sustainable building materials

Sustainable Building Materials: Introduction DRAFT, August 1998 Sustainable Architecture • 1

SustainableBuildingMaterials

Jong-Jin Kim, Assistant Professor of ArchitectureBrenda Rigdon, Project Intern

The University of MichiganCollege of Architecture and Urban Planning

Architectural Compendium for Environmental Education:

2 • Sustainable Architecture DRAFT, August 1998 Sustainable Building Materials: Introduction

Published by:The National Pollution Prevention Centerfor Higher EducationUniversity of Michigan, Dana Building430 East University Ave.Ann Arbor, MI 48109-1115• Phone: 313-764-1412• Fax: 313-936-2195• E-mail: [email protected]

The mission of the NPPC is to promote sustainable developmentby educating students, faculty, and professionals about pollutionprevention; create educational materials; provide tools andstrategies for addressing relevant environmental problems; andestablish a national network of pollution prevention educators.In addition to developing educational materials and conductingresearch, the NPPC also offers an internship program, profes-sional education and training, and conferences.

Your Input is Welcome!We are very interested in your feedback on these materials.Please take a moment to offer your comments and communicatethem to us. Also contact us if you wish to receive a documentslist, order any of our materials, collaborate on or review NPPCresources, or be listed in our Directory of Pollution Preventionin Higher Education.

We’re Going Online!The NPPC provides information on its programs and educationalmaterials through the Internet’s World Wide Web; our URL is:http://www.snre.umich.edu/nppc/

Please contact us if you have comments about our onlineresources or suggestions for publicizing our educationalmaterials through publications or through the Internet.Thank you!

Pollution Prevention Educational Resource CompendiaGoal Statement and Summary:

Education offers one of the greatest opportunities for achieving a more sustainable society. Today’s students will betomorrow’s leaders. With them in mind, the NPPC offers pollution prevention compendia for faculty in a varietyof disciplines. These compendia, developed by NPPC staff as well as university faculty nationwide, contain backgroundmaterials, annotated bibliographies, course syllabi, selected readings, teaching tools, and lists of resources relevant to eachdiscipline. The NPPC produces and disseminates these compendia to help faculty incorporate the concepts and principlesof pollution prevention into their courses; members of industry, government, and non-profit organizationsmay also find them useful when pursuing pollution prevention initiatives. As the scope of pollution prevention evolves, sowill the compendia. The NPPC encourages contributions from business, industry, and academia.

This is the Sustainable Architecture compendium. Other compendia cover disciplines such as Accounting, Agriculture,Business Law, Chemical Engineering, Chemistry, Corporate Strategy, Environmental Engineering, Environmental Studies,Finance, Industrial Ecology, Industrial Engineering and Operations Research, Marketing and Operations Management.For more information, contact the NPPC directly.

© Copyright 1998 by the Regents of the University of Michigan.Educators may freely reproduce these materials for non-commercial educational purposes..


ContentsPart I: Introduction 5

Life Cycle Design 5

Three Phases of Building Materials 5

Pre-Building Phase 5

Building Phase 8

Post-Building Phase 9

Features of Sustainable Building Materials 9

Part II: Materials 21

Key Sources of Building Materials 21

Selecting Sustainable Building Materials 24

Pre-Building Phase: Manufacture 25

Building Phase: Use 26

Post-Building Phase: Disposal 27

Examples 28

Part III: Application 41

References 43

Part IV: Building Materials Bibliography 45

Part V: Building Materials Annotated Bibliography 51


Part I: IntroductionCareful selection of environmentally sustainable building mate-rials is the easiest way for architects to begin incorporatingsustainable design principles buildings. Traditionally, price hasbeen the foremost consideration when comparing similar mate-rials or materials designated for the same function. However,the “off-the-shelf” price of a building component representsonly the manufacturing and transportation cost, and does notinclude the social or environmental cost.

Life Cycle Design

A “cradle-to-grave” analysis of building products, from the gath-ering of raw materials to ultimate disposal, provides a betterunderstanding of the long term costs of materials. These costsare paid not only by the client, but also the owner, occupants, andthe environment.

The principles of Life Cycle Design provide important guide-lines for the selection of building materials. Each step of themanufacturing process, from gathering raw materials, manufac-turing, distribution, and installation, to ultimate reuse or disposal,is examined for its environmental impact. A material’s life cyclecan be organized into three phases: Pre-Building; Building; andPost-Building. These stages parallel the life cycle phases of thebuilding itself (see this compendium’s “Sustainable BuildingDesign” module). The evaluation of environmental impact ateach stage allows for a cost-benefit analysis over the lifetime ofa building, rather than simply initial construction costs.

Three Phases of Building Materials

Based on the flow of materials, three phases of the buildingmaterial life cycle can be defined: Pre-Building, Building, andPost-Building (see Figure 1).

Pre-Building Phase

The Pre-Building Phase describes the production and deliveryprocess of a material up to, but not including, the point ofinstallation. This includes discovering raw materials in natureas well as extracting, manufacturing, packaging and transporta-tion to a building site. This phase has the most potential for


causing environmental damage. Understanding environmentalimpacts in the pre-building phase will lead to the wise selectionof building materials. Raw material procurement methods, themanufacturing process itself, and the distance from the manu-facturing location to the building site all have environmentalconsequences. An awareness of the origins of building materialsis crucial to an understanding of their collective environmentalimpact when expressed in the form of a building.

The basic ingredients for building products, whether for con-crete walls or roofing membranes, are obtained by mining orharvesting natural resources. The extraction of raw materials,whether from renewable or finite sources, is in itself a source ofsevere ecological damage. The results of clear cutting forests andstrip mining once-pristine landscapes have been well docu-mented.

Mining refers to the extraction, often with great difficulty, ofmetals and stone from the earth’s crust. These materials exist infinite quantities, and are not considered renewable. The refiningof metals often requires a large volume of rock to yield arelatively small quantity of ore, which further reduces to an evensmaller quantity of finished product. Each step in the refiningprocess produces a large amount of toxic waste.

Materials that can be harvested, like wood, are theoreticallyrenewable resources and theoretically more easily obtainedwithout ecological devastation. However, a material is onlyconsidered a renewable or sustainable resource if it can be grownat a rate that meets or exceeds the rate of human consumption.Hardwoods, for example, can take up to 80 years to mature.

Figure 1: Three phases of the build-ing material life cycle.

Pre-BuildingPhase

BuildingPhase

Post-BuildingPhase

Reuse

Manufacture Use Disposal

Recycle


Pollution causing activities related to the gathering of naturalresources and their conversion into building materials includeloss of habitat, erosion, water pollution, and air pollution.

Loss of habitat: Cutting forests for lumber or removing vegetationfor mining results in loss of habitat, for animal and plant species.Removal of vegetation by clear cutting forests or strip miningeliminates animal habitats and leaves the ground open to ero-sion. Habitat refers to the natural environment in which aspecies is found; generally, this means undeveloped areas. Amicro climate may be immediately and severely altered by theremoval of a single tree that provides protective shade to theplants below.

As wilderness declines, competition for food, water, and breed-ing territory increases. Some species, like Michigan’s KirklandWarbler, are so highly specialized that they can only thrive in aspecific, rare ecology. Damage to these special ecosystems leadsto extinction. A record number of species are disappearing everyyear, due to loss of habit. The consequences of this loss are as yetunknown, but many biologists believe that such a severe reduc-tion in diversity threatens the long-term adaptability, and thussurvival, of plants, animals and humans alike.

Plants return moisture to the air through respiration, filter waterand air pollutants, and generate the oxygen necessary for peopleand animals to survive. Tropical rain forests are a main route forthe movement of water from the ground into the atmosphere:trees, like people, expel moisture as part of their respirationcycle. A decrease in the amount of atmospheric water may leadto a decrease in world wide rainfall, resulting in drought andfamine.

Tropical rain forests support a vast range of plants and animals.They also absorb carbon dioxide from the atmosphere, as part ofthe photosynthesis process. The widespread destruction of rainforests to make way for mining and farming operations has beenlinked to increased levels of carbon dioxide in the atmosphere,which in turn has been linked to global warming.

Erosion: Removing trees and ground cover also leaves an areavulnerable to erosion. The erosion of topsoil and runoff intostreams and rivers has become a major environmental concern.Active surface mining accounts for the erosion of 48,000 tonsof topsoil, per square mile mined, per year.1 In addition to


depleting the area of fertile soil, the particulate matter sus-pended in water reduces the amount of sunlight that penetratesto plants below the surface. The resulting plant die-off triggersa reaction that moves up the food chain. As plants die, theamount of oxygen available to other life-forms decreases. Even-tually, a stream or lake can become clogged with decaying plantsand animals, and can no longer be used as a drinking source bywild life, or humans.

