Understanding the Energy Behind Building Materials

In the realm of construction, there’s a hidden aspect called embodied energy, a term that encapsulates all the non-renewable energy used in the entire life journey of a building material. This journey encompasses extraction, manufacturing, construction, maintenance, and disposal. To put it simply, it’s the total carbon footprint, or greenhouse gas emissions, associated with a material throughout its life.


The Significance of Embodied Energy in Building Sustainability

Embodied energy is a crucial factor when evaluating the overall sustainability of a building. It’s a measure that directly connects to the lifespan and environmental impact of constructed structures. Let’s delve into the types of embodied energy and their significance.


Breaking Down Types of Embodied Energy

Embodied energy isn’t a one-size-fits-all concept. It comes in different flavors:
1. Initial Embodied Energy

  • This is the energy consumed during the procurement of raw materials, processing, manufacturing, transportation, and construction.
  • Take the example of a steel window, where energy is expended from mining to manufacturing and finally reaching the building site.

2. Recurring Embodied Energy

  • This type of energy is used for ongoing maintenance, repair, restoration, refurbishment, or replacement of building materials throughout its life.

3. Operating Energy

  • Recurring energy used for heating, cooling, ventilation, and lighting within buildings.
  • The age of the building directly affects operating energy, with initial embodied energy becoming less significant over time.

Zeroing In on Initial Embodied Energy

In the construction industry, the spotlight often falls on initial embodied energy. Concrete, a ubiquitous material, contributes significantly to CO2 emissions. Nearly 7% of the world’s CO2 emissions stem from cement production, making it a major player in embodied carbon in the built environment.


Quantifying Embodied Energy: A Complex Endeavor

Expressed in Mega Joules (MJ) or Giga Joules (GJ) per unit of weight or area, calculating embodied energy is a complex process. Factors such as geographical location and manufacturing methods play a pivotal role in this intricate computation.


Setting Boundaries for Embodied Energy Assessment

The Inventory of Carbon and Energy (ICE) from the University of Bath outlines three boundary conditions for evaluating embodied energy:

  • Cradle-to-Gate: From material extraction to manufacturing gate.
  • Cradle-to-Site: From material extraction to the building site.
  • Cradle-to-Grave: From material extraction to end-of-life.

For a broad overview, Cradle-to-Gate conditions provide general data on building materials. For more detailed analyses, Cradle-to-Site conditions may be considered.


The Mission: Tackling Carbon Emissions

Civil engineers and architects have a pressing mission – to reduce carbon emissions from buildings. The study of embodied energy or carbon in building materials is a fundamental step in creating eco-conscious projects.


Tools for a Greener Tomorrow: Life Cycle Assessment (LCA)

Life Cycle Assessment (LCA) acts as a valuable tool for identifying environmental impacts in a building’s life cycle. It involves comparing different materials with similar functions, like steel, timber, or concrete frame structures.


Data Dive: University of Bath’s Inventory

Table-1 provides selected data from the Inventory of Carbon and Energy (ICE) by the University of Bath (UK), showcasing the energy and carbon footprint of various materials.

Material Energy MJ/kg Carbon kg CO2/kg Material density kg/m3
Aggregate 0.083 0.0048 2240
Concrete (1:1.5:3) 1.11 0.159 2400
Bricks (common) 3 0.24 1700
… (and the list goes on)

Identifying Energy Guzzlers

Not all building materials are created equal. Cement, aluminum, and steel production stand out as major consumers of non-renewable energy. Hence, caution is advised when utilizing these materials in construction.


Smart Moves to Reduce Embodied Energy

Reducing embodied energy involves strategic decisions, such as using locally available materials, designing for low maintenance, ensuring flexibility in use, and tailoring the design to suit climatic conditions. In the quest for sustainable construction, these choices matter, shaping a greener future for our built environment.