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Performance-Based Design

18 August 2010 | Posted By Naomi Cole 2,021 views No Comment

Authored by “The Dream Team” at The Cascadia Center for Sustainable Design and Construction

Cascadia CenterThe Cascadia Center for Sustainable Design and Construction strives to be the first of its kind: an urban mid-rise Living BuildingTM.  The vision of the Bullitt Foundation and its director, Denis Hayes, is to develop a game-changing place that creates a ripple effect to change the way designers, cities, and occupants think about their buildings.

One of the many unique factors of the project is the development process and the fact that the players have been willing to think differently at each step of the way. In essence, the team that enables this kind of performance includes the designers/developers, the tenants, and also the city. “We all feel like we have a chance at promoting much larger change if we can get others to do this kind of building,” says Chris Rogers, principal at Point32, the project’s developer .

The Cascadia Center is a 50,000 SF commercial structure in Seattle’s central district slated for completion in late 2011. The team includes Point32, The Miller | Hull Partnership, PAE Consulting Engineers, and general contractor Schuchart as well as the University of Washington’s Integrated Design Lab with support from the BetterBricks initiative of the Northwest Energy Efficiency Alliance. The Bullitt Foundation is the anchor tenant, but will only occupy half of one floor; other leases are in negotiation.

A Performance Driven Team

The process was almost entirely driven by the project’s energy goals, which are to meet the net-zero energy imperative of the Living Building Challenge.

Rogers says that these energy goals were the “most intriguing part of the process and has influenced every step of the design.” Before the design team was even hired, the Integrated Design Lab was engaged to develop an energy profile for the hypothetical building.

When the Miller | Hull/PAE design team began its work, aesthetic design was not up for discussion until every aspect of the technical performance was understood. Craig Curtis, partner at Miller | Hull, says the team refers to it as “performance-based design.”

Big ideas about how to reduce and capture energy drove the highly iterative design process. According to Rogers, this was largely due to the openness of the team. The architects were willing to let the performance vision drive the design, allowing for a highly collaborative relationship where the engineers were as much in the drivers seat as the architects.

Similarly, the contractor was brought on early and was able to weigh in regularly with cost checks to keep the concept within a reasonable budget.

Major energy savings will be achieved through a highly efficient envelope (preassembled and delivered to the site air tight); automated shading; and heat recovery on the mechanical and ventilation systems. As the architecturally imposed loads headed towards net zero, the internal equipment load took over. The team realized they needed an expert in computer and server loads.

The building and systems designs were so highly calibrated that every tweak threw the energy concept slightly out of balance. Joel Loveland, Director of the Integrated Design Lab, explains the need for a “facile modeler as part of the engineering team to pick up the results of small and nuanced energy changes during Schematic Design.”

The performance requirements even affected the program. Early plans included a coffee shop on the ground floor, but the internal loads were too high to meet the net zero goals, so a restaurant tenant was out of the question.

Loveland describes Miller | Hull and PAE as a dream team. “Everyone has been incredibly dedicated, way beyond the call of duty. It is pretty exceptional.”

An Open Minded City

In addition to the highly capable and dedicated design and development team, the City of Seattle has made the unique process all the more manageable.

Last fall, Seattle passed an ordinance that allows twelve projects to go through a process that identifies regulatory obstacles to achieving the Living Building Challenge. Rogers characterizes it as the city essentially saying, “Let’s use the Cascadia Center and 11 other buildings to explore how our current codes and methods for supporting the building design and development process could be modified to achieve better performance.”

Part of the process is for the design team to help the City to think differently about its regulatory structure and to understand performance-based design. In the case of the Cascadia Center, the City will allow a zoning exemption for a larger rooftop solar array (essential for meeting net zero targets) than is typically permitted in urban areas.

The idea is for the building to not only be a point of departure from a performance standpoint, but also from a regulatory perspective for the local policy agenda.

This is essential because, as Curtis points out, “everything about the design is unique to this particular location in the world.”

Flexible Occupants

The final members of the performance team are the occupants. Design and technology can only take the performance so far; the final increments of energy savings depend on the tenants of the building.

Occupant behavior is a fundamental factor in meeting the net zero goals. Plug loads are the primary occupant-imposed energy loads and are expected to be half of typical building use.

The design team developed a survey for prospective tenants, to determine how many people expect to bike to work, shower at the office, and the length of each shower. The energy and water impacts of these habits will ensure availability of excess water for irrigation and the ability to not exceed energy use allotted to water heating. In this way, every individual action plays into energy assumptions, to ensure adequate resources to meet other needs. If someone takes too long a shower, the plants in the greenhouse will bear the consequences.

Given that the major energy consumers are expected to be the computers and server systems, the team is exploring new ways of sharing these services across companies with the expectation that tenants become more collaborative.

One idea that is being explored is an internal cap and trade system among tenants, by which a high energy user may be able to trade credits with a light energy user.

The Opportunity

Ultimately the goal is a building that inspires more of its kind. While some may dismiss Living Buildings as one-off solutions, only possible with an owner who values innovation and is willing to pay more for it, The Cascadia Center team is committed to a design solution that is broadly applicable to the industry and thus has the potential to be transformative. At every decision point, the team was thoughtful about the replicability of a particular design. The initial design concept included an unusually shaped floor plate with atrium to optimize solar potential, but the shape would be difficult to emulate (and far exceeded average construction costs) so a more conventional floor plate was selected to fit the urban grid and still maximize daylight.

As Rogers says, “The goal is for the building to become a catalyst, not to stand alone” The project is being designed for a 250-year lifespan, to adapt to evolving needs and technologies, chances are it will soon be standing among similar buildings that it inspires.

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