There are complete books on the market that give detailed descriptions of the vast array of building materials available. As soon as a book is published, though, it is out of date, not only due to the continued invention of new products and innovations in existing ones, but also due to the results of continued research into just how green all of these products are. Additionally, not all products are available, or even appropriate for use, in every market. Your best resource for building materials is through a reputable green architect, homebuilder or building supply outlet that specializes in these types of products and has a knowledgeable staff to help guide you.
There are very few perfect green products. Generally products are categorized by certain attributes that are considered green, and some products will have more green attributes than others. So, it is important to recognize products by shades of green. As an example, look at one of the earliest recognized green products around — straw, as used in straw bale construction. Straw is a waste product of cereal grain production, and so, as we will discuss a little later in this article, that’s a good green attribute. It’s even better if the cereal grain is grown nearby, as local material sourcing is also a great green attribute. In using straw for your building system, it can be durable and provide good thermal performance. It also does not off-gas toxic fumes, so it will not affect indoor air quality. In fact, we would say straw is just about dark green- as perfect a green product as you can get if it meets all of these criteria. Unfortunately, we don’t build many homes with it.
On the other end of the spectrum, let’s look at recycled glass content fiberglass batt insulation. Yes, it is recycled, but batt insulation typically does not provide good thermal performance due to installation errors, may have added urea- formaldehyde binders that will off-gas toxic volatile organic compounds, affecting indoor air quality, and probably is not produced locally. So many would consider this product pale green.
The reality is that there are many trade-offs in the designation of green products. Some aspects can make or break your expectations of the benefits your green home should provide, while others just represent added value. What you need to know is which attributes are important.
Main Considerations
You should start your analysis of building materials by thinking about what materials are appropriate for you to use on your project and specifically in your climate. Just as construction methods are climate specific, so is our use of building materials. As you will see throughout this chapter, some products are specific to hot and humid climates, while others are best used in cold, arid or marine climates. In some instances, it’s not the product itself, but how it is used that is determined by climate type. Also, we need to be sure we have checked what applications are appropriate for our site conditions and building design.
Building science research continues to advance, ushering in new technologies and product developments to the market, now at exponential rates. It is important that we make sure the contractors that are installing them are properly trained so that we get a good installation quality. Sometimes it’s not the product itself but how well we use it that makes it green. If you consider yourself an early adopter and like being the first to own the latest gadgets or the most expensive model with all the bells and whistles, you can bet you will spend more money than this website suggests. Just about all new technologies must recover the initial cost of research and development and their start-up manufacturing costs, so you are better off if you can wait until prices stabilize. You will also find that time saves you the grief of working out the kinks that are inherent to new product development.
We also need to think about how well products support our energy and water efficiency goals. And, as was the case with designing for risk assessment in later article, you must specify building materials able to stand up to your assessed risk for tornados, hurricanes, floods, termites and other potential hazards. Certainly wood siding would not be a good choice if you live in an area with a high termite risk.
Performance and Impact on Health: It is equally important to recognize what characteristics you are looking for in each product category, so as not to give more weight to a green attribute than the value you actually need from the product. Your review of any building material should begin with an analysis of what function you need the product to perform and any concerns you should be aware of with using it.
For example, with any insulation material, you first want good thermal performance, and second you do not want any product that will adversely impact indoor air quality and your family’s health. Any products used within the wall, floor or roof structure or interior finishes can off-gas toxins into the living space, impacting the health of workers manufacturing and installing them and, of course, the home’s occupants. This will be discussed in depth in later article, so for now we will only recognize that it is an important consideration for selecting some building materials. Once a building material has passed those two tests, you can consider other green attributes (recycled or waste content, locally sourced, etc.) in your final selection. We will review the important considerations for each type of building material later in the article.
Longer Maintenance, Repair and Replacement Cycles: We do not generally set aside money in our monthly budgets to address maintenance and repairs over time. But if we did, and we had to amortize those lifetime costs into a monthly budgetary allowance, we would see the value of investing in better-quality products to begin with. A primary goal of building science and green building is to achieve a home that is durable with less maintenance. Part of how this is achieved involves attention to the details of what it is built of as well as how the house is built. Choose materials that will hold up over the long run and that are less susceptible to damage from pests and weather events. Natural stone, cement and clay products provide excellent durability when it comes to the exterior façade of the home (from siding to roofing materials). These products also work well in the interior (ceramic tile or concrete flooring, clay plaster walls and natural stone or other solid-surface countertops).
