Delivering High-Performing Student Housing Facilities

It’s been two years since the Lofts of Washington University opened on the Delmar Loop in St. Louis. The bustling 213,000 ft² mixed-use student housing development was designed to house more than 450 students, provide 220 underground residential parking spaces, and include 22,000 ft² of retail space. The four-building complex also provided a positive environmental impact by adding to the neighborhood green space and educating the community about sustainability in the process.

The approach taken by the design team and Washington University to develop, analyze, and incorporate sustainable design features into the Loop Student Living Initiative helped it to achieve USGBC LEED Platinum certification and successfully deliver energy performance that met projections anticipated during the design.

Energy Efficiency and Environmental Impact

Projected annual energy savings for the Lofts were 47% compared to ASHRAE 90.1-2007 requirements, the US standard that provided requirements for energy performance for buildings certified under the LEED rating system used for this project. This is equivalent to approximately $162,000 per year, with an overall life cycle cost payback for incorporated energy conservation measures of less than 10 years. These projections were nearly spot on after reviewing the Actual Energy Consumption data measured from July 2015 through June 2016.

Sustainable Design Approach

Critical success factors in delivering a high-performing student housing facility are identified at the beginning of every student living project through a customized design and cost-benefit analysis. For the Lofts of Washington University, where sustainable design was a key focus, we identified the critical success factors utilizing the following three steps:

1. Minimize Peak Load Demands

Building envelope performance was enhanced through motorized external shading fins that were incorporated onto the south-facing glass wall and a green roof over a portion of one building. Extensive indoor and outdoor LED lighting was effectively employed and accounted for 13% of the total energy savings. Total enthalpy heat recovery wheels for ventilation and exhaust systems were utilized, which not only reduced peak load requirements but also improved indoor air quality. Additionally, low-flow plumbing fixtures were outfitted throughout the complex.

2. Optimize Mechanical and Electrical System Operating Efficiencies

The team focused on utilizing high-efficiency cooling and heating systems. A water-cooled, variable primary chiller plant incorporating twin-screw variable-speed compressors along with a winter water-side economizer was designed. This accounted for 12% of the total energy savings. A variable primary heating plant utilizing condensing boilers was also designed.

Matching system operation to occupancy is vital to energy performance. Variable ventilation and occupancy setback controls for apartments, triggered by a keycard relay system, contributed to another 12% of total energy savings. Occupancy setback controls for lighting were incorporated through occupancy sensors in each room. Although inconclusive, we believe continued education for occupants on the benefits and operation of the keycard relay system would further improve energy performance.

Additionally, a low friction loss duct design was applied, incorporating static regain.

3. Employ Renewable Energy Sources

The Lofts project relied on the use of Solar photovoltaic and Solar Thermal to garner renewable energy sources. Solar photovoltaic power generation provided roughly 10% of the buildings’ peak electrical demand and accounted for 4% of the total energy savings. A solar thermal domestic hot water heating system was designed and sized to generate 30% of the buildings’ peak hot water demand, accounting for another 4% of the total energy savings. While reviewing data of the Lofts, we learned that additional storage to capture heating capacity during afternoon periods of low hot water usage would further reduce the need for fossil fuel-generated hot water.

Other energy conservation measures that were considered but not incorporated into the Lofts included a geothermal heat pump system, triple plane windows, and magnetic bearing chillers. Those measures were projected to provide an additional 7% annual energy savings but had a negative net present value (NPV) when looking at their life cycle cost.

Lessons Learned

The actual utility for the Lofts confirmed the design team’s approach to sustainability not only met the energy conservation goals for the complex but slightly exceeded them. The lessons learned over the past two years from observing student behaviors, the actual performance of systems and equipment, and review of the adjustments made to improve performance have helped refine our process for delivering high-performing student housing.

Introba has designed more than 55 student living complexes throughout the country, more than 20 of which have received LEED certification or higher. To learn more about our sustainable designs on college and university campuses, check out the Higher Education & Research Market page.

About the Contributor: 

Jeff has over 25 years of professional experience in all aspects of mechanical engineering and project management. As the Director of the Higher Education & Research Market, he has applied his skills and knowledge in the analysis, design, and construction of building systems for educational and research facilities across the country, on projects of all types and sizes. Additionally, Jeff has been a driver for Introba’s mission to provide national leadership in sustainability.