Materials selection, embodied carbon and capstone

Every material in a building has a story that begins long before it reaches the site and continues long after the building is handed over. Raw materials are extracted, processed, manufactured and transported; materials are installed with some waste; buildings are operated, maintained and renovated; and eventually materials are demolished, reused, recycled or landfilled. Each stage consumes energy, emits greenhouse gases and affects health and the environment. Construction managers increasingly influence these impacts through procurement, substitutions, waste management and documentation. This final lesson introduces material selection criteria, life cycle thinking, embodied carbon and environmental product declarations, low-carbon strategies for the materials covered in this course and in CON-110, construction waste management, healthy materials, and the policies and rating systems that drive them. It ends with a capstone that pulls the course together. CON-430 covers sustainable construction and rating systems in depth.

Selecting materials

Material and system selection balances many criteria, and construction managers contribute through constructability reviews, value engineering, pricing and procurement advice:

• Performance: strength, stiffness, fire resistance, acoustic and thermal properties, durability in the expected exposure.
• Cost: first cost, installation labor, maintenance and replacement over the building's life (life cycle cost).
• Schedule: lead times, speed of installation, weather sensitivity, prefabrication potential.
• Availability and supply chain: local suppliers, qualified installers, price volatility and tariffs.
• Code compliance: construction type, combustibility, fire ratings and energy code requirements.
• Environmental impact: embodied carbon, recycled content, responsible sourcing, end-of-life options.
• Health: emissions of VOCs and other chemicals of concern during and after installation.

Value engineering should compare alternatives on all these criteria, not only first cost. A cheaper cladding that fails in fifteen years, or a substitute insulation that is combustible and requires a new fire test, is not real value.

Life cycle thinking

Life cycle assessment (LCA) is a method for quantifying the environmental impacts of a product or building over its life. For buildings, standards such as ISO 14040/14044 and EN 15978 divide the life cycle into stages:

• A1 to A3, product stage: raw material extraction, transport to the factory and manufacturing ("cradle to gate").
• A4 and A5, construction stage: transport to site and installation, including construction waste.
• B1 to B7, use stage: use, maintenance, repair, replacement, refurbishment, and operational energy and water.
• C1 to C4, end-of-life stage: demolition, transport, waste processing and disposal.
• D, beyond the system boundary: benefits and loads from reuse, recovery and recycling.

Embodied carbon refers to the greenhouse gas emissions associated with materials and construction (stages A, B excluding operational energy, and C), measured in kilograms of carbon dioxide equivalent (kg CO₂e). Operational carbon comes from energy used to run the building. As buildings become more energy efficient and electricity grids cleaner, embodied carbon becomes a larger share of a building's total life cycle emissions, and unlike operational carbon, most of it is emitted before the building opens.

Environmental product declarations

An environmental product declaration (EPD) is a standardized, third-party verified report of a product's environmental impacts, usually for stages A1 to A3, prepared according to product category rules (PCRs) under ISO 14025 and ISO 21930 or EN 15804. EPDs can be industry-wide averages, published by trade associations for typical products, or product-specific EPDs for a particular manufacturer and plant, which are more useful for procurement. EPDs report global warming potential (GWP) in kg CO₂e per declared unit, such as per m³ of concrete of a given strength, per metric ton of steel or per m² of insulation at a given RSI, along with other impacts such as acidification and smog formation. Databases and tools such as the EC3 tool from Building Transparency let project teams compare products and set procurement limits.

Calculating embodied carbon

At its simplest, the embodied carbon of a building element is the sum of each material quantity multiplied by its emission factor, increased for construction waste:

where \(Q_i\) is the quantity of material \(i\), \(EF_i\) is its emission factor in kg CO₂e per unit, and \(w_i\) is the waste factor for that material. Quantities come from the same takeoffs estimators use for pricing, which is why construction managers are well placed to help.

