Energy Consumption of the Monitored Office Buildings

At the beginning of 2003, twenty demonstration buildings were registered in the fund­ing programme. Six projects are already completed, eleven buildings are monitored and three are within the planning and building process. On the SolarBau homepage (see reference 2) a detailed description is given for each project.

Figure 2 summarises the results from projects which are used primarily as office buildings and for which data from at least one year were available at the beginning of 2003. Five of the nine buildings have a primary energy consumption of less than the limit of 100 kWh m-2a-1 for HVACL. The LEO building, an older low energy office which was completed in 1996, exceeds the limit together with the other four buildings. However it is satisfying to see that the consumption of all monitored buildings is much lower than in comparative buildings. A primary energy consumption between 300 and 600 kWh m-2a-1 is reported in different other studies for office and administration buildings in Germany and Switzerland. The limit of 100 kWh m-2a-1 was exceeded mainly because of an unexpectedly high heating energy consumption (DB, FH BRS) or a high electricity consumption for lighting (FH BRS, ECOTEC) and heating/cooling via reversible heat pumps (ECOTEC). Some of the reasons can clearly be referred to the planning concept, but most of them could have been avoided by better operation management. It is evident that with a high heating energy consumption the band for electricity consumption is rather small if the overall limit shall not to be exceeded.

Even on the level of end energy, the Lamparter and Wagner buildings fulfilled the expectations of Germany’s first non-residential passive buildings. Despite an unex­pectedly high heating energy consumption during the first year of 73 kWh m-2a-1, the Pollmeier building avoided high consumption values for primary energy by burning wood chips from its own sawmill. Also the KfW bank (not listed in fig. 2) is heated with wood pellets. Co-generation plants benefit from a primary energy credit (Wag­ner, ISE) as well as PV plants (ECOTEC, ISE, LAMPARTER). PV systems are the favoured solar applications because of the small hot water demand in most projects. In the Lamparter building the PV system covers 37% of the whole electric energy consumption (primary energy); for the Energon project, also a passive building (not listed in fig. 2), a coverage of 65% is expected with a PV generator of 1300 m2 on the close-by garage.

For the Solvis factory (not listed in fig. 2) a zero-CO2-emission concept was realised on the basis of a co-generation plant fuelled by rape oil and solar systems (PV and thermal collectors with a large storage). A large thermal collector system has been installed on the Wagner building together with a seasonal storage.

As the funding only included additional planning costs and the monitoring, the total investment costs were only determined by the available budget of the building owner or investor. Besides the economic situation in the building sector and site-specific conditions (e. g. foundations, underground garages), the total construction costs, i. e. the costs of "building construction" and "building services technology", are strongly determined by the costs of indoor architecture. Thus, the comparative costs in the building cost index cover a wide range, where most of the demonstration projects can be found within. A general experience of the projects is that expenses associated with energy savings and use of solar energy affect the building costs much less than

the general standard of interior architecture. It is interesting to see that the Lamparter building, which shows an extraordinarily low energy consumption, is also the one with the lowest total construction costs.

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