The folks at Lake Superior State University in Sault Ste. Marie, Mich. recently published the 34th annual “List of Words to Be Banished from the Queen’s English for Mis-use, Over-use and General Uselessness.” Leading the list were the words green and carbon footprint.
No surprise here. As they point out, we now have green lifestyles, green initiatives, green legislation and policies, green solutions, green technology, etc. What do all these people mean when they use the word “green”?
In the simplest of terms, being green means being environmentally-friendly. Thus, I think we use the word “green” because it rolls off the tongue much easier than “environmentally-friendly.” It also sounds less academic, which I think makes it more palatable to folks weary of environmental extremism.
Diktats of the green movement
To understand the green building movement you must first understand the two main diktats of being environmentally friendly. These two diktats are herein referred to as Law 1 and Law 2:
• Law 1 is to minimize harm to the natural environment. This means minimizing habitat destruction during raw material extraction, and minimizing harmful emissions (emissions that negatively impact the environment). Reduction of harmful emissions translates into a reduction of emissions to the air, water and land that result in acidification, stratospheric ozone depletion, cultural eutrophication, smog and numerous other conditions that alter the existing natural balance of our environment by making it increasingly more toxic to certain plant and animal life.
• Law 2 is to use only natural resources at rates that do not exceed their rate of regeneration. This means that we use natural resources that are renewable, and if not renewable, extremely plentiful so that future generations can enjoy them as we do today. The major problem here is our consumption of fossil fuels (natural gas, oil and coal) which are finite resources that took eons to generate. Most other resources are either quite plentiful, or like wood, can be easily regenerated at a rate that exceeds our use rate. Interestingly, while we should be focused on reducing our consumption of fossil fuels because of their finite supply and the harmful gas emissions associated with their combustion, it would appear that their reduction in the U.S. is driven by national security concerns over our economy’s dependency on foreign governments that control much of our oil supply.
Life cycle assessment
Designing and constructing buildings that are more environmentally-friendly begs the question, “How do you determine which building products and practices are most environmentally-friendly?” The answer to this question lies in the realization that you must be able to quantify to what extent you are meeting (or not meeting) Laws 1 and 2 with respect to every building product and practice you implement.
The procedure used for this quantification is called a life cycle assessment (life cycle analysis or LCA for short). LCA is used to account for all the inputs and outputs associated with the life cycle (production, implementation, operation and disposal) of a building product.
LCA begins with an identification of all unit operations (unit processes) associated with a product throughout its life. This is called system delineation, and in theory, each building product is associated with an infinite number of unit operations. Thus some of the major decisions surrounding LCA involve determination of which unit operations to include and which to exclude from various analyses. Even for a very simple product an LCA may still include hundreds of operations.
This is not surprising if one considers all handling, storage, transportation and processing operations associated with each raw material used somewhere in the development of a product, as well as all operations that support these operations, and all activities that surround implementation, use, eventual removal and perhaps reuse of the product.
With unit operations delineated, the next LCA step is to identify all mass and energy flowing into and out of each unit operation. Once this is complete, all materials and energy flowing into and out of the natural environment for the entire system (all unit operations) can be summarized. This concludes the first portion of the LCA, commonly referred to as a life cycle inventory (LCI).
The final LCA phase, called life cycle impact assessment (LCIA), is used to score the impact of product use on the environment. This would include determinations of how a product, over its lifetime, contributes to ecological toxicity, stratospheric ozone depletion, global warming, acidification, fossil fuel depletion, reduced indoor air quality, habitat alteration, water consumption, human health, smog, criteria air pollutants, cultural eutrophication, etc.
One of the main outputs of LCA is the estimation of embodied energy, the total amount of energy required to transform raw materials into products, to install products and to eventually dispose of the products. Embodied energy is frequently broken into categories of renewable versus nonrenewable. Non-renewable energy is from fossil fuels (petroleum, natural gas, coal) and uranium. Renewable energy includes all other energy (hydropower, wind, wave, photovoltaic (PV), passive solar, geothermal, biomass).
