Documentation of the performance gap

It is the general experience that energy efficient new or renovated buildings perform differently than expected with regard to energy consumption. The buildings often have higher energy con-sumption than expected.
The reasons for the difference between the calculated energy demand during the design phase and the realized usage are typically:
• errors in the input to the design tool or the design tool cannot handle specific features of the building correctly,
• changes in the design of the building and/or constructions as well as energy service sys-tems during the building process,
• other demands and usages than the standard conditions used in the applied design tool,
• different climatic conditions compared to the weather data used in the design tool,
• faults, inadequate balancing and commissioning of the building constructions and the energy service systems of the building.
The performance of energy efficient buildings is furthermore more sensitive to differences be-tween the assumed and the actual design than earlier, less energy efficient buildings. Therefore, it is not possible simply to compare the calculated annual energy demand from the design phase with the measured annual energy usage when evaluating if a building fulfils the requirements specified during the design phase.
Based on the above bullet points (Jensen, 2013) describes a method on how to evaluate if a building performs as expected. This method has been utilized in the following.