Assessing Green Building Materials

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The notion of building green has become mainstream in recent decades, thanks to the efforts of a small number of builders on the fringe of the building industry.
High-performance doesn’t necessarily equate to “green”—for example, petroleum products, such as foam insulation, have high embodied energy and major impacts on ecosystems.
Concrete has advantageous building and thermal properties, but is high in embodied energy and very high in carbon dioxide emissions.
Lumber is a renewable resource, albeit slow to regenerate. Its embodied energy depends on the distance between origin and use.
Straw bales are an agricultural “waste” product, with low embodied energy and good thermal performance.
Forest products may travel long distances between their material harvest and end use, which drives up their embodied energy.
Often, it’s the final energy performance of the structure that dominates its classification as being “green.” But this is only one aspect of an ecofriendlier building.
Per ton-mile, ships use only 1.3% of the fuel consumed by trucks. However, goods are usually transported over longer distances, resulting in high embodied energy.
Trains use only 0.8% of the fuel used by trucks to move freight; shipping by train significantly reduces a product’s embodied energy due to transportation.
When available, natural building materials, sourced and processed locally, are often the best bet for “green” solutions.

The notion of “building green” has become mainstream in recent decades, thanks to the efforts of a small number of builders on the fringe of the building industry.

But in the rush to jump on the green bandwagon, not much time gets spent considering what it means to create a more sustainable building. Some think a label declaring a material to be “green” is all that is required—but figuring out how to make a measurable difference in our environmental impact takes a bit more effort.

The Tools to Do It Right

With almost everyone selling some version of green, it is up to each homeowner and builder to do the research to make better choices. That research must go beyond the product sales sheet to examine how the product is made. Here are some common-sense factors to apply to decisions.

Petroleum

Products made from petrochemicals have a large ecological footprint. Regardless of any “green” marketing, crude oil is responsible for vast amounts of ecological damage—and all petrochemical products bear a share of that harm. And most petrochemical products will persist in the environment long after their useful life as building materials.

Example: Foam insulation carries a dire environmental footprint in its manufacturing, and in its use and eventual disposal.

Heat

Products manufactured using high quantities of heat have large environmental impacts. They consume a lot of fuel and create a lot of pollution in the process. The greater the amount of heat required, the greater the impacts.

Example: Portland cement requires heating limestone to 1,100°F in the calcining process, and then to 2,640°F to sinter the material.

Manufacturing

The more complex the manufacturing process, the more impacts the product is likely to have. Natural materials, such as straw bales, which require little or no modification prior to use, are likely to have fewer impacts.

Example: Cereal straw is cut in the field during the harvesting process and compressed in a simple mechanical baler.

Toxins

Products that contain toxic ingredients are unhealthy. Many products that offgas toxins are commonly used in buildings. At best, any toxic ingredients in a product are deemed to be “stable” in their final form. But those toxic ingredients have effects and impacts in the manufacturing process and to construction workers that predate their “stable” form—and are likely to have effects after their useful life in the building.

Example: Even low-VOC paints and stains contain a wide range of chemicals that are toxic during manufacturing and in the home, including glycol ethers, formaldehyde, biocides, amines, monomers, acrylic polymer latex, titanium dioxide, ammonium hydroxide, benzisothiazoline, methyl-isothiazolin, benzene, and toluene.

Transportation

Products that travel long distances have larger environmental impacts because of fossil fuels used in their transport. The heavier the material and the longer the travel distance, the greater the impacts—especially for materials that are moved by trucks.

Example: Lumber is often shipped across the continent, and can sometimes double its travel distance as it makes its way from mills to distribution centers to retailers, resulting in high amounts of fuel used.

Planned Obsolescence

“Maintenance-free” often means that something will last for a specific length of time and then need to be replaced. Materials that require some maintenance can often be refurbished repeatedly over decades or even centuries, but most materials that require no maintenance cannot be repaired, and end up as landfill.

