Taking an Efficient Route to Net-Zero Energy

On my drive home from work the other night, highway congestion slowed me down to a crawl. My smart phone chimed in, “You’re on the fastest route despite normal traffic.  You will arrive at your destination at 5:45pm.”  A quick glance at the screen showed that alternative, slower routes should be avoided.  Sitting there, suddenly grateful for this handy service, I was reminded of the work we’ve been providing the Saint Paul Port Authority (SPPA).  They have been looking for a way to facilitate the development of a net-zero energy (NZE) office-warehouse by 2020, but acknowledging the sizable first-cost implications of such a development they knew that any old route wouldn’t do.  So, they asked us to provide our research toward “the most probable path to building a NZE office-warehouse.”  Like me in my car the other night, they were looking for the most efficient route.

To date, only one NZE building exists in the State of Minnesota. Our climate poses some difficulty in achieving NZE.  But when you look at the traditional warehouse as a potential NZE building type, you notice how many of them there are (see chart below), and how inefficient they typically are (think several gaping doors in the middle of winter).  Our work would clearly be impactful. But to realistically arrive at a NZE prototype, we would have to rely on more than our technological savvy; we would have to look at the bottom line.

US EIA, 2012 CBECS Survey

Essentially, to reach NZE you must take a traditional office-warehouse (see chart below), reduce its energy consumption, and likely also produce some energy on site, both of which cost money. Our goal was to find cost-efficiencies that would accelerate the developer’s return on investment (ROI). We front-loaded the design with an integrative process that brought several disciplines together to learn from each other and see if we could engage potential project synergies.  For this project, our integrative design team learned, for example, that finding a site where the building’s dock doors could be oriented toward the south helped us capitalize on the winter sun to melt snow around the docks, thereby warming the air right where building infiltration is the most critical. Oftentimes, traditional warehouse construction avoids this step, deferring instead to a ‘tried and true’ method, which is budget-friendly in the short-term but rarely cheap in the long-term.

 

Several other priorities were identified, which helped us focus our efforts in the design of an office-warehouse prototype. The SPPA dictated a marketable size and flexible layout, but various building components were weighed within a simulated energy model and cost-estimate.  The simulation indicated which building systems were the least costly to optimize.  Furthermore, by assuming the current price of solar photovoltaics (PV), we could find the marketable sweet spot between the cost of reducing the building’s energy and paying for PV on the roof.

The few surprises we found along the way—various energy model configurations that either performed better or much worse than expected—only helped to demonstrate the importance of modelling different paths. We took the opportunity to determine what the best route is.

Authored by Derek Petersen, December 4, 2017

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