques. The program needs building data like materials and dimensions, orientation, area, shading and climatic data for estimating heat loss to outdoor and earth, total thermal capacity, solar radiation (direct, normal, total horizontal, direct horizontal, diffuse horizontal), outdoor temperature (average, minimum and maximum), wind speed (average, minimum and maximum), average indoor temperature, humidity, earth temperature, heating and cooling degree days.

Annual heating need of the building is 2207.999 GJ for south oriented building while it is 2336.397 GJ for west oriented building. It means 6% gains from total heat load of the building.

Three parts for attached greenhouse analysis divide the building. Zone 2 and zone 3 are estimated as attached greenhouse and without greenhouse. The annual heating need of the building is 5818.370 GJ for the tower without greenhouse while it is 5407.940 GJ for the towers are estimated with attached greenhouses. It means 7% gains from total heat load of the building.