How accurate are Energy Performance Certificates indicated energy savings of building retrofits?

With the impending nearly zero energy building (NZEB) regulations for residential new builds and retrofits for the European Union (EU) housing stock and the percentage of new buildings relative to existing buildings is increasing at a rate of only 1% per year, retrofitting is recognised as the most immediate, pressing and cost effective mechanism to reduce energy consumption and carbon emissions in the building and construction sector. Currently, an Irish residential building Energy Performance Certificates (EPC) indicates the estimation of a buildings’ annual energy usage that is assessed by the Dwelling Energy Assessment Procedure (DEAP). DEAP is the standard method for assessing the energy savings that are made by a residential building through retrofitting its technical characteristics to greater energy efficiency standards. This paper presents the pre-retrofit DEAP results of a sample set of urban social houses in Ireland and compares them to the actual energy usage of the houses highlighting the limitations of DEAP in estimating the pre-retrofit energy usage of the sample set of urban social housing. As many Irish government policies promoting the uptake in residential buildings base their energy savings on DEAP, the need for a more robust assessment procedure for determining the impacts retrofitting a building to a higher energy standard is discussed in addition to the need for engineers to start understanding the behaviour and attitudes towards energy consumption of the people living inside them in order to develop a holistic retrofit design that incorporates both technical and behavioural interventions.