Civil Engineering Reference
In-Depth Information
Performance Requirements based on the expectable Technological Development
According to Erhorn et al. (
2012
), a second possibility for estimating the devel-
opment of cost-effective efficiency measures is the approximation of the future
development based on recent decades. Although the energy price remained quite
stable in Germany between 1970 and 2000, the energetic requirements for insu-
lation and HVAC systems have been strengthened significantly during this time
(see Fig.
3
). This was possible as available technologies have developed consid-
erably and thus become much more efficient. If analysing Fig.
3
under this aspect,
it can be seen that in the illustrated case of a one-family house, the primary energy
demand has been reduced by approximately 180 kWh/m
2
a in 30 years. This is
equal to an average yearly reduction of 6 kWh/m
2
a (initially about 8, today about 4
kWh/m
2
a). A stringent forward projection of this trend would lead to a further
reduction of about 30 kWh/m
2
a until 2020. This would implicate a reduction
potential of about 60 % compared to today's values. Thus, this target value would
be comparable to today's KfW building standard 'Effizienzhaus 40' (efficiency
house 40) which has already been constructed almost 13,000 times in Germany so
far (status 30 September 2012 (KFW
2012
; Schimschar et al.
2011
)). The KfW
efficiency house 40 standard requires a primary energy demand of about 25-30
kWh/m
2
a (depending on the kind of building) (Schimschar et al.
2011
).
Erhorn et al. (
2012
) finally propose to determine the nZEB requirements based
on this latterly described approach. As already explained, for the range until 2020,
a yearly primary energy reduction of 3-4 kWh/m
2
a seems to be realistic. This
would lead to a reduction potential of at least 50 % by 2020, and an interim
reduction target for 2015 could be in a range of about 20 %.
In order to improve public understanding and to show how these buildings can
be constructed, the future requirements could refer to today's KfW classification of
building standards that exceed the requirements of the EnEV (for example, effi-
ciency house 70 as from 2015, efficiency house 85 as from 2018 and efficiency
house 40 as from 2020). Table
1
shows examples for the realisation of today's
existing KfW efficiency houses.
As Offermann et al. (
2013
) is still under development, specific outcomes cannot
be addressed here. However, it is expected that the proposed level of Erhorn et al.
(
2012
) of about 30 kWh/m
2
a seems to be achievable.
The German government has to define and publish the specific national defi-
nition for nearly zero-energy buildings soon as member states need to come up
with national plans for how to define such buildings and how market introduction
is planned until 2021. Additionally, plans need to be developed for ambition level
and introduction of existing buildings renovated to nearly zero-energy buildings.
According to Erhorn-Kluttig et al. (
2011
), the German definition of nZEB will
consider the following aspects:
• Assessment parameters (energy performance indicators): both delivered energy
and primary energy (non-renewable part).
• Balancing period: one year of operation.
