Contents

1. Cost data
2. Construction costs for new buildings
3. Energy efficiency level and construction costs
4. Focus on energy source costs
5. Lifecycle costs

What does energy efficiency cost? And are energy-optimised buildings actually more expensive than conventional buildings? How are the construction costs compared to the lifecycle costs? What effects does this have on the foreseeable trend for the value of buildings?

There is a new subject focus, namely “Economic viability”, within the accompanying research on the EnOB model projects. Two academic groups at the Universities of Wuppertal and Karlsruhe are dealing with the interrelationships between construction costs, building usage costs and lifecycle costs, as well as the associated optimisation potential as regards minimised CO2 emissions.

1. Cost data

Energy characteristic values and cost data have been systematically collected for EnOB model projects involving new buildings and refurbishment projects. However, the analysis of economic characteristic values is complicated, as the data has to be recorded under various cost groups as per DIN 276 and also related to specific floor areas. The costs monitored are net values in euros, and may relate to a cost estimate, cost calculation, quotation or to actual established costs. The cost data should also be compared on a regional and time-indexed basis. All this means that comparative interpretation of the data is only possible after a great deal of detailed analysis work.

The following data information are also useful in the comprehensive economic analysis of a given building: cost data on overall construction costs as per cost groups 200, 500, 600 and 700 in DIN 276; cost data on interim costs, moving costs and interest costs during construction; rental and refinancing costs; and details on planning and the construction period. It is not yet clear if this data can be determined as part of the accompanying economic analysis.
When the evaluation of data and calculation of characteristic values was complete, the comparative costs were investigated using the building costs index (BCI) for the type of construction in question in order to take reference costs into account.

2. Construction costs for new office buildings

A comparative cost analysis for a new office building project will be described here as a case study (see Fig. 2). It is noticeable that the costs for EnBau model projects vary considerably for the cost groups 300 and 400, but still lie within the BCI standard values with the exception of one project, namely the Federal Environment Agency building in Dessau. The cost bracket ranges from around 700 up to 1,750 euros per square metre of gross floor area (GFA).

If one analyses the ratio of construction costs to the amount of area (GFA) per user for the same buildings, no correlation can be identified. All the projects – with one exception – are distributed in the range of 20 to 60 square metres of GFA per user, independent of the level of construction costs. Expensive and inexpensive office projects with high area efficiency all exist. This can be explained by the fact that the number of users per square metre of GFA is dependent on the use type and on other factors; it is not yet possible using current knowledge to identify a clear relationship to construction costs.
The first set of data and its evaluation, as presented here, is part of a work in progress.

3. Energy efficiency level and construction costs

For this comparison, the primary energy consumption is determined by multiplying the characteristic values for final energy consumption by the primary energy factors for each energy source as per DIN V 18599-1:2007-02. The reference area here is the heated net floor area. This corresponds to the specifications of the DIN and the current German Energy Saving Ordinance (EnEV), but does not correspond to the cost characteristic values in DIN 276, which are related to the GFA.
Note: For buildings with photovoltaic electricity generation, the grid remuneration is deducted from the characteristic value for overall primary energy consumption using the primary energy factor (non-renewable) for the German electricity mix. In this case, one speaks of balanced primary energy consumption.

However, it is not easy to derive and interpret a systematic relationship between construction costs (cost groups 300 and 400 as per DIN 276-1:2006-11) and characteristic values for primary energy consumption. In the cost groups 300 and 400, cost types are added together that have either no or else only little influence on the energy quality of a building – e.g. 310 for foundation digging. In order to be able to better identify energy-relevant cost contributions and compare them with (primary) energy consumption characteristic values, the construction costs should be itemised at least to level 2 of detail as per DIN 276.

The following example demonstrates why meaningful correlations between construction costs and primary energy consumption levels are only possible with a sufficiently detailed knowledge of the cost structure.

A building with local or district heating has a lower primary energy consumption because of the favourable primary energy factor. At the same time, the amount invested in the heating system (cost group 421) is significantly less compared to buildings without district heating, since only a transfer station is needed instead of a heat generator. This means that the building has been constructed with lower construction costs, which could lead to false conclusions if one was not aware of the cost groups mentioned above. A similar situation also holds for buildings which have low primary energy consumption levels based on the balancing method described above. The additional costs for a PV system are not included in cost group 400, meaning that the high additional investment required is not reflected in the figures presented. In the case of heating as part of contracting models, the investment costs for heat supply units (cost group 420) do not actually apply, which also leads to the effects described above.

4. Focus on energy source costs

In the usage cost analyses to be conducted in 2009, energy source costs for the projects will also be taken into account if they are available. The goal here will be to investigate and describe the potential financial effects associated with the choice of energy concept (and of energy sources and energy suppliers too) and purchasing strategy.

5. Lifecycle costs

All costs associated directly and indirectly with buildings should be taken into account when analysing the lifecycle of real estate projects. Up until now, analyses have mainly concentrated on the construction costs of a given building and its technical equipment.

In the future, the EnOB research initiative will focus on an accompanying analysis of model projects: in these times of rising energy prices, the follow-on costs of a building over its whole lifecycle are so significant that they cannot be neglected any longer. Just as in the case of the construction costs as per DIN 276, the building usage costs will also be itemised. The building usage costs can be structured using DIN 18960:2008-02, the GEFMA 200 guideline and, to supplement the DIN, the VDI 2067 guideline.

In addition, a balancing investment analysis that is based on structured cost data will be used. All buildings in the EnOB model projects will then be subject to a consistent economic analysis.

Authors: Guido Spars, David Lehmann, Thomas Lützkendorf, Matthias Unholzer
Editor: Johannes Lang