[ad_1]
For years, the construction industry has focused on reducing operational energy targets. Better insulation, tighter buildings, improved mechanical systems and more stringent energy codes have all helped lower the energy required to heat and cool our buildings. More recently, however, attention has expanded to include embodied carbon, the greenhouse gas emissions associated with extracting raw materials, manufacturing building products, transporting them to the jobsite and installing them in a building. The hidden carbon impact of a building begins during construction. Complex building assemblies and material choices can significantly influence a project’s embodied carbon footprint long before the building is ever occupied.
As designers, contractors and owners begin to place greater emphasis on embodied carbon, an interesting question emerges: are we spending enough time evaluating the carbon impact of entire building assemblies, or are we becoming overly focused on individual products? In many cases, high-performance wall and roof assemblies have evolved into increasingly complicated systems consisting of multiple layers of insulation, membranes, tapes, wraps, fasteners, clips and supplemental control layers. While each component may have a legitimate purpose, the cumulative environmental impact of these increasingly complex assemblies is often overlooked.
A walk through a modern construction site quickly demonstrates how much building enclosures have changed over the past two decades. A typical wall assembly may include exterior insulation, a moisture/air barrier, transition membranes, primers, tapes, structural sheathing, cavity insulation, a vapour retarder, service cavities and interior finishes. Individually, none of these materials appear significant. Together, however, they represent a substantial amount of manufactured material that must be produced, packaged, transported, installed, and eventually maintained throughout the life of the building.
The challenge is that embodied carbon assessments often focus on major building components while paying less attention to the collection of supporting materials required to make an assembly to function effectively. Designers may compare the carbon footprint of one insulation product to another while overlooking the fact that a particular assembly may require thousands of square meters of membranes, tapes, adhesives, flashings and mechanical attachments. These supporting materials frequently represent what could be described as “hidden carbon” within the building enclosure.
Embodied carbon represents the greenhouse gas emissions generated throughout the life cycle of a building material, from raw material extraction to its incorporation into the completed building. The issue is not that membranes, tapes, or accessories are inherently problematic. In fact, many are essential for durability and long-term enclosure performance. The issue is that the industry rarely evaluates the carbon impact of these materials collectively. As building assemblies become more complex, the number of supporting products grows, and so does the overall embodied carbon footprint of the enclosure.
Transportation adds another dynamic layer to the discussion. Canada presents unique challenges due to its vast size and geography (ever watch Ice Road Truckers?). Products often travel considerable distances before arriving on a construction jobsite or a material distribution location. One building component may be manufactured in Ontario, another in Quebec, a membrane may originate in Europe and fasteners may arrive from the United States. By the time all of these materials arrive and are installed on a project, multiple transportation networks have contributed to the assembly’s overall carbon footprint. It can take up to 18 trucks of board stock for the equivalent yield of one truck of spray foam insulation.
This transportation burden is often invisible during design. Drawings rarely indicate the distance a product has travelled, or the number of manufacturing facilities involved in producing a complete building assembly. Yet transportation emissions can represent a meaningful portion of embodied carbon, particularly when assemblies rely on numerous specialized components sourced from different locations. In some cases, reducing the number of materials required within an assembly may provide a larger carbon benefit than making incremental improvements to individual products.
Beyond carbon considerations, increasingly complex assemblies can introduce practical construction challenges. Building science professionals regularly investigate enclosure failures that occur not because materials were defective, but because systems became difficult to coordinate, detail and install correctly (darn those manufacturer’s written instructions). As additional layers are introduced, so too are additional interfaces, transitions, penetrations, compatibility and sequencing requirements. Every membrane termination, taped joint, fastener penetration, and material transition creates another opportunity for human error. Contractors are expected to integrate products from multiple manufacturers, often under difficult site conditions, tight construction schedules and a summer snowstorm in Calgary. Even the most experienced trades can struggle when assemblies require numerous steps and precise coordination between several different trades.
From a building science perspective, simplicity often contributes to reliability. A simpler assembly generally contains fewer transitions, fewer interfaces and fewer opportunities for discontinuities within the control layers. It is easier to inspect, easier to install, and often easier to maintain through the life of the building. While complexity is sometimes necessary, it should not be viewed as a measure of performance. This is where the concept of multifunctional materials becomes particularly interesting. Historically, separate materials were often required to address thermal control, air control, moisture control and vapour control. Today, some materials are capable of performing multiple functions simultaneously. Rather than serving a single purpose, these materials may provide insulation, air sealing, moisture resistance and vapour control within a single application.
