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Dick van DijkEPB Center,
Weena 505, | Jaap HogelingEPB Center,
Weena 505, |
The set of Energy Performance of Buildings (EPB) standards, developed under a mandate from the European Commission to support the EPBD, has been published in summer 2017. This set of standards enables to assess the overall energy performance of a building. Several key EPB standards are available at global level (the EN ISO 52000 family of standards), while others are for the moment only available at European level (CEN standards). The revised European Directive on the Energy Performance of Buildings (EPBD), published in June 2018, obliges the EU Member States to describe their national calculation methodology following the ‘national annexes’ of the so called ‘overarching’ EPB standards. This will force the Member States to explain where and why they deviate from these standards and will lead to an increased recognition and promotion of the set of EPB standards across Europe and beyond. This paper provides background information and tips on how to put the EN ISO 52000 family of standards into practice.
The set of
Energy Performance of Buildings (EPB) standards has been published in summer
2017. This set of standards enables to assess the overall energy performance of
a building; in most cases, but not exclusively, by calculation. A number of key
EPB standards are available at global level (the EN ISO 52000 family of
standards), while others are for the moment only available at European level
(CEN standards).
The revised
European Energy Performance of Buildings Directive (EPBD:2018 [1]) requires (in
Annex I):
“Member States
shall describe their national calculation methodology following the national
annexes of the overarching standards, namely ISO 52000-1, 52003-1, 52010-1,
52016-1, and 52018-1, developed under mandate M/480 given to the European
Committee for Standardisation (CEN). This provision shall not constitute a
legal codification of those standards.”
So,
although the new EPBD does not force the Member States to apply the set of EPB
standards, the obligation to describe the national calculation methodology
following the national annexes of the overarching standards will push the
Member States to explain where and why they deviate from these standards. This
will lead to an increased recognition and promotion of the set of EPB standards
across the Member States and beyond.
In the
following, background information and tips are given on how to put the EN ISO
52000 family of standards into practice.
The set of
standards and accompanying technical reports on the energy performance of
buildings (set of EPB standards) have been prepared under a mandate, given to
CEN by the European Commission and the European Free Trade Association, to
support the EPBD (Mandate M/480, 2011 – 2016) [2].
Figure 1 shows a simplified flow chart of
the main modules or elements in the assessment of the energy performance of
buildings. Each of these modules is covered by one or more EPB standards.
As Figure 1
illustrates, the input needed in one EPB standard is provided as output by
another EPB standard and, eventually, by product data (e.g. component
properties), project data (e.g. geometry) and boundary conditions (e.g. climatic
data, conditions of use). Evidently, it is extremely important that overall
consistency is secured and maintained in terms, definitions and symbols and in
the overall approach.
The teams
who were responsible for the development of the set of EPB standards
collectively worked out a set of quality documents, rules and templates (with
the basis formed by [3], [4]). These quality documents were immediately put
into practice during the development of the standards and are, based on the
experience, gradually (being) updated.
A complete
overview of all EPB standards is given at the EPB Center
website (www.epb.center, [5]). More background information can also be found in recent
articles, e.g. in the REHVA Journal ([6], [7]).
Figure 1.
Flow chart of the set of EPB standards with position of the five ‘overarching’
EPB standards (in bold).
In the
past, energy performance requirements were set at component level – minimum
thermal insulation levels and minimum efficiencies of products. This, however,
leads to sub-optimal solutions and creates a barrier to the necessary
technology transitions.
The set of
EPB standards is based on the holistic or systemic approach: the assessment of
the overall energy performance of a building. This implies
that all types of building related energy uses (heating, lighting, cooling, air
conditioning, ventilation) and outdoor climatic and local conditions, as well
as indoor climate requirements are considered, including the sometimes complex
and dynamic interactions between these various aspects.
This also
implies that any combination of technologies can be used to reach the intended
overall energy performance level, at the lowest cost. Due to this 'competition'
between different technologies, the holistic approach is a key driver for
technological innovation and change. Countries using the approach for several
years – take, for instance, The Netherlands – have experienced large scale
implementation and cost savings on a variety of new technologies.
