True Green

Green building design has made tremendous strides in the last decade, with numerous projects here and abroad successfully demonstrating that sustainability, functionality, and economic viability are not mutually exclusive objectives. However, published and anecdotal evidence has also pointed to some green building problems, ranging from unexpectedly high energy use to substandard occupant comfort. These deficiences suggests that we need to focus more clearly on what green building design should be trying to achieve.

Before we can design to be “green,” we need a clear vision of what “green” means. The most pervasive error is to define green in terms of building attributes and characteristics rather than measurable performance outcomes. The result is that green technologies become the end rather than the means. This is “green-wash” at its worst. The solution is that the definition of green, and by extension green design, must be performance rather than attribute-based.

There have been a number of international initiatives directed at developing a consensus, performance-based green building rating system on a global scale. Most notable of these is GBTool, the framework developed under the Green Building Challenge. GBTool is a Canadian initiative with over 20 supporting countries, and has been under continuous development since 1996. It uses a comprehensive qualitative and quantitative scaling system to produce numerical performance comparisons against a typical-practice reference building.

One of the early lessons learned during the development of GBTool is that green design is contextual — climate, socio-economic and cultural factors affect what is considered environmentally prudent. Consequently, the system is adaptable to allow for these types of adjustments.

The difficulty with systems such as GBTool is that their rigour and complexity make them difficult and expensive to apply. The industry response has been the development of simplified rating systems such as LEED and BREEAM. These tools provide a much more user-friendly characterization of green building performance and provide a common green language. However, they can lead to “points chasing” as opposed to incorporating what is truly appropriate for a given building. In short, although we are making advances toward standardized definitions of a green building, the field is rather contentious and continues to be a work-in-progress.

The objective should be to produce an environmentally responsible building from the perspective of performance outcomes, not a building with specific green features, characteristics, or a “look”. Consideration and clarification of design and performance objectives, and monitoring of progress relative to those objectives is critical to a successful green project.

Equally important is the implementation of an integrated design process (IDP) as pioneered by the CANMET C-2000 program for commercial buildings. The integrated design process emphasizes a holistic, multi-disciplinary and synergistic approach, as opposed to the more traditional method of each consultant and sub-consultant addressing performance within the confines of their individual discipline. Using the integrated design process, performance issues are identified and resolved at the root level on a building-wide basis, with creative and intelligent design supplanting technology as the primary tool. Note that of the dozen or so successful C-2000 projects to date, none essentially use any exotic or high profile technologies that would normally be associated with “green.” Yet these buildings meet the demanding energy and sustainability criteria of the program, including using less than half the energy used by a reference building based on the Model National Energy Code for Buildings (MNECB). This is not to say that exceptional buildings cannot be designed using the more “prominent” green technologies. However, it does illustrate that they are by no means automatically necessary, and that they are certainly not a defensible replacement for intelligent, integrated design.

Energy analysis at the root level

The prerequisite for identifying and resolving performance issues at the root level is understanding what a building is doing at that root level, particularly from a thermodynamic perspective. It is no coincidence that the integrated design process and energy engineering have co-emerged as the two main underpinnings of successful green building design.

The integrated design process is inherently reliant upon analytical resources to evaluate and predict the performance of design postulations and strategies. These analytical resources are the “eyes” and without them the integrated design process is figuratively lost, blindly developing solutions to problems that may or may not even exist. In this design environment the natural tendency is to defer to myth and folklore, or at the very least to follow the most current trends and fads.

The analytical sphere must also be holistic, comprehensive and sophisticated, and must be able to predict outcomes on a micro (system) and macro (building-wide) basis. Analytical tools must go beyond simple first-principle analyses. No less important is the fact that rigorous analysis lends credibility to performance claims and renders green-wash readily apparent.

Energy analysis techniques, primarily computer building simulation, have progressed to the point that we are now largely able to construct and operate a building in thermodynamic virtual reality. DOE 2.1e, developed mainly by the U.S. Department of Energy, has led the way. However, DOE has its limitations, particularly with respect to fluid flow and thermal transport — the dynamics upon which emerging technologies such as natural ventilation and double facades are based. Solar transmission and daylighting modeling also leave something to be desired. In many respects the latest green technologies have outstripped the capabilities of DOE, and while some practitioners have managed to more or less keep pace by developing supplementary and advanced simulation techniques, it is clear that the innate limits of the core simulation engine are being severely stressed. Software packages such as TASS have emerged to fill niches such as computational fluid dynamics, and numerous sources offer specialty software in areas ranging from daylight analysis to refrigeration design. Unfortunately, as would be expected, these supplementary packages generally fall short in other areas. The result is that, at least until very recently, rigorous building energy simulation has required using an amalgam of software and manual analytical techniques, none of which work particularly well together. This situation has made an already daunting analytical challenge even more problematic.

Fortunately, a solution appears to be emerging in the form of EnergyPlus, sponsored by the U.S. Department of Energy and intended as the replacement for DOE. EnergyPlus is simulation software in the purest sense, with systems being constructed from first-principles building blocks as opposed to pre-configured system templates. In addition to thermal modeling, EnergyPlus simulates fluid and mass transport and in theory provides almost limitless simulation flexibility. The simulation engine has just completed beta testing and has been released for distribution.

The arguable downside of EnergyPlus is that it is even more complex to use than DOE, and although the future development of “front-ends” will mitigate this difficulty somewhat, the software will undoubtedly move building energy engineering and simulation even further into the realm of specialization. However, many would argue that this is a positive result, raising the profile and importance of competent energy analysis in green building design.

The current state of green building design is really not that complicated. While over-enthusiasm has admittedly resulted in some hard lessons, sober thought is beginning to take over the green building movement. As engineers, we have a professional and technical role to advocate and preserve that sens
e of temperance while contributing to the advancement of this exciting and important field of endeavour.

Gordon Shymko, P.Eng. is principal of G.F. Shymko & Associates of Calgary, a multi-disciplinary firm working in energy and environmental design.