Designing office space: Sustainability and energy efficiency
Office building clients demand sustainability, flexibility, and cost conservation in both new and existing buildings.
Michael F. Cooper, PE, LEED AP, Managing Principal, Harley Ellis Devereaux, Southfield, Mich.
Kurt Karnatz, PE, CEM, LEED AP, HBDP, HFDP, President, Environmental Systems Design Inc., Chicago
Kent W. Peterson, PE, FASHRAE, LEED AP BD+C, BEAP, Vice President/Chief Engineer, P2S Engineering Inc., Long Beach, Calif.
CSE: What software or systems do you use to model the energy consumption of the building?
Cooper: Initial predictive energy modeling is usually done with either the Trane Trace or Energy Pro software packages. We also utilize elements of the Green Builder software bundle to help conceptualize system requirements and performance in the early stages of design.
Peterson: Energy modeling is a powerful design tool to review the relative energy savings of various energy-saving features. We use a number of software platforms since one may be better than the others for a given project utilizing certain systems. I still believe the current state of energy modeling software is insufficient to predict actual energy use of a building but is adequate for comparing options to each other. We must also realize the energy models for building energy code compliance (Standard 90.1 or Title 24) prescribe the occupancy loading and building operating times to determine compliance with the energy codes. The results will not reflect how much energy the building will actually use.
Karnatz: We use multiple modeling engines to help us determine the performance and energy consumption of buildings including eQuest, COMcheck, HAPP, Trace, Window, Ecotect, Therm, Flo-Vent, and Vasari.
CSE: In general, what payback period do building owners expect from an office building?
Karnatz: Typically our office building owners are looking for quick payback windows in the range of three to seven years.
Peterson: In our experience, office building owners are typically looking for three-year paybacks.
Cooper: Though expected payback varies based on the type of building owner (developer, owner, owner/tenant, etc.), “as soon as possible” remains the common denominator. In general, we see expectations on the order of five to seven years, but design buildings to achieve the most aggressive payback possible. It is important that such economic modeling is done early in the design process so that financial objectives are in alignment with the technical goals of the project.
CSE: Describe window treatments (glazing, louvers, etc.) you have recently designed.
Karnatz: When designing regionally, it is important to look at opportunities that the site provides to the building. Controlling direct sunlight on and into the building is important in minimizing building envelope loads while maximizing daylight capture. We use both passive and active shading strategies such as high-efficiency glass systems, exterior shading, interior mechanized shades, and light shelves.
Cooper: Window treatments, like most building elements, are features that are integral to the building design as a whole. We utilize glazing, window surface texture, louvers, light shelves, solar film, and other materials as part of comprehensive building solutions.
CSE: Describe any energy modeling you’ve used to design new office space. What programs did you use? What were the results?
Cooper: As stated, Trane Trace and Energy Pro regularly are used for modeling of new office space. Comparative evaluations of proposed building solutions are made with not only HVAC systems, but lighting and envelope as well. Results are good and getting better. As energy modeling software, building information modeling, building materials, and construction techniques are improving, our ability to more accurately predict energy consumption in new buildings is also improving.