Of all the aspects of Green building, material selection is probably the most difficult, if for no other reason there isn't good information generally available, and when it is, its usually provided by the manufacturer, who may or may not be reliable.  To really understand the impact of a material you need to understand Life Cycle Analysis (LCA), which looks at all the impacts of a product from the raw materials that it is made of, through manufacturing, its use during its lifetime and finally its disposal.  Even if manufacturers were upfront about what went into a products, there are so many variables involved with its use and disposal (whether recycling, reusing or throwing it out), that generating any kind of hard numbers is quite difficult.  Of course there are always averages, or reasonable expected outcomes, and it can certainly be argued that making some assumptions is better than have no information at all.  Until better information is available, a good rule of thumb is "buyer beware", because no matter what a manufacturer claims, many products just haven't been around long enough to know how they will perform in the long term.

Just selecting a green material doesn't guarantee that overall result could be considered green, because there is an aspect of how much you use also.  In this sense, small home advocates will argue that no matter what material they are using, the impact is less, because they are using less of it (see the design section for more on this).  While the square footage of a home isn't an accurate indicator of how much material is used in it, it still is the case that using less material is often the biggest impact you can have.   Beside designing a home to be just the right size, two other techniques have been used to reduce material consumption: design to minimize waste and using structural materials a finish surface.

Designing to minimize waste can involve a lot of things, some of which are fairly easy to do and others are more difficult. The simplest thing is to plan for the use of materials up front as much as possible: you often can make it so that if you cut a pile of wood a certain way, many of the short pieces are also useful.

In the big picture, the motto is the same as anywhere else: "Reduce, Reuse, Recycle".

What Makes Something Green?
Determining whether a product or material is "green" has been a challenge ever since the first time the question was asked, and continues to be one, but various people and organizations have developed guidelines to help sort it out.  The general rule is that a product has to have a significantly better environmental impact than whatever the commonly used product is, and can't have any really terrible impacts.  Of course these decisions are subjective, and some find them relatively arbitrary, but in most cases there is fairly common agreement as to what is green. The principles used to determine whether a product is green, are generally as follows:

First, the product must be made of materials that at least have the potential to be used sustainably.  This implies that the product is either reusable, recyclable into the same end product (not one of lower value), or can be harvested sustainably.  Products that have a greater longevity are generally preferable, as they are generally closer to sustainable use than shorter lifetime ones, that tend to end up in the landfill.

Second, the manufacture, use and disposal of the product must not release significant toxic byproducts into the environment.

Third, a product which uses less energy in creation is preferable. This energy (called the embodied energy) is a part of the final product as much as the other raw materials that go into it.

There is a wide variety of strategies to satisfy these principles, and any strategy that keeps materials from ending up in the landfill is likely to be at least a very good start.   The old slogan "reduce, reuse, recycle" applies to construction as well as anywhere else.  The first question to ask is whether you need to use the product at all ("reduce") .  The next question is can you reuse a material that have been used before.  The key to reuse in most cases is find products that can be used with minimal processing, although some materials (e.g. an quarter-sawn solid oak door, or other finish woodworking) have high value and are worth the time and money to restore.  Ruling those option out, using a recycled product is an improvement over using new because you are adding another lifetime to a material before it ends up in the landfill.  Unfortunately, recycling often results in a different product than the original, and often that recycled product itself cannot be recycled, for example dimensional lumber ends up as particle board and can never be dimensional lumber again.  Because recycled products are also often a conglomerate of materials, there is an additional barrier to recycling because you typically have to separate out the components to recycle them (in the case of particle board, you'd have to eliminate the glue to recycle the wood particles, or alternatively separate out the glue to use as a raw material). Until there is pressure and/or financial incentive to do so, there is little hope of developing the technology to recycle all products, and construction "waste" will continue to fill landfills everywhere.  Obviously any process that works by separating components while its recycling is likely to be better than one that requires separation as a separate step. 

For a material that is renewable (wood, straw, etc), the strategy is usually to avoid over harvesting it, reuse it however possible (even if its in a lesser material), the let it biodegrade when it is no longer reusable.

Some inorganic materials (cement, metal) are easily recyclable provided you can separate out the material you want from what ever it is bound up with.  In the case of cement, its most often found as concrete which is only about 15% cement.  For metals, its a mater of stripping away whatever wood, plastic or other metals to get at the one of interest.

