Overview
The preceding sections on measures of sustainability indicate just how complicated environmental assessments of buildings can become in practice. Due to this complexity, most measures of sustainability have been incorporated into labeling or certification programs, and evaluation tools for buildings.

In a sustainable world, legislation would regulate the environmental impact of human interventions within established thresholds, setting limits on many aspects of building design. Not absolute limits, but limits established through consensus processes guiding the environmental assessment of buildings. Many of the programs and evaluation tools described below may well represent the future of conventional practice.

Why should we voluntarily adopt these programs and evaluation tools? There are several important reasons:

· To raise the awareness of environmental impacts associated with buildings among practitioners, clients and builders.

· To provide a consensus set of criteria and targets to guide design.

· To advance sustainable practices, and in this process to stimulate the construction market to consider sustainable alternatives.

· To implement a verifiable method and framework enabling future policies and regulations leading to environmentally responsible minimum standards.

· To improve the quality and sustainability of buildings.

What are the barriers to implementation? There are many limitations associated with environmental assessments of buildings:

· Practicality dictates that procedures are somewhat simplified to cope with the complexity of modern buildings, and critics claim they risk becoming over-simplified and unreliable.

· The weighting or prioritization of criteria remains problematic and often inconsistent between building projects, calling into question the objectivity of the evaluation process.

· The availability of competent assessors, and the cost of performing assessments, present formidable barriers to broad implementation.

· The entry level of knowledge needed to constructively participate in the evaluation process is relatively high, causing stakeholders to often abandon this approach.

Despite these obstacles, explicit evaluation processes have the potential to address issues of integration more deeply and diversely. Even when some of the ideas being advanced are rejected, the process spawns thinking that can potentially improve future design.

The following provides a brief outline of various environmental assessment programs for buildings. It has been assembled by excerpting overviews from a number of Web sites whose links have been provided for further reference.

The next section deals with Environmental Assessment Programs.