So just what is a carbon footprint? A carbon footprint is a way to measure how much of the greenhouse gas carbon dioxide (C02) is generated in the entire life cycle of a product - everything from extracting the materials necessary to make something, the means to produce it into a final product, the delivery and installation of that product, and its eventual disposal, as well as the fuel and equipment to perform all those steps.
Common sense would jump to the conclusion that a product shipped from a distance would actually produce a larger carbon footprint than one produced locally. This can be true, if all you look at is the C02 created in the delivery of products, but there are more variables to consider when assessing a carbon footprint. The C02 produced in the extraction of a material for a product can vary greatly. Windows can be made with wood, aluminum, vinyl, or fiberglass frames (or a combination of materials) with Aluminum producing many times more C02 during its production than wood.
“Aha!” you decide, “I’ll buy wood windows!” But what if wood windows do not last as long and need replacing sooner because the wood itself will decay and need painting or replacing. How would several cycles of wood windows compare to one cycle of aluminum windows, and what if recycled aluminum was used, or a thin aluminum coating over a wood window to protect it from external weather demands (and thus less aluminum used for the window)??? If you decided on a window based on the carbon generated to produce the main materials, it’s possible you would still not be choosing the lowest carbon footprint product.
Figuring just what to include and not include when calculating carbon footprints has been a matter of debate. True, the fuel to power the equipment to extract the material should be considered, but what of the fuel expended to create the machine that extracts the material, or that used to power the car the worker drove to get to work, or the fuel expended in building the car he drove… you really could get down to a hair splitting amount of figuring. At some point the amount of C02 produced by these lower level steps is negligible to the primary calculation, though are of extreme importance in other calculations such as when deciding the carbon footprint of the individuals’ commute to work.
Fortunately there are those who walk among us that take on the challenge of all the math and the splitting of hairs. Mike Eliason of the Brute Force Collaborative is just one such individual. He took on the challenge of calculating the carbon footprint of importing highly efficient windows from Europe to use in Passive House construction in the Pacific Northwest and compared that to several window brands and styles found in North America.
Instead of just comparing the carbon generated by transportation and manufacturing, Mike also considered the efficiency of the windows and their impact on the fuel usage of the structure for heating purposes as well as the C02 that would be generated to create the amount of extra insulation needed if the European windows weren’t used. For the windows he chose and the comparisons that he made, he discovered that the European windows were the better choice for our area with all things considered. If local manufacturers increased their efficiency or changed material choices, that could change, but for the comparison he made with the data available for existing conditions, it was a rather surprising result. If you would like to see his calculations and logic, please read his blog posting at the Brute Force Collaborative website.
This really drives home that it is important to consider more than just one aspect or material selection when making decisions. There are many choices to be made when planning a project or figuring its value and some will have a higher priority than others. Cost is measured in more than just dollars and comes in many shades of green. What color is your project and what size shoes does it wear?