Other inorganic materials (brick, stone, tile) could be reused as is for a few lifetimes, if  you can separate them from the cement or glue that are set in.  Polished stone slabs can also be reused, but since they usually have holes cut in them (sinks), there is less flexibility in subsequent uses.

As a rule of thumb, the more components a product has, the harder it will be to recycle.

Since a discussion of the thousands of building products available is far beyond the scope of this document, we will cover just the most commonly used raw materials and just a few common used products.  For a brief comparison of the various structural building techniques, see the construction section.  For information on the toxicity of various materials, see the toxics section.

Wood/Wood Products

Although less common in other parts of the world, wood use in residential construction is ubiquitous in the United States and Canada, for a number of very good reasons:  In most of the regions it is relatively plentiful, it is easy to work with, it is durable when taken care of, and can be made to withstand earthquakes relatively easily.  On the flip side of the coin, we have consumed our wood resources beyond their ability to grow back for so many years that we are now a major importer of wood.  Politically, environmental groups, the government agencies, timber companies and other people affected by logging have been battling over what is reasonable for many years, and although it sometimes appears that both sides are coming to a reasonable compromise, it may be a long time yet before they actually agree on anything substantial.

As environmentalists, but also as wood users, we believe that a reasonable compromise is possible, and a key component of that is to reduce the overall demand for wood products by using them more carefully. We can no longer use any old growth, unless we are going to set aside land to regenerate whatever old growth we log off, and politically there seems to be no desire to do that: on the contrary there is pressure to continue to log the little bit that's left and convert it to rapid rotation forestry.  As designers and builders, we have to avoid specifying and buying it, and the problem will then fix itself.

In the push to improve the way we manage our timber resources, a couple of programs have been created to sell wood that comes from better managed forests.  The Forest Stewardship Council (FSC) is an independent, environmentally minded organization that acts as a third party certifier for companies that handle wood products.  Under the FSC program, a forest owner pays to have their timber harvesting program inspected on a regular basis and receives a certification only if they meet FSC's fairly strict rules which are tailored to the climatic zone and specific ecology of the land in question.  When a customer purchases FSC certified wood, not only has the timber harvest been certified sustainable, but everyone along the "chain of custody" who processes that wood has been certified as to their ability to accurately track certified and non-certified so that the customer knows they are buying certified wood.

To compete with FSC, the timber industry has their own program of self monitoring, but given the number of people in the industry with aggressive anti-environmental stances, it is not likely that many consumers will trust a system that is akin to the fox watching the chickens.  The biggest failing of any of these programs is that sustainability is "forever" (or at least a very long time), and there is little to stop anyone from dropping out of the program, which in some ways invalidates any claim they've made in the past.  Since the programs are relatively recent, and represent only a small portion of the wood cut every year, only the future will tell what effect these programs will have. In our view, no significant change will result until society as a whole assumes and demands that our forests be maintained sustainably, and rather than resorting to best case scenarios about what sustainable means for a particular parcel, companies will take the concept seriously and consumers will seriously punish those who don't.

Wood use in homes can be divided into three categories: framing lumber, of which the house is built out of, exterior finish lumber such as siding, roofing, casing, fascia, soffits and barge boards,  and interior finish lumber, which includes flooring, cabinets and trim.   There are a range of substitute products for both situations, and each has its own set of limitations.  As with any other product, the key concepts are always "reduce, reuse, recycle".

Framing

Homes use a lot of lumber: according to NAHB the average house uses 13,127 board feet of framing lumber.  One possible way to reduce wood use is to use an alternative building method to build walls, such as straw-bale or cob, but in each case there are complex tradeoffs, and actual wood use will depend on many factors (for a more complete discussion, see the construction section).  Without taking any radical departures in building technique, there are a number of ways to use wood more efficiently in building.

Build small, simple structures
While building small will generally requires less wood use, the shape and complexity of the structure is equally important (see design for more info). Unless you do framing layout on a computer, there is no easy way to compare the lumber use of one design .vs. another.

Use only the minimum amount of wood necessary to make the house structurally sound
This question has no easy answer, and certainly depends on the conditions you want the house to be able to withstand: earthquakes, tornadoes, hurricanes, snow loads and a room full of dancing people, being the most common.  Local building codes define a base level of structural integrity, but whether this level is actually a good choice isn't as clear.  The idea behind "advanced" framing (circa 1980), was to give a set of framing techniques that reduced wood use, increase energy efficiency all while preserving structural integrity.  For various reasons, its not clear if those techniques are actually used.

