Environmental Impacts of Multi-Storey Buildings Using Different ...

- 46 -The HVAC system used in the simulations (chosen from many default possibilities inDesignBuilder) was hot water radiators for perimeter heating and mixed-mode betweennatural ventilation and mechanical HVAC. Above 26°C, air conditioning keeps thetemperature constant and below 22°C, heating warms the building.5.2.5 ScheduleAll four buildings were simulated as typical office buildings, using schedules for simulationbased on NZS 4243. Three schedules were developed to determine the percentage of loadsfor items such as occupancy, plugs, lighting and equipment and HVAC operation.Table 5.4 summarises the simulation load level.Table 5.4: Schedule for HVAC simulations (figures represent percentage of assigned load).12-8am 8-11am 11-6pm 6-10pm 10-12am1 OccupancyWeek 0 95 95 5 0Saturday 0 10 5 0 0Sunday 0 5 5 0 02 Plug and LightingWeek 5 90 90 30 5Saturday 5 30 15 5 5Sunday 5 5 5 5 53 Operation HVAC Typical NZ officeWeek 0 100 100 0 0Sunday 0 0 0 0 05.2.6 Energy sourcesNatural gas is used as fuel for the heating system and domestic hot water. Electricity is usedfor cooling, lighting and office equipment energy. The outcome of the operational energysimulations produced results which showed the annual fuel consumption segregated intonatural gas and electricity.This energy mix is important when considering GWP since two buildings having the sametotal energy might use different proportions of gas and electricity. Thus buildings with thesame total operational energy use may not result in the same GWP emissions, as LPG has amuch higher CO 2 coefficient than electricity.5.3 Life-Cycle Operational Energy UseAn energy performance simulation was undertaken to assess the operational energyconsumption of each of the four alternative building designs which were designed to havevery similar operational energy consumption.The underlying difference between operational energy consumption between the buildings ismostly due to the amount of concrete (acting as thermal mass) involved in each building.