Total embodied energy associated with production, construction, operation and retirement of a building is, by far, the single best measure of how environmentally-friendly a building is over its lifetime. Given that there is a fairly direct relationship between total embodied energy and overall cost to construct and operate a building, one can conclude that overall cost is a good measure of environmental-friendliness. When comparing buildings on such a cost basis, it is important to also look at the ratio of non-renewable embodied energy to renewable embodied energy, as renewable energy costs more but has a lower environmental impact than non-renewable forms of energy.
Status of life cycle assessment for buildings
LCA for building analysis is in its infancy. For this reason, be extremely cautious of basing a major building decision on LCA data. Realize that a substantial amount of work is required just to obtain accurate and complete information on a single unit operation, and each product is associated with hundreds of unit operations. Also realize that even though two products may appear virtually identical, the unit operations associated with them could be markedly different.
Whereas one product may be manufactured locally using modern facilities and processes, the other may be manufactured overseas using technology/equipment that is much less friendly to the environment. The LCA for each product should take into account specific facilities and equipment used in production, and specific methods and equipment used to transport raw materials as well as finished products.
Inasmuch as LCA information can help you make a more informed decision, you should use it where applicable LCA data is available. That said, you should realize that it will never give a definitive answer to which design option is best. This is because there are numerous environmental impacts to consider, and seldom will one particular product appear better than another in all environmental assessment areas. Simply stated, every building product is “green” for one reason or another.
Checklists and rating systems
In the absence of complete and accurate LCA data, green building decisions are based on prescriptive criteria that various individuals feel will reduce negative environment impacts. Although many ideas for improving the “greenest” of buildings have been around for a long time, in more recent years they have been increasingly assembled into “green building checklists.” In theory, the more checklist items incorporated into a building, the greener the building.
To facilitate comparison of buildings, developers of green building checklists assign a point value to each checklist item — a value meant to reflect the relative value of the item in improving the overall environmental-friendliness of the building. With point values on all checklist items, building designs receive an overall green building rating score.
Shortcomings of checklists
Checklists are good when they focus attention on a practice that is not environmentally-friendly and provide alternatives that, in the end, lower the total embodied energy and harmful emissions associated with a structure’s life cycle. Unfortunately, prescriptive criteria like those that comprise green building checklists frequently fail in this regard.
First, no single criterion equally addresses all areas of concern when it comes to environmental impact. A product prescribed because it is generated from renewable resources may consume measurable quantities of non-renewable resources during fabrication and transportation, or may be linked to a particular harmful emission. Although designers will use this product because it is prescribed, in the end, it may be several times more harmful to the environment than a product that designers are awarded points for NOT using.
Second, two virtually identical building products manufactured by two different companies can have vastly different impacts on the environment. Prescriptive criteria seldom differentiate “greenest” by product manufacturer.
Third, prescriptive criteria do not account for specific site conditions, nor do they account for the distance between the jobsite and specific building material and labor resources.
Fourth, where and how a product is used generally trumps what particular product is used. No one should be awarded points, for example, for using a particular window, when an overall building analysis would show that the window is not needed and use of the window has a huge negative environment impact over the structure’s life.
Fifth, some checklist items simply drive design in a less environmentally-friendly direction. This can be partly attributed to the influence on checklist development of trade associations and other groups with a primary interest in the financial well-being of the companies they represent.
One example of a questionable practice is the pushing of products that incorporate rapidly renewable materials (materials obtained from plants with a harvest rotation of 10 years or less) over products that use other renewable materials. Depending on the accounting practice, it can easily be argued that rapidly renewable resources are, on average, more harmful to the environment than other renewable resources. Rapidly renewable materials used in construction include, for example, bamboo, straw, soybean flour, hemp, jute, cotton and sisal. In all cases, these are intensively-grown products that require yearly fertilization to replenish soil fertility tillage to prepare seed beds and, in most cases, frequent application of herbicides and insecticides for pest control. Given that commercial fertilizers rely on non-renewable fossil fuels, tilled agricultural land is much more susceptible to wind and water erosion than land that’s not tilled, and pesticides adversely affect virtually all animals as well as those plants not being cultivated, why promote rapidly renewable materials such as wood?
