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Abstract: In the domestic heating sector a number of different mathematical models are used to evaluate the economic viability of thermal retrofit measures. Currently, however, none of these models incorporate the effect of fuel price elasticity of demand. This paper offers a method for incorporating a factor for fuel price elasticity into models for assessing the net present value and payback time of thermal retrofits of existing homes. A set of working equations is developed, and empirically tested in a case study, a housing estate retrofit project in Ludwigshafen, Germany. The value used in these equations for year-on-year price elasticity, −0.476, is derived from further empirical studies. The inclusion of price elasticity is found to lower the net present value by 14–24% and lengthen the payback time by 5 years in some cases, and hundreds of years in others. It also shows CO2 saved over the technical lifetime of the retrofit measures to be 15–24% lower than anticipated. These findings have implications for government policy and investment decisions of businesses, private households and housing providers. [Copyright &y& Elsevier]

It is important to treat waste properly in physical input–output analysis and a series of publications discussed this topic in this journal recently. In this paper, we propose a new approach to deal with physical input–output table (PIOT) measured in a single mass unit, by which the structure of PIOT need not be changed. The new approach yields consistent and reasonable results. It not only is simpler than the existing approaches but also can reflect the physical reality of economic systems. We first discuss and clarify the concept of different kinds of inputs and outputs of economic systems. We then present the details of the new approach. During the process we define a new multiplier, which builds a bridge between the total input and the final demand in PIOT, just like the traditional Leontief inverse in MIOT. We select the three-sector PIOT for Germany 1990 as a case study to show the validity of the new approach. Finally, we prove the equivalence between the new approach, Suh's approach and Dietzenbacher's approach and the equivalence of non-waste part and waste part multiplier of the new approach and Dietzenbacher's approach. [Copyright &y& Elsevier]