Buildings account for about 40% of the primary energy use in the EU and US. The life span of buildings lies between 50 and 100 years. This is why approximately 60% of the current building stock will still be in use by 2050. This means that any endeavor to reduce the energy consumption needs to include buildings, in particular retrofitting of existing buildings.
However with buildings, there is the issue of the performance gap, which occurs when the calculated energy demand differs from the measured energy demand of a building. For building retrofits, the performance gap can be separated into two effects: the prebound effect and the rebound effect. The prebound effect occurs with old buildings that are in need of a refurbishment. There, the energy consumption is usually overestimated, i.e., the actual buildings consume less energy than what the calculation would suggest. The rebound effect appears in new buildings or newly retrofitted buildings. In these cases, the measured energy consumption is usually higher than what the calculation suggests. The reasons for these differences are erroneous assumptions of the building properties, occupants and building systems (e.g., set points, occupancy, material properties, aging of materials, etc.).
These effects lead to imprecise building assessments, which necessitate a large safety factor for retrofit measures.
We argue that visual inspections of the building could be complemented with on-site measurements. With measurements, we can replace estimations needed for the calculations by measuring building parameters and occupant behavior. For this, we developed a wireless sensor kit that can be deployed in occupied buildings to gather information about the actual state of the building.
For more information on the performance gap can be found here.