nZEB presentation in Milano ComfortExpo 28.3.2012

1. REHVA – AICARR Seminar on
Zero Energy Buildings
Milan, 28 March 2012
nZEB Buildings: experiences and
case studies from Central and North
Europe
Jarek Kurnitski
SITRA
Jarek.Kurnitski@sitra.fi
Federation of European Heating, Ventilation and Air-conditioning Associations

2. nZEB buildings
• Many pilot projects across Europe which may be called as nZEB
buildings
• Variation in the definitions and performance levels
• Primary energy (simulated) typically between 50-100 kWh/(m2 a) if all
energy use included (plug loads/user electricity incl.)
• Some buildings with measured data
• Buildings may be extremely complicated which may have implications
in operation and maintenance
• Simple and reliable solutions based on high performance components
and careful system design another nZEB trend
Jarek Kurnitski 28.3.2012
© Sitra

3. nZEB case studies
• nZEB office buildings in France, Netherlands, Switzerland and Finland
• Reported in REHVA Journal (3/2011 and 2/2012)
Jarek Kurnitski 28.3.2012
© Sitra

4. nZEB case studies – presentation outline
• Two buildings in more detail
- One from Central Europe, another North Europe
- Some technical concepts similar – suit for both climate
- Some different – depending on climate
- Simulated and measured energy performance
- nZEB extra cost
• Some key technical concepts based on nother buildings
• Can common features of nZEB office buildings be identified?
• Performance specification recommendations for nZEB
Jarek Kurnitski 28.3.2012
© Sitra

5. System boundary – REHVA nZEB definition
System boundary of net delivered energy
System boundary of delivered energy
Solar and internal 15.0 PV electricity,
from which 6.0 used
heat gains/loads in the building and
9.0 exported
NET ENERGY NEED (47.2 kWh/(m2 a)) NET ENERGY NEED
Appliances BUILDING TECHNICAL
(47.2 kWh/(m2 a))
(users') SYSTEMS
10,8 Lighting
Boiler DELIVERED ENERGY
3.8 heating 3.8/0.9 = 4.2
Space Fuel 4.2
21,5 heating Free cooling
1,1
Heating of 11.9 cooling
0,6 4.0/10 = 0.4
3,2
air in AHU Compressor cooling
Cooling in 21.5 appliances Electricity 33.8
Net delivered energy
room units
7.9/3.5 = 2.3
Cooling of 10.0 lighting Ventilation 5.6
10
air in AHU
Appliances 21.5
Heat exchange Lighting 10.0
through the
(Sum of electricity 39.8)
building envelope
EXPORTED ENERGY
Electricity 9.0
Primary energy:
4.2*1.0 + (33.8-9.0)*2.5 = 66 kWh/(m2 a)
• Electricity use of cooling, ventilation, lighting and appliances is 39.8 kWh/(m2 a)
• Solar electricity of 15.0 kWh/(m2 a) reduces the net delivered electricity to 24.8 kWh/(m2 a)
• Net delivered fuel energy (caloric value of delivered natural gas) is 4.2 kWh/(m2 a) and primary
energy is 66 kWh/(m2 a)
Federation of European Heating, Ventilation and Air-conditioning Associations

6. Paris, Elithis Tower
(Hernandez REHVA Journal 3/2011)
© Sitra

7. © Sitra

8. Key solutions
• Rounded shape (-10% envelope reduction) + external solar shading shield
• Mechanical balanced ventilation with heat recovery
• Room conditioning with chilled beams
• Night ventilative cooling with mechanical exhaust ventilation from atrium
• Adiabatic + compressor cooling
• Large windows for max daylight, 2 W/m2 installed lighting power + task
lighting, occupancy and daylight control
Jarek Kurnitski 28.3.2012
© Sitra

9. Mechanical ventilation + ventilative cooling
Three operation modes:
1. In the heating season the heat
recovery ventilation, i.e. air
handling units are operated.
2. Ventilative cooling: boost with
façade intakes and low pressure
atrium exhaust fans. Used in
midseasons, when air handling Façade intake
units are operated together with
atrium low pressure exhaust
fans.
3. Night time ventilative cooling. Air
handling units are stopped and
only atrium low pressure fans
are operated.
Jarek Kurnitski 28.3.2012
© Sitra