Minimize waste
Although some promote the idea of designing to take advantage of standard lumber sizes, this is much easier said than done, especially in small houses where every space is designed to be just the right size. One alternative is to layout wood use so that a piece cut off one place can be mostly used some place else. Since doing this is difficult, a second best system would be to keep piles of cutoffs, and go looking in the pile every time you need a less than whole piece. Of course, this involves extra effort on the framer's part, although some simple strategies can help, like always going to the cutoff pile when you need a piece of blocking.  If it were cost effective to build wall panels off site (like is done for roof trusses), then someone could layout the each wall panel on a computer and the factory could not only reuse many of the cut off pieces, but could potentially use the short pieces to make finger jointed wood on site.

Use reclaimed wood
Building departments won't let you use reclaimed wood for structural uses unless its been graded by a certified inspector, but it can still be used for non-structural uses, and that can be a lot of lumber.

Use engineered wood products
Engineered lumber  uses smaller diameter pieces of wood glued together to form a larger unit.  In some cases the engineered component uses less wood volume than the comparable solid wood component (TGIs), but in other cases it doesn't (glu-lams).  Many engineered wood products are made of small dimension trees, which more closely matches the forest management strategies of timber companies, but is not necessarily more environmentally friendly.  Some products, like particle board and finger-jointed lumber are made from the waste from producing other wood products, and so increase the efficiency in which the tree is used.  Many builder have converted over to using engineered lumber for a variety of non-environmental reasons: cost, product availability, and comparable quality.  The last issue is interesting, because as old growth lumber disappears and smaller diameter trees are used, the general quality of dimensional lumber has gone down, and problems with warping have gone up.  Engineered lumber products are made to be very straight and stay that way.  On a performance basis, engineered lumber compares very well  with comparable solid wood products and in most cases will not fail any faster under extreme conditions (e.g. fire, rot), but there are clearly exceptions.  

Plywood & OSB
Plywood was one of the earliest forms of engineered lumber and was used largely to replace 1x8 board sheathing and subflooring, and actually has far superior shear stress properties than the wood it replaced.  Unfortunately plywood was originally made from old growth logs, and over time mills have converted to using smaller logs.  Plywood still requires somewhat larger logs than OSB, because the logs are peeled to produce the layers that make up the plywood, while OSB is made from small slices of wood that can come from very small trees.  Of  course, just because younger trees can be used, doesn't mean that the forest has been well managed, and in fact many have accused the industry of doing just that.  Even if OSB was a more environmental product, some builders will not want to use it because it is more vulnerable to water damage than plywood (apparently due to having more exposed end grain, which soaks up water faster).  The current state of affairs is that most builders use OSB instead of plywood because it is cheaper.

Exterior Finish Lumber

Even if wood is not used for siding or roofing, there is still often a lot of exterior wood used, especially in a house with a "traditional" look.  There are currently few or no alternative products for most of these applications.

Wood siding - although popular in the past, in most climates wood siding, whether the clapboard style, cedar shingles or panels like T-111 siding, will decay rapidly if not painted or stained, and requires frequent re-applications.  For this reason, wood siding is not common any more.  Louisiana-Pacific makes and engineered siding, usually called LP siding, which is just like OSB.  In its original formula it was prone to moisture damage, and the result was a large class action lawsuit against the company.  They now have a replacement product which they claim eliminates the problem of moisture damage (check details).

Roofing - Cedar shake roofs are a traditional look in some regions of the country (in particular the pacific northwest), but due to decay have also become much less popular.  Cedar is a limited and diminishing resource and many products are superior to it.  Asphalt composition roofing is the most common product used.

Decks - While wood was always the product of choice, many people have turned to various plastic lumber products for decking (e.g. Trex), most of which are made out of recycled plastic bags.  Since these products are inherently not structurally strong, the deck supports still need to be wood.

Interior Finish Lumber

In many ways wood is the perfect material for interior finish because it is easy to use and considered beautiful by many people.  Because there is no structural requirement for finish lumber, a wider variety of wood products are suitable, including reclaimed and finger-jointed lumber.  FSC certified flooring and other hardwood products is often available in a number of wood species.  

