Page 34 - Zero Net Energy Case Study Buildings-Volume 2

CASE STUDY NO. 7
DPR CONSTRUCTION OFFICE BUILDING
22
Zero Net Energy Case Study Buildings: Volume 2
Energy Design Analysis and Energy Performance:
Modeling versus Post-Occupancy Measurements
Energy Use — Modeling
The energy modeling for the DPR Office Building was carried out using OpenStudio 1.4. The modeling analysis early in the design process showed a total energy use of 151,000 kWh per year, or an EUI of 21.5 kBtu/sq. ft. per year. This was below the original target of EUI = 24.0.
Energy Use — Actual Measurement and Comparison to Modeling Results
Electrical circuits were metered and data results are recorded, accessible via online platform. The energy dashboard in the reception area provides real-time display of energy performance, including the energy produced by the solar PV system. Monitoring began immediately after the building was initially occupied in May, 2014, and a full year of data was collected thereafter.
The measured results show that the building energy use over this year has been less than that indicated by the energy modeling, while the PV panels have produced more than enough electric energy to offset this demand. The actual energy used was 132,000 kWh (EUI = 18.7 kBtu/sq.ft. per year), while the energy produced was 157,000 kWh per year.
Note that the total gross floor area within the “ZNE boundary” includes the tenant space, as does the total amount of energy used and measured. The tenant participates knowledgeably in the energy performance of the building.
The metering system is not set up to distinguish between heating and cooling operation, so the measured data, lumped together in the “Mechanical” category, records both types of energy use. The measurements show for the 2014-2015 period that more energy was used during the cool- ing season than modeled for that period, while less energy was used during the heating season than indicated by the energy modeling. Since this particular measurement period was a severe drought year, with warmer temperatures and clearer skies than normal, the energy used for heat- ing and cooling would understandably have this pattern compared to the “typical year” weather data used for energy modeling.
A contributing factor to the much lower energy use during the heating season could have been the organized staff efforts to conserve energy, which was undertaken after the first six months of occupancy when the higher energy use for cooling was reported. The latter indicated that ZNE performance might not be achieved in the first year, so DPR staff focused on following suggested practices to reduce unnecessary energy use. (See Post-Occupancy: Occupant Behavior, p. 27)
The following pages show the annual energy use (pie-charts) and monthly energy use (bar charts) for both the energy modeling results and the first full year of actual measured perfor- mance data for the building. Note that all energy used for heating, cooling, fans, pumps and DHW system is included in the category “Mechanical”. The metering is not set up for determining a finer category breakdown for energy consumption since the system heating and cooling come from the same system (the heat pump).