Example: Vinyl siding is often touted as being maintenance-free, but cracks, splits, and warping cannot be repaired. Within a couple of decades, entire vinyl siding installations will need to be replaced.

Complexity

Complexity in a product, assembly, or system often leads to malfunction, breakdown, and waste. When parts of a complex building fail, it can lead to cascading problems. Simpler systems that rely on time-tested principles tend to be more long-lived.

Example: Basement foundations in wet areas often rely on automated sump pumps, which have several components that can wear or fail and rely on a continuous electricity supply to function. When they do fail, flooring, walls, insulation, and mechanical devices in these spaces can be ruined. On-grade foundations keep all these elements well above the water line and don’t need any mechanical devices to stay dry.

Labor

Using human labor is more sustainable than machine-made or machine-installed. Both environmentally and economically, craftsperson work is the least impactful.

Example: Plasterers using local ingredients in a wet plaster sys­tem can have dramatically lower impacts than drywall, tape, and “mud” manufactured and shipped from a central factory.

Overall Design

People make the buildings—the materials are only a part. A building is a manifestation of human ingenuity and relationships. It takes the right people to make a building that approaches sustainability, and finding them is equally important to material choices.

Example: Straw-bale walls built poorly by an inexperienced builder can have greater compromised energy efficiency than well-built stud-framed and conventionally insulated walls.

If a product claim sounds too good to be true, it probably is. There is no perfect building material. If a material scores lots of “green” points in one or two areas, it probably has drawbacks in others. Find out both the pluses and minuses before making a decision.

Find trustworthy sources to help your decisions. Third-party certification (especially those overseen by boards that aren’t dominated by industry representatives) is a good way to ascertain a product’s environmental claims.

Beautiful buildings tend to receive care and maintenance, and last a long time. If nobody cares about a building, even if it scores lots of sustainable points for its material selection, it is more likely to have a short lifespan. Create something that future generations will appreciate, and they will shepherd it through time.

Setting Sustainable Goals

Greenwashing—where environmentally harmful products and materials are marketed as being green—is a large barrier to reducing our impact. Without considering the entire life cycle of the elements in our buildings, we cannot know if we are minimizing our impacts.

Homeowners or builders must first establish their environmental goals, and then consider materials that perform well without undermining overall environmental performance. Environmental merit can be judged in three categories:

Low overall energy consumption in the finished building. This may be the most comprehensive way to judge the “greenness” of a material or system. Energy Star, EnerGuide, and a host of energy modeling software programs can be used to compare energy impacts of materials and systems.

Reduced toxics or environmental impacts. Using recycled material, reducing embodied energy, responsibly harvesting and producing, durability, and reducing or eliminating waste are all included in this metric. The Inventory of Carbon & Energy (download at bit.ly/ICEdwnld) is a free database for comparing embodied energy of materials. Free software programs like the Athena Institute’s Life Cycle Assessment (athenasmi.org) can help with understanding environmental impacts over a material’s life span.

Creation of a nontoxic interior environment. Clean air and water; proper humidity and ventilation; access to natural light; comfortable interior temperatures; and reducing or eliminating radon are included. Greenguard (greenguard.org) is a reliable third-party rating system for a product’s impact on indoor air quality; the Pharos Project database (pharosproject.net) has in-depth information on chemicals in building materials.

These three areas constitute a building’s life-cycle analysis. Ideally, for each product, materials research follows the path of all materials and systems—from harvesting raw ingredients to manufacture, transport, and use, to waste and disposal issues.

