Civil Engineering Reference
In-Depth Information
This means that this level is the maximum allowed level of energy demand of a
building, but more stringent requirements are possible. For more information about
the cost-optimality methodology, please see Boermans et al. (
2011a
).
Erhorn et al. (
2012
) have analysed two possible approaches for defining suitable
performance requirements within a German nearly zero-energy building definition:
(1) based on economic aspects (as this is also required through the 'energy con-
servation act') and (2) based on the expectable technological development of
relevant building components. The following descriptions are mainly based and
translated from Erhorn et al. (
2012
).
Performance Requirements based on Economic Aspects
In Germany, the 'Energy Conservation Act' (EnEG) requires that the energy
performance obligations for buildings need to be cost-effective. Nevertheless, the
EnEG allows wider interpretation that it is usually required in the German building
code 'Energy Saving Ordinance' (EnEV). The EnEG allows the extension of the
payback time up to the time span of the usual lifetime of the measure, whereas the
EnEV often requires payback times of less than 20 years (for more information,
also see
Sect. 3.2.1
)
. The usual lifetime of structural and technical components is
often considerably longer than 20 years (Association of German Engineers
2000
;
Bahr and Lennerts
2010
; BBSR
2009
,
2011
).
The consideration of the cost-effectiveness requires a full understanding of
various parameters, such as:
• Efficiency of energy efficiency measures
• Investment costs for efficiency measures
• Maintenance costs for efficiency measures
• Lifetime of efficiency measures
• Development of energy costs
• Changes in interest rates on the capital market.
The development of each parameter is not 100 % predictable. For example,
from the historical development of the crude oil price during the last 40 years, it is
not possible to make any clear future projection.
In the same way, the further development of the energy efficiency of different
measures and associated costs cannot be reliably predicted until 2020. For
example, considering the development of the heat conductivity of high-quality
insulating materials, a wide technical spectrum of materials already exists today,
implicating that there is further potential. However, in the construction praxis, this
potential is only partially exploited due to current relatively high investment costs
of these materials. New production methods may significantly improve the cost-
effectiveness of high-end products. Therefore, it does not seem suitable to develop
future 2020 requirements based on the present technological and economical
assessment parameters. This would probably lead to pessimistic requirements.