10. Simulated and measured energy performance
• Office appliances are the major component in the energy balance…
Jarek Kurnitski 28.3.2012
© Sitra

11. Helsinki, Environmental Centre
Ympäristötalo (Kurnitski REHVA Journal 2/2012)
© Sitra

12. General data
• Gross floor area 6791 m2
• Construction cost:
- 16.5 M€ (2430 €/m2)
• nZEB extra cost:
- 0.5-0.7 M€
- 3-4% of construction cost
Jarek Kurnitski 28.3.2012
© Sitra

13. Key solutions
• Compact massing
• Window to wall ratio 23 %
• South facing double facade with integrated PV
(60 kW/570 m2 providing 17% of electricity use)
• District heating
• Air conditioning with balanced ventilation, heat
recovery and chilled beams
• Cooling is 100% free cooling from boreholes:
- 25 boreholes each 250 m depth
- 15/20C cooling water dimensioning for AHUs and chilled
beams
Jarek Kurnitski 28.3.2012
© Sitra

14. Key solutions
• Large mechanical rooms on the top floor and low pressure ductwork
• Specific fan power of main AHUs 1.4…1.6 kW/(m3/s)
• Heat recovery (wheels) temperature ratio 78…80 %
Jarek Kurnitski 28.3.2012
© Sitra

15. Integrated ventilation and AC with free cooling
Air handling unit
TE
a)
TC
TC
Supply
TE Chilled beam
Return
Cooling water from boreholes Room TC TE
controller Room
a)
ME TE
Supply
Thermostat
Return
District heat substation
• CAV for cellular and open plan offices, DCV for other rooms
• Active chilled beams in offices and passive chilled beams for other rooms for
24 h cooling (max cooling need 40 W/m2)
Jarek Kurnitski 28.3.2012
© Sitra

16. Heat recovery from toilets – no separated exhausts
• Separated exhaust fans replaced with a small 0.5 m³/s air handling unit with
rotary heat exchanger
• Supply air to toilets, heat recovery of 80%
Jarek Kurnitski 28.3.2012
© Sitra

17. Room conditioning and lighting
• Active chilled beams (CAV) in offices
• Lighting fittings of T5 fluorescent lamps with 7 W/m² installed power.
• Daylight, occupancy and time control is used in larger rooms, and
occupancy and time control in cellular offices
Jarek Kurnitski 28.3.2012
© Sitra

18. Energy performance (simulated)
Net energy Delivered Energy Primary
need energy carrier energy
kWh/(m2 a) kWh/(m2 a) factor, - kWh/(m2 a)
Space and ventilation heating 26,6 32,2 0,7 22,6
Hot water heating 4,7 6,1 0,7 4,3
Cooling 10,6 0,3 1,7 0,5
Fans and pumps 9,4 9,4 1,7 16,0
Lighting 12,5 12,5 1,7 21,3
Appliances (plug loads) 19,3 19,3 1,7 32,7
PV -7,1 1,7 -12,0
Total 83 73 85
Major differences compared to Central Europe:
• much more heating (almost by factor 10)
• only slightly less cooling
• more lighting electricity
Jarek Kurnitski 28.3.2012
© Sitra

19. Simple or complex ventilation systems?
• Hybrid systems tend to be highly complicated (many actuators + complicated
control) or are to be controlled by user – simulations provide often optimistic
results compared to real operation
• Mechanical systems centralized (as in two case studies) or decentralized
• Centralized systems may be complex or not
Jarek Kurnitski 28.3.2012
© Sitra

20. Example of decentralized ventilation
(Achermann, IUCN building, REHVA J 3/2011)
• Air intakes from facade, a
filter unit, a fan and a
heating/cooling coil
• CO2 sensor located at the
exhaust damper
integrated into a panel
mounted on the ceiling
• No supply air ductwork
Jarek Kurnitski 28.3.2012
© Sitra