Water Pollution: Waste and toxic by-products of the mining andharvesting operations are also carried into the water. Like soilerosion, they can increase the turbidity, or opacity, of the water,blocking sunlight. Many of these by-products are acidic, andcontribute to the acidification of ground water, harming plantand wildlife. Oil and gasoline from engines and toxic metalsleftover from mining may also leech into the ground water,causing contamination of drinking supplies.

Air Pollution: Mining and harvesting operations contribute to airpollution through machinery that burns fossil fuels and fromparticulate matter stirred up by the processes. Combustionengines emit several toxic gases: carbon monoxide, carbon diox-ide, sulfur dioxide, and nitrous oxide. Carbon monoxide ispoisonous to most life. Carbon dioxide, known as a “greenhousegas,” has been linked to global warming. Sulfur dioxide andnitrous oxide contribute to “acid rain”: precipitation acidified byatmospheric gases, that can damage buildings or kill plants andwildlife. In the United States, the Northeast has been particu-larly hard hit by acid rain. Forests and lakes have “died” as aresult of increasing acidity in the water and soil.

Building Phase

The Building Phase refers to a building material’s useful life.This begins from the point of its assembly into a structure,includes the maintenance and repair of the material, and extendsthroughout the life of the material within or as part of thebuilding.

Construction: The material waste generated on a building con-struction site can be considerable. The selection of buildingmaterials for reduced construction waste, and waste that can berecycled, is critical in this phase of the building life cycle.


Use/Maintenance: Long-term exposure to certain building mate-rials may be hazardous to the health of a building’s occupants.Even with a growing awareness of the environmental healthissues concerning exposure to certain products, there is littleemphasis in practice or schools on choosing materials based ontheir potential for: outgassing hazardous chemicals; requiringfrequent maintenance with such chemicals; or, requiring fre-quent replacements that perpetuate the exposure cycle.

Post-Building Phase

The Post-Building Phase refers to the building materials whentheir usefulness in a building has expired. At this point, amaterial may be reused in its entirety, may have its componentsrecycled back into other products, or it may be discarded.

From the perspective of the designer, perhaps the least consid-ered and least understood phase of the building life cycle occurswhen the building or material’s useful life has been exhausted.The demolition of buildings and disposal of the resulting wastehas a high environmental cost. Degradable materials mayproduce toxic waste, alone or in combination with other materi-als. Inert materials consume increasingly scarce landfill space.Adaptive reuse of an existing structure conserves the energy thatwent into its materials and construction. The energy embodiedin the construction of the building itself, and the production ofthese materials will have effectively been wasted if these “re-sources” are not properly utilized.

Some building materials may be chosen over others because oftheir adaptability to new uses. Steel stud framing, for example,is easily reused in interior wall framing, if the building’s pro-gram should change and interior partitions need to be redesigned.Modular office systems are also popular for this reason. Ceilingand floor systems that provide easy access to electrical andmechanical systems make adapting buildings for new usesquick and cost-effective.

Features of Sustainable Building Materials

We identified three groups of criteria, based on the material lifecycle, that can be used for evaluating environmental sustainabil-ity of building materials. The presence of one or more of thesefeatures in building materials make it evironmentally sustain-able.


Pollution Prevention Measures in Manufacturing

Pollution prevention measures taken during the manufacturingprocess can contribute significantly to achieving environmentalsustainablity. Identical building materials may be produced byseveral manufacturers using various processes. Some manufac-turers are more conscientious than others about where their rawmaterials come from and how they are gathered. While allindustries are bound to some extent by government regulationson pollution, some individual companies go far beyond legalrequirements in ensuring that their processes pollute as little aspossible. These companies are constantly studying and revisingthey way they produce goods to both improve efficiency andreduce the amount of waste and pollutants that leave the factory.In effect, they perform their own life cycle analysis of internalprocesses.

Selecting materials manufactured by environmentally respon-sible companies encourages their efforts at pollution prevention.Although these products may have an initially higher “off-the-shelf” price, choosing products that generate higher levels ofpollution promotes the exploitation of the environment.

The “law of supply and demand” also works in reverse: reduceddemand for a product results in lower production. Loweredproduction means less waste discharged and less energy con-sumed during manufacturing, as well as a lower volume of rawmaterials that must be gathered. A classic example “demandand supply” economics occurred when permanent press cloth-ing came on to the market: dry cleaning, a highly toxic,petroleum-based process, nearly disappeared overnight. Envi-ronmentally sound packaging can also be a pollution preventionfeature, as the way in which a product is packaged and shippedaffects the total amount of waste generated by the product.

Water is used in large quantities in many manufacturing pro-cesses, especially in the production of paper, cement, and metals.This water is sometimes discharged directly into the environ-ment. The waste water is often released directly into streams,and can contain toxic substances. Dye used for coloring paperand carpet fiber is also an environmental risk that escape freelyinto the waste stream.

By becoming aware of what manufactures use environmentallysustainable manufacturing methods, specifying their products,


and avoiding goods produced through highly polluting meth-ods, architects can encourage the marketing of sustainablebuilding materials.

Waste Reduction Measures in Manufacturing

The waste reduction feature indicates that the manufacturer hastaken steps to make the production process more efficient, byreducing the amount of scrap material that results. This scrapmay come from the various molding, trimming, and finishingprocesses, or from defective and damaged products. For prod-ucts with this feature, scrap materials can be reincorporated intothe product, or removed for recycling elsewhere. Some indus-tries can power their operations by using waste productsgenerated on site or by other industries. These options reducethe waste that goes into landfills.

Reducing waste in the manufacturing process will increase theresource efficiencty of building materials. Oriented strand boardand other wood composite materials are made almost entirelyfrom the waste produced during the milling of trees into dimen-sional lumber. Kilns used to dry wood can be powered byburning sawdust generated on-site, reducing both the waste thatleaves the mill (to be disposed of in landfills) and the need forrefined fossil fuels. Concrete can incorporate fly ash fromsmelting operations. Brick, once fired, is inert, not reacting withthe environment. The firing process can be used to encapsulatelow-level toxic waste into the brick, reducing the dangers oflandfill disposal. Water used for cooling equipment or mixingcan be filtered and reused, rather than discharged into the wastestream.

Recycled Content

A product featuring recycled content has been produced partiallyor entirely of post-industrial or post-consumer waste. Theincorporation of waste materials from other industrial processesor households into usable building products reduces the wastestream and the demand on virgin natural resources.

By recycling materials, the embodied energy they contain ispreserved. The energy used in the recycling process for mostmaterials is far less than the energy used in the original manufac-turing. Aluminum, for example, can be recycled for 10-20% ofthe energy required to transform raw ore into finished goods.2


Key building materials that have potential for recycling includeglass, plastics, metals, concrete or brick, and wood. Thesegenerally make up the bulk of a building’s fabric. The manufac-turing process for all of these materials can easily incorporatewaste products. Glass, plastics, and metal can be reformedthrough heat. Concrete or brick can be ground up and used asaggregate in new masonry. Lumber can be resawn for use asdimensional lumber, or chipped for use in composite materiallike strand board.

Embodied Energy Reduction

The embodied energy of a material refers to the total energyrequired to produce that material, including the collection of rawmaterials. (Fig. 2) This includes the energy of the fuel used topower the harvesting or mining equipment, the processingequipment, and the transportation devices that move raw mate-rial to a processing facility. This energy typically comes from theburning of fossil fuels, which are a limited, non-renewableresource. The combustion of fossil fuels also has severe environ-mental consequences, from localized smog to acid rain. Thegreater a material’s embodied energy, the greater the amount ofenergy required to produce it, implying more severe ecologicalconsequences. For example, the processing of wood (harvestedin a sustainable fashion) involves far less energy and releases lesspollution than the processing of iron, which must be extractedfrom mined ores.

A revision of a manufacturing process that saves energy willreduce the embodied energy of the material. A conventionalmaterials with a high embodied energy can often be replaced bya low embodied energy material, while using conventionaldesign and construction techniques.

Use of Natural Materials

Natural materials are generally lower in embodied energy andtoxicity than man-made materials. They require less processingand are less damaging to the environment. Many, like wood, aretheoretically renewable. When natural materials are incorpo-rated into building products, the products become moresustainable.

Embodied Energy ofCommon Building Materials

Product

103,500 Btu/lbat point of use

Aluminium

Plastic Resins 38,400-48,500Btu/lb

Steel

Paper 15,650 Btu/lb

Wood Framing 91,618 Btu/cuft

Particle Board 7,000 Btu/lb

Fired Clay Brick 4,000 btu/lb14,000 btu/brick

PortlandCement

2,401-4,060 btu/lb

ConcreteMasonry Units

731-964 Btu/lb24,126-31,821 Btu/ea

Semi-stabilizedAdobe

123 btu/lb3,700 btu/brick

Figure 2: Table comparing embodiedenergies of common building materi-als. Values are taken from the AIAEnvironmental Resource Guide,1992.