The
holistic approach is a key instrument to set and evaluate policy targets. Clear
and consistent policy targets play an important role in driving innovation in
the building sector ([8]).
The revised
EPBD, quoted in the Introduction above, mentions explicitly five so called
‘overarching’ standards:
·
EN ISO
52000-1 [9],
·
EN ISO
52003-1 [10],
·
EN ISO 52010-1
[11],
·
EN
ISO 52016-1 [12], and
·
EN
ISO 52018-1 [13].
Figure 1 (roughly) shows which elements are covered by these standards (bold and numbered). These five ‘overarching’ EPB
standards have in common that each of them describes an important step in the
assessment of the energy performance of building.
It is very
fortunate that these five EPB standards are also available as ISO standards,
which creates a strong basis for the roll-out of the other (CEN) EPB standards
at worldwide level as well [14]. Harmonization of EPB assessment methodologies
at global level will strengthen innovation on EPB solutions and products.
Each EPB
standard needs to be as concise and unambiguous as possible: fit to be
implemented or referenced in national or regional building codes. For that reason,
each EPB standard contains purely normative procedures, with only brief notes
(not part of the normative text) where unavoidable.
However,
there would be a risk that the purpose and limitations of the EPB standards
would be misunderstood, if the background and context to their contents – and
the thinking behind them – would not be explained in some detail to readers of
the standards. Therefore, each EPB standard (or sometimes a cluster of EPB
standards) is accompanied by an (informative) technical report in which such
kind of information is made available (including calculation examples), to
properly understand, apply and nationally or regionally implement the EPB standards.
One of the instruments
to check the necessary overall consistency and coherence, in terminology,
approach, input/output relations and formats, was the preparation of a
spreadsheet for each EPB calculation standard. These spreadsheets, prepared on
the basis of a common template, intend to demonstrate the correctness of the
EPB calculation procedures and to enable a check of the list of input and
output variables; in particular with respect to the interconnections between
the standards, as mentioned above.
Because
each spreadsheet was developed in parallel with the corresponding EPB standard,
and was used to detect omissions in the standard and mismatches in input-output
relations between the EPB standards, the most recently available version of the
spreadsheet in many cases reflects a draft version of the standard (from 2014
or 2015) and has not or not yet been updated to the level of the published
version (summer 2017) of the standard. These spreadsheets can be downloaded
from the EPB Center website.
In the
context of a Service Contract [17] with the European Commission, the EPB Center intends to upgrade the spreadsheets of the most
important standards during 2019 and 2020 and prepare case studies. See more
under section 6 of this paper.
The set of EPB standards offers an internationally agreed set of methods to assess the energy performance of buildings in a harmonized, modular and transparent way. At the same time, the individual countries can tailor the standards to their national building regulations, building tradition, technology infrastructure and climate. They thus combine the benefits of an internationally harmonized approach with specific national or regional features.
For this
purpose, each EPB standard has an “Annex A”: a template providing choices:
·
choices
between specific methods (e.g. simple or more detailed),
·
including
choices of references to other EPB or national standards for specific elements
of the calculation, and
·
choices
of input data; these covers technical, policy related or climate related data.
The choices
according to the Annex A template, made by the Member States and/or National
Standards Bodies, are to be laid down in National Datasheets (e.g. annexed to
the building code) or in National Annexes to these standards (referenced by the
building code). In any case, each of these National Datasheets or National
Annexes shall comply with the template of Annex A of the corresponding EPB
standard.
In the context of the afore mentioned Service Contract with the European Commission [17], the EPB Center will collect and distribute examples and tips on the preparation of National Annexes. And also provide support on how to use the template of Annex A to report a (deviating) national methodology, as requested in Annex I of the revised EPBD [1], as quoted in the Introduction above.
A rough
impression of the types of choices provided in the EPB standards can be
obtained by looking at the main types of choices provided in the five
‘overarching’ EPB standards:
EN ISO 52000-1(On the general EPB framework, [9]): About 30
tables with choices. For instance, on:
·
Physical parameters (e.g. gross calorific values).
