It could be a tricky issue to determine which building products are to be considered as green. Standards and thresholds tend to evolve over time as the life-cycle environmental impacts of different materials become quantified. These impacts are weighed so that it would be clear which material is better from an environmental standpoint.

Generally categorizing materials as green is a lot different from determining material selection for a given project. The greenest of projects will not ensure that only green products will be used nor does the use of green materials guarantee a green structure. The creation of a green building means matching the products and materials to be used to the specific design and site to minimize the overall environmental impact.