Detailed energy efficiency strategies for converting an existing office building to NZEB: a case study in the Pacific Northwest

This paper is an attempt to identify a methodology for converting conventional energy consumption buildings to net-zero energy buildings (NZEB). The first step was rather different from the usual energy audit, which is to analyze a facility’s energy consumptions from both macro- and micro-scales. To implement such an approach, a governmental office building (Metro) in Portland, OR, was chosen as a case study. After a building model was validated against a real measurement, it was then used to evaluate different energy efficiency strategies (EESs) so as to reduce the energy consumption. The EESs showed a reduction in energy use intensity (EUI) from 166 to 66 kWh/m2.year, which is 60% less than the current consumption. The remaining energy demand of the building will be compensated by implementing renewable energy technologies (RETs), namely photovoltaic. The photovoltaic (PV) panels showed viability since they will produce 532 MWh on-site throughout the year, which is sufficient for the future remaining energy demand of the building (490.5 MWh). In conclusion, the simple payback period (SPP) and the life cycle cost analysis proved the feasibility of EESs and RETs. Environmentally, a total of 106 tons of CO2 was prevented per year; in addition, 64.6 tons of CO2 will also be avoided by the PVs on a yearly basis.