If one is truly concerned about the environment, then using non-renewable resources should be magnitudes worse than using a product that takes 20 instead of 10 years to grow. In the end, the only thing that matters is whether or not future generations will have access to the same volumes of natural resources that we have today.
Going a step further, I’d note that many folks in my area of the country would question the intelligence of one who believed bamboo flooring to be a more environmentally-friendly option than flooring fabricated from local hardwoods. In addition to the above points regarding rapidly renewable materials, bamboo is not grown locally. There are major transportation costs associated with its use. Also, bamboo’s conversion into a flooring material is more complex than that for hardwood flooring (and this manufacturing is often done in overseas facilities that tend to be less “green” than local facilities).
Additionally, bamboo plantations are not managed to the extent of local forests. In fact, bamboo expansion has come at the peril of some tropical forests, and many bamboo plantations are on steep slopes that should never be clear-cut.
Although an accurate LCA would seldom show bamboo flooring to be as environmentally-friendly as locally produced hardwood flooring, virtually all green building checklists give more points for using bamboo flooring unless the wood comes from certified sustainably managed forests. The irony is that few people question where the bamboo comes from, or for that matter, where any non-wood raw material originates.
Shortcomings of rating systems
The creation of rating systems based on prescriptive criteria has resulted in designers chasing building points. Invariably, as designers work to increase green building points, initial construction costs and embodied energy increase. This increased cost is often dismissed with statements that “It will be recovered during building operation” or “It’s the cost associated with saving our natural environment.”
While this is true in many cases, it’s not true all the time. The law of diminishing returns applies to many building products (particularly insulation) and building systems (PV, wind) meaning that at some point, the cost to install and maintain the products and or systems cannot be economically justified. In other cases, investments cannot be justified on the basis of total embodied energy. The latter applies, for example, when the non-renewable embodied energy required to produce a product or system is greater than the non-renewable embodied energy saved with its incorporation into the building.
Using rating systems that rely on checklists of prescriptive criteria have two major shortcomings.
First, they do not provide a very good measure of how environmentally-friendly a building is. Some of the highest point-rated buildings frequently have some of the highest total lifetime embodied energy. I would argue that total initial and operating cost is a much better predictor of embodied energy and hence “building greenness” than is the point total obtained with some current rating systems.
Second, they redirect attention away from where it should be focused (on designs that truly address Laws 1 and 2), and thus stifle creativity. This problem is not unique to the prescriptive criteria that are part of building rating systems; it is also a problem with the prescriptive codes that are pervasive in the residential sector. In the end, what are simply needed are performance-based criteria that place limits on total non-renewable embodied energy and harmful emissions.
Current rating systems do a very poor job of penalizing designers for doing things that unnecessarily increase total embodied energy. For example, anytime a “jag” is placed in an exterior wall, one or more interior corners are added, and
the ratio of usable floor space to total exterior thermal envelope area decreases. See figure 1, above.
This means an increase in heat loss per square foot of usable space. It also requires more wall material and construction labor to complete and generates more waste from “drop-offs.” In addition, a meandering wall is generally associated with a meandering eave and a more costly roof system. All these negatives come with no positives. So why aren’t designers penalized every time an interior corner is added to an exterior wall? To understand the irony in all of this, realize that virtually all rating systems give points for reducing from 3 to 2 the number of studs used to frame a corner. So which is better? Four corners with 3 studs per corner or 10 corners with 2 studs per corner?
One of the biggest beefs with residential rating systems is that they do not penalize individuals for building large homes. While they say they do, they really don’t. Point penalties for size are often based on the number of bedrooms and not on the number of individuals that will occupy the home (e.g. call your home office a bedroom and “ta-dah!” – your home is now platinum rated instead of gold rated). Ideally, no one person deserves to use up more natural resources than another. To this end, the green rating of a new home should be based on total embodied energy per building occupant. This value should be divided by the usable life of the building to account for overall durability. In the end, it’s how much energy we use each year that dictates our personal imprint on this planet.
The greenness of post-frame
Construction that is considered sustainable is construction that is both affordable and environmentally-friendly. Based on my previous arguments, all buildings that are truly environmentally-friendly are low cost and thus affordable, which automatically makes them sustainable. The fact that many of the most highly-rated buildings (based on current prescriptive building rating systems) are very expensive, their construction cannot be sustained. As I have previously argued, their high cost is also an indication that they are most likely not as environmentally-friendly as folks would have you believe.
In fact, post-frame buildings represent some of the most affordable, functional, environmentally-friendly, commonly-built structures currently erected in our society. To this end, there is no surprise that they dominate the agricultural sector, where cost and functionality are everything. This makes them the most sustainable building system in the world for many applications, and it is time that post-frame builders realize this and take advantage of it.
My current research looks at making post-frame buildings more structurally efficient (and less expensive), quicker to construct, more energy efficient, and easier to disassemble for reconfiguration/reuse. All these lower the total embodied energy of the structure and make it that much greener.
Prophets of the green religion
As a structural engineer, I am not fond of prescriptive structural building codes. They are based on overly-simplistic assumptions that must be counteracted by higher factors of safety. This results in a majority of buildings being over-designed (using more materials than necessary), which means that buildings designed in accordance with prescriptive codes are generally not as environmentally-friendly as those designed in accordance with performance-based codes. The only reason that we have prescriptive structural building codes is that they enable individuals without engineering knowledge to design a building more easily.
With their prescriptive criteria, green building checklists are no different than prescriptive building codes. They are not nearly as effective in achieving their goal of producing environmentally-friendly buildings as would be performance criteria that establish limits on harmful emissions, total embodied energy, etc. For the most part, these checklists have been established to give individuals with little or no formal training in building design and life cycle analysis ideas on how buildings can be made greener.
A current concern that I share with others revolves around efforts within the green building movement to push municipalities into adopting into law some prescriptive criteria found in current green building rating systems. For aforementioned reasons, some of these prescriptive criteria are items that should not be mandated.
Explaining fundamental concerns about various prescriptive criteria to individuals that are part of the green building movement can be difficult, and frustrating. This largely stems from the fact that a number of organizations within the green building movement are saturated with individuals who have a poor and/or warped understanding of science fundamentals. Discussing concerns with a poorly-educated person is tough because (1) they lack the knowledge to follow the arguments, (2) their position (and every other position in the world for that matter) is supported by one or more quacks who claim to be experts in the field, and (3) they lack the knowledge to be able to figure out who are the quack experts and who are the truly knowledgeable researchers. Obviously, in areas outside of my own area of technical training, I’d have the same difficulties separating fact from fiction.
More difficult to deal with are folks that consider themselves anointed prophets of the green building movement. These people, most of whom have absolutely no fundamental knowledge of physics or thermodynamics, have attended a two-day training program and have been designated green building certifiers. They believe in the gospel of the checklist, and they believe that they are building science experts and true guardians of the environment. Beware of these prophets! These individuals tend to be dogmatic in their advice, one of the first signs that you should view their gospel with skepticism.
There is nothing more dangerous than a little education. There is nothing more frustrating than being told what to do by someone who has a measurably lower understanding of the situation than you have (and we have all been in that boat sometime in our lives).
While I’ve been inundated, like everyone else, with so much green stuff for so long that my brain is now green mush, I remain a very strong advocate of sustainable development which, at its heart, requires the construction of very affordable, functional, environmentally-friendly “green” buildings.
In my humblest opinion, I believe that properly applied, post-frame buildings fit the green mold as well as or better than any other framing system in use today. At the NFBA’s annual convention and trade show, Frame Building Expo, I presented a program called “Post-Frame: As Green as it Gets.” During this presentation I outlined very specific items that make post-frame an extremely environmentally-friendly building system.
I am working with the NFBA to create an online educational training module based on that presentation. It will be available to NFBA members via the NFBA Builder Academy. I encourage those who were unable to see the presentation at the Expo to join NFBA, review the training module and use your creativity and imagination to discover new ways to grow your business with the knowledge that post-frame buildings are indeed “…as ‘green’ as it gets.”
David Bohnhoff, Ph.D., P.E., teaches at University of Wisconsin-Madison