21. Constant pressure nZEB compliant simple ventilation
(Gräslund REHVA Journal 3/2011)
• 1-2 step larger ducts and AHUs
• No need for silencers and most of dampers
Jarek Kurnitski 28.3.2012
© Sitra

22. nZEB solutions: Natural lighting and solar shading,
(Scartezzini and Lamy REHVA AM 2011)
3.5 W/m2 installed lighting power achieved!
Federation of European Heating, Ventilation and Air-conditioning Associations

23. nZEB solutions: Solar fired absorption chiller
(Virta et al. REHVA GB 16 HVAC in sustainable office buildings)
• An example of a free cooling solution – many possible solutions
• The solar fired absorption chiller operates with hot water from
the roof mounted concentrating solar collector and the wall
mounted coil solar collectors
Federation of European Heating, Ventilation and Air-conditioning Associations

24. nZEB case studies: common solutions
• nZEB = demand reduction + effective systems + on site renewables
• Energy sources used: heat pumps, DH, bio-CHP, solar PV and thermal
• Heat recovery ventilation, often demand controlled, by centralized or
decentralized systems sometimes combined with natural stack effect
ventilation for ventilative cooling purposes
• Free cooling solutions combined with mechanical cooling via boreholes,
water to water HP, evaporative or ventilative cooling etc.
• Optimized building envelope and effective external solar protection
• Utilization of natural light + effective demand controlled lighting
• High efficiency heat recovery and low specific fan power, CO2, presence
and temperature control typical in nZEB
• Water based distribution systems and VRV heat pumps
• Utilization of thermal mass and other passive measures
• Office appliances have become major component in energy balance…
Jarek Kurnitski 28.3.2012
© Sitra

25. Key performance specification for nZEB
(Virta et al. REHVA GB 16 HVAC in sustainable office buildings)
Unit Low energy Nearly zero energy
SFP of air handling unit kW/m3 /s < 2.0 < 1.5
Heat recovery efficiency % > 60 > 80
Demand controlled ventilation meeting rooms all spaces
Installed lighting power W/m2 < 10 <5
Lighting control time, daylight time, daylight, occupancy
U-value of window W/K,m2 < 1.2 < 1.0
g-value of window < 0.7 adaptable (seasons)
Solar shading yes automated
Infiltration (q50 ) m3 /h,m2 < 1.5 < 0.6
Share of renewable energy % > 10 >20
• Some indicative values for key low and nZEB energy design criteria in cold and
temperate climates
Jarek Kurnitski 28.3.2012
© Sitra

26. Central Europe vs. North Europe
• Large windows for max daylight to • Small windows for lowest acceptable
save lighting electricity average daylight factor
• Moderate insulation (Uwindow=1.1 , • Highly insulated envelope (Uwindow
Uwall=0.30) =0.6…0.8, Uwall=0,15)
• More cooling need than heating need • Slightly less cooling but a lot of heating
• External solar shading • External shading for low solar angle
• “Glass” buildings with external shading • Double façade to be used for “glass”
possible buildings
• Free cooling combined with • 100% free cooling possible with
compressor cooling or solar cooling borehole water
• Water based distribution system for • Water based distribution systems for
cooling (or VRV) heating and cooling (or VRV)
• Heat recovery ventilation • Heat recovery ventilation
• Demand controlled ventilation and • Demand controlled ventilation and
lighting lighting
• PV panels • PV panels
Jarek Kurnitski 28.3.2012
© Sitra

27. Experience from nZEB design process
• Energy simulations needed in very early stage to compare massing
alternatives (starting from scoping)
• Reserving enough space for mechanical rooms and risers – 1-2 step larger
AHUs and ductwork – this space may be difficult to find in a later stage
• Simulations of a typical floor often enough for decision making of basic
solutions (concept stage)
• Facades to be optimized (concept stage) for a relevant combination of
daylight, solar protection cooling and heating needs
• To achieve targets, careful verification and commissioning needed
• Sometimes official monthly based calculated methods may provide too
optimistic results not achieved in practice
Jarek Kurnitski 28.3.2012
© Sitra