Towards Net Zero Energy Buildings: Dynamic Simulation of office Building in Three Climate Zones of Europe

Nusrat Jung1,2, Jari Shemeikka1, Risto Lahdelma2, Jyri Nieminen1

1VTT Technical Research Centre of Finland2Aalto University, Department of Energy Technology, Finland

EES Annual Seminar 2013, Aalto

Building Level Simulation with IDA ICE

Climate zones Northern Europe Central Europe Southern Europe

Climate data files

Helsinki, Finland London, U.K. Bucharest, Romania

Simulation cases

BaseE-Efficient

Zero Energy

BaseE-Efficient

Zero Energy

BaseE-Efficient

Zero Energy

Sensitivity analysis

Sensitivity analysis was performed only for Zero Energy Helsinki case: Window, thermal mass, VAV sizing, night time set

point, lighting & equipment

Future researchFurther optimization of Zero Energy case to continue. System

level decisions with renewable energy sources such as PV, ground heating cooling, etc.

IAQ & Building operation parameters

Floor plan and simulation zones of the exemplary office building

Winter temperature 21°C

Summer temperature < 25°C

CO2 concentrations < 900 ppm

Mechanical airflow (CAV+VAV)

1.5 – 5 l/s, sqrm

Lighting levels (at desk) 500 lux, 9W/m2

Office operation timesMon.-Fri., 06-18

at 15 sqm/occupant

Indoor air quality & building operation parameters

Building Envelope Properties: HelsinkiComponent Base Case Energy

EfficientZero

Energy Wall U value, W/m2K 0.17 0.16 0.12Roof U value, W/m2K 0.09 0.08 0.05Floor U value, W/m2K 0.16 0.14 0.1Air tightness, n50 1/h 2 2 0.5Window U value, W/m2K 1.0 0.9 0.45Window g value 0.35 0.25 0.24Ext. door U value, W/m2K 1.0 1.0 0.7Heat recovery 0.45 0.79/0.59 0.85/0.75Ventilation air flow control type CAV CAV VAV

Approx. LightNo light control

No light control

Presence & daylight control

Appliances 100% 100% 70%

*Helsinki base case values are based on Finnish building codes D2, D3, and D5. Energy efficient and zero energy case values are based on expert knowledge.

Simulation results: Helsinki

Simulation Delivered Energy, kWh/year Specific energy, kWh/m2/year

  Base Case Energy efficient Zero Energy Base CaseEnergy

efficient Zero

EnergyHeating 799,754 594,172 188,204 85.4 63.4 20.1Cooling Elec. 33,998 31,446 35,733 3.6 3.4 3.8Electricity 593,142 534,322 339,349 63.3 57.1 36.2

Thermal energy losses (heating): Helsinki

Walls5% Roof

1%Floor1%

Windows20%

Doors0%

Ther-mal

bridges2%Infiltra

tion & Open-ings16%

Ventilation 53%

Base Case

Walls6% Roof

1%Floor2%

Windows22%

Doors0%

Ther-mal

bridges

3%

Infiltra tion & Openings

20%

Ventilation 45%

EE Case

Walls10%

Roof1%

Floor3%

Windows23%

Doors1%

Thermal

bridges

4%

Infiltra tion & Openings

10%

Ventilation 48%

Zero Energy Case

Case Walls Roof Floor Windows DoorsThermal bridges

Infiltration & Openings

Ventilation

Base Case 74,664 15,476 19,632 268,108 5,074 30,599 220,816 723,417Energy

Efficient69,970 15,417 18,829 242,201 5,045 30,541 220,369 493,545

Zero Energy

52,148 8,167 15,331 127,209 3,508 20,390 56,670 244,622

Building Envelope Properties: London

Component Base Case Energy Efficient

Zero Energy

Wall U value, W/m2K 0.26 0.25 0.1Roof U value, W/m2K 0.18 0.18 0.1Floor U value, W/m2K 0.22 0.22 0.15Air tightness, n50 1/h 10 m3/(hm2) 3.0 m3/(hm2) 2.0 m3/(hm2)

Window U value, W/m2K 1.80 1.60 0.5Window g value 0.40 0.40 0.2Ext. door U value, W/m2K 2.20 2.20 0.7Heat recovery None 0.85 0.85Ventilation air flow control type CAV CAV VAV

Approx. Light 3.5=17.5 1.5=7.5Presence & daylight

control

Appliances 100% 100% 70%

*London base case values are based on National Calculation Methodology (NCM) modelling guide (for buildings other than dwellings in England and Wales, 2010 Edition) reference building. Energy efficient case values are based on Target Zero 70% improvement in Part L emissions for an office building (www.targetzero.info).

