Labels’ Standard Deviation in Energy Performance Certificates: Portuguese Housing

Abstract

Energy Performance Certificates (EPC) went from a solely bureaucratic process to a differentiating factor capable of raising a property’s value. The regulation, as conceived, is thoroughly suitable for new buildings, given their characteristics and available information. Contrary to the aging building stock, which lacks documentation and construction evidence. Surveys demonstrate pressure on qualified assessors to deliver higher EPC labels. The assessor tends to increase the grade to the detriment of a more rigorous approach aligned with the regulatory guidelines, raising the property market value, and benefitting building owners. The research oversees 30 EPCs, strictly following the regulation criteria, and concluded a global (−)8.77% average against the official EPCs, representing (−)21.93% on a 250% scale, which should not change the (letter) grade, except when close to the threshold. The following tendency shows different behavior considering the “C” threshold, when above lowers by (−)7.70% and under that level and including increases by (−)34.37% on the same scale against official EPCs: mainly, upon the uncertainty of isolation presence on opaque façade elements. The study outcome unveils a defaulted regulation mechanism introduced in 2013 (and reset in 2021), the “Simplification Rules”, which intended to surpass the lack of technical information with a prudent judgment by assessors, but became a popular shortcut on existing buildings, representing 16/30 of the random research sample.