Embodied Energy

19,200 Btus/lb


Reduction of Construction Waste

Minimizing construction waste produced during installation re-duces the need for landfill space and also provides cost savings.Concrete, for example, has traditionally been pre-mixed withwater and delivered to the site. An excess of material is oftenordered, to prevent pouring delays should a new shipment beneeded. This excess is usually disposed of in a landfill or on thesite. In contrast, concrete mixed on the site, as needed, eliminateswaste, and offers better quality control.

Designing floor intervals that coincide with standard lengths oflumber or steel for framing also reduces waste. Taking advan-tage of the standard sizes of building materials in the designphase will reduce waste from trimming materials to fit — as wellas reducing the cost of the labor for installation.

Local Materials

Using locally produced building materials reduces the air pollu-tion produced by vehicles by shortening travel distances. Oftenlocal materials are better suited to climatic conditions, and thesepurchases support area economies. It is not always possible touse locally available materials, but if materials must be importedthey should be used selectively and in as small a volume aspossible. The decorative use of marble quarried half-way aroundthe world is not a sustainable choice. Steel, when required forstructural strength and durability, is a justifiable use of a mate-rial that is generally manufactured some distance from thebuilding site.

Energy Efficiency

Energy efficiency is an important feature in making a buildingmaterial environmentally sustainable. The ultimate goal inusing energy efficient materials is to reduce the amount ofgenerated energy that must be brought on to a building site. Thelong-term energy costs of operating a building are heavilydependent on the materials used in its construction.

Depending on type, the energy efficiency of building materialscan be measured using many different factors such as R-value,shading coefficient, luminous efficiency or fuel efficiency. Pre-ferred materials slow the transfer of heat through a building’sskin, reducing the need for heating or cooling. Quantitative


measurements of a building material’s efficiency are available tohelp in the comparison of building materials and determiningappropriateness for certain installations.

R-Value: Building envelopes are generally rated by their insulat-ing value, known as the R-value. Materials with higher R-valuesare better insulators. Materials with lower R-values must beused in thicker layers to achieve the same insulation value. R-values can be measured for individual materials, such asinsulation, siding, wood paneling, and brick, or calculated forcomposite structural elements such as roofing, walls, floors, andwindows. Many types of insulation materials are available, fromorganic cellulose made from recycled paper to petrochemicalderived foams.

Shading Coefficient : Although daylighting is the most pleasantand cheapest form of illumination, the accompanying heat gainfrom direct solar radiation is not always welcome, particularly inhot climates. The shading coefficient (SC) is a ratio of the solarheat gain of a building’s particular fenestration to that of astandard sheet of double-strength glass of the same area. Thisallows a comparison of the sun-blocking effectiveness of variousglass types, shading devices and glazing patterns. Shadingdevices can be designed to block solar heat gain at certain timesof the day or year: overhangs are often used to block highsummer sun but admit direct light during the winter. Certaintypes of glass or applied films allow selective transmission of thevisible radiation (light) while preventing or reducing the trans-mission of infrared radiation (heat).

System Efficiency: Electrical and mechanical systems are respon-sible for over 50% a building’s annual energy costs.3 Heating,ventilation, and airconditioning (HVAC) systems should beselected for the greatest efficiency at the most commonly expe-rienced temperatures. A system that offers peak efficiency at anoutdoor temperature experienced by the building’s climate only5% of the time will not necessarily be the best choice. Regularmaintenance programs are also necessary to keep equipmentoperating at peak efficiency.


Water Treatment/Conservation

Products with the water treatment/conservation feature eitherincrease the quality of water or reduce the amount of water usedon a site. Generally, this involves reducing the amount of waterthat must be treated by municipal septic systems, with accompa-nying chemical and energy costs. This can be accomplished intwo ways: by physically restricting the amount of water that canpass through a fixture (shower head, faucet, toilet), or by recy-cling water that has already entered the site. Gray water fromcooking or hand washing may be channeled to flush toilets.Captured rainwater can be used for irrigation.

Water Conservation issues address efficient use of water as well asoverall reduction in the volume consumed. Water-saving showerheads and toilets are now familiar in both residences and com-mercial buildings. Even in the Great Lakes region, with itsabundant freshwater, conservation becomes an issue as munici-pal water treatment plants and septic systems are strained byurban sprawl. With the exception of buildings utilizing wellwater and septic systems, all water that comes into or leaves abuilding must be treated.

Vacuum-assisted or composting toilets use very little water andtherefore produce less waste. The advantages of compostingtoilets are that no waste enters the already overburdened wastestream, and the resulting compost can be used as fertilizer. Thepotential to separate the waste water stream into gray water(dirty from washing or cooking but not containing human oranimal waste) and black water (sewage, containing biologicalwaste or factory effluent) can be incorporated into plumbing andfixture design. Restrooms in Japan commonly direct water fromthe sink drain to the toilet tank, where it is used to flush toilets.The use of indigenous plants that are drought tolerant reducesthe need for irrigation, as important a consideration for thehomeowner in Detroit as in Phoenix.

Rainwater collected from roofs or paved parking lots can also beused to flush toilets and for landscape irrigation. The buildingitself can be designed to act as a collector of rainwater, stored ina cistern for later use. For health reasons, current building codesprohibit the use of this gathered water for human consumptionbut it is possible that water purification devices may be devel-oped in the future that will make on-site water safe to drink at alower cost than current municipal water treatment.


Use of Non-toxic or Less Toxic Materials

Non or less toxic materials are less hazardous to the health ofconstruction workers and a building’s occupants. Many materialsadversely affect the indoor air quality and expose occupants tohealth hazards. Some building materials, like adhesives, emitdangerous fumes for only a short time during and after installa-tion, others can contribute to air quality problems throughout abuilding’s life.

Air Quality and Reduced Toxicity: The rush to make buildings air-tight in the wake of the 1970s oil crises created a new healthproblem: “sick building syndrome.” The sick-building syndromeoccurs when natural or artificial ventilation is inadequate toremove odors and chemicals emitted by certain building mate-rials. These substances may be hazardous, even carcinogenic.The resins in plywood, particleboard, and the chemicals used infoam insulation have been implicated in sick building syn-drome. Formaldehyde, benzene, ammonia, and other hazardousor cancer-causing chemicals are present in many building mate-rials, furnishings, and cleaning solutions.

Previously, the infiltration rate of outside air through the gapsand cracks in its envelope compensated for contamination of theinside air by human respiration, bacteria or molds, and materialsemissions. The problem of outgassing is magnified by theincreasing air tightness of buildings. Super-insulating buildingsin attempts at energy conservation has caused reduced infiltra-tion, meaning occupants are exposed to a higher concentrationof toxins for a longer period of time. The health effects of thesetoxins must be considered when selecting materials and calcu-lating air exchange rates. By selecting materials with lower ornon-existent levels of these materials, environmental healthproblems of indoor occupants can be avoided and the need forinstalling expensive air scrubbers can be reduced.

Material toxicity is of increasing concern with the growingnumber of building products containing petroleum distillates.These chemicals, known as volatile organic compounds (VOCs)can continue to be emitted into the air long after installation. Theseverity of this process, called outgassing, is dependent on thechemicals involved, rate of outgassing, concentration in the air,and length of exposure. Many adhesives, paints, sealants, clean-ers, and other common products contain VOCs. Often, thesubstances are only exposed for a short time during and after


installation; the outgassing diminishes drastically or completelyonce the offending materials have cured, or been covered byother building materials. Therefore, higher than air cycling ratesare recommended during materials installation and for severalmonths following building occupation.

Renewable Energy Systems

Building sites are surrounded by natural energy in the form ofwind, solar radiation, and geothermal heat. Renewable energysystems can be used to supplement or eliminate traditionalheating, cooling, and electrical systems through the utilizationof this natural energy. Components that encourage daylighting,passive and active solar heating, and on-site power generationare included in this category. Solar power can be utilized inmany forms, both for heating and production of electricity.Wind power is feasible in many parts of the country to generateelectricity and pump water. Active solar or geothermal heatrequires outside electricity for pumps but overall saves energyover the operation costs of traditional mechanical systems.

Longer Life

Materials with a longer life relative to other materials designedfor the same purpose need to be replaced less often. This reducesthe natural resources required for manufacturing and the amountof money spent on installation and the associated labor. Durablematerials that require less frequent replacement will requirefewer raw materials and will produce less landfill waste over thebuilding’s lifetime.

Durability: The durability of materials is an important factor inanalyzing life cycle costs for a building. Materials that last longerwill, over a building’s useful life, be more cost effective thanmaterials that need to be replaced more often. By looking atdurability issues, the selection of initially expense materials likeslate or tile can often be justified by their longer life spans.

