Pergamon Renewabl.e Ea~ergy, Vol.5, Pm't n. pp. 1159.1166, 1994 ElsevierScience Ltcl Printedin Great Britain 0960-1481194 $7.110.1.0.00 "MULRES-ENERGY" - A CAD Tool for Determining the Optimum Configuration of Multifamily Residential Buildings I.G. Capeluto and E. Shaviv Faculty of Architecture and Town Planning Technion - Israel Institute of Technology Haifa, 32000, Israel ABSTRACT We present a new method and the design tool MULRES-ENERGY that allows the presentation and energy usage evaluation of all possible solutions for grouping apartment units into a multifamily residential complex. This design tool may help the designer to determine the best massing configuration of the building, and its preferred proportions and orientation. Successive application of the model to many cases leads to a nomogram, in which all possible solutions of building configurations are presented, for example the number of units in the building, the number of floors, the number of apartments in each floor and the building's orientation. Since the nomogram presents all possible solutions, it does not impair the freedom of the architect to create a variety of new solutions, on the contrary, it can inspire new innovative ideas. KEYWORDS Passive cooling, Passive heating, CAD, Design tool, Multifamily residential buildings, Building geometry, Building massing, Building orientation. INTRODUCTION A significant part of the population lives in multifamily large residential complexes. Energy conservation considerations may be local, say what is best for a single particular unit, or global, namely optimizing the energy consumption over the entire apartment complex. The latter approach is particularly attractive to and endorsed by government supported housing authorities. One of the characterizing features of a multifamily residential building is the fact that each apartment unit may behave thermally in a very different way when compared with other units in the same building complex. The thermal performance of such units depends heavily on the unit's orientation and the area of its external elements like walls, roof and floor (Lekov & Balcomb, 1988, Shaviv and Capeluto, 1990). For example, an apartment under the roof in a hot-humid climate, like the one of Tel Aviv, requires energy for heating and cooling, while the energy required to create comfort conditions in an internal apartment is mostly spent on cooling. Also, the best orientation for the apartment under the roof is the South, while for the inner one it is the North (see Fig. 1 left). Moreover, the above conclusions may change with different climatic conditions. In a temperate-cool climate like the one of Jerusalem, the best orientation for both units is the South and both of them require energy only for heating, but the energy required by an inner apartment is significantly less than the energy used by the external one (see Fig. 1 right). When the analysis is restricted to a single residential unit, it was found that the unit's proportions have a small influence on its thermal behavior. However, this situation changes when we consider the configuration of the whole residential building. Here, the building's proportions have a profound effect on the global energy consumption. This is because the number of the inner apartments with almost no external walls can change relative to the number of external apartments with large external envelope. 1159