Embodied Energy: The Hidden Environmental Cost

When we compare the environmental impact of different buildings, we most often focus on operational energy: the energy used to heat, cool, and power the building over its lifetime. This is important, but it ignores the energy that was consumed before the building was ever occupied. Producing a single kilogram of Portland cement emits approximately 0.8 kilograms of CO₂. A typical house uses several tonnes of cement in its foundation, frame, and finishes. Structural steel requires enormous energy to smelt and is typically transported thousands of miles from mill to site. Aluminum, one of the most energy-intensive materials in common use, requires roughly 12 times as much energy per kilogram as wood. The embodied energy of a conventionally constructed house can equal 20 to 80 years of its operational energy consumption, meaning that all of the operational savings from high-efficiency mechanical systems may be offset by the energy invested in…