Low Maintenance: Maintenance consumes a significant portion ofa building’s operating budget; over the building’s lifetime main-tenance can easily exceed the original construction costs. Thisincludes the cost of labor, cleaning/polishing materials, equip-ment, and the replacement of items valued at less than $5000.4

Less frequent cleaning of materials reduces the exposure of thebuilding occupants and janitorial staff to cleaning chemicals.


This is especially important for surfaces or systems that must becleaned with petroleum-based solvents.

Reuse

Reusability is a function of the age and durability of a material.Very durable materials may outlast the building itself, and canbe reused at a new site. Other materials may have many usefulyears of service left when the building in which they are installedis decommissioned, and may be easily extracted and reinstalledin a new site.

Some building materials, because of exceptional durability, canbe reused from one structure to the next. Windows and doors,plumbing fixtures, and even brick can be successfully reused.Timber from old barns has become fashionable as a reclaimedmaterial for new construction. The historic preservation move-ment in this country has spawned an entire industry devoted tosalvaging architectural elements of buildings scheduled fordemolition. These materials are used both in the renovation ofold buildings and in new construction. In many cases, thequality of materials and craftsmanship displayed by these piecescould not be reproduced today.

Recycle

Recyclability measures a material’s capacity to be used as aresource for the creation of new products. Steel is the mostcommonly recycled building material, in large part because itcan be easily separated from construction debris by magnets.

Many building materials that cannot be reused in their entiretycan be broken down in to recyclable components. Often, it is thedifficulty of separating rubble from demolition that preventsmore materials from being recycled. Glass is very easy to recycle,once separated. Post-consumer glass is commonly used as a rawmaterial in making window glass, as well as ceramic tile andbrick. Concrete, unlike steel and glass, cannot be re-formed onceset, but it can be ground up and used as aggregate in newconcrete or as road bedding. Currently, very little concrete andglass from site demolition is recycled because of difficulty inseparation.


Plastics could be easily recycled but are often integrated intoother components which makes separation difficult or impos-sible. Plastic laminates are generally adhered to plywood orparticle board, making these wood products also hard to recycle.Some foam insulation can be reformed, but the majority cannot.Foam insulation can, like glass, be used as filler in concrete androad beds.

Biodegradibility

The biodegradability of a material refers to its potential tonaturally decompose when discarded. Organic materials canreturn to the earth rapidly, while others, like steel, take a longtime. An important consideration is whether the material inquestion will produce hazardous materials as it decomposes,either alone or in combination with other substances.


Part II: Materials

Key Sources of Building Materials

Limestone

Limestone is perhaps the most prevalent building material ob-tained through mining. It is used as a cladding material andplays and important role in the production of a wide range ofbuilding products. Concrete and plaster are obvious examplesof products that rely on limestone. Less obvious is the use oflimestone in steel and glass production.

An abundant natural resource, limestone is found throughoutthe world. In the U.S., the states of Pennsylvania, Illinois,Florida, and Ohio are the largest producers of limestone.5 Themining of this sedimentary rock generally takes place in open pitquarries. Pit mining requires the use of heavy equipment tomove the topsoil, vegetation, and overlaying rock (collectivelyreferred to as “overburden”). Large blocks of stone are removedfrom the rock bed by controlled drilling and explosions. Theseblocks may be cut down into smaller units for use as structuralmasonry or veneer material. Most limestone is crushed at thequarry, then converted to lime, by burning, at another location.

The burning of limestone creates sulfide emissions, a majorcontributor to acid rain. Limestone (primarily calcium carbon-ate, or CaCO

3) is converted to quicklime (calcium oxide) through

prolonged exposure to high heat. This removes water andcarbon from the stone, and releases carbon dioxide into theatmosphere. The quicklime is then crushed and screened. Be-fore it can be used in plaster or cement, the quicklime must behydrated, or mixed with water, and then dried. The hydratedlime then becomes an ingredient in concrete, plaster, and mortar.

Steel

Steel requires the mining of iron ore, coal, limestone, magne-sium, and other trace elements. To produce steel, iron must firstbe refined from raw ore. The iron ore, together with limestoneand coke (heat-distilled coal) are loaded into a blast furnace. Hotair and flames are used to melt the materials into pig iron, withimpurities (slag) floating to the top of the molten metal. Steel isproduced by controlling the amount of carbon in iron throughfurther smelting. Limestone and magnesium are added to


remove oxygen, making the steel stronger. A maximum of 2%carbon is desired. Other metals are also commonly added at thisstage, to produce various steel alloys. These metals includemagnesium, chromium, and nickel, which are relatively rareand difficult to extract from the earth’s crust. The molten steel iseither molded directly into usable shapes or milled.

Aluminium

Aluminum, derived from bauxite ore, requires a large amount ofraw material to produce a small amount of final product. Up tosix pounds of ore may be required to yield one pound ofaluminum. Bauxite is generally strip-mined in tropical rainforests; this requires removing vegetation and topsoil from largeareas of land. When mining is completed, the soil is replaced.The land may then be allowed to return to rain forest, but is morelikely to be used as farmland.

Aluminum manufacturing is a large consumer of electricity,which in turn comes from burning fossil fuels. The refinedbauxite is mixed with caustic soda and heated in a kiln, to createaluminum oxide (Al

2O

3). This white powder, in turn, must

undergo an electrolytic reaction, where direct electrical currentis used to separate out the oxides and smelt the material intoaluminum. The material must be heated to almost 3000˚ F for thisprocess to occur. The processing of bauxite into aluminumresults in large quantities of waste, called “mud,” which containstraces of heavy metals and other hazardous substances. A by-product of the smelting process called “potliner” contains fluorideand chlorine, and must be disposed of as hazardous waste.Approximately 0.02 pounds of potliner are produced for everypound of aluminum.

Because aluminum has such a high embodied energy content(103,500 BTUs at point of use) it is best applied where its lightweight, corrosion resistance, and low maintenance can be usedan advantage. Recycling aluminum requires only about 20% ofthe energy of refining bauxite into usable metal. Althoughrecycling of aluminum beverage containers is common, onlyabout 15% of aluminum used in construction is ever recovered.6

Bricks and Tile

Clay and adobe soil must also be mined. They are usually foundin shallow surface deposits, and manufacturing is often donenearby, reducing extraction and transportation costs. Except for


adobe, bricks and tiles must be fired to be useful in buildingproducts. The firing process exposes the formed clay to high,prolonged heat, producing a hard, waterproof and permanentbrick or tile. The firing process can take hours or even days, andrequires a large amount of energy. Glazed bricks and tiles arefired twice: first, to make the shape permanent, then to melt andadhere the glazed finish, which usually contains glass. The endproduct has a high embodied energy, but is also very longlasting. Even without firing, adobe bricks, properly maintained,can last 350 years or more.

Petrochemicals

The building industry is highly dependent on materials derivedfrom petroleum and natural gas. They are used in a wide rangeof products including plastics, adhesives for plywood and par-ticle board, laminate countertops, insulation, carpeting, andpaints. Drilling for oil and gas is both hazardous and expensive.Heavy machinery is required, and contamination of the groundwater and soil is common.

Wood

Wood is the harvested material most commonly used in build-ings and building products. Dimensional lumber is used inframing the majority of residential buildings and many commer-cial structures. Wood products, such as plywood, particle board,and paper are used extensively throughout the constructionindustry. Until recent years, the most common method ofharvesting wood was clear-cutting, a process wherein all vegeta-tion within a given area is removed for processing. Now, whereclear cutting takes place, the lumber companies are required toreplant the area.

Some lumber is now being produced on tree farms, or “planta-tions.” However, replanting alone does not replace the naturalbiological diversity that existed before harvesting. Monocul-ture, or same-species, plantings of trees are particularly vulnerableto disease and insects. More companies now practice selectivecutting, choosing only those trees large enough or valuableenough to remove, and leaving the surrounding vegetationintact.

Sustainable forestry practices include a professionally adminis-tered forestry management plan in which timber growth equalsor exceeds harvesting rates in both quantity and quality. Rivers


and streams are protected from degradation, damage to theforest during harvesting is minimized, while biodiversity andfair compensation to local populations is emphasized.

Selecting Sustainable Building Materials

Criteria

An informal survey of building materials manufacturers con-ducted at the University of Michigan revealed environmentallysustainable replacements for use in every building system. Rep-resentative products have been selected from this survey toillustrate the wide variety of materials available that are de-signed and manufactured with environmental considerations.The selection criteria include sustainability in regard to a widerange of envionmental issues: gathering of raw materials, manu-facturing processes, construction techniques, and disposal ofdemolition waste.

Figure 3 is a chart of the criteria, grouped by the affected buildinglifecycle phase. This chart is designed to aid in comparing thesustainable qualities of different materials used for the samepurpose. The presence of one or more of these "green features"in a building materials can assist in determining its relativesustainability.

Figure 3: Key to the Green Featuresof Sustainable Building Materials.

