The building sector accounts for about 40% of total final energy use and harbours enormous potential to save energy and reduce CO2-emissions in a cost effective way. In order to reduce the energy use of buildings, policy makers impose ever more stringent requirements with regard to energy performance of new buildings and renovated buildings, and the use of renewable resource. Most compliance checks and labelling of the energy performances of buildings are done in the design phase by calculating the theoretical energy use. But, despite regulation and policy enforcements, monitoring of actual energy performances reveals in many cases a significant gap with theoretically designed targets. Sources of deviation between the actual and expected performances can be attributed to the design phase (limitations, inaccuracies and assumptions in the numerical models used to predict the energy performance), the construction phase (quality of workmanship and differences between assumed and actual installed materials, components and systems) and the operation phase (ill functioning of systems and/or no match between assumed and actual building usage). The currently observed performance gap, in combination with the increasing integration of innovative systems such as intelligent elements, low energy technologies, active solar systems, etc., accentuate the need to develop reliable methods and procedures that can be applied on site to assess the actual performance of buildings.

Within IEA EBC Annex 58 a first step has been taken to characterize the actual energy performance of buildings based on full scale dynamic measurements. Annex 58, however, was mainly restricted to the thermal performance of the building envelope, making use of rather intrusive tests and focusing on scale models or test buildings. The current project aims to make the step towards monitoring in-use buildings to obtain reliable quality checks of daily building construction practice to guarantee that designed performances are obtained on site.

To achieve this global aim, the current research proposal has two main objectives:

1. Support the development of replicable characterisation and quality assurance methodologies embedded in a statistical and building physical framework to characterise and assess the actual energy performance of buildings.
    
2. Disaggregate the building energy use to its three main sources: building fabric, systems and users.

The project will focus on residential buildings, both on the level of individual dwellings as well as on the level of building communities. On the building level, methodologies to assess and characterise occupied buildings, controlled with the buildings‘ own services will be explored. Compared to the current assessment methods, this means that the intrusive, dedicated tests are left behind in favour of assessment methods based on on-board monitoring systems. On the aggregated level (to be interpreted as a cluster of individual dwellings, be it an apartment building, small neighbourhood or district) the aim is to develop procedures to assess large - but often rather crude - data sets, that allow the identification of opportunities at the stock level. At both levels the development of characterisation methods as well as of quality assurance methods will be explored. Characterisation methods aim to translate the (dynamic) behaviour of a building into a simplified model that can be used in model predictive control, fault detection, optimisation of district energy systems,... Quality assurance methods aim to pinpoint some of the most relevant actual building performances, such as the overall heat loss coefficient of a building, the energy efficiency of the heating (cooling) system, air tightness and solar absorption,...

Within the project, different case studies in different countries will be used to develop the necessary methodologies and to show the application of on site assessment.