Integrated cost estimation methodology to support high-performance building design

Prasad Vaidya, Lara Greden, David Eijadi, and Tom McDougall, The Weidt Group, USA
Ray Cole, Axiom Engineers, USA

Keywords

integrated design, first cost, decision-making, high-performance buildings, HVAC systems, downsizing

Abstract

Design teams evaluating the performance of energy conservation measures (ECMs) calculate energy savings rigorously with established modelling protocols, accounting for the interaction between various measures. However, incremental cost calculations do not have a similar rigor. Often there is no recognition of cost reductions with integrated design, nor is there assessment of cost interactions amongst measures. This lack of rigor feeds the notion that high-performance buildings cost more, creating a barrier for design teams pursuing aggressive high-performance outcomes.

This study proposes an alternative integrated methodology to arrive at a lower perceived incremental cost for improved energy performance. The methodology is based on the use of energy simulations as means towards integrated design and cost estimation. Various points along the spectrum of integration are identified and characterized by the amount of design effort invested, the scheduling of effort, and relative energy performance of the resultant design. It includes a study of the interactions between building system parameters as they relate to capital costs. Several cost interactions amongst energy measures are found to be significant.

The value of this approach is demonstrated with alternatives in a case study that shows the differences between perceived costs for energy measures along various points on the integration spectrum. These alternatives show design tradeoffs and identify how decisions would have been different with a standard costing approach. Areas of further research to make the methodology more robust are identified. Policy measures to encourage the integrated approach and reduce the barriers towards improved energy performance are discussed.