Name three materials with relatively low embodied energy suitable for green construction.

• A. Concrete, aluminum, and plastic composites.
• B. Glass, steel, and gypsum board.
• C. Rammed earth, reclaimed wood, and recycled-content steel.
• D. Hardwood flooring, vinyl siding, brick.

Answer: (C)

Embodied energy is the total energy consumed to extract, process, manufacture, transport, and install a material. Materials with low embodied energy usually rely on abundant, natural or reused resources and involve less energy-intensive processing.

Rammed earth fits this well because it uses on-site soil and minimal processing, sometimes with a small amount of stabilizer, which keeps energy use to a minimum. Reclaimed wood is another strong example because it avoids the energy costs of harvesting and milling new timber; it repurposes existing material, lowering overall energy demand. Recycled-content steel leverages scrap steel as a feedstock, reducing the energy needed compared with producing steel from ore, while still providing the strength and durability needed in construction.

In contrast, many common materials like concrete or aluminum require significant energy for cement production and metal refining, and others such as glass, gypsum board, or brick involve energy-intensive processes as well. Vinyl and virgin hardwood carry higher energy footprints than the trio above. So the combination of rammed earth, reclaimed wood, and recycled-content steel offers a notably lower embodied energy option for green construction.