This week we are continuing our discussion about the many hidden costs of traditional building construction. In this second post, let’s look at unsustainable concrete.

Sustainable building

The modern housing industry is so unstainable in so many ways – it’s difficult to even know where to start.

According to the National Renewable Energy Laboratory (NREL) in Golden, buildings consume 40% of the total energy use in the United States and represent 35% of the nation’s carbon emissions. And it’s not just the energy used to operate the buildings, e.g., lighting, temperature control, appliances, etc. It’s also the energy needed to create the building materials, such concrete, steel, and glass.

We’ve already discussed the operational energy consumed by buildings, see Hidden-Costs-of-Traditional-Home-Construction and Embodied-Energy-and-Operational-Energy.  In this week’s blog we’ll spend some time discussing the energy needed to create the building in the first place, technically known as embodied energy or embodied carbon (think carbon footprint).

Concrete

Let’s start with concrete. Concrete is the most used construction material in the world, for good reasons; it is strong, easy to work with, and importantly inexpensive. But concrete is very energy and carbon intensive.

Concrete Production

Concrete is a mixture of cement, sand, gravel, and water. The sand and gravel themselves don’t emit any carbon, but they do require huge machines to mine the material and transfer it to a concrete plant. Those large excavators and other machines burn copious amounts of diesel fuel.

Cement on the other hand is an entirely different story.  To produce cement, we mix limestone (80%) and clay (20%), together with small amounts of other additives. To obtain the limestone, large open-pit mining operations extract the rock (with explosives), crush it, and then transport it to a cement plant. At the cement plant, operators mix the limestone and clay, then heat the mixture to about 2,750°F. Heating tones of limestone and clay obviously requires a great deal of energy, about 6% of the global energy production is used to make cement.

But wait – it gets worse. The production of cement also involves chemical reactions. The high temperatures mentioned above cause the limestone to liberate large amounts of CO2 as a byproduct. Those chemical reactions release about 1/2 pounds of CO2 for every pound of cement produced. Between the energy required and the chemical reaction, for every pound of cement produced about 0.9 pounds of CO2 are produced. To add to the fun, we also get sulfur oxides and nitrogen oxides. For a short video, check out Where do concrete emissions come from?

Concrete in House

Let’s put that 0.9 pound of CO2 into perspective. A typical 3000 square-foot (SF) home built slab on grade uses around 40 cubic yards of concrete in its construction, which accounts for the footings, foundation walls, the driveway and garage. Concrete weighs around 4000 lb/cubic yard, so we’re talking about 160,000 pounds of concrete. Contained in that concrete is about 32,000 pounds of cement (which could be more or less depending on the required concrete strength). So, the concrete in that typical home released about 28,000 pounds of CO2 during its production. Obviously, concrete production is unstainable.

Solutions

The good news is there are solutions to reduce the CO2 emissions. Depending on the unique requirements of your home, we can consider using a concrete-free slab construction. Potentially, cutting your concrete usage by nearly half. The use of frost-protected shallow foundations can reduce the required depth of the foundation walls by more than 50%, thereby reducing the amount of concrete needed. Taken together, we could reduce your concrete demand by as much as 75%.

At Delta Energy Solutions, we are always on the lookout for new ways of doing things. Some solutions include, using less steel, concrete, and other unsustainable materials, where possible and substituting unstainable materials with greener, more sustainable materials. It’s not rocket science, but it does require thought from an environmental point of view.

To learn more, schedule a free 30-minute consultation, please contact us.