Low-carbon strategies by material

Many reductions are available without changing the building's design:

• Concrete: use Portland-limestone cement (Type GUL in Canada, Type IL in the US), supplementary cementitious materials such as slag and fly ash, performance-based specifications that allow longer curing times (56 or 90 days) for strength, and optimized mixes; avoid over-specifying strength. Carbon mineralization technologies inject captured CO₂ into fresh concrete.
• Steel: specify steel from electric arc furnaces with high recycled content and low-carbon electricity where available; optimize member sizes and avoid waste; reuse steel where practical.
• Wood: use responsibly sourced, certified wood, such as FSC, SFI or CSA Z809; mass timber can replace higher-carbon materials, though forest management and end-of-life assumptions affect the result.
• Insulation: choose low-GWP blowing agents (many foams historically used high-GWP HFCs, now being phased down) and consider mineral wool, cellulose and wood fiber.
• Aluminum and glass: specify recycled content and low-carbon smelting for aluminum; size glazing areas sensibly, since curtain walls carry high embodied carbon per m².
• Finishes: replaced several times over a building's life, so durable, low-impact finishes and carpet tile take-back programs reduce B-stage impacts.
• Design efficiency: shorter spans, less structure, reusing existing buildings and avoiding unnecessary basements and parking reduce embodied carbon more than any material swap.

Construction waste management

Construction and demolition waste makes up a large share of landfill volume. A construction waste management plan sets targets for diversion, identifies materials to separate (wood, metals, concrete, drywall, cardboard, plastics), arranges haulers and recycling facilities, and tracks results with weigh tickets. Strategies include accurate ordering with realistic waste factors, prefabrication, just-in-time delivery, reusing formwork and packaging, returning surplus materials, separating drywall offcuts for recycling, and deconstructing rather than demolishing where possible. Many green building programs and municipal by-laws set diversion targets, such as 75 % by weight.

Healthy materials and indoor air quality

Building materials can emit VOCs, formaldehyde and other chemicals that affect occupants and installers. Strategies include specifying low-emitting paints, adhesives, sealants, flooring and composite wood (tested to standards such as CDPH Standard Method v1.2), avoiding chemicals on red lists, ventilating during and after installation, sequencing absorbent materials such as carpet and ceiling tiles after wet-applied products have cured, protecting ductwork from dust, and flushing out the building before occupancy. A construction indoor air quality management plan formalizes these practices, and is required by many rating systems.

Policies and rating systems

In the United States, the federal Buy Clean program that set low-embodied-carbon limits for concrete, steel, glass and asphalt on federally funded projects was canceled in 2025, but several states, including California (Buy Clean California Act and CALGreen embodied carbon provisions), Colorado, New York, New Jersey, Oregon and Washington, have their own Buy Clean or embodied carbon rules, and many owners set their own limits. Rating systems include LEED (U.S. Green Building Council, with LEED v5 placing more emphasis on embodied carbon), Green Globes, the ILFI Zero Carbon certification and ENERGY STAR for operations.

Capstone: putting the course together

Consider a four-story office and lab building with a steel frame and composite deck floors, a CLT roof over the top-floor atrium, cold-formed steel backup walls with mineral wool exterior insulation and brick veneer and metal panel cladding, a unitized curtain wall at the main entrance, a modified bitumen roof with tapered insulation, steel stud partitions with fire-rated corridors and shafts, and resilient, carpet tile and porcelain tile finishes. As the construction manager, work through these questions using the lessons in this course:

• Procurement and lead times (Lessons 1, 5 and 8): which packages would you release first? Typically steel mill orders, curtain wall and CLT, followed by windows and brick.
• Structure and erection (Lessons 1 to 3): where are the crane, laydown and delivery routes; how is the frame braced during erection; when do decking, studs, inspections and concrete follow?
• Envelope (Lessons 6 to 9): can you trace the water, air, vapor and thermal control layers through every transition on the wall sections, including shelf angles, window openings, the curtain wall interface and the roof-to-wall junction? What mock-up and field testing would you require?
• Interiors and finishes (Lessons 10 and 11): which walls are fire-rated, and how will you control fire-stopping when many trades penetrate them? When will slab moisture testing be done for the resilient flooring?
• Sustainability (Lesson 12): where are the largest embodied carbon reductions available, and which submittals require EPDs?

This course has moved from the frame of a building to its skin and then to its interior. Structural steel and timber give the building strength and shape; cold-formed steel and light wood framing fill in walls and floors; the envelope keeps out water, air and heat; and interiors and finishes make the building usable and beautiful. Throughout, the construction manager's role is the same: understand how each system works, plan the sequence and logistics, coordinate trades at the interfaces, verify quality before work is covered, and keep the owner's goals for cost, schedule, performance and sustainability in view. CON-240 builds on this course with structural analysis, CON-345 with quality management and CON-430 with sustainable construction.