We, as a society, need products that last longer. It is senseless to continue to use our energy and natural resources to manufacture more, simply due to our failure to choose a product initially that was durable enough to last. We cannot continue to produce products that are cheap and disposable and just throw them away. Our planet, Earth, is all that we have, there is no “away.”
We are discarding a greater volume of products daily than Earth can decompose and regenerate back into new resources. Choose materials that reduce the volume of resources required over time. Tile floors do not need to be replaced as often as carpet flooring. Engineered wood products experience less twisting and warping, so there is less building failure over time that requires replacement resources.
Aesthetics: Choose materials that are pleasing to look at – classic styles, not fads. Many resources are wasted in remodeling or redecorating because poor initial choices were made. This is an especially concern for interior finish products, many of which off-gas toxic fumes for years after installation. Just about the time the initial product ends its toxic period, it is out of style and replaced by a new product, which has to begin the off-gassing cycle all over again.
Life Cycle Assessment: One of the verification tools we use to determine a product’s shade of green is called a life cycle assessment or LCA for short. As the term indicates, this type of assessment provides an analysis of something over its entire lifetime. For building materials, this means analyzing the impact of extracting or harvesting raw materials, processing or manufacturing the product, installation on the jobsite, the maintenance and operations through the product’s useful life, to the end-of-life removal and whether it can be repurposed, recycled, or ends up in the landfill. The assessment also includes all the energy embodied in the product from the generation of the energy required to make all these processes happen and in the transportation required to get the product from one process to the next.
LCA studies have been done on a wide range of topics, like how much energy, water or natural resources something consumes over its lifetime, or maybe the impact of living in the home on our family’s health over its lifetime or the total cost of ownership over its lifetime. Most of you will never have the opportunity to see any of these studies in your research of building materials. What we would like for you to take away from this discussion is that you can pretty much do the same type of analysis yourself, just by giving some thought to how the products are going to perform over time, how they benefit your long-term goals, where the raw materials come from and what processes are required to get them to you in a usable state and, finally, how those processes might affect the world that we live in over the long run and the generations to come after us. This requires consideration of a product’s durability, life expectancy and ease of maintenance. It also requires us to think about making more sustainable choices, such as those in the following discussions.
Man-made vs. Natural Products: Products made from natural resources deplete those resource reserves. Just as fossil fuels are in limited supply on this planet, so are other naturally occurring materials such as lime, which is used to make Portland cement, wood used for everything from structures to flooring, and gypsum, used to make drywall. In the case of natural products, we also need to consider if the raw material source is renewable or finite.
Sustainably sourced wood lumber for framing is grown on farms, and many of the companies in this industry have already realized that to stay in business they must replant after every harvest to assure future supplies. However, many exotic wood species come from regions of the world where these practices have not been adopted. For example, ipe is a wood species that is only found in Central and South America. Most of it on the market today is being illegally harvested in Brazil. On average, only one or two ipe trees grow per acre of rain forest, yet the entire acre is cut to harvest these two trees. When the rain forest is gone, it’s gone forever.
On the other hand, man-made products generally have higher embodied energies due to the manufacturing and processing. This includes products made from synthetic materials, such as plastics. It also includes products made with recycled content, so there is a trade-off between the energy required to manufacture new synthetics and the energy needed to collect and ship recycled materials back to the manufacturer and reprocess them into a new product. We need to create economically profitable paths for manufacturers to recover these waste streams.
There are many green man-made products on the market, too many, in fact, to even attempt a list. It is important to recognize that some products are both natural and man-made. This refers to materials that use ingredients that are natural but must be processed to be usable, such as products made from glass (silica), metals and gypsum (drywall). These products both deplete natural resources and have higher embodied energies. Recycling these products protects against excessive natural resource depletion.