·
Differentiation
into different building and space categories (distinction between -for example- single
family house, apartment building, office, hospital, education, assembly, sport,
restaurant, hotel, holiday home, etc.; or e.g. a less refined differentiation).
Plus, related issues such as: which categories
are kept outside the boundaries of the EPB-assessment (for instance industrial sites,
workshops, indoor parking; or any other choice of building or space categories).
This categorization has a strong influence on
the EP assessment: each category is linked to an assumed set of conditions of use(temperature,
IAQ, DHW, lighting, …). By the way, the (assumed, standard) settings for these conditions of use are also determined nationally, in
the relevant other EPB standards; see Figure 1.
Via these conditions of use, the categorization has also a strong effect on the need to partition the building into different zones or sections for the
calculation: e.g. spaces with different temperature settings may require
separate calculation (separate thermal zones). This, in turn, leads to more
input data (e.g. the floor, façade and window area per zone).
Moreover, the more refined the categorization
and the distinction in conditions
of use, the more
likely it is that the minimum EP requirements need to be refined (see also EN ISO
52003-1 below).
But on the other hand, if the categorization is
less refined, the predicted energy performance may be less close to the energy
performance in practice.
·
Energy
performance boundaries (e.g. whether PV surplus to the gridis rewarded in the energy performance or not. Or
whether “distant” and/or “nearby” renewable energy sources (with –national- specification
of “nearby”) are included in the renewable energy contribution or not.
·
Policy factors (e.g. Primary energy factors). The
choice of PE factors for electricity versus e.g. gas and oil will have a direct
effect on the competitiveness of technologies that use the one or the other
energy carrier.
EN ISO 52003-1 (On EP indicators, requirements and
ratings, [10]):
·
Standardized
tables for reporting in a structured and transparent manner the choices that
are to be made with respect to overall EPB requirements. For example: choice on
the numerical EP indicator and the EP rating method (classes).
The tables are non-restrictive, thus allowing
for full regulatory flexibility. The aim is to offer choices together with the
rational (motivation, pro or con) behind each choice:
−
To
offer possibility for harmonization.
−
To
bring in more transparency (comparison, exchange of best practices).
The EPB procedures are very refined (many
standards, dealing with all kind of details), so it would be unproductive if
the energy performance requirements are formulated in a (too) simple crude way,
which would be not cost optimal or cost effective for many buildings …
EN ISO 52010-1(On conversion of climatic data for energy
calculations, [11]):
·
The
weather station and climatic data set.
·
Method
to estimate direct solar (beam) irradiance if not available from weather
station (needed for conversion to tilted and vertical planes and for calculating
solar shading by external obstacles).
·
Solar
reflectivity of the ground (fixed value or e.g. function of snow coverage).
·
(Default)
solar shading from surroundings (horizon) included or not.
EN ISO 52016-1(On the energy need for heating and cooling and
indoor temperatures, [12]):
·
Main
choice: hourly and/or monthly method (choice may differ per category of
buildings).
·
Second
main choice: specific rules for thermal zoning (in 10 steps); each step can be
modified or replaced.
·
Other
typical national choices:
−
Options
of thermally unconditioned zone types and default values for simplifications.
−
Choice
between calculations with thermally coupled or uncoupled thermal zones.
−
Details
such as: convective fractions, solar absorption coefficient of external opaque
surfaces, view factor to the sky, etc.
−
Rules
for operation of solar shading devices.
−
Choices
between options and methods for calculation of shading by external objects.
·
Additionally,
for the hourly method only:
−
Choice
between a few specifically allowed alternative choices in modelling (without
compromising reproducibility and transparency).
·
Additionally,
for the monthly method only:
−
The
values of various correlation factors (gain utilization factors, intermittency,
…
−
The
parameters for effect of movable shading devices, simplified (fixed) shading
calculation, …
EN ISO 52018-1(On partial EP indicators to building fabric
and building thermal balance, [13]):
·
Similar
as for EN ISO 52003-1. For instance, choices to set requirements on partial
energy performance features (with optional choices on further details). Such as
yes or nominimum requirements on one or more of the
following aspects:
−
Summer
thermal comfort
−
Winter
thermal comfort
−
Energy
needs for heating and/or cooling (with further specification of assumed
ventilation, etc.)
