Embodied energy is a term that often comes up when discussing the benefits of building with natural materials over synthetic, manufactured, or more conventional building components. It’s an important concept — embodied energy is “the sum of all the energy required to produce any goods or services, considered as if that energy was incorporated or ’embodied’ in the product itself.”

Attempting to actually calculate or understand the full implications of embodied energy is a mighty challenge, however, and honestly a bit befuddling, since it’s going to be completely different depending on your location. However, this table from The Natural Building Companion book is an excellent reference — not the end-all be-all of data necessarily, but an excellent case example comparing the differences in embodied energy between natural materials like straw, sand, and timber to concrete, paint, fiberglass insulation, and others.

Table illuminating various embodied energy values of both conventional and natural building materials

Embodied Energy in Building Materials

Here’s a few notes about this table. The source is from a study conducted in the UK by Hammond and Jones, so like I said above — this is a very specific case example. The numbers presented are for a particular place, and everything changes according to location (with differences in how these materials are manufactured, acquired, transported, etc. — all these will factor into the total embodied energy values.)

If I’m understanding it correctly, the “Embodied energy” is just that — the total calculation of the sum of energy required to produce/acquire the material. The period during which the embodied energy is analyzed is called “cradle-to-gate”, which includes all energy used in the resource extraction, manufacturing, production, transportation to the building site, inclusion in the building itself, and the disposal of the material.

“Embodied CO₂“ is the carbon dioxide produced in the creation and delivery of the specific material. Carbon dioxide, of course, is the most common and heavily produced greenhouse gas from human sources. “Embodied CO₂e” is the embodied CO₂ equivalent, since CO₂ is used as the baseline when determining the value of impacts. This is all the other “stuff” produced in the creation and delivery that has its own impact, presented as a value relative to embodied CO₂. Make sense?

As you can see, the embodied energy of manufactured materials is on average much higher than those from natural sources. Plastics and polystyrene foams have very high embodied energy figures, as does paint, and fiberglass insulation. Aluminum is practically off the charts in comparison to other materials, and copper and glass are also quite high. Surprisingly, concrete is very low, especially when compared to hydrated lime, which I am still trying to make sense of. Jacob Deva Racusin and Ace McArleton have this to say about lime in particular:

As we see from the chart, lime has a comparable embodied energy to cement — by some calculations, even greater — despite lower kiln temperatures in its firing (potential causes include longer firing times, fuel sources, and production efficiency.) However, its embodied carbon cradle-to-grate is lower, and these metrics do not factor in carbon sequestration during the curing process, which is greater for lime than cement.

Interesting food for thought. Ace and Jacob also draw out some other notable statistics. Softwood has 32% less embodied CO₂e than a glue-laminated member, 5% cement-stabilized soil has 55% less embodied CO₂e than reinforced concrete, and straw has less than 0.75% of the embodied CO₂e of fiberglass insulation.

This table is a fascinating example of embodied energy comparisons between different materials. I think of it as a potentially useful guide when considering different materials for different applications in natural building. There are countless times when one has to weigh the pros and cons of choosing to go a certain route, and for me personally, ’embodied energy’ has always been an important consideration, but difficult to really conceptualize in more than an abstract way.

This study at least gives us some sense of what the ecological expense of both common and natural building materials are. I wouldn’t quote these numbers as absolute, but at least meaningful and enlightening.