Green Features

Manufacturing Building WasteProcess Operations Management

Waste Energy BiodegradabilityReduction Efficiency

Pollution Water Treatment RecyclablePrevention & Conservation

Recycled Nontoxic Reusable

Embodied Renewable OthersEnergy Reduction Energy Source

Natural Longer LifeMaterials


Pre-Building Phase: Manufacture

Waste ReductionThe waste reduction feature indicates that the manufacturer hastaken steps to make the production process more efficient, byreducing the amount of scrap material that results. This scrapmay come from the various molding, trimming, and finishingprocesses, or from defective and damaged products. For prod-ucts with this feature, scrap materials can be reincorporated intothe product, or removed for recycling elsewhere. Some indus-tries can power their operations by using waste productsgenerated on site or by other industries. These options reducethe waste that goes into landfills.

Pollution PreventionThe pollution prevention feature indicates that a reduction of air,water, and soil pollution associated with the manufacturingprocess has been achieved, implying measures that exceed thelegislative minimums required of manufacturers. These reduc-tions may be achieved through on-site waste processing, reducedemissions, or the recycling of water used in the manufacturingprocess. Environmentally sound packaging can also be a pollu-tion prevention feature, as the way in which a product ispackaged and shipped affects the total amount of waste gener-ated by the product.

Recycled ContentA product featuring recycled content has been produced partiallyor entirely of post-industrial or post-consumer waste. Theincorporation of waste materials from other industrial processesor households into usable building products reduces the wastestream and the demand on virgin natural resources.

Embodied Energy ReductionThe embodied energy of a material refers to the total energyrequired to produce that material, including the collection of rawmaterials. A revision of process that saves energy will reduce theembodied energy of the material. Some low-embodied energymaterials may also be substituted for traditional materials withhigher embodied energy, while using conventional design andconstruction techniques.

Use of Natural MaterialsNatural materials are generally lower in embodied energy andtoxicity than man-made materials. They require less processing


and are less damaging to the environment. Many, like wood, aretheoretically renewable. When natural materials are incorpo-rated into building products, the products become moresustainable.

Building Phase: Use

Reduction in Construction WasteMany building materials come in standard sizes, based on th 4 x8 module defined by a sheet of plywood. Designing a buildingwith these standard sizes in mind can greatley reduce the wastematerial created by the installation process. Efficent use ofmaterials is a fundamental principle of sustaoinability. Materi-als that are easily installed with common tools also reduceoverall waste from trimming and fitting.

Energy EfficiencyEnergy efficiency is an important feature in making a buildingmaterial environmentally sustainable. Depending on type, theenergy efficiency of building materials can be measured usingmany different factors such as U-value, shading coefficient,luminous efficiency or fuel efficiency. The ultimate goal in usingenergy efficient materials is to reduce the amount of artificiallygenerated power that must be brought on to a building site.

Water Treatment/ConservationProducts with the water treatment/conservation feature eitherincrease the quality of water or reduce the amount of water usedon a site. Generally, this involves reducing the amount of waterthat must be treated by municipal septic systems, with accompa-nying chemical and energy costs. This can be accomplished intwo ways: by physically restricting the amount of water that canpass through a fixture (shower head, faucet, toilet), or by recy-cling water that has already entered the site. Gray water fromcooking or hand washing may be channeled to flush toilets.Captured rainwater can be used for irrigation.

Use of Non or Less Toxic MaterialsNon- or less-toxic materials are less hazardous to the health ofconstruction workers and building occupants. Many materialsadversely affect indoor air quality and expose occupants tohealth hazards. Some materials, like adhesives, emit dangerousfumes for only a short time during and after installation; otherscan reduce air quality throughout a building’s life.


Renewable Energy SystemsRenewable energy systems replace traditional building systemsthat are dependent on the off-site production of electricity andfuel. Solar, wind, and geothermal energy utilize the naturalresources already present on a site. Components that encouragedaylighting, passive solar heating, and on-site power generationare included in this category.

Longer LifeMaterials with a longer life relative to other materials designedfor the same purpose need to be replaced less often. This reducesthe natural resources required for manufacturing and the amountof money spent on installation and the associated labor. Durablematerials that require less maintenance will produce less landfillwaste over the building’s lifetime.

Post-Building Phase: Disposal

BiodegradabilityThe biodegradability of a material refers to its potential to natu-rally decompose when discarded. Organic materials can returnto the earth rapidly, while others, like steel, take a long time. Animportant consideration is whether the material in question willproduce hazardous materials as it decomposes, either alone or incombination with other substances.

RecyclabilityRecyclability measures a material’s capacity to be used as aresource for the creation of new products. Steel is the mostcommonly recycled building material, in large part because itcan be easily separated from construction debris through mag-nets. Glass can theoretically be recycled, but is difficult to handleand separate from a demolition site.

ReusabilityReusability is a function of the age and durability of a material.Very durable materials may outlast the building itself, and canbe reused at a new site. Other materials may have many usefulyears of service left when the building in which they are installedis decommissioned, and may be easily extracted and reinstalledin a new site.


Examples

Site and LandscapingRecycled plastic has been developed into a wide range of land-scaping products. Plastic lumber is already in wide use foroutdoor furniture and decking. The lumber is manufactured byshredding and reforming post-consumer plastic containers, suchas pop bottles and milk jugs. Some brands incorporate waste orrecycled wood as well. The product has advantages over woodin that it is impervious to moisture, and will not warp, rot, orcheck. The lumber is available as dimensional stock, or in a widevariety of manufactured garden furniture and accessories. Traf-fic stops and bumpers are also being made from recycled plastic,replacing concrete and asphalt.

By recycling plastic, a major contributor to landfill waste is putto a new use, and raw materials are conserved. Water conserva-tion also results, because recycling plastic uses less water thanprocessing new plastic, wood, or concrete. When used in soilerosion control products, recycled plastic also prevents top soilloss and the resulting consequences of increased water turbidity.The recycled plastic products can themselves be recycled whentheir useful life has ended. As the material is inert, it will notdegrade into toxic substances if discarded in landfills.

Landscape pavers made from recycled plastic can be used inplace of bricks. Pavers are produced in a range of colors andstyles, and can be used to replicate any traditional brick pattern.An open-grid rigid plastic mat product has also been intro-duced. This product allows grass to grow in the open areas of thegrid and permits water to drain through it, unlike paving. It isidea for use in playgrounds, and provides a rigid surface forwheelchair access onto lawns.

Conventional paving materials like asphalt are also beginning toincorporate recycled materials. Old asphalt is ground up, re-heated, and used to repave surfaces. This is standard now inhighway and street construction. Recycled rubber from tires,ground glass, and plastic are being used in the asphalt mix,reducing significant waste products. These materials also pro-vide greater durability than traditional paving methods, meaninglonger life and less frequent repaving. This reduces material andenergy used over the lifetime of a project.

MP BO WMWR

RCEER

WTCNT

LL

RCRU

Plastic Lumber, Pavers

Figure 5: Porous pavement systemmade from recycled plastic. This al-lows grass to grow while providing afirm surface for foot and vehicle traf-fic. Excellent for providing wheelchairaccess to parks and playgrounds.

Figure 4.

Figure 6.

MP BO WMWR

RCEER

LL

RC

O

Recycled Asphalt


Figure 7: Prefabricated drainage sys-tem, using EPS chips instead ofgravel.

One new type of drainage system replaces gravel, which must bequarried, with pieces of polystyrene, which would otherwise bedumped into landfills. The polystyrene can simply be used in

place of gravel, and is inert in the environment. A prefabricatedsystem combining perforated drainage pipe surrounded byplastic chips, held in place with plastic netting, is also available.The light weight and prefabrication save time and labor duringconstruction. Gravel trucks and are eliminated, cutting down onair pollution. Either type of product can be used around founda-tions, in drainage fields, parking lots, and anywhere traditionalsite drains are used.

FoundationsPoured-in-place concrete and concrete block foundations havelong been a staple in the construction industry. They providethermal mass insulation value and have a long life. Significantimprovements have been made that reduce the installationwaste produced on site and increase the insulation value of thesefoundation systems. These systems are collectively known assuper insulated foundations.

Two of the major drawbacks of poured in place concrete are thetime and materials required to erect form work. Generally,plywood and dimensional lumber are used to construct theforms, then discarded after the concrete has set. This essentiallywastes the energy involved in production of wood and plywood,which can be high given the drying of wood and the petroleumused to make the binding resins. Furthermore, because of theresins, the plywood is difficult to recycle, and usually ends up ina landfill. Permanent form work has been developed using rigidplastic foam. The foam sheets or blocks are used to contain theconcrete during pouring, and improve compressive strength byretaining the heat produced as the concrete sets, resulting in a25% stronger wall. The systems result in an R22-R24 equivalent.