Simulation results: London

Simulation Delivered Energy, kWh/year Specific energy, kWh/m2/year

  Base CaseEnergy efficient Zero Energy Base Case

Energy efficient

Zero Energy

Heating 798,309 306,880 129,407 85.2 32.8 13.8Cooling Elec. 54,537 53,784 40,897 5.8 5.8 4.4Electricity 594,631 535,097 335,506 63.5 57.1 35.8

Thermal energy losses (heating): London

Case Walls Roof Floor Windows DoorsThermal bridges

Infiltration & Openings

Ventilation

Base Case 81,927 21,141 16,541 342,334 3,480 22,320 152,835 864,180Energy

Efficient82,714 21,614 16,550 275,177 7,805 22,725 47,337 439,689

Zero Energy 39,094 12,666 14,167 99,606 2,437 15,331 31,647 305,550

Walls5%

Roof1%

Floor1%

Windows23%

Doors0%

Therma

l bridge

s1%

In-fil-tra

tion &

Open-ings10%

Ventilation 57%

Base Case

Walls9%

Roof

2% Floor2%

Windows30%

Doors1%Thermal bridges

2%Infiltra tion & Open-ings5%

Ventilation 48%

EE Case

Building Envelope Properties: Bucharest

Component Base Case Energy Efficient

Zero Energy

Wall U value, W/m2K 0.80 0.45 0.30Roof U value, W/m2K 0.40 0.30 0.1Floor U value, W/m2K 1.50 1.00 0.25Air tightness, n50 1/h 4 5.0 3.0 0.6Window U value, W/m2K 3.00 2.00 0.45Window g value 1 0.9 0.6Ext. door U value, W/m2K 4.00 2.50 1.60Heat recovery None 0.73 0.80Ventilation air flow control type VAV VAV VAV

Approx. Light No light control No light controlPresence &

Daylight control

Appliances 100% 100% 70%

*Bucharest base case values are based on the Romanian norm C107-2005 modified in year 2010. The energy efficient and zero energy case vales are based on expert knowledge.

Simulation results: Bucharest

Simulation Delivered Energy, kWh/year Specific energy, kWh/m2/year

  Base CaseEnergy efficient Zero Energy Base Case

Energy efficient

Zero Energy

Heating 1,202,335 601,305 168,063 128.4 64.2 17.9Cooling Elec. 213,011 181,057 31,446 22.7 19.3 11.5Electricity 616,795 563,003 534,322 65.9 60.1 35.2

Thermal energy losses (heating): Bucharest

Case Walls Roof Floor Windows DoorsThermal bridges

Infiltration & Openings

Ventilation

Base Case 211,573 34,730 24,661 482,718 11,092 20,759 374,356 789,582Energy

Efficient123,662 29,724 23,373 35,5912 7,063 21,119 233,584 506,164

Zero Energy 46,051 10,537 21,130 95,031 3,174 14,716 49,647 328,983

Walls11%

Roof2%

Floor1%

Windows25%

Doors1%

Ther-mal

bridges1%

Infiltra tion & Openings

19%

Ventilation 41%

Base Case

Walls10%

Roof2%

Floor2%

Windows27%

Doors

1%

Thermal

bridges2%

Infiltra tion & Openings

18%

Ventilation 39%

EE Case

Walls8%

Roof2% Floo

r4%

Windows17%

Doors1%

Thermal bridges3%

Infil-tra tion &

Opening

s9%

Ventilation 58%

Zero Energy Case

Sensitivity analysis results

• Intelligent window thermal loss control -10% savings in heating

• VAV sizing can be between 2-3 l/s according to the space needs for ducting

• Night time set point temperature can only achieve minor energy savings and higher morning peaks

• Effect of thermal mass (150, 100 & 60 mm concrete slab) in energy consumption is small

Comparison of cases    Specific energy, kWh/m2/year    Base Case Energy Efficient Zero Energy

Helsinki

Heating 85.4 63.4 20.1Cooling Elec. 3.6 3.4 3.8Electricity 63.3 57.1 36.2Total 152.3 123.9 60.1

London

Heating 85.2 32.8 13.8Cooling Elec. 5.8 5.8 4.4Electricity 63.5 57.1 35.8Total 154.5 95.7 54

Bucharest

Heating 128.4 64.2 17.9Cooling Elec. 22.7 19.3 11.5Electricity 65.9 60.1 35.2Total 217 143.6 64.6

• Helsinki was reduced to 60 kWh/m2/year (60% beyond the base case)• London was reduced to 54 kWh/m2/year (65% beyond the base case)• Bucharest was reduced to 64.6 kWh/m2/year (70% reduction beyond base case)

Conclusions

• In low-energy solutions the electricity consumption dominated the total energy consumption profile (also when compared with heating)

• Greater reductions in Bucharest case due to significant improvements in the thermal properties of the building envelope

• Window and wall ratio is moderately larger for London as compared to Helsinki and Bucharest

• Harnessing solar energy gains in Bucharest are high• Future research continues to reach zero enery goals in all three climate

zones • Underground Piles and Solar panels are being evaluated to balance the

energy consumption

Discussions