Towards Net Zero Energy Buildings: Dynamic Simulation of office Building in Three Climate Zones of Europe Nusrat Jung 1,2, Jari Shemeikka 1, Risto Lahdelma 2, Jyri Nieminen 1 1 VTT Technical Research Centre of Finland 2 Aalto University, Department of Energy Technology, Finland EES Annual Seminar 2013, Aalto

Building Level Simulation with IDA ICE Climate zonesNorthern EuropeCentral EuropeSouthern Europe Climate data files Helsinki, FinlandLondon, U.K.Bucharest, Romania Simulation cases Base E-Efficient Zero Energy Base E-Efficient Zero Energy Base E-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 research Further 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 CO 2 concentrations< 900 ppm Mechanical airflow (CAV+VAV) 1.5 – 5 l/s, sqrm Lighting levels (at desk)500 lux, 9W/m 2 Office operation times Mon.-Fri., at 15 sqm/occupant Indoor air quality & building operation parameters

Building Envelope Properties: Helsinki Component Base Case Energy Efficient Zero Energy Wall U value, W/m 2 K Roof U value, W/m 2 K Floor U value, W/m 2 K Air tightness, n50 1/h Window U value, W/m 2 K Window g value Ext. door U value, W/m 2 K Heat recovery / /0.75 Ventilation air flow control type CAV VAV Approx. Light No light control Presence & daylight control Appliances100% 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 SimulationDelivered Energy, kWh/yearSpecific energy, kWh/m 2 /year Base CaseEnergy efficientZero EnergyBase Case Energy efficient Zero Energy Heating799,754594,172188, Cooling Elec.33,99831,44635, Electricity593,142534,322339,

Thermal energy losses (heating): Helsinki CaseWallsRoofFloorWindowsDoors Thermal bridges Infiltration & Openings Ventilati on Base Case74,66415,47619,632268,1085,07430,599220,816723,417 Energy Efficient 69,97015,41718,829242,2015,04530,541220,369493,545 Zero Energy 52,1488,16715,331127,2093,50820,39056,670244,622

Building Envelope Properties: London Component Base Case Energy Efficient Zero Energy Wall U value, W/m 2 K Roof U value, W/m 2 K Floor U value, W/m 2 K Air tightness, n50 1/h 10 m 3 /(hm 2 )3.0 m 3 /(hm 2 )2.0 m 3 /(hm 2 ) Window U value, W/m 2 K Window g value Ext. door U value, W/m 2 K Heat recovery None0.85 Ventilation air flow control type CAV VAV Approx. Light 3.5= =7.5 Presence & daylight control Appliances 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 (

Simulation results: London SimulationDelivered Energy, kWh/yearSpecific energy, kWh/m 2 /year Base Case Energy efficientZero EnergyBase Case Energy efficient Zero Energy Heating 798, ,880129, Cooling Elec. 54,537 53,78440, Electricity 594, ,097335,

Thermal energy losses (heating): London CaseWallsRoofFloorWindowsDoors Thermal bridges Infiltration & Openings Ventilation Base Case81,92721,14116,541342,3343,48022,320152,835864,180 Energy Efficient 82,71421,61416,550275,1777,80522,72547,337439,689 Zero Energy39,09412,66614,16799,6062,43715,33131,647305,550

Building Envelope Properties: Bucharest Component Base Case Energy Efficient Zero Energy Wall U value, W/m 2 K Roof U value, W/m 2 K Floor U value, W/m 2 K Air tightness, n50 1/h Window U value, W/m 2 K Window g value Ext. door U value, W/m 2 K Heat recovery None Ventilation air flow control type VAV Approx. Light No light control Presence & Daylight control Appliances100% 70% * Bucharest base case values are based on the Romanian norm C modified in year The energy efficient and zero energy case vales are based on expert knowledge.

Simulation results: Bucharest SimulationDelivered Energy, kWh/yearSpecific energy, kWh/m 2 /year Base Case Energy efficientZero EnergyBase Case Energy efficient Zero Energy Heating 1,202, ,305168, Cooling Elec. 213, ,05731, Electricity 616, ,003534,

Thermal energy losses (heating): Bucharest CaseWallsRoofFloorWindowsDoors Thermal bridges Infiltration & Openings Ventilation Base Case211,57334,73024,661482,71811,09220,759374,356789,582 Energy Efficient 123,66229,72423,37335,59127,06321,119233,584506,164 Zero Energy46,05110,53721,13095,0313,17414,71649,647328,983

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/m 2 /year Base CaseEnergy EfficientZero Energy Helsinki Heating Cooling Elec Electricity Total London Heating Cooling Elec Electricity Total Bucharest Heating Cooling Elec Electricity Total Helsinki was reduced to 60 kWh/m 2 /year (60% beyond the base case) London was reduced to 54 kWh/m 2 /year (65% beyond the base case) Bucharest was reduced to 64.6 kWh/m 2 /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