Building energy efficiency assessment considering IEQ and sustainability certification data for German office buildings

Assessing a building’s energy efficiency is a major goal to avoid unnecessary and inefficient energy-consuming renovations. Currently, building energy efficiency is measured primarily by the energy demand of the building. However, the higher energy efficiency of the building is not always aligned with the greater comfort of the occupant, which is the main benefit a building provides. In this study, indoor environmental quality (IEQ) ratings and building energy demand are considered together to evaluate building energy efficiency. It compares the IEQ comfort achieved to the energy demand of the building. An example IEQ index calculation based on certification data of two buildings assessed by a German building sustainability certification system is used. The data include scoring of different IEQ categories and information on energy usage for the buildings. In addition, a survey on IEQ factors was conducted among building users and the results were compared to those based on the certification assessment data. The IEQ rating of the building certification data based on building design and measurement data for the individual factors differed from the subject study results by up to 50%. The overall performance of the considered buildings ranged from 0.13 to 0.16 IEQ-Score per MJ m−2 a−1 for the certification data and survey results.