Energy, economics and architecture

We present a method, a model and a simple design tool for evaluating the construction, investment and energy costs of different possible design alternatives for grouping apartment units into a multifamily residential building. The added investment cost of each design alternative, compared with a bench-mark solution, is expressed in terms of Additional Annualized Mortgage Payment (AAMP) and is traded-off against possible saved Additional Annual Electricity Payment (AAEP) for in-house climate control. Assembling all possible examined building configurations in a graph, the axes of which are the AAMP and the AAEP, allows the designer to choose the preferred building configuration from the point of view of the consumer and the planning authorities. Such a graph can serve as a design tool that allows the architect to decide about the best building configuration, preferred proportion, orientation and number of floors, that yields the minimum energy consumption on one hand, or the minimum initial building cost on the other. On top of it, lines of equal total AAMP and AAEP can be drawn on the graph. The family of solutions that lies on the minimum annual payments can be selected. The existence of a family of solutions  means that the solution  is not unique, hence the optimization process does not impair the freedom of the architect to create a variety of design alternatives; on the contrary, it may inspire new innovative ideas.