Modern credit-systems like LEED do a good job of expressing a life-cycle spirit, but in some crucial areas, they fall short of reflecting a buildings objective environmental impact. This is particularly in the area of materials selection. As the ATHENA Institutes Trusty and Horst (2002, p. 2) write, [An] example is the LEED credit for the use of rapidly renewable materials. The stated intent of that credit is to, reduce the use and depletion of finite raw, and long cycle renewable materials by replacing them with rapidly renewable materials. Rapidly renewable is defined as a rotation period of less than 10 years. Among a number of problems with a credit like this, is the fact that it ignores the value of land as a finite resource as well as the implications of all of the fertilizers, pesticides, insecticides, etc., that may be used in the process of producing rapidly renewable materials. Nor is there any a priori scientific reason for preferring a short cycle renewable over a long cycle renewable, let alone an arbitrary 10 year rotation over a 12, 15 or 20 year rotation. Trustys solution is a better integration of rigorous LCA tools (that can more systematically account for full impacts) within the accreditation systemprimarily through the use of the level 2 tools like ATHENAs and Eco-Quantum. But this depends, in turn, on the broadening of these tools applications and an improvement in raw data quality in many regions. And it also requires a seamless integration of the calculation tools into the certification process. Doing this is easier said than done for many of the reasons discussed in previous sections: gaps in data, assumptions required, determining functional equivalence, etc. LCA is complex, but LCA for buildings involves multiple complexities. The difficulty of establishing functional equivalence is especially problematic for buildings. Not only does a designer have to consider comparability in terms of loads, spans, space enclosure and surface coverage in comparing building assemblies or products, but he/she must also take into account all their relevant properties and relationships over the buildings life. For example, concrete and steel have very different thermal mass and conductivity, and