The effect of the Estimated Service Life on the sustainability of vacancy strategies

Abstract

In the ‘Actieprogramma leegstaande kantoren’ the strategies of redevelopment, transformation and demolition of existing office buildings are suggested to reduce the high vacancy rate in the Dutch office market. Available research on which strategy is most sustainable did not incorporate the estimated service life of the strategies, but applied a standard expectation, which leads to an inaccurate estimation of the environmental load per year of service life. Because the strategy is chosen in the initiative phase of a project, the design is often not present for all strategies. A perfect design for the new-build structure is often assumed leading to an unequal comparison of designs. To find the effect of the estimated service life (ESL) on the sustainability of vacancy strategies the S3 model is developed that includes ESL and replaces the design of a strategy with ambition levels. The sustainability of three real and one averaged case is assessed and the effect of the ESL on these results is analyzed. The model does not include financial or social factors. Sustainability has been defined as ecological sustainability as calculated by Greencalc+ 4.0. A comparison is made between the linear deduction in the lifespan accounting model and an annuity deduction. To prevent negative ESL values the improved factor method by Van Nunen (2010) is adapted and a piecewise formula is used to determine the ESL. A method that standardizes the assessment of ESL factors has been developed. Score tables describe the requirements for a building to be assigned a certain score, which are later translated to factors. The results show that the estimated service life does influence the measurement of the sustainability of vacancy strategies. Because the environmental load caused by materials is deducted over the entire service life, a higher ESL reduces the load per year for materials more than a lower ESL. This means that strategies with a higher ESL are advantaged. Excluding the remaining environmental load decreases this effect because it decreases the environmental load caused by materials. A positive annuity deduction method will cause a higher remaining environmental load and will increase the effect of including the ESL. A negative annuity will cause a lower remaining environmental load and will decrease the effect of including the ESL.