As everyone knows, an engineer loves numbers; so reducing sustainability down to a nice formula would make any engineer in the industry happy. This is unlikely to occur given the number of variables, not least of which is the human mind; developing such an equation would be nothing short of solving the Unified Theory of Everything, which the physics community has been working on for decades, and may still be for centuries.

What quantifies Green?

One of most difficult challenges facing the industry today is to develop the metrics and indices by which we “benchmark” or judge sustainability. Even though we have started to develop benchmarks for energy performance through ASHRAE 90.1 and local energy codes, such as California’s Title-24, the indices we have today are far from complete and still do not shed light on two important questions: How much energy conservation/reduction is enough? And how much can we consider sustainable? In addition, site and source emissions are only investigated during the most sustainable “intensive” projects.

We are only beginning to develop benchmarks for metrics such as occupant comfort (ASHRAE Std. 55-2004), and productivity. Other metrics remain relatively unexplored. For example: Construction waste: what designs lead to efficient construction? Program waste: how is the building operated/used in relation to consumable products, paper waste? True life-cycle analysis: what is the energy cost of the building from inception, construction, occupancy, through to its eventual renovation or destruction?

Green Tools

The second issue, connect to the first, is developing the tools that allow design teams to efficiently explore different systems. At present, the building simulation industry lags behind design work, which makes sustainable systems more time consuming to develop and thus more costly. For example, displacement ventilation, which has been around for decades, cannot be accurately modeled with the standard industry software. More recent developments such as variable speed chillers, variable flows, and radiant panels must be calculated using a spreadsheet, and modern equivalent of doing the calculation by hand with a pen and paper.

These tools are becoming more important as design engineers need to provide quantifiable metrics that can be understood and absorbed by the rest of the design team and the owner. The lack of efficient design tools inhibits the team’s ability to explore sustainable designs, and as a result retards the exploration of additional sustainable applications.

At the Core

Away from the metrics, indices and numbers, at the core of sustainability is an understanding how a space (building) integrates and interacts with people, both now and in the future.

Open spaces; a connection or view of the outside; a breeze from natural ventilation; or direct sunlight do not by themselves make a building sustainable; it is the interaction a person has within the space and their desire to inhabit the spaces make them sustainable; in short these are the type of spaces people want to be in. By their nature these buildings are energy efficient, have high indoor air quality and create a comfortable environment, but these are only byproducts of the design that we can measure; including these ingredients as part of a building’s design does not necessarily make the space sustainable. This is not to discount the need to develop the metrics, indices and benchmarks that we use to measure sustainability, but it means that we also need to start a dialogue on sustainability as an idea. One of the key discussion points, in my view, is how the flexibility of a space is considered over its complete life cycle. This includes considering systems and program flexibility and the flexibility (if any) of building materials and structure. Flexibility is also an important part of the design process and does lend itself to defining sustainability for a project: every project has a budget into which we (the design team) must constrain our design to achieve the greatest possible design with the funds available. This often involves being flexible and compromising to achieve the best possible sustainable design that fits within the budget and other project constraints.

At its core, sustainability is a way of thinking and in order for it to take shape, architects, engineers and design teams will need new modes of thinking beyond the conventional methods of today; new thought processes that involve more than just metrics and indices.