Green star SA certified buildings : actual vs expected energy performance

Abstract

Certification of buildings under the various environmental performance schemes such as LEED, BREEAM, Green Star, etc., has increased globally in response to the environmental challenges facing current and future generations. The rating schemes place particular emphasis on building energy efficiency, aiming at reducing the effects of Global Warming, including climate change, habitat destruction, rising sea levels and reduced global food security. Energy related categories make up roughly 25% to 30% of the typical Green Start rating schemes (Doan et al., 2017). The reduced environmental impact of energy consumption in buildings is assessed as part of the certification process through mathematical modelling of energy performance. No actual performance data is used in this process. The certification of buildings, and in particular their modelled energy performance results, creates expectations of actual performance. Building owners expect improved efficiencies over the norm to justify the increased capital outlay and increased lease rentals of this type of building. Tenants on the other side, expect improved efficiencies that translate into real operational savings, thereby justifying the increased rentals.

The aim of this research is to verify if Green Star certified buildings exhibit energy performance in line with expectations created during the certification process. This was done through: a) A comparison of the actual energy performance of twelve office buildings in Johannesburg with their expected (modelled) energy performance derived during the certification; and b) Structured interviews with the facilities managers / representatives of these twelve buildings.

The results of the structured interviews empirically confirm a positive correlation between key Green Star energy related requirements and operational practices on the one hand, and energy performance on the other hand. These include comprehensive commissioning, building tuning, effective metering strategies, etc. At the same time, the energy performance analysis suggests that buildings included in this sample generally underperform when compared to their modelled normalised energy performance, i.e. certification alone does not guarantee energy efficient buildings. The findings of this research are intended to assist various property sector stakeholders to improve the energy performance of buildings they develop, design, certify, operate, occupy or invest in.