−
Thermal
insulation of envelope and/or individual elements
−
Thermal
bridges
−
Windows
energy performance
−
Air
tightness
−
Solar
control
The
overarching EPB standard (EN ISO 52000-1, [9]) lists different options for the
time interval for the calculation of the energy performance: hourly, monthly,
seasonal, yearly and bin. In most countries a choice is made between monthly
and hourly calculation procedures.
Overall
consistency is needed in the choice of time interval for the successive
modules/elements in the calculation (see Figure 1). This, however, does not mean that
the choice for an hourly time interval implies that every calculation element
(such as the U-value of constructions) is assumed
to be varying on an hourly basis.
For use in
the context of building regulations it is essential that the procedures to
calculate the energy performance of a building are not only accurate,
but also robust (applicable to a wide range of cases). It is
also essential that they are reproducible (unambiguous) as well as transparent and verifiable (e.g. for municipalities, to check
compliance with national or regional minimum energy performance requirements)
and applicable/affordable (e.g. for inspectors, assessing the
energy performance assessment of an existing building).
The
accuracy of the model should always be in proportion with the limits and
uncertainty in input data and with the required robustness and reproducibility
of the method, but at the same time the calculation should provide a sufficient
and realistic appreciation of the wide variety of available energy saving
technologies: a balanced accuracy.
This
concept was introduced more than a decade ago by B. Poel ([16]). It implies
that the most accurate, complete and state of the art method is not necessarily
the most appropriate method for a specific application. This is in particular
true for calculations in the context of building regulations.
On the
other hand, many technologies, in particular for low energy buildings aiming to
meet today’s energy performance requirements, are strongly and dynamically
interacting with the hourly and daily variations in weather and operation
(solar blinds, thermostats, needs, occupation, accumulation, mechanical
ventilation, night time -free cooling- ventilation, weekend operation, heat
pump, solar panels, etc.). This has a strong effect on the calculated energy
performance.
In the
past, the dynamic effects had less prominent effects (Figure 2, from [12]). But in low energy buildings these effects can become very
large (Figure 3). This strongly influences the
pro’s and con’s of the
monthly versus hourly calculation method.
Figure 2. Illustration of the thermal
balance in case of buildings in the past: the difference between the heat losses and the heat gains (~ the
energy need for heating) is large and much less fluctuating as in low energy
buildings (compare Figure 3).
Figure 3. Illustration of the thermal balance in case of low energy buildings: the difference between the heat losses and the heat gains (~ the energy need for heating) is small and more fluctuating.
5.4.1 EN ISO 52016-1:2017: successor
of EN ISO 13790:2008
The choice
between hourly or monthly calculation procedures is most prominently visible in
the calculation of the energy needs for heating and cooling and indoor
temperatures: EN ISO 52016-1 from 2017 ([12]).This standard superseded the
well-known EN ISO 13790 from 2008. Like its predecessor, EN ISO 52016-1
contains, side by side, both a monthly and an hourly calculation method.
5.4.2 Monthly method in EN ISO 52016-1
The monthly
calculation method in EN ISO 52016-1 has not been fundamentally changed
compared to EN ISO 13790:2008. It contains correction or adjustment
factors to account, in a kind of statistical way, for the dynamic effects that
are mentioned in 5.3 above. These factors are usually pre-calculated, based on
a large series of building simulations with e.g. variations of daily weather,
conditions of use and building design.
However,
for low energy buildings and buildings with dynamically (inter-)acting
technologies, the monthly method is no longer the simple transparent method
that it used to be. Due to the necessity to introduce an increasing number of
correction or adjustment factors, the original transparency and robustness of
the monthly method has been lost. The more of the above-mentioned dynamic
technologies and processes are included in the monthly calculation method, the
less transparent the monthly calculation method becomes, and the more an hourly
method becomes the transparent alternative.
