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Author: Søren Peper
Passive House Institute, Rheinstr. 44/46, 64283 Darmstadt, Germany
Basic conditions need to be taken into account for the comparison of the previously calculated heating demand of a building and the subsequently measured heating energy consumption. These are specified here and the procedure is described.
For a reliable comparison with the actually built situation of the building (materials, thermal bridges, measured air tightness, etc.), verification using a suitable energy balance tool (e.g. PHPP) must take place. Deviations from the planning always exist. Only an accordingly adjusted (possibly complex) balance calculation is suitable for comparison.
In all circumstances, the actual weather conditions (outdoor temperature AND global radiation) and the indoor temperature should also be entered in the adjusted balance calculation. These influences can have a great effect on the heating demand. In case of energy efficient buildings, a building that is 1 K warmer normally increases the heating demand by more than 2 kWh/(m2a). Various weather conditions may have an even greater influence. Measurement of the heating energy consumption must take place in such a way that the actual consumption of heating energy can be determined. Other consumption parameters such as the hot water consumption, conversion losses and distribution losses must be deducted from the measured values before the comparison. Only then reliable data will be obtained which is suitable for a comparison. Only when this is available, it will be possible to ascertain any deviations, and investigation of the reasons can be started.
A comparison of calculated values in an energy balance for a building using measured consumption values can only succeed if the balance data has been compared with the actual building, and if the actual conditions during the measurement period have been taken into account and the consumption values have been adjusted for other consumption values.
A comparison of these values is only possible if the energy balance of a building and the measurement of the consumption have been accordingly processed correctly. Only then it will be possible to draw conclusions about any deviations, errors and user influences.
This article was written in the framework of the EU-funded project Sinfonia and is part of its Set of Solutions giving insight in the experiences and lessons learned from a smart city project.
This project has received funding from the European Union’s Seventh Programme for research, technological development and demonstration under grant agreement No 609019.