What’s embodied energy, and is there any reason to pay attention to it? Embodied energy is the energy it takes to manufacture building materials. Until recently, it was safe to advise builders that it wasn’t worth worrying about embodied energy, because the amount of energy (especially heating energy and cooling energy) used to operate a building over the building’s lifetime dwarfed the relatively small amount of energy embodied in the building materials.
As builders choose to install thicker and thicker layers of insulation in their buildings, however, the old rules of thumb aren’t working as well as they used to. Installing 6 inches of rigid foam insulation under a slab on grade may make sense in a cold climate; but if a Passivhaus builder decides to specify an additional 6 inches of foam, bringing the thickness of the sub-slab insulation up to 12 inches, it’s unlikely that the final 6 inches of foam will ever save as much energy as was required to manufacture the foam.
The embodied energy of a building component or of an entire building is calculated by adding:
Some, but not all, definitions of embodied energy include a few other inputs:
An embodied energy calculation differs from a life-cycle analysis. A life-cycle analysis includes embodied energy, but also encompasses additional environmental impacts, such as the environmental effects of resource depletion and pollution.
There are several ways to report the embodied energy of a building. Assuming that one is capable of making the necessary calculations, embodied energy can be reported in energy units (for example, in joules or MMBTU). If a building is being demolished (and its age is known), you can report embodied energy as a percentage of the total lifetime energy use of by the building, or in “years of operating energy.”