Sustainability is a worthwhile objective. The problem lays in what is behind. Some focus on the environmental aspects. We, however, believe sustainability embraces overall performance of a building. Comfort, indoor air quality and related energy consumption are part of that, as is economy expressed in terms of investments and annual costs. Better energy efficiency decreases the annual costs. From that perspective some dream of zero annual energy cost buildings, i.e., buildings that produce energy and sell it at a price that compensates for the costs of the energy consumed. To arrive there, investments increase, meaning that ever more money is drained to efficiency measures. Zero energy cost may thus not be the optimal choice from an economical and even overall sustainability point of view.

The paper discusses a total actual cost analysis for a series of dwellings, wherein thermal insulation of roofs, façades and floors, the glazing used, the ventilation system chosen and the hydronic central heating applied were the variables. The results show that not some extremes, but simple common sense combinations of measures come out as economically optimal.

IAQ 2007 Conference held in Baltimore, Maryland, October 14-17, 2007

Units: SI