Life Cycle Cost Analysis of Extensive Green Roofs in Switzerland and the Netherlands

Abstract

Extensive green roofs in Switzerland and the Netherlands are economically sustainable when considering the added energy savings, municipal incentives and storm water fee reductions. By combing surveys, interviews, and reviews of municipal regulations for fifteen projects the Life Cycle Cost (LCC) was calculated by discounting green roof cash flows over a 50 year time period to determine a Net Present Value (NPV). This research finds that an extensive green roof NPV in Switzerland costs 27%-37% less than a conventional flat roof. Similarly in the Netherlands, the NPV of green roofs is determined to be 16%-26% less than a conventional flat roof. Presented here is summary of the results and the explanation of local influences of municipal incentives.