5.4.3 Hourly method in EN ISO 52016-1
An hourly
calculation method can directly calculate the effect of dynamic interactions
and, consequently, it does not need the series of correction factors that the
monthly method requires. But the challenge for an hourly method is to avoid the
need for too many input data from the user. More input data would introduce more
uncertainties that could easily lead to a loss of overall accuracy, or lead to
significantly higher assessment costs.
The hourly
calculation method in EN ISO 52016-1 has been improved drastically compared to its
predecessor (EN ISO 13790:2008) in two ways:
(1) EN ISO 13790:2008 contained a very simple,
aggregated (few lumped parameter nodes) model in which all building elements
surrounding a thermal zone (except windows) were aggregated to a single overall
thermal transmittance, including such different elements as roofs, walls and ground
floor... This is a loss of available information (U-value, size, orientation and mass of each
building element) and –consequently- to problems in e.g. the estimation of the
effective thermal mass and effective solar energy gains.
In contrast to this, EN ISO 52016-1 contains a full
dynamic method, in which the U-value, size, orientation and mass
of each building element are used directly, without aggregation.
(2) At the same time, the details of this hourly
method in EN ISO 52016-1 have been tailored to the goal: one of the main accomplishments
of this new hourly method is that the method does not require extra input from
the user compared to the monthly calculation method.
In short:
the hourly and the monthly method in EN ISO 52016-1 are closely linked:
they have been developed side by side and they use, all together, the same
input data and assumptions.
5.4.4 Hourly method in EN ISO 52016-1
to derive monthly correlation factors
Consequently,
the hourly method is also very well suited for the derivation or validation of
the correction and correlation factors of the monthly method. For instance, by
carrying out many hourly calculations runs for a specific range of building
categories, with a variety of building types and designs. This is illustrated
by the flow chart in Figure 4.
Normally,
another dynamic simulation tool is needed for such purpose; with therefore that
differences in assumed conditions and differences in model approaches lead to a
lot of noise in the derivation/validation of the correction or correlation
factors. This is eliminated by comparing the side by side developed hourly and
monthly method from EN ISO 52016-1.
5.4.5 Link with EN ISO 52010-1
One of the
additional causes for the kind of “noise” mentioned above is the amount of
solar irradiation at vertical and tilted planes, calculated on the basis of the
measured solar irradiation at horizontal plane. This is an important input for
the calculation of energy needs and indoor temperatures, especially in case of
low energy buildings.
The main
internationally available building simulation tools use quite similar but yet
different algorithms for this conversion. This is probably one of the reasons
why in the so called BESTEST cases ([18]) discrepancies between building
simulation tools occur on the calculation of energy needs for heating and
cooling and indoor temperatures. With the introduction of
EN ISO 52010-1 [11], this algorithm has now been harmonized which
eliminates this additional noise. This is explained in more
detail in 7.2.1 of the Technical Report accompanying EN ISO 52016-1 [19].
Figure 4. EN ISO 52016-1: links between the hourly and the monthly method provided in this standard.
One could
easily defend that the assessment of the smart readiness of a building, one of
the new concepts in the revised EPBD [1], requires hourly (or sub-hourly)
calculation intervals. It is quite evident that in different buildings the same
“smart” service or technical feature can result in different outcomes.
According to the revised EPBD ([1]) the ‘Smart Readiness Indicator’ (SRI)
should focus on the building’s adaptation to user and grid needs. Only
assessment of the performance of the building by calculation or measurement can
provide a realistic quantification of the ‘smart readiness’.
Evidently, a monthly calculation method lacks the possibility to reveal the potential to adapt to the user and grid needs. In fact, the use of monthly average data (e.g. monthly mean electricity surplus or shortage), intrinsically leads to over-optimistic results. The set of EPB standards offer the possibility for hourly calculations to provide meaningful results.
The
European Commission awarded a service contract (Sept.2018 – Sept. 2021) to a team
led by ISSO ([17]), to support the uptake of the EPB standards. Examples of
activities under this contract:
·
Support
to EU Member States and National Standardization Bodies that wish to complete
the National Annexes of the EPB standards.
·
Set
up a public frequently asked questions database on filling in National Annexes,
on practical application of the standards, etc.