Transportation Impacts

An average house uses about 175 tons of materials, so transportation impacts can be a high proportion of the building’s total embodied energy. The distance materials must travel to reach your building site, the weight of those materials, and the mode(s) of transportation all impact a material’s embodied energy and “greenness.” The U.S. Department of Energy estimated the following for freight transportation in 2006:

Trucks: 4,074 Btu (0.3 gal. diesel fuel) per ton-mile

Rail: 330 Btu (0.0025 gal. diesel fuel) per ton-mile

Ship: 571 Btu (0.004 gal. diesel fuel) per ton-mile

The raw materials for construction products are often close to the point of manufacturing, but distances to point-of-use can be quite long. If your project needs 1 ton of insulation material, as little as 30 gallons of diesel fuel might be consumed if you are 100 miles from the manufacturer—or as many as 900 gallons of diesel might be used if the material has to cross the entire country to reach you.

Materials that travel by rail or sea have lower impacts per travel mile, but tend to cover long distances. For example, 1 ton of insulation coming from China may travel upward of 6,000 miles and use as little as 24 gallons of diesel fuel. However, that insulation must travel from a sea freight terminal to its final destination—which may be hundreds or thousands of miles away by truck. Only thorough research can give you an accurate sense of the transportation impacts.

Comparing Like to Like

Once choices are narrowed to a particular product or system, there can still be major impacts based on brand or supplier. Consider lumber products: While embodied energy and life-cycle figures are similar for all trees, the specifics of how and where they were harvested and processed can reveal a wide range of impacts. Poor cutting practices can be devastating to local ecosystems, destroying wildlife habitat, encouraging soil erosion, and negatively affecting waterways. Milling operations can be major polluters of air and water, and transporting lumber over long distances consumes vast amounts of fossil fuels.

Third-party certification programs for lumber can help you determine if forestry practices are in place to minimize impacts. If you buy uncertified wood, you have no idea where that wood is being harvested, what forestry practices are in place, and whether or not it was milled appropriately. Here are some tips for selecting “greener” lumber.

Keep it local.  If possible, visit the harvest site and the sawmill. Many small mills cannot afford to be certified “sustainable” by a third party, but still use very sustainable practices.

The Forest Stewardship Council (FSC) provides third-party certification of sustainable harvesting and processing of wood products. Lumber with an FSC certification is an indication that environmental impacts may be reasonable.

The Sustainable Forestry Initiative (SFI) is an industry organization founded as a response to the FSC. While they have made efforts to distance themselves from direct ties to the industry by diversifying their board, the lumber industry is still a central player. They have recently worked to be seen as a legitimate certification and have improved their standards to be similar to FSC.

Industry Pathways

The building industry is at an interesting junction. While most people realize that the status quo is becoming less viable, there is no consensus about what strategies and materials will lead the way.

New products are entering the market daily, all trying to improve upon the mix of environmental performance, affordability, durability, and ease of installation. None are perfect, but many are worth considering. Informed choices will go a long way to encouraging those with the highest environmental standards, helping to achieve buildings with high performance and low impact—and at an affordable cost.

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Comments (4)

Byrdhouse9's picture

The article in the paper magazine includes a table called "Comparing Materials", showing the embodied energy per kilogram for various insulation materials. Is there data available that corrects for the fact that some kinds of insulation provide much more R value per unit weight than others? Light insulation like fiberglass and polyurethane foam would fare much better if the comparison showed energy per unit of R value.

Michael Welch's picture

Energy per R-value would be a great indicator to have.

Byrdhouse9's picture

There is a typo in the "Transportation Impacts" paragraph. The 0.3 gallons of fuel per ton mile for trucks should be 0.03. Typical mid-size trucks achieve this, and heavy trucks often do as well as 0.01 gallons per ton mile. For example, my old F-350 gets a pathetic 10 miles per gallon when hauling 3 tons, but that works out to 0.033 gallons per ton mile .

Allise Burris's picture

Sliding that decimal would mean that ships and trains consume approximately 10% and 30%, respectively, of the fuel required by trucks for the same tonnage. I believe the ~1% and ~3% numbers of the photo captions could be correct.

Also, do pickups and semi-trailers really achieve nearly the same fuel efficiency by weight carried? Or do we define "heavy" trucks differently?

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