1. REHVA nZEB technical definition – 2013 revision
CA EPBD III MEETING IN MALMÖ
October 10, 2013
REHVA nZEB technical definition – 2013 revision
Jarek Kurnitski
Professor, Vice-president REHVA
Tallinn University of Technology
Aalto University

2. Presentation outline REHVA nZEB technical definition
Implementation – some national examples

3. REHVA nZEB definition 2013
Is intended to help the experts in the Member States in defining the nearly zero energy buildings in a uniform way – so that local conditions are taken into account, but the uniform methodology used
Proposes a technical definition for nZEB buildings following EPBD recast and Cost-optimal regulation
Provides energy calculation framework and system boundaries associated with the definition, prepared in the level of detail to be suitable for the implementation in national building codes for the primary energy and renewable energy ratio indicators’ calculation

4. EPBD recast established targets for cost optimal and nZEB
EPBD recast (2010/31/EU) requires that energy performance minimum requirements are to be set with a view to achieving cost optimal levels using a comparative methodology framework established by the Commission:
Cost optimal performance level is defined as the energy performance in terms of primary energy leading to minimum life cycle cost
EPBD recast established the target of nearly zero energy buildings (nZEB) for all new buildings (Article 9):
By 31 Dec 2020, all new buildings are nearly zero energy buildings
After 31 Dec 2018, public authorities that occupy and own a new building shall ensure that the building is a nearly zero energy building

5. EPBD recast – Nearly zero energy buildings nZEB
In the directive ‘nearly zero-energy building’ means a building that has a very high energy performance. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby.
nZEB = very high energy performance + on-site renewables
Definition of “a very high energy performance“ and “significant extent of renewables” let for Member States

6. EPBD definition for energy performance
EPBD definitions (article 2):
‘energy performance of a building’ means the calculated or measured amount of energy needed to meet the energy demand associated with a typical use of the building, which includes, inter alia, energy used for heating, cooling, ventilation, hot water and lighting
Other services may or may not be included in the rating – included in REHVA definition

7. Energy flows to be covered by nZEB definition for EPP calculation
Primary energy indicator EPP
Small changes
On site renewables inside the system boundary
Layout chages: system boundary shown
Simplified primary energy equation (the same factors for delivered and exported – in the detailed equations different factors can be used depending on national definition)
For thermal and electrical energy it applies:
Delivered – exported energy = energy use – on site renewable

8. Some most debated questions in the preparation of nZEB definition
The order of demand reduction and RES measures?
Equal treatment – may be decided on cost optimal bases (on site renewable energy is inside the system boundary, i.e. is directly subtracted from energy use)
Was confirmed in the EC’s Cost-optimal regulations (No 244/2012). Quote: “the RES-based active technologies enter into direct competition with demand-side solutions, which is in line with the purpose and intention of the cost optimal calculation to identify the solution that represents the least global costs without discriminating against or favouring a certain technology.”
Which primary energy factors are to be used? The development of national factors:
EC’s Cost-optimal regulations requires the use of non-renewable primary energy in the cost optimality assessment
(in reality, national factors include energy policy, e.g. for renewable fuels often in between of the total and non-renewable)

9. REHVA nZEB definition 2013
net zero energy building (net ZEB) Non-renewable primary energy of 0 kWh/(m2 a).
NOTE A net ZEB is typically a grid connected building with very high energy performance. A net ZEB balances its primary energy use so that the primary energy feed-in to the grid or other energy network equals to the primary energy delivered to ZEB from energy networks. Annual balance of 0 kWh/(m2 a) primary energy use typically leads to the situation where significant amount of the on-site energy generation will be exchanged with the grid.
nearly zero energy building (nZEB) Technically and reasonably achievable national energy use of > 0 kWh/(m2 a) but no more than a national limit value of non-renewable primary energy, achieved with a combination of best practice energy efficiency measures and renewable energy technologies which may or may not be cost optimal.
NOTE 1 ‘reasonably achievable’ means by comparison with national energy use benchmarks appropriate to the activities served by the building, or any other metric that is deemed appropriate by each EU Member State.
NOTE 2. Renewable energy technologies needed in nearly zero energy buildings may or may not be cost-effective, depending on available national financial incentives.
net ZEB has exact performance level of 0 kWh/(m2 a) primary energy
nZEB depends on national conditions

10. nZEB def is based on detailed system boundaries
”Double” boundary (delivered energy) removed, because obvious
Only layout changes:
Building body added: the box of technical systems shows that systems can be partly out of building (solar collectors, heat pump collectors/outdoor units etc.).
Techical systems cover both HVAC and on site energy production – no separation
System boundaries (SB) for energy need, energy use and delivered and exported energy calculation. The last one may be interpreted as the building site boundary.
Demand reduction measures can be distinguished from RE solutions in the energy use SB, not in the delivered/exported energy SB

11. Example – nZEB Office building
an office building in Paris
a gas boiler for heating with seasonal efficiency of 90%
free cooling from boreholes (about 1/3 of the need) is used and the rest is covered with mechanical cooling
for borehole cooling, seasonal energy efficiency ratio of 10 is used and for mechanical cooling 3.5
Ventilation system with specific fan power of 1.2 kW/(m3/s) will use 5.6 kWh/(m2 a) fan energy
a solar PV system providing 15.0 kWh/(m2 a), from which 6.0 is utilized in the building and 9.0 is exported to the grid

12. Example of nZEB office – primary energy
Electricity use of cooling, ventilation, lighting and appliances is 39.8 kWh/(m2 a)
Solar electricity of 6.0 kWh/(m2 a) reduces the delivered electricity to 33.8 kWh/(m2 a)
Net delivered fuel energy (caloric value) is 4.2 kWh/(m2 a) and primary energy is 54 kWh/(m2 a)

