[ARTICLE] The Mirabella at South Waterfront: Building Performance One Year Later

by Mitch Dec, Senior Energy Analyst

Glumac recently completed a performance study on The Mirabella Portland project, located in Portland’s South Waterfront district. The study analyzed the building's energy and water consumption relative to its design goals. The first year’s data demonstrates the Portland facility is operating 15% better than its sister facility in Seattle (located in the South Lake Union neighborhood) and 38% better than a comparable facility built  to code minimum requirements. Feedback regarding the performance has been beneficial to both the design team, led by Ankrom Moisan Associated Architects, as well as the building developer and owner, Pacific Retirement Services (PRS).

The Vision
PRS engaged the design team to deliver a minimum of a LEED Silver project. The 500,000 sf+ building consists mostly of living units for an active, retired community. It also includes assisted living facilities, healthcare-related support spaces, pools, fitness center, two commercial kitchens and below grade parking.

Energy and water conservation were the areas of most interest to the development arm at PRS. PRS historically holds on to their properties for the long-term, and reduced operating expenses are very important to their business practices. Glumac worked with Ankrom Moisan to develop a list of more than 30 improvement strategies to target utility bill reductions, including modifications to the building envelope, internal loads, HVAC system, and plumbing system. The strategies were developed alongside the basis of design concepts. They were then reviewed by the project’s financial evaluators. The intent was to target a strategy that would reduce the assumed pro-forma utility bills from a regional comparable of $2.50/sf down to between $1.00 and $1.50/sf.

The Strategy
Through a collaborative design approach, Ankrom Moisan and Glumac evaluated the proposed design and identified that LEED Gold certification was feasible with a couple small modifications. However, LEED Platinum certification would likely require additional capital investments on the order of $1 million. Such proposed strategies not in the basis of design consisted of:

• Increasing wall insulation
• Tuned glass selection for the north and south windows
• Occupancy sensors for stairwell and parking garage lighting
• Changing the model number for the water source heat pump selection
• A more efficient HVAC fan option
• Modification of the cooling tower selection
• Selection of low flow plumbing fixtures
• Solar thermal water heating

These options would add value not only by increasing energy savings, but also by reducing light pollution, improving water conservation goals, and enhancing refrigerant standards relative to environmental considerations. After reviewing the potential incentives and reduced operating expenses, PRS determined implementing these improvements would result in a life cycle payback of less than three (3) years. Following approval by PRS' financing staff, the package of measures was implemented into the final design, and the pursuit of LEED Platinum certification was initiated.

The Reality
The Mirabella at South Waterfront succeeded in receiving LEED Platinum certification, and by doing so became the very first Platinum-certified project of its building type. In addition to celebrating this accomplishment, the design team was eager to learn how the building was actually operating.

Upon collecting the building’s first full year's worth of utility bills, the team was happy to see Mirabella was performing in-line with their expectations:

• The building operates with an Energy Use Intensity (EUI) of 50 kBtu/sf/yr. This is 38% better than a climate-adjusted baseline, and greater than 50% better than 2030 Challenge national comparisons.
• Annual energy charges cost $0.97/sf and annual water & sewer charges cost $0.19/sf. Thus, the total utility costs are approximately $1.16/sf.
• Annual utility bills run 54% less than the comparables used by lenders; this yields a reduction of over $690,000 annually compared to the annual expenses assumed for determining credit limits.
• The building’s water and sewer consumption is aligned with its projected use as well as with expected reductions agreed upon with the City of Portland to earn Sewer Development Charge reductions. Staff from PRS, Ankrom Moisan and Glumac scheduled a meeting with the City of Portland to review the project’s water and sewer bills. Representatives from The City of Portland reported that the Mirabella was the first of their pilot projects to be brought to the city for review of actual performance. After removal of anomalies from the building's first year of bills, its performance appears to be meeting projected water and sewer use reductions.

While the project has operated and lived up to the benchmark expectations from the energy model and calculated performance, the design team also identified opportunities to further improve the building’s energy efficiency. As important it is to have a system operate properly from day one, it is even more important to resolve systems that are not meeting performance expectations. It is from these experiences that we can continue to improve a building’s operation after the project is built, and also provide an opportunity to learn and improve our design documents and specifications moving forward.

One of the systems found to be in need of improvement was the commercial grade solar hot water system, as it had not been  producing the full yield of annual energy projected. Upon investigating the controls and sensors in the system, Glumac noted a missing sensor needed to cycle the system properly. Though a third party commissioning of the system was completed, the missing sensor would have been difficult to identify without extensive experience with solar water heating systems; its absence causes the system to only restart cycling during mid-day operation. Glumac will be working with PRS to remedy this defect this spring, tracking its performance throughout the summer to verify proper operation. 

The Mirabella post occupancy assessment is a prime example of where the industry needs to be headed. While the project is operating on the high end of the performance goals and metrics established early in Schematic Design and better than its sister project in Seattle, the design team was committed to follow up with the building owner to make sure all systems were working as intended. We are now moving ahead by fine tuning systems to ever improve performance.

Though often it is easier for designers to focus attention on the next project in the queue, critical to creating green buildings that work is revisiting completed projects to verify and optimize design intent.