BY JOE NASVIK 

This is the fourth and final article of the Building Back Better series. 

After the decision is made to build a house, the next issue to resolve is how it should be built. The best building system is one that will be best for the current and future occupants. Using sustainability and resilience guidelines is a way to ensure that. 

When building a house, consider the amount of greenhouse gases (GHGs) produced in the construction, how safe the building will be in light of increasing climate change risks, how much energy it will take to maintain living conditions over time, the amount of waste and toxic material created when a house is demolished and the adaptability of your home to meet the needs of future owners. 

After it was established that global temperatures rise in relation to the amount of carbon dioxide (CO2) and other heat-trapping gases in the atmosphere, hence the term GHGs, scientists began to focus on where they were coming from and in what quantities. Consultants such as Emily Lorenz, owner of SevGen Consulting in Chicago, Ill., calculated how much GHG was created in the production of the products we make. The sustainability movement favored moving away from using products that produce larger amounts of GHGs in their manufacture, advocating for those that produce less. “Green” products were thought to be the best of all—products that could easily be produced by growing a new crop. For example, wood was a good building material because a new crop of trees could be planted to replace the ones that were cut down. Using straw bales to build the walls of a home was an even better idea because a new crop could be harvested every year, and straw is a byproduct in the production of food grains, so it was a “carbon free” building material. 

The word “sustainability” became a marketing term for various materials. Evan Reis, the executive director of the U.S. Resiliency Council, San Francisco, Calif., says that sustainability has traditionally been defined as “green design” where we build to have a low impact on the environment. In the world of sustainability, the production of portland cement is not favored because limestone, the key ingredient of Portland cement, has to be heated to temperatures of approximately 2,800 degrees Fahrenheit. This heating causes GHGs to be emitted from two sources: the fuel used in the kiln and the chemical reaction calcination (the decomposition of limestone), which converts the raw materials into clinker. The U.S. cement industry has made improvements to the manufacturing process over the years, but still approximately 0.8 to 0.9 ton of atmospheric carbon dioxide is produced in the creation of a ton of portland cement. And because cement is used in concrete, many think we should stop using concrete and find other materials to replace it. 

Resiliency 

Reis says it has become apparent that focusing only on green design wasn’t enough; true sustainability requires that we consider resilience as well—where we build so that the environment has a low impact on us. 

Resiliency focuses on the entire life of a building, how safe it is in an increasingly unpredictable climate, the amounts of energy required to heat and cool it, the combustibility of a building and the toxic materials used in the construction. Current sustainability practice in the U.S. largely focuses on the amount of GHG created in the production of something at a moment in time, while resiliency takes the long view. Taken together, both resiliency and sustainability are important. 

Life of the structure 

When considering resiliency, the focus on the amount of GHGs created during the entire life of a structure is important. When considering the cradle-to-gate sustainability of a material, the focus is only on the amount of GHG emitted or absorbed during its production. Following this logic, the CO2 created in manufacturing lumber is much lower than the amount created in the production of concrete, therefore wood is more sustainable than concrete. But what if a house is built with wood, burned to the ground (as in the case of the fires in Los Angeles), the toxic debris is then removed and hauled to a landfill site (where it must be safely stored forever), and then the house is rebuilt? How many GHGs are created in the total chain of events compared to building the house only once with a non-combustible material like concrete? 

Safety 

The resiliency movement places value on the safety of a structure; a home must be a safe place to live, and it should be habitable after a disaster so that life can proceed with little disruption. But safety levels keep changing because extreme events such as fires, hurricane wind forces and tornadoes keep increasing in number and intensity due to increased global warming. So, safety codes for home construction must increasingly be changed too. 

Energy use over time 

Resiliency ratings take into account the amount of energy required to heat and cool a building during its life. Due to fuel sources for energy in the U.S., Lorenz says that the most GHGs are created by the energy needed to heat and cool a building over time, not in the construction of it. The amount of energy needed to heat and cool a home depends on the materials used to build it. She adds that, in one study, insulating concrete forms (ICF) homes were compared to standard wood frame houses, and the energy needed for heating and cooling was much less for ICF homes. “The greenhouse gas created by the construction process of the ICF homes was larger, but when looking at the full life cycle, the total greenhouse gases emitted by both building systems were approximately the same.” This is because concrete homes can be built tighter so less energy escapes, and because concrete is good at storing energy. 

Toxic debris 

Reis says the debris left after fires is a concern, too. Los Angeles has huge amounts of toxic debris after their recent fires, and it must all be removed and hauled to landfill sites with the hope that it will remain safely stored forever. “The problem is that there is no such thing as forever,” he adds. “Water leaching through landfills will cause toxic debris to spread over increasingly larger areas.” 

Repurposing 

Buildings tend to be built to satisfy one person or group’s requirements. When it is sold a new owner sometimes requires that the building be demolished so that their own aesthetics can be honored. The problem is that huge amounts of good material are wasted and deposited in landfills. Perhaps in the future designers will be able to design basic structures that will remain while aesthetics are changed from owner to owner. That said, one of concrete’s advantages is that it can be recycled to become aggregate for fine grading below concrete and asphalt. The steel reinforcement is also recycled. Most landfill sites don’t accept concrete. 

Closing thought 

Sustainability is fairly easy to measure. Researchers quantify the amount of GHGs created in the manufacture of materials with numbers frequently reported in equivalent tons of CO2, and buildings can also be given scores for their greenness. It is also possible now to assign resilience scores to buildings. To learn more about this, visit the U.S. Resiliency Council website at usrc.org. 

When you build a house or business office, sustainability and resiliency should both be considered. By doing so, you are doing the right thing for yourself and your neighbors.