13. New element in the system boundary
RER system boundary
New element in the system boundary
Thermal energy from ambient heat exchangers to be accounted (in the delivered/exported energy calculation calculated with COP)

14. RER Equation (based on total primary energy)
The renewable energy ratio is calculated relative to all energy use in the building, in terms of total primary energy
Ambient heat sources of heat pumps and free cooling are to be included to the renewable energy use system boundary

15. RER: Example of nZEB office
The same input data as in previous example

16. System boundary for nearby RE
System boundary for nearby RE plants contractually linked to the building (a share of the capacity/production can be linked to the building)
National legislation needed to allocate new RE capacity to the building/developement with a long term contract

17. System boundary for multiple buildings

18. Summary: REHVA nZEB 2013 ZEB, net ZEB, PEB and nZEB definitions
A set of system boundaries to calculate:
Energy need
Energy use
Delivered and exported energy
Primary energy
Renewable energy ratio
Nearby energy production
Sites with multiple buildings
Load matching and grid interactions
Worked examples
National low energy and nZEB requirements/targets from selected countries

19. Implementation – some national examples
Latest updates of regulation – nZEB under preparation:
Germany
Sweden
nZEB definitions:
Denmark
Estonia
Norway

20. Towards nZEB:
Roadmap of some countries towards nearly zero energy buildings to improve energy performance of new buildings
Many countries have prepared long term roadmaps with detailed targets
Helps industry to prepare/commit to the targets

21. nZEB definitions European definitions based on EPBD recast:
REHVA 2013 – REHVA has revised its nZEB technical definition and set of system boundaries for primary energy indicator and RER calculation in cooperation with CEN, soon available
CEN is working with overarching EPBD standard prEN 15603:2013, which will include calculation bases for primary energy and RER
National definitions – Concerted Action CA EPBD (March 2013 data) has collected detailed information from 19 countries:
of which six have their national application of the nZEB definition included in a legal document (Cyprus, Denmark, Estonia, Lithuania, Slovak Republic and France) – 9 countries Oct 2013 data
six other countries have their application developed, but not yet fixed in a legal document
and the remaining seven countries have documented their current plans

22. Situation with energy frames
In most of countries, on site renewable energy production is subtracted from delivered energy
Differences in energy frames:
primary energy not yet used in all countries
Some countries (Germany, France) use reference building method, fixed values in other countries
Both simulation (Estonia, Finland) and monthly methods (Germany, Denmark) used
Inclusion of energy flows depends on country:
Germany/residential – heating energy only (space heating, DHW and heating of ventilation air)
Germany/non-residential – cooling and lighting also included (appliances not)
Denmark – appliances and in residential also lighting not included
Sweden – appliances and user’s lighting not included (facility lighting incl.)
Estonia, Finland, Norway – appliances and lighting included (all inclusive)

23. Energy frames, exported energy
Exported electricity can be taken into account on annual basis (full utilization), monthly bases (limited to the amount of the delivered electricity each month and the rest of exported is not accounted) or is not taken into account
Full utilization (annual bases):
Denmark, Estonia, net plus energy program in Germany
Monthly bases:
Germany, Sweden? (not decided)
Not accounted
Finland, Norway, Italy
Most of energy frames not yet ready to support exported energy

24. Development of primary energy requirements for heating in Germany

25. Latest Swedish energy performance requirements on delivered energy
Requirements for delivered energy use from the 1st of Jan 2013
Previous building codes 2006 and 2009, nZEB definition 2015

26. Towards nearly zero energy buildings Denmark
Characteristic values
Energy frame
Energy frame
Energy frame
Maximum of primary energy to
Residential buildings (houses, hotels, etc.) /A
in kWh/m²a /A
20 kWh/m²a
Non-residential buildings (offices, schools, institutions and other buildings) /A /A
25 kWh/m²a
Conversion factors
Electricity
2.5
1.8
District heating
1.0
0.8
0.6

27. Towards nearly zero energy buildings Estonia
Primary energy requirements for 9 building types (apply from Jan 9, 2013)
nZEB and low energy requirements officially given (not yet mandatory)
Conversion factors:
Electricity 2.0
Fossil fuels 1.0
District heat 0.9
Renewable fuels 0.75

28. Towards nearly zero energy buildings Norway
Energy frame [kWh/m²y]
Building Code
TEK07
TEK10
TEK15 - Passive house
TEK20
TEK25
TEK30
Residential
(detached house)
135
130 80
(Heating: 15, Cooling: 0, DHW: 30)
nearly ZEB
Inter- mediate
Net ZEB
(apartment block)
120
115
Non-residential
(office)
165
150
75*
(Heating: 20, Cooling: 10, DHW: 5)
* the low value is largely due to improvement in electrical appliances and adoption of demand controlled lighting and ventilation, on top of envelope improvements. Furthermore, the low amount of hot water required in offices makes the total energy need lower than for residential units.
Requirements for energy need for 13 building types
Energy balance is between energy need and delivered energy (generation not included, HVAC-electricity and cooling included)
All inclusive energy frame (appliances, lighting and cooling included)
nZEB definition under development

29. How to compare min. requirements? Detached house (CLIMA 2013 data)
Recalculation from primary energy to delivered energy needed, which can be compared in all countries
150 m2 detached house considered
Degree-day correction (base 17°C) to Copenhagen, energy use for hot water heating 25 kWh/(m2a)
The figure shows maximum allowed delivered energy without household electricity (i.e. delivered energy to heating, hot water and ventilation systems) in each country for fossil fuel or electrical heating

30. Apartment and office buildings with district heating
Maximum allowed delivered energy for heating, hot water and ventilation systems in apartment buildings and for office buildings (lighting included) with district heating