The holes in concrete block, designed to reduce weight and makehandling easier, are a potential insulation site. Loose-fill insula-tion is often used to fill the holes as the wall is constructed. A newtechnique customizes the block’s hollows and uses a tightly fit,rigid foam insert. The foam inserts come into contact at the endsof the block, providing a continuous thermal shield the length ofthe wall.

Figure 8.

MP BO WMWR EE

LL

Insulated Foundations

Permanant formwork for poured con-crete walls. Made from rigid plasticfoam, it eliminates disposable ply-wood forms and increases thestrength of the resulting wall.


In both styles of super insulated foundations, the insulationvalue of the foam becomes integrated into the total R-value of thefinished foundation. This is especially useful in residential con-struction, where basements are often converted to habitablespace. The foam production process does not use fluorocarbons,and generates only pentane. This is generally burned off and notreleased into the atmosphere.

Structural FramingAs the price of virgin wood rises, and the quality declines, steelframing is becoming an economical alternative to wood studframing in residential construction. It has been long favored incommercial construction for its ease of assembly and uniformityof quality. Until recently, the price of steel studs and the custom-ized nature of home design made its use impractical. However,because steel is stronger, fewer members are required to supportthe same load. Although steel has a very high embodied energycontent, it can easily be reused and recycled. One major draw-back to the use of steel in exterior walls is its conductive nature:more insulation is needed to provide the same R-value as atraditional wood stud wall.

Joist and truss systems, using fabricated lumber or a combina-tion of dimensional lumber and steel, are also moving fromcommercial to residential construction. Open-web joists andtrusses are more economical than traditional 2 x 12 wood, andthe manufacturing system insures even quality. Wood, a naturalproduct, is subject to a wide range of variable that can affect itsstructural strength. Less lumber, mostly 2x4 material, is usedoverall, and metal webs can be made of recycled steel. Improvedsound ratings are also a benefit of these systems.

Lumber recovered from demolition is being used in renovationsand new construction, for both environmental and aestheticreasons. Timber-framed structures are often dependent uponrecycled wood, due to the difficulty in obtaining large logs.Timbers, flooring, trim and paneling are salvaged from thedemolition of old houses and barns, then cleaned up and resawnif necessary. The resulting product reduces landfill waste, isnontoxic, recyclable, and of better quality than commercialavailable virgin lumber today.

Figure 9: Concrete blocks with foaminserts.

Figure 11: Wood and steel open-webjoist.

MP BO WMWR EE

LL

Insulated Foundations

MP BO WM

RC

NM

NT

LL

BDRCRU

Steel Framing


Building EnvelopesPlywood and oriented strand board are the conventional sheath-ing materials used to enclose buildings once the frame is in place.Both materials are wood-based: plywood consists of large sheetsof veneer sandwiched together, while strand board incorporateswaste wood particles. The resins used to bind the wood fiberstogether are petroleum by-products. Volatile, sometimes haz-ardous, chemicals evaporate from the boards over the life of theproduct, contributing to indoor and outdoor air pollution. There-fore, these materials are best used where they will be covered orsealed in by other building products, such as siding and drywall.

Alternatives to wood-based sheathing and toxic resins are beingdeveloped from agricultural waste products. Straw paneling,assembled with water-based adhesives and fiberglass tape, isavailable for use as exterior sheathing. Like the wood in strandboard, the straw is shredded and compressed to form a light-weight, monolithic panel that can be assembled into roof andwalls with specially developed latex adhesives and coatings.This replaces conventional materials such as wood, steel, andcement. This product turns agriculture waste that is generallyburned (contributing to air pollution) into a valuable commod-ity, and preserves other natural resources. The product is nontoxic,biodegradable, energy efficient, and long lived.

Wood, aluminum or vinyl siding is generally installed oversheathing to protect it from the weather. All three materials havedisadvantages. Wood is difficult to maintain and increasinglyscarce. Aluminum and vinyl both have high embodied energy,and are generally unsuccessful in their attempts to imitate wood.However, both can be composed primary of recycled materials.Alternative siding materials are also available, ranging fromother products that are imitations of wood to advanced stuccomaterials.

Fiber-chemical siding and shingles imitate the look of woodwithout the maintenance, and without the high embodied en-ergy content of aluminum or vinyl. Formed of fiberglass orplastic resins, they are nontoxic, noncombustible, lightweight,and moisture resistant.

Enhanced stucco materials do not hold water. Their greaterflexibility than traditional stucco prevents cracking, providing alonger life. The material is easily applied by spraying or by

MP BO WM

NT

LL

Fiber-chem Siding

Figure 13.

Figure 12.

Composite lumber made from wastewood.

MP BO WMWRPPRCEERNM

EEWTCNT

RESLL

BD

Straw-based Sheathing


MP BO WM

RC

NM

EE

NT

LL

RUO

Bricks, CMU

Figure 15.

Figure 16: Structural building panels.

troweling. A polymer sealant in the mix allows walls to breath,and the color, which is incorporated into the mix, won’t fade. Theproduct is available in variety of textures, and custom colors,and can be applied over many substrates. A mesh of wire orfiberglass is attached to the substrate, then covered with thestucco material. Rigid foam insulation systems may also beinstalled, then covered with stucco. This system is quicker andeasier to install than traditional stucco, which requires manycoats and is subject to cracking. Supplementing the coating withrigid polystyrene foam can yield an insulation value of R-21without increasing wall stud depth.

Structural EnvelopesStructural envelopes combine the two-step process of framingand infill. The most common example is true masonry construc-tion, where stone, brick, or concrete masonry units (CMUs)provide the structural strength of the building, and are not usedas veneers or infill between wood or metal framing members.Stone, which must be quarried, is expensive and difficult totransport, and so is almost never used in solid masonry today.Brick and CMUs are still used structurally, generally in residen-tial or light commercial applications.

Although clay for brick must be quarried, clay is abundant andcan be easily obtained from surface deposits. Bricks are com-monly manufactured and sold near the quarry site, reducingtransportation costs and air pollution. The firing of bricks im-parts a high embodied energy content. Most brick is colored withorganic pigments, but some glazing materials and pigments canbe hazardous to the environment. CMUs do not require firing,but are often kiln dried. The burning of limestone to produce thelime used in cement and mortar also consumes a great deal ofenergy. However, bricks and CMUs are long lasting materials,have a thermal mass insulation value, and are inert if discardedin a landfill. They can also incorporate industrial waste productssuch as fly ash, glass, plastics, even hazardous waste.

Traditionally thought of as building types limited to the South-west U.S. and other arid regions, adobe and rammed-earthconstruction is undergoing a renaissance. Globally, 40 percent ofthe world’s population is housed in earthen shelters. Adobe andrammed-earth, properly constructed, have a very long life.Materials can be obtained locally, even on the building site itself.Materials are nontoxic, biodegradable, and waste from manu-


facturing or installation can be reincorporated into new materi-als. Plastic binders in the earth-mix and improved stucco systemshave increased water resistance, allow earth construction tospread beyond arid regions into the damp climates. Adobe andrammed-earth are nonpolluting, nontoxic, recyclable, and highlyenergy efficient. Structures 350 years old are still in existence.

Super insulated stress-skin panels are giant sandwiches of rigidinsulation encased in plywood or strand board. Some brands ofpanels are load-bearing and can be used as the load-bearingstructure. Standard sizes are four feet wide with various lengthsup to 24 feet. The panels go together easily, often with a tongueand groove feature. As the wall is uniform, insulation is morecomplete. Built-in channels carry electrical and plumbing.

The use of these panels offers significant waste reduction, timeand labor savings, and long life. The foam core can be made withrecycled expanded polystyrene, and the wood used in the ply-wood or strand board comes from renewable crop lumber andmill waste. Because there is no airflow through the panels,windy days have less of an effect on the heating and coolingcosts. Energy savings of 40% - 60% over 2 x 6 stud constructionsare common. Because many of the materials used in the stressskin panels are recycled, far less energy is required to producethe panels than other building materials.

InsulationThorough insulation is one of the best ways to reduce energyconsumption and building operating costs. Insulation also offersacoustic benefits. In contemporary construction, the familiarfiberglass insulation has been supplemented by hi-tech poly-mers and old-fashioned cotton.

Rigid foam insulation is applied in panels in new construction,and can offer a very high R-value per inch of thickness. Theenergy saved by installing these materials far exceeds the energyconsumed in production. The R-value is not affected by mois-ture, and the plastic foam is not edible by insects.

Because of the high embodied energy content of plastics and thepotential hazards of volatile chemicals outgassing from them, areturn to organic insulation has begun. Several brands of insula-tion currently on the market are made from recycled newspapersor recycled textiles. They are available in batting, loose-fill, orspray-on applications.

MP BO WMWRPPRC

EE

NTRC

O

Recycled Polystyrene

Figre 14.

Figure 17: Insulation made from re-cycled newspapers.


A spray-applied thermal and acoustic insulation made fromrecycled paper fibers and an acrylic-based adhesive offers an R-value of 4.54 /inch. Using 100% post-consumer paper conservestrees, water, and land fill space. The acrylic binder is nontoxic,and keeps the insulation in place, preventing settling over timethat leads to reduced R-values. The spray-on application alsoallows the insulation to easily fill in around pipes and electricaloutlets, unlike batting. Flame retardents and insecticides areadded to the fibers in the manufacturing process.

Cotton insulation is made from recycled textile fabrics thatnormally end up in a landfill. R-values are available from R-11 at3.5” thick to R-38 at 12” thick. The process used to recycled thecotton uses very little energy, is nontoxic, and can incorporatewaste materials. No air pollutants or harmful emissions resultduring the production process. As with cellulose insulation,flame retardants and insecticides are added to the fibers in themanufacturing process.

GlazingWindows and skylights allow daylight to reach the interiors ofbuildings, reducing the need for artificial light. Operable unitsassist in ventilation and cooling, reducing or eliminating theneed for mechanical equipment. However, windows are theweakest point in the building envelope for energy loss, andmuch research has gone into developing more efficient windowsystems. Improved glazing techniques offer low-emissivity glassand inert gas-filled air spaces between panes. The window sashand frame have also been improved with added insulation andseals.

Heat gain through direct solar radiation is the easiest to prevent,by providing shading devices and using low-emissivity (low-E)glass. Low-E glass acts as a radiation mirror: infrared (heat) raysare reflected back to the source. This prevents solar heat gain inthe summer, and retains heat within the building during thewinter.

Heat loss or gain through windows also occurs due to conduc-tion. Double- and triple- paned glass uses an airspace betweenpanes to block the transfer of heat. By filling the air space with aninert gas such as argon, the conductivity is further reduced. Theair space can also be used to hold low-E films or integratedshading devices. Glazing is available with a solar control film

Figure 18: An illustration of double-paned glass with films formingadditional airspaces and UV protec-tion.


encapsulated within the glass layers. The film divides the air-space, creating two air spaces, and further reducing conductivity.The transparent film allows daylight to enter the room, butblocks ultraviolet radiation (UV). UV is responsible for fadingand deterioration of textiles, and a primary cause of skin cancer.The film reduces heat gain and saves energy during coolingseasons, while it maximizes daylighting. Nontoxic materials areused to avoid pollution during manufacturing, and the filmharmlessly biodegrades when exposed to the environment.

Vinyl and aluminum windows are popular for building exteri-ors because they require little maintenance. Often, the windowsash and frame are constructed of wood, then clad with alumi-num or vinyl. The wood provides a better insulating value thanvinyl or aluminum alone, and adds strength to the frame. Thesewindows are particularly desirable in residential construction,as the wood can be left exposed on the interior of the window.High-quality lumber is required, even in the areas not exposed,in order to control warping. Steel is sometimes used in thewindow frames for added strength. Both cladding materials,especially aluminum, have high embodied energy contents.

Fiberglass window systems offer advantages over aluminum orvinyl. Like vinyl and aluminum, they are low maintenance, butthey will not warp or rot, and they have a longer life and lowerembodied energy than vinyl or aluminum. They require nowood or steel for framing, and the frames are filled with polysty-rene foam for improved insulation. Silicone, not steel, spacingbars are used between multiple panes of glass. The fiberglasssash is more receptive to the airtight sealing required whenusing argon gas-filled airspaces between panes. As fiberglass,being composed chiefly of strands of glass, has a thermal expan-sion coefficient similar to glass itself, the materials expand andcontract at approximately the same, meaning less stress to thesealants and the material of the windows as a whole. Althoughthere is currently no recycling process for fiberglass, there is thepotential for reuse, due to the long life span of the product.

Skylights and skyroofs are increasingly popular in both residen-tial and commercial construction, as a way of bringing daylightdeep into the interior of a structure. New sealants and flashingtechniques have reduced the leakage problem common in olderinstallations. Operable skylights are excellent for ventilation. Adisadvantage of skylights is the heat gain associated with large Operable skylights provide daylighting

and natural ventilation.


panes of glass, particularly on roofs where there are no over-hangs to reduce direct sunlight. Many brands of manufacturedskylights therefore incorporate a shading device that is eithermanually or electronically controlled.

An alternative to large panes of glass is available. A device canbe installed in the ceiling of a room and up through the roof. Theperiscope-like device has a sunlight-gathering acrylic dome onthe roof, internal reflectors, and a diffuser lens that emergeswithin the room. This brings the advantages of natural daylightinto a space, without the heat gain of traditional skylights. Thesize of the tube allows it to be installed between roof rafters, sono cutting and rerouting of structural members takes place. Thedevice is designed for the do-it-yourself homeowner, but showspotential for use in commercial installations. A 13" diameter tubeprovides a summer noon output equivalent to 600 incandescentwatts of lights, and illuminates up to 150 square feet.

RoofingProperly installed roofing is vital to the structural integrity of abuilding. Given the large surface area of most roofs, and theirexposure to the elements, the choice of roofingmaterialsIntegrated sheathing and insulation, pre-taperd for flatroofs. can also have a significant impact on the energy efficiencyof a structure. Roofing materials and labor are expensive, and soa long roof life reduces operating costs, material waste, andpromotes energy savings.

The roofing material with the longest life span, slate, is also themost expensive and difficult to install. The weight of slaterequires a reinforced roof structure, and the material is difficultto work, requiring skilled labor. Yet a slate roof can last hun-dreds of years. The aesthetic quality of slate is also popular:homeowners and businesses alike appreciate the texture andimplied richness.

New imitation slate materials offer a longer life than asphalt orother shingles, at a fraction of the cost of real slate. The tiles areproduced from 100% recycled, re-engineered materials, includ-ing rubber and cellulose. The material is cast into a variety oftraditional slate patterns, using molds made from 100-year oldslate to accurately reproduced the texture and appearance. Be-cause the material is lightweight, no structural reinforcement isneeded. Waste reduction is considered during design. A small

Figure 19: Fiber-resin compositionroofing tiles cast from 100-year-oldslates for an authentic look.

Integrated sheathing and insulation,pre-taperd for flat roofs.


amount of waste results from installation, and all waste can berecycled into new product. The material is partially foamed, andthe resulting airpockets add insulating value. The tiles can be cutwith ordinary knives, making installation as easy as asphalt. Theproduct has a 100-year life expectancy.

Weatherproof shingles manufactured from recycled aluminumalloys combine the look of wood shakes with durability of metal.Unlike wood, they are also fireproof. The aluminum reflectsradiant heat, and reduces summertime attic heat gain by 34% incomparison to standard asphalt shingles. The 12x24" aluminumpanels interlock on all sides for wind resistance, and come witha 50-year transferable warranty. All production and installationscrap can be recycled, as can the product itself when the usefullife has ended. Because of aluminum’s light weight, the shinglescan often be installed directly over an old roof, eliminating theneed for stripping and disposing of old asphalt shingles.

Interior FinishesInterior walls can be finished in a variety of ways. Generally,gypsum board or wall board is used to enclose the wall studs,then paint, wallpaper, or other decorative treatments are ap-plied. Largely in response to strict air-quality laws in California,which virtually prohibit traditional oil-based paint because ofoutgassing, a wide range of paints, stains, and finishes areavailable that are nontoxic and easy to clean up. Casein paint, atechnology at least 5,000 years old, is made from natural pig-ments, milk solids, lime, talcum, and salt. Generally sold dry, itis mixed with water as needed, reducing waste.

Sisal wall coverings offer a natural, durable, and sound absor-bent alternative to vinyl and paper wall coverings. Unlike vinyl,sisal fibers are a renewable resource. Unlike paper, large amountsof water are not consumed in the manufacturing process. Sisalgenerally contains no toxic pigments from dying or printing, andis ideal for covering rough, uneven walls.

Architectural quality wood veneer paneling is available fromcertified forestry sources. Certified operations employ sustain-able harvesting and planting techniques. This is particularlyimportant when choosing exotic or tropical woods for a project.Two veneer cores are available a nontoxic, honeycombed re-cycled paper product; or a non-formaldehyde based particle

Figure 20: Shingles made from re-cycled aluminum.


Figure 21, 22: Access flooring allowelectrical configurations to be easilychanged when the building's usechanges (top). Some systems haveintegrated ventilation modules (bot-tom).

board. It comes in 4x8 sheets and custom dimensions, and issuitable for interior paneling and furniture. Veneer is an ex-tremely efficient use of wood products.

FlooringFinished flooring is available in a wide range of materials andstyles. The decision about the type of flooring (carpeting versustile, for example), is generally determined by the program of thebuilding. However, within each category of flooring are materi-als that can be judged for toxicity, embodied energy content, andother environmental factors.

Traditional wool carpeting, while nontoxic and made a fromrenewable resource, has not been able to compete with cheappetroleum products. While still available, it is generally costprohibitive. The majority of carpeting and carpet cushioningsold today is made from petrochemicals. Not only is petroleuma dwindling natural resource, the final products can continue toemit volatile gases long after installation, becoming a healthhazard to building occupants. The health risk is compoundedwhen petroleum-based adhesives are used to install the backingand carpet.

Natural fiber carpet cushions can be made of jute felt: recycledburlap or virgin jute fiber with some animal fibers (camel,cashmere) added for softness and resilience. Jute is a renewablecrop material, with a very little energy required in the growthand manufacturing process. It biodegrades upon disposal, andcan be recycled. Coatings help protect the fiber from mildewgrowth. The material has a higher density and longer life thancomparable synthetics.

Another available carpet cushion is made from recycled groundtire rubber. The disposal of automotive tires in landfills createsan environmental and health hazard. By reusing the rubber fromtires, landfill waste is reduced, as is the need for new petroleumproducts. Tires are also being used to make floor tiles andinterlocking pavers. The natural resilience of rubber makes thisflooring ideal for health facilities and areas where people standa lot. The material is slip-resistant, and meets the AmericanDisabilities Act safety guidelines.

Linoleum, a product made of linseed oil, compressed cork andwood flour, resin binders, and pigments, is a low-tech and low-


energy alternative to vinyl. Made of natural nontoxic materials,VOC emissions are primarily from the oxidation of the linseedoil, and are classified as fatty acids. The raw materials of lino-leum are primarily from natural, renewable resources that arecultivated without endangering the environment.

Natural cork tile has seen renewed interest because of indoor airquality issues. Cork is harvested from the bark of cork trees,which shed bark naturally in a seven-year cycle. The manyfeatures of cork include shock absorption, acoustic and thermalinsulation, and long life. Flooring made of cork requires sealingwith wax or polyurethane. Both linoleum and cork are very longlasting.

Ceramic tile is another flooring material noted for its long life,even in high traffic areas. Tile is nontoxic, stain-resistant, andinert when discarded in landfills. Glazed and unglazed tile canbe made using recycled glass as filler, which allows lowering thefiring temperature.

PlumbingWater conservation issues and overburdened septic systemshave led to a re-examination of our traditional plumbing meth-ods. There have been three areas of focus: reducing fresh wateruse; recovering and reusing “gray” water; and, reducing sewagethat enters the munincipal waste stream.

Several recent toilet designs have emphasized low water con-sumption. Generally, these toilets use differential air pressureinstead of water and gravity to transport sewage. Compared toa standard five-gallon toilet, a vacuum-assisted toilet requiresonly three pints of water. The reduced sewage means smallerpipes can be installed, leading to lower materials cost.

Vacuum-assisted toilets also have the advantage of being able toflush horizontally or upward, allowing maximum flexibility inthe routing of pipes. Because no slope is required, as in gravitysystems, floor to floor spacing can be reduced, again savingmaterials. Venting stacks are also eliminated. Two parts com-pose the system: the bowl and a vacuum tank or pump. Onevacuum tank can service several fixtures, or even several build-ings. The atmospheric pressure causes the “flush” when thevalve to the vacuum tank is opened. Sewage can then be storedfor discharge at off-peak times.

Figure 22: Vacuum toilet systems.


Other toilet systems route the sewage to a central holding tank,where it is composted. Hence, there is no burden on the munici-pal water treatment facilities. The compost can then be used aslawn fertilizer. The composting tanks incorporate odor-controldevices.

VentilationEnergy recovery ventilators are designed to bring in fresh airand exhaust stale air, while recovering up to 85% of the energythat was used to heat or cool the outgoing air. The incoming andoutgoing airstreams don’t mix: there is an energy transfer discthat moves heat from one stream to the other. Moisture isremoved and released by a silicon coating on the disk. Unlikehumidifiers, there is no drain pan to promote bacterial growth.In winter, the ventilator can use electricity to pre-warm air,although even without electricity it recovers enough heat towarm incoming air up to 60% of room temperature.

Figure 23: Heat and moistureexchange disk in a heat-recoveryventilator.


Part III: Application

Guidelines

The process of specifying environmentally friendly buildingproducts is no different than that for conventional buildingproducts: the materials needed must be determined, data mustbe gathered on comparable materials, and products must beevaluated. Environmental considerations need not be the only,nor even most important, factor when selecting building mate-rials. The key consideration is appropriateness for certainfunctions. The longevity or insulation value of certain materialswith a high embodied energy can sometimes justify the environ-mental costs of their manufacture. Overall, becoming moreinvolved in materials and systems choices means the architectgains more control over the quality of the finished building.

Determining Need

Considering materials in more general terms based on function(“flooring” over “carpeting”) is useful for opening up possibili-ties to use alternative materials. Floor coverings are available inwide range of materials. Is carpeting necessary for the area inquestion, or would more durable tile be a better choice? Ifcarpeting is deemed necessary, can wool be used instead ofpetrochemical-based fibers? In many cases, the performance ofnatural materials meets or exceeds that of synthetics, at a muchlower environmental cost.

The quantity, as well as type of materials to be used in construc-tion are important. CAD systems with integrated spread sheetsmake calculating required square footage or volume of materialsmuch easier. This helps the architect focus on the materials withthe largest potential impact on the environment. Use environ-mentally friendly materials particularly when the volume ofmaterial needed is large, or it is exposed to air or contact withusers. By using high embodied energy materials only whereneeded for their specific qualities, natural resources are pre-served and pollution is reduced. Aluminum, for example,should be used only where its light weight and anti-corrosioncharacteristics cannot be matched by another material. Usingrecycled aluminum is even better. Plywood used as sheathing isgenerally sealed behind drywall, where glue emissions cannot


enter the breathable air. Materials used in interiors that emitvolatile organic compounds (VOCs), like plywood for furniture,can be sealed in plastic laminate or with a painted finish, reduc-ing or eliminating outgassing. This however adds to the cost,and the laminate or paint can create their own outgassingproblems. A better choice would be plywood made withoutglues that outgas.

Determining how much of a material will be used and where isthe first step. The timing of the installation process is alsoimportant. Materials that are to be installed with adhesives thatoutgas should be installed well in advance of building occu-pancy, and the ventilation rate of the building should be increasedfor at least the first year. Repairs or replacements of suchmaterials should be scheduled to coincide with a building’sdown time, (over the holidays, for example) so the impact isreduced.

Analyzing Products

The data gathering part of the materials selection process iscurrently the most difficult, as sustainable building materialscompose a small percentage of the market. The AmericanInstitute of Architects has published its “Environmental Re-source Guide” to assist in the selection of general types ofproducts based on analysis of the raw materials. Manufacturer’sproduct data sheets are still the best source for specific brands ofproducts, but it must be recognized that these are promotionalmaterials. Product specification sheets, produced for marketingpurposes, may not provide objective data, and the data may notbe easily comparable with competitive products. Architects arein a position to encourage the production of wider variety ofsustainable materials by contacting manufacturers for morespecific information and refusing to specify materials madethrough highly pollution processes. Insist that product datasheets list chemicals used in manufacturing or that will beemitted by a material over time. Fire safety is also an issue, asmany otherwise benign substances (like foam rubber) can be-come toxic when exposed to high heat or flame. Contactingmanufacturers for more specific information serves two pur-poses: it increases the architect’s knowledge base of materials,and makes the manufacturer aware of interest in sustainablematerials. Only through knowledge of the entire life cycles ofotherwise comparable building products can an intelligent, in-


formed choice be made. By insisting that manufactures revealtoxicity levels and the environmental impact of the manufactur-ing process, architects can also apply pressure for manufacturersto clean up.

Evaluating Performance

Some sustainable building materials rely on new technology,others reinvigorate centuries old methods. The latter have atrack record that makes performance easier to anticipate andevaluate. New technologies require testing by time. Advicefrom other architects and building owners using new technolo-gies can assist in determining long range effectiveness. Regularpost-occupancy studies of buildings - conducted periodicallythrough a building’s life — are also extremely valuable fordetermining how well a new material functions and how itaffects the comfort of the building occupants. This information,when shared with other architects and building industry profes-sionals, can become a powerful tool for advocating sustainablematerials.

References1 American Institute of Architects, Environmental Resource

Guide Subscription, (Washington: American Institute ofArchitects, 1992).

2 Ibid.

3 Paul Graham McHenry, Jr., Adobe and Rammed EarthBuildings: Design and Construction, (New York: John Wiley,1984).

4 Alphonse J. Dell’Isola and Stephen J. Kirk, Life CycleCosting for Design Professionals, (New York: McGraw-Hill, 1981).

5 American Institute of Architects, Environmental ResourceGuide Subscription.

6 Ibid.

7 McHenry.

sustainable building materials

Documents

phases of building materials

educational materials

building phase building

background materials

similar materials

dana building

building component

gathering of raw materials