·
Preparation
of practical case studies to support the use of standards and dissemination and
development of calculation tools for individual standards.
·
Set
up of a large network of practitioners and support of the uptake of the EPB
standards by organising regular hands-on workshops, training sessions, etc.
The EPB Center, founded by ISSO and REHVA, will be the
communication platform to offer these services. More information will gradually
become available at the website (www.epb.center). The web site also offers the possibility to provide feedback,
suggestions and questions on the set of EPB standards and their implementation.
With the
publication of the set of EPB standards (2017) a powerful set of internationally
harmonized assessment procedures on the energy performance of buildings has
become available. These harmonized procedures offer flexibility to take into
account the national or regional situation via so called national annexes or datasheets.
The EPB Center provides information and technical support for and
collects feedback on the uptake of the set of EPB standards at national and
regional levels.
This set of methods is a key instrument to set and evaluate the national and international policy targets and will play an important role in driving innovation in the construction sector.
[1] EPBD:2018, Directive (EU) 2018/844 of 30 May 2018 amending Directive 2010/31/EU on the energy performance of buildings and Directive 2012/27/EU on energy efficiency. (2018).
[2] Mandate M/480, Mandate to CEN, CENELEC and ETSI for the elaboration and adoption of standards for a methodology calculating the integrated energy performance of buildings and promoting the energy efficiency of buildings, in accordance with the terms set in the recast EPBD (2010/31/EU), December 14, 2010 (2010).
[3] CEN/TS 16628, Energy Performance of Buildings – Basic Principles for the set of EPB standards (subject to revision) (2014).
[4] CEN/TS 16629, Energy Performance of Buildings – Detailed Technical Rules for the set of EPB standards (subject to revision) (2014).
[5] The
EPB Center information and communication platform, www.epb.center
[6] J. Hogeling (ed.), Special issue “EPB standards”, 53, 3 (2016).
[7] J. Hogeling (ed.), Special issue "EPB standards published for formal vote", REHVA Journal, 53, 6
(2016).
[8] J. Hogeling, The implementation of the new EPB-standards will boost product and HVAC system innovation and create new market opportunities for the HVAC industry, editorial REHVA Journal, 54, 1 (2017).
[9] EN ISO 52000-1, Energy performance of buildings — Overarching EPB assessment – Part 1: General framework and procedures (2017).
[10] EN ISO 52003-1, EPB – Indicators, requirements, ratings and certificates – Part 1: General aspects and application to the overall energy performance (2017).
[11] EN ISO 52010-1, EPB – External climatic conditions – Part 1: Conversion of climatic data for energy calculations (2017).
[12] EN ISO 52016-1, EPB – Energy needs for heating and cooling, internal temperatures and sensible and latent heat loads – Part 1: Calculation procedures (2017).
[13] EN ISO 52018-1, EPB – Indicators for partial EPB requirements related to thermal energy balance and fabric features – Part 1: Overview of options (2017).
[14] D. van Dijk, Spotlight on the EN ISO 52000 family of EPB standards, REHVA Journal, 54, 6 (2017).
[15] D. van Dijk, EPB standards: Why choose hourly calculation procedures?, REHVA Journal, 55, 1 (2018).
[16] B. Poel, Contribution to Applying the EPBD to improve the Energy Performance Requirements to Existing Buildings – ENPER-EXIST, Final Report of WP1 of ENPER-EXIST, (2007).
[17] Service
Contract No ENER/C3/2017-437/ SI2.785185 with
the European Commission, DG Energy (Sept. 2018 – Sept. 2021), Support the Dissemination and Roll-out of the
Set of Energy Performance of Building Standards developed under EC Mandate
M/480.
Coordination and contact: Jaap Hogeling, ISSO (NL)
(2018).
[18] ANSI/ASHRAE standard 140, Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs (2014).
[19] CEN ISO/TR 52016 2:2017, Energy performance of buildings - Energy needs for heating and cooling, internal temperatures and sensible and latent heat loads - Part 2: Explanation and justification of ISO 52016 1 and ISO 52017 1.
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