Schematic rendering of the proposalA four-person interdisciplinary team, with limited prior experience in energy modeling and HVAC design, collaborated across three time zones to complete a successful entry to the ASHRAE LowDown Showdown competition using Sefaira Architecture and Sefaira Systems. Here’s how they did it.

Meet the Team

The competition team included Shan He, an architecture research associate at Iowa State University, Ken Thomson, an engineer at AE Smith Australia, Sravanthi Musunuru, an energy modeler at Building Science Corp USA, and Manalee Nabar, an energy modeler at Bright Power Inc. USA. They were coached by Andrew Corney, Director of Product at Sefaira UK.

The Project Brief

  • Project type: New construction
  • Location: Chicago, Illinois, USA
  • Building program: Commercial office building for rental purposes
  • Floor area / stories / occupancy: 53,600 sq. ft./3 floors/268 occupants
  • Performance Baseline: ASHRAE 90.1 2013
  • Performance Goal: Net Zero Energy

To begin, the team reviewed the competition requirements to better understand the modeling guidelines, and the expected outputs for the proposal.

Model RequirementDiagram showing modeling guidelines and considerations

A Performance-Based Approach

With a clear understanding of the project requirements, the team defined a Performance-Based Design workflow that would take advantage of Sefaira’s full product suite:

Diagram of team structure and workflowDiagram of team structure and workflow

The real-time capabilities of the Sefaira Architecture PlugIn would be used for testing design options and multiple iterations during the initial fast-paced concept development stage, while Sefaira Systems would be used to carry out HVAC system comparisons and optimizations later on.

The process ensured that every design decision would consider performance impacts; the software ensured that model rework and additional setup time would be reduced, if not eliminated, as the project solution evolved from initial to final concept.

The Design Concept

Shan He – the team’s architectural designer, proposed an open floor plan to increase flexibility and facilitate multiple tenancies. Taking the site’s location within a newly developed business park into account, Shan proposed locating their building close to an existing recreation centre and other useful amenities.

Masterplan & Form StudyLeft: Site plan showing building in bottom left corner Right: Building form options

Once she had created whitebox models for each concept in SketchUp, she was able to test their energy and daylight performance using Sefaira’s Architecture Plugin. (This process is made easier thanks to the “visibility controls analysis” paradigm Sefaira follows. You can see that in action here.)

Initial Analysis and Insight

Although the square design option achieved the lowest EUI, its internal spaces received the lowest amount of natural daylight. The team agreed to focus on the L-Shaped building form because it balanced daylight and energy performance better than the strip and box-shaped options. It would also accommodate the desired number of units per floor and ensure that all building entrances and exits would be closer to the shared outdoor space as desired.

Diagram showing the impact of various building depths on energy and daylight performanceDiagram showing the impact of various building depths on energy and daylight performance

Design Development

Shan focused on a typical office unit to investigate the impact that different interior layouts, glazing ratios, window orientation, shading devices and fabric specifications would have on its energy and daylight performance.

Zoning & Glazing Ratio TestsInterior layout tests investigating zoning strategies (below left) & glazing orientation and ratios (right).

Shading comparisons showed that a multi-finned shade provided the most optimal daylighting to the interior spaces as compared to an option with no shading and another with a simple horizontal projection.

Sefaira daylight visualisationSefaira daylight visualisation

Using Sefaira’s real time plugin, Shan was able to test over 70 different models in less than 4 hours! The result of this iterative process was a significant increase to Spatial Daylight Autonomy with no negative impact on EUI.

HVAC Systems & Renewable Energy

The team uploaded their optimized building form to Sefaira Systems, and used the Department of Energy’s envelope and schedule specifications for a prototype medium-sized office to define the baseline. Next, they tested multiple HVAC design options, all with the same baseline values to ensure a controlled comparison.

The baseline HVAC system was a Packaged Rooftop VAV with Reheat per ASHRAE 90.1-2010. Sefaira Systems calculated its EUI at 51kBTU/ft2/yr. In comparison, one of the team’s proposed systems, a Variable Refrigerant Flow System with DOAS, had an EUI of 2.4 — a 95% reduction in EUI and a 28% reduction in annual utility costs.

To reach the Net Zero Energy goal, the team combined the optimised envelope and HVAC system with the energy produced by on-site solar panels (20% efficiency) across the entire roof.

Sefaira Systems analysis grid showing various HVAC strategies and the corresponding resultsSefaira Systems analysis grid showing various HVAC strategies and the corresponding results

Final Outcome

With the final strategy applied, the team just narrowly missed the Net Zero Energy mark: 94% of the building’s energy demand would be met by on-site generation. It is important to highlight that while their final proposal was extremely similar to the solutions proposed by the other teams, Team Sefaira spent a fraction of the time coming to the solution than any of the other teams. In fact, all their energy analyses (over 400 simulations from concept to final design) were completed within a total of 6 hours!

Competition outcomes

The team’s success highlights the ability of Sefaira to reduce the time and cost associated with high-performance design solutions and also to increase a team’s ability to collaborate meaningfully on a challenging project. For architectural designer Shan He, it was particularly useful that she could optimise the design such that the energy modeller’s more rigorous analysis in Sefaira Systems confirmed her choices.

By incorporating performance analysis from the start of the design process, designers can minimize rework in the late stage, avoid design compromises and reduce the chances of value engineering. If you’d like to learn how to incorporate Sefaira and implement a Performance-Based approach to design on your projects, the following articles are a great place to start: