Biogenics and Less

BY Timothy Lock, AIA 

With realities of climate change bearing down on humanity, all disciplines and human practices have been forced to face their individual impacts. This is often done through exhaustive assessment of data, number crunching, and then ultimately comparison to conventional ways of doing things, in an effort to prioritize positive climate action. There is nothing wrong or inaccurate in this approach. However, what are we to do when any essential generalization would yield a very basic result across all human activities? We simply need to use less stuff. 

In the last decade of building design and construction, great strides have been made in understanding and assessing the direct impacts on climate change. The revolution in carbon dioxide emissions reduction in buildings grew out of a movement several decades old that promoted sustainable and “green” design, coalescing first around energy use reduction and energy modeling. At that time, the shared understanding of global warming’s impact — within the discipline of building design and construction, and within the public at large — was tied directly to fossil fuel combustion for energy use. A focus on miles per gallon in automobiles, which somehow outweighed total miles driven, begat a general understanding of methods to reduce energy use in buildings in a similar, efficiency focused, design approach. This focus made sense as deliberate analysis of global warming's impact yielded data illustrating that approximately 80 percent of emissions (over the lifespan of a building) result from building operations.  

This first step into climate-data driven design was, generally, highly successful. In the last decade, there has been a significant reduction in energy use on average in buildings. Architecture 2030, citing data from the U.S. Energy Information Administration, has cited a reduction in operational carbon dioxide equivalent emissions of nearly 30 percent across all buildings in use; meanwhile, the amount of total building stock has increased by just over 22 percent. Add to that a rapidly decarbonizing energy grid, buildings transitioning away from using direct combustion of fossil fuels for onsite energy, and overall increases in efficiency, and the success is compounded. This progress has produced a new focus on that other 20 percent: what has traditionally been called “embodied energy” or “embodied carbon.”  

This shift opened up a new criteria for building assessment, dubbed Life Cycle Assessment, or “LCA.” LCA protocols allow for the designer (or their consultant) to attempt to account for all of the potential global warming impact of a chosen design. Typically completed in concert with a Building Information Model (BIM), an LCA tabulation allows the designer to see the impact of specific materials and assemblies, potentially tweaking the design by modifying selections to lower the global warming potential. This is very similar to the ways in which energy modeling software allowed a designer to be responsive to energy use.  

Perhaps the most hotly debated category of materials that perform well in whole building Life Cycle Assessments are “biogenic” materials. Biogenic materials are plant based, absorb carbon dioxide from the atmosphere while alive, and store it as solid carbon in their material structure. The traditional breakdown of an LCA groups impacts from various life stages of materials, or “modules,” from extraction of raw resources all the way through demolition of the building and potential reuse of the material in another life cycle. Given the sheer quantity of solid carbon stored in biogenic materials and the relative ease of extracting the resources, biogenic materials can yield a negative global warming potential within the resource extraction and product manufacturing module of an LCA, effectively offsetting emissions at a greater than one-to-one rate. To much fanfare, biogenic materials such as cross-laminated timber, wood fiber insulation, hempcrete and hemp insulation, and straw insulation have become extremely popular. Unfortunately, an overly myopic approach ignores the underlying objective to simply use less of everything. 

After reading this far, you might assume that I am not an advocate for carbon storing and biogenic products within the built environment. This could not be further from the truth. At my practice, OPAL, where I am management partner and director of building ecology, we have been early adopters of many biogenic materials. In concert with Executive Partner Matthew O’Malia, and Design Partner Riley Pratt, we designed one of the first all-cross-laminated timber buildings in the country, our “Little House on the Ferry” project in Maine, all the way back in 2014 [above]. Further, O’Malia co-founded a sibling company, TimberHP, which produces wood fiber insulation (currently the only domestic producer) from lumber industry residuals. Since that initial “all-wood” project, we have gone on to design and build many fully-biogenic assemblies. So why am I skeptical of the role of biogenic materials in overall carbon emissions reduction in buildings? 

The primary reason is quite simple: It’s math. Our practice has had to crunch a lot of numbers internally to feel comfortable with proposing new products and assemblies, particularly wood-based products in buildings conventionally constructed with concrete and steel. We were early adopters of advanced energy efficient design strategies, longterm proponents of Passive House design, and very comfortable allowing data modeling to dictate a design approach for a desired ecological outcome. We have consistently executed projects with over 80 percent reduction in energy use, and have become confident in the numbers. This data-driven approach informs the design process directly and starts in the initial conceptual phase. It helps question pre-conceived design intentions. While it can seem like a process of designing to a number, the goal, ultimately, is to allow the design and data to inform each other in an iterative process. To build our confidence when broadening the scope to whole building Life Cycle Assessment, we were exhaustive and curious.  

We quickly realized that while many biogenic material providers would claim negative emissions, they were only measuring the production of the material and storage of solid carbon in the material [see diagram on page 25]. This is simply not comprehensive, even within the material itself, let alone the entire building. The approach fails to account for the rest of the life of the material itself: transportation to the site, maintenance over time, and potential replacement over the life of the building. It fails to account for portions of the source material left to decompose in place. There is also the important fact that, upon demolition, the majority of the stored carbon is released back into the atmosphere as carbon dioxide as the material decomposes.  

But some will say, rightly, that biogenic materials require far less energy to produce and are thus still a lower carbon alternative. This is currently true, but the returns are diminishing. Think of all the emissions from a building as slices of a pie. If we know that over the entire life of a building, operational emissions account for around 80 percent, then embodied emissions are already only 20 percent of the total. The reduction applied specifically to the selection of biogenic materials is a smaller subset of that 20 percent, since there are many components of a building which have no way of using bio-based materials at this time (most significantly, concrete foundations). 

In a recently completed project, the College of the Atlantic Collins House, a student dormitory, we can see an excellent test case for these assumptions. Having completed a previous project with the College, one with an aggressively low energy use goal, we conceived of a more in-depth approach to building ecology. The building is nearly all wood. The superstructure is a mass timber frame of glue laminated beams and columns, and CLT floor decks and (stair and elevator) shafts. The wall framing is wood lumber and all of the insulation, with the exception of the roof and foundation insulation, is derived from wood fiber (much of it locally produced by TimberHP). The building was designed to Passive House-levels of energy use efficiency, utilizing high performance triple-glazing throughout, robust insulation thicknesses, continuous air-sealing, and the highest efficiency ventilation and heating systems. The design was an attempt to be the lowest emitting building possible. So how did it fare?  

Not surprisingly, getting to a very low overall whole life emissions was a cumulative process. Having this test case project allowed us to run comparisons with conventional versions of the same design, which was critical to the development of these ideas in our office. We conducted Whole Life Cycle Assessment at a 60-year life span on both the constructed design and a conventional “average” version of the same design. The “average” version assumed non-biogenic assemblies and merely code-compliant levels of energy use. We then categorized the reductions from the conventional version to assess what percentage of the overall reduction pie each was responsible for. Given the cumulative nature of compounding energy use over time, energy use reduction, that old initial approach to “building performance,” combined with onsite energy production from solar panels, accounted for over 82 percent of the overall reduction. Next in line, surprisingly, was not the reduction attributable to biogenic materials, but rather a unique design to limit refrigerant volume, and thus emissions from refrigerant leakage, at 7 percent.  

The reduction for use of biogenic materials was third at a mere 2.5 percent [see diagram above]. This may seem extremely low given the amount of wood used in the project, but it makes sense when one considers the overall whole that is being assessed. That said, the use of biogenic materials here is critical.  

I have had the pleasure of leading a small national working group on establishing targets for overall building emissions with the Biden-Harris Administration Climate Policy Office. Our goal is to encourage the building industry to do its part in staying below overall global warming thresholds. It is clear to us that, similar to our example project, ALL possible levers must be pulled in order to reduce emissions while the overall energy industry transitions away from fossil fuels. In that very same project, the use of mass timber and wood fiber insulation reduced the traditional category of “embodied emissions” by over 20 percent. This is quite significant, because we are currently limited in the number of tools we can use as designers to reduce overall emissions. While a 2.5 percent reduction of the total whole life emissions may seem irrelevant, it was still the absolute best that could be done for that category of emissions. Until we have a plethora of low or zero emissions material options to choose from, particularly for massive elements like building superstructure, leaning into biogenics is our best bet, but meeting overall standards, literally takes everything we can do, including using far less. 

I believe that too intense a focus on biogenic materials ignores the lesson of why promotion of lower energy use in buildings was so successful. Using less energy had a direct social comparison — fuel efficiency in cars — that the public intuitively grasped. Further, we understood that using less energy, a.k.a. being more efficient, equated to lower costs (and still does). The same cannot be said for the mental model around biogenic materials, or even whole life emissions reductions more broadly. Always go back to the initial premise: We need to simply use less stuff. Less of everything. We need to “drive fewer miles,” not only reduce the impact of miles driven. So if the ultimate goal is as low an impact building as possible that still serves our communities, let’s design to that goal. Suddenly, under this mental model, “efficiency” is once again at the forefront, a word everyone can appreciate. Be it coal-produced electricity or the greenest natural carbon storing products, these are all resources we draw from our ecosystem. We can and should always strive to use less of them.  

Timothy Lock, AIA is the Management Partner of OPAL, an architectural practice in Belfast, ME. He serves on the AIA National Strategic Council, the AIA Maine Board of Directors, and is co-chair of Maine AIA COTE.