Multi-functional insulation materials, such as closed-cell SPF, can provide thermal insulation, an air barrier, vapour control and moisture management in a single product. By consolidating multiple control layers, these systems can reduce the number of materials required in the building enclosure, an important consideration when evaluating embodied carbon.
The significance of this approach extends beyond labour savings. If a material can eliminate multiple layers within an assembly, the potential benefits include reduced material consumption, fewer transportation requirements, simplified installation, and potentially lower embodied carbon. The discussion should not be about whether one product category is inherently superior to another. Rather, it should focus on understanding how the assembly performs as a complete system and whether the same performance objectives can be achieved using fewer materials. This shift in thinking may represent the next evolution of embodied carbon analysis. Too often, sustainability discussions become centered on product versus product comparisons. Which insulation has the lowest global warming potential? Which membrane contains the lowest embodied carbon? Which material has the most favorable environmental product declaration? These are important questions, but they may not always be the most meaningful ones. A better question might be: which assembly achieves the required performance with the fewest materials, the simplest installation sequence, and the greatest likelihood of long-term success?
Evaluating assemblies through this concept encourages designers and contractors to think beyond individual products and consider the total environmental impact of the system. A material with an exceptionally low carbon footprint may ultimately contribute to a higher carbon assembly if numerous supporting products are required to make it function. Conversely, a product with a higher embodied carbon value on a per-unit basis may contribute to a lower carbon assembly if it significantly reduces the total number of materials required.
Assembly-level research paints a clearer picture
In 2023, RDH Building Science and Toronto Metropolitan University, funded by The Atmospheric Fund, published what was the first study of its kind: a comprehensive Embodied Carbon Resource Guide that evaluated full building enclosure assemblies rather than individual products. While EPDs provide verified product-level data, no single product tells the full carbon story of an assembly. Every component; cladding, sheathing, structure, insulation, membranes and finishes contributes to the total embodied carbon footprint. Without that full picture, architects and designers are making decisions based on incomplete information. The RDH/TMU guide was created specifically to move the industry from product-level carbon targets to real, design-based decisions. It provides pre-calculated, easily comparable assembly-level data for 36 common wall, roof, and floor configurations to inform early design decisions, before enclosure details are established.
Durability is important
Durability must remain part of the embodied carbon conversation. The lowest-carbon building assembly is not necessarily the one with the lowest initial embodied carbon, it is the one that continues to perform reliably over the life of the building. When assemblies fail prematurely, they require repairs, replacement materials, additional transportation, and new construction activities, all of which add carbon emissions and generate waste. Moisture damage can force otherwise serviceable materials into landfills decades before the end of their intended service life. This reality highlights the close relationship between sustainability and durability. Long-lasting assemblies reduce resource consumption over time and help avoid the environmental costs associated with remediation and replacement. In many cases, simpler assemblies are better positioned to achieve this goal because they contain fewer components that can fail or be installed incorrectly.
As embodied carbon becomes a larger part of project decision making, the industry has an opportunity to rethink how building enclosures are evaluated. Rather than focusing exclusively on individual materials, designers can begin examining the environmental impact of complete assemblies. This broader perspective recognizes that every layer, membrane, tape, fastener and accessory carries a carbon cost.
High-performance buildings remain essential to Canada’s future, but performance should not be confused with complexity. The industry has become exceptionally good at adding layers to solve problems. The next challenge may be determining which layers are truly necessary and which have simply become part of conventional building practice. The path toward lower-carbon construction may not always involve adding more materials or more sophisticated systems. In some cases, the most sustainable solution may be the simplest one: a building assembly that achieves its performance objectives with fewer components, lower material volumes, reduced transportation impacts and a greater likelihood of performance and resiliency.
As we continue to advance the conversation around embodied carbon, perhaps the most important question is no longer, “What is the carbon footprint of this product?” but rather, “What is the carbon footprint of this building assembly?” The answer may reveal opportunities to reduce carbon, simplify construction and improve durability all at the same time…oh ya, and the building owners favourite words, REDUCE COST!
Rockford Boyer, B. Arch. Sc., MBSc, BSS, is a building science leader at Elastochem Specialty Chemicals and brings over 20 years of technical knowledge in sustainable building design. Regarded as an expert in the field of building performance, Rockford works closely with architects using energy modeling technology to implement sustainable design strategies. Rockford has completed his undergraduate studies in Architecture and holds a Master’s Degree in Building Science. In addition, he has a diploma in civil engineering.