To assess the true benefits of green building technologies, consultants need to add up more than the economic value. Here is a method that takes a more rounded view.

The following is an adapted version of a paper presented at the Green Buildings Challenge conference in Vancouver in October.

The very nature of engineering, architecture and construction is such that every problem has more than one solution. As a result the evaluation of alternative solutions has long been an important part of the industry. The nature of building technology design and decision making was well put by Ove Arup, founder of the consulting engineering firm of the same name. He said, "Engineering is not a science. Science studies particular events to find general laws. Engineering design makes use of these laws to solve particular problems. In this it is more closely related to art or craft; as in art, its problems are under-defined, there are many solutions, good, bad, or indifferent. The art is, by a synthesis of ends and means, to arrive at a good solution. This is a creative activity, involving imagination, intuition and deliberate choice."

In moving towards environmental building design, however, the problem we face is that traditional models cannot effectively evaluate the complex and often ill-defined decisions inherent in evaluating green technologies.

The use of green building technologies has, in the past, been limited by the inflexibility of the traditional evaluation methods. These tools have been primarily financial models--an alternative is selected purely for its economic benefit. However, the nature of green building technologies is such that benefits are often subjective rather than objective or purely financial. It is important, therefore, that we should develop an evaluation tool that effectively deals with the "soft" benefits of green building technologies and approaches if they are ever to be more widely implemented and given the opportunity to prove themselves.

The need for an improved evaluation methodology is also evident from the increased reporting of dissatisfied green building owners and occupants. In an article in the U.S. publication HPAC magazine of February 1998, J. H. Heerwagen and J. A. Wise noted that, in a green manufacturing plant and office, only 40 per cent of all workers perceived their new green building as "healthier" than the old building from which they had moved.

The green building technology evaluation model we are proposing draws on techniques used in information technology (IT) project evaluation and in the field of value management. The most significant influences we have drawn from these sources are:

-- the use of a value hierarchy to establish and weigh decision criteria

-- an expanded definition of project "costs" and "benefits"

-- the use of a decision matrix and sensitivity analysis.

• green building, sustainable building : true benefits