I have been extremely busy working on my thesis these days, but I suddenly find the need to resume writing, putting my thoughts out there with the hope that people who share these interests will read them and comment.
I have come to realize during this learning process that there are many unanswered questions in the environmental impact assessment of buildings and other elements of the built environment. When I began documenting my literature search, I saw a myriad of approaches, the most scientific (or the ones most cited by other researchers) having a Life Cycle Assessment (LCA) component.
In case you are not familiar with LCA, it is basically a material and flow accounting process that begins with the extraction of raw materials, continues through processing and manufacture, use, maintenance and disposal (end of life being more politically correct as we hope things are reused or recycled), as well as all the transportation links in between. However, it is more than this mere accounting of flows (which would technically be called the Life Cycle Inventory, a step in the whole LCA), and attempts to offer the potential impact. I will always emphasize the word potential, since LCA's greatest weakness, at the moment, is that it does not keep track of time or place of the material and energy flows.
As you can imagine, when we speak of impacts (things like Eutrophication, Global Warming Potential, Smog Formation...) we believe that they are strongly correlated to where and when a relevant discharge occurs. For example, what is the impact of car exhaust in a highway near a forest as opposed to in the face of a cyclist. The one in the highway will have impacts on the immediate natural surroundings, while the urban case will have an impact on the poor cyclist breathing in the toxic fumes. So, as I was saying, in LCA we would know the amount of exhaust gases, but we would not know in sufficient detail when or where they occur to create a realistic estimate. Hence, LCA gets around this by saying potential impacts.
My feeling with all this is that we now have tools like GIS, better computers and such. Let's start attempting to understand impacts and collecting relevant data. One part of me still thinks this may be a losing battle as going back to the exhaust example, some people may be affected differently by breathing in car exhaust. Is the cyclist me or my grandma? However, even in this last question, I am secretly proposing an answer as we can guess to some degree of certainty, what the likelihood of the cyclist being my grandma is... Anyways, all I'm proposing is that we should move to a more predictive stage rather than offering uncertain estimates that may misdirect our decisions from our true intentions.
This is not to say that all impact categories in LCA are like this. Global Warming Potential, expressed as kg of CO2e appears to be the one category where there is some consensus and standardization in its application. The difference, is that this impact is one of the more global ones.
Finally, I will just say that the biggest challenges I see to the application of LCA is that it truly does require a high degree of expertise. The most common way of doing LCA is through the use of software like Athena's Impact Estimator, which is focused on the conceptual stage and assembly based, or some more refined program like PRé's SimaPro which requires a lot more detailed input which can be even more time consuming and expensive (but perhaps more powerful and informative). My general feeling about all this is that we should go back and create models that require simpler, more reasonable input that gives us good estimates for conceptual stages and for analysis. A final comment is that SimaPro can handle most things, but it is tailored for products (buildings are very complex), while Athena is focused on buildings in North America.
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