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energy systems are not subject to a payback analysis of their embodied energy over the
lifespan of the building or components.
More fundamental is the fact that occupancy rates and behaviour have a considerable
impact on the energy use within buildings and that as buildings become more efficient
the relative scale of this impact increases dramatically (Passivhaus and Zero Carbon –
Technical briefing document, 2011).
Conclusions
The above discussions highlight that a clear European wide definition of Zero Energy
and/or CO
2
emissions is required as is the strengthening of EN ISO 13790 and
associated standards to more clearly define national calculation methodologies NCMs.
For a calculation methodology to be reliable it needs to be calibrated against a
statistically significant data set, which in turn can provide a benchmark against which to
judge performance via Energy Performance Indicators (EPIs) (Nikolaou et al., 2011)
The blur between standards and calculation methodologies and the natural focus on the
former means the mechanism to deliver those standards is poorly understood by those
using the calculations on a day to day basis, this is particularly the case with the “black
box” approach of SBEM. Furthermore an almost total lack of “in use” data for calibration
(the only exception to this is some initial data from Germany and Austria for PassivHaus
Certified projects which gives some corroboration to the original PHPP calculations) is
yet another glaring need. Over time it will be useful to see if UK / non-PassivHas projects
deliver similar corroboration. We therefore recommend:
1.
That the HEED database be revised to include building information model (BIM)
IFC files as these would provide the input data needed to allow existing calculation
methodologies and/or dynamic simulation models to be run and hence calibrated
(Kolokotsa, et al, 2011) against either sub-meter readings or where these are not
available from estimates of energy consumption derived from utility bills (Fumo,
Mago and Luck, 2010). Such a database would also ensure that as calculation
methodologies are revised EPCs could be refreshed on a comparative platform
and that simplified parametric studies (Chlela, et al, 2009) used to scenario
planning policy and regulation options.
2.
Whatever calculation methodology is used and whatever the compliance
mechanism adopted (target or benchmark) these must prioritise fabric performance
as this will outlast the building services. The cost effectiveness of this approach will
vary country by country (Marszal, Heiselberg, 2011), (Kurnitski, et al, 2011)
however the Danish example is likely to be more akin to the majority of north
European countries including Scotland.
3.
The calculation structure inherent in SBEM lends itself more readily to a BIM
structure as all the criteria needed for the calculation can be included in an IFC file.
It also allows the assumptions regarding the use of spaces which influence internal
gains from metabolic rate and appliance etc to be modelled zone by zone. This
means that default values can be adopted for asset based compliance and EPC
calculations and actual occupancy values adopted to calibrate the calculation
methodology with actual energy usage and scenario plan improvements on a
building by building, user by user basis.
