Implementation of a multi-criteria and performance-based procurement procedure for energy retrofitting of facades during early design

Abstract

Decisions taken during the early design of facade retrofits have a major influence on the final performance of buildings. However, current procurement procedures do not promote the evaluation of how facade systems design affects the overall building performance, which includes energy efficiency, comfort, cost and their complex interactions. Tenders are commonly based on single values which describe single properties of façade components like thermal transmittances and solar gain factors and do not consider interrelation between these components, the dynamic behavior of buildings and specific local climate. This paper presents a concept to drive public procurement processes based on overall building performance criteria. The methodology is operationalized by a user-friendly tool (FIT) predicting the overall performance according to façade design variations. These performance criteria are integrated into tenders by calculating a total score for every design proposal. This approach sensitizes designers and contracting authorities to consider the overall performance of a façade from the very early design and helps in making informed design decisions. An application in a simulated case study of a public school building shows its potential to guide public procurement processes and that further research and validation in actual procurement procedures is needed.