Particle board/MDF/MDO - composed of sawdust and glue pressed together with glue, these products make use of a waste product (sawdust) and so have some environmental appeal.  Unfortunately most particle board uses Urea formaldehyde glue ("interior glue"), which off-gases formaldehyde for many years.  Recent innovations in Europe have found additives that force the Urea Formaldehyde glue to off-gas quickly, which is necessary to meet the European E1 standard for formaldehyde emissions.

Medium Density Fiberboard (MDF) is a particle board that has more glue in it, and so is one of the worst offenders for off gassing when you buy "interior" grade.  Select a MDF that is exterior grade, or is sold as a low VOC product (for example Medex and Medite).  MDF is also a common building product, used mostly in finish trim.  

Strawboard, made out of compressed straw is available as a replacement for particle board.  Strawboard typically is made with little or no glue since the lignin in the straw will bind together when subjected to heat and pressure.  Most strawboard is also covered in a melamine veneer, which is derived from petrochemicals (find out where this sits in toxicity of manufacture).  A better option is to find a strawboard that is covered in a wood veneer.  Straw is a waste product from growing grains and is very plentiful, although virtually all grains are grown using petrochemical based fertilizers  (Note: verify its really a waste product, especially in the case of organic grains.

Cement/Concrete

Like wood, cement is ubiquitous in construction, being a part of concrete, brick mortar, and fiber cement products. The manufacture of cement accounts for five percent of the world's total energy consumption, and the average home requires 14 tons of concrete (about 7.5 cubic yards), which takes the equivalent energy of 75 gallons of gasoline to manufacture (this number seems way low, it ought to at least 25 yards if not 40, depending on whether there is a basement).  (any info on percent in residential/commercial/roads?) Of course cement is also an incredibly flexible product for which there is no substitute.

Pure Portland cement is an excellent glue, but is otherwise not strong at all, so cement is always mixed with other materials and is only the glue that hold them together.  Concrete is a mixture of gravel, sand and cement; mortar is a mixture of sand and cement, and fiber-cement products use various fibers (wood, fiberglass) mixed with cement.  In all cases, water is added to cement and it undergoes a chemical reaction which causes all the cement molecules to bind to each other.  Not every Portland cement is the same, and there are hundreds if not thousands of formulas for concrete. The main identifying feature of concrete is its compressive strength (the amount of weight it can hold up), and that is largely due to how much Portland cement is put into it.  Because concrete is not flexible, it has little resistance to bending, and as a result almost all applications of concrete require some kind of metal reinforcing: either re-bar or wire mesh is typically used.

Since the biggest environmental impact of concrete is the energy used to make the Portland cement, the focus of environmental building has been to use less of it.  There are three approaches typically used: substitute flyash, use insulating concrete forms and substitute a completely different material.

Flyash is a byproduct of coal burning power plants or waste from blast furnaces (iron making) and has properties similar to Portland cement, and since it is a waste product it makes a better environmental choice.  Flyash comes in two varieties, called "class C" and "class F", with the difference being that class C can directly replace Portland cement, while class F can reduce the amount of Portland cement used, but not replace it.  (See EBN,V8#6 for a more complete discussion) Different kinds of coal produce different flyash. In both cases, flyash typically makes a stronger, more chemical resistant concrete, but achieves its strength over a longer period (Concrete strength is usually given as the strength is gets in 28 days: flyash concrete can take twice as long to achieve that strength.  In residential construction, flyash concrete is still strong enough in a couple of days to begin framing, and so does not impact schedules)  Flyash is often an added to concrete to make it flow better, and in that case it does not reduce the amount of Portland cement used. Unfortunately much of the flyash produced has too many impurities in it (typically carbon) to make a good cement, and in addition since much of it is the result of burning coal, it is clearly not a renewable resource.

Assuming cement quality flyash is available, is can be used to replace anywhere from ten to fifty percent of the Portland cement needed for a particular concrete mix.  The downside is that it finishes different from normal cement, and so the concrete installers have to be experienced with it- particularly when using it for slabs.  Flyash concrete also doesn't reach it full strength for much longer than normal cement: the standard is that it reach full strength in 28 days, while flyash concrete can take up to three months.  In spite of these drawbacks, many people are learning to work with it, and some are experimenting with using greater than fifty percent.   As a rule of thumb, using 15-20% flyash as a replacement for Portland cement is easy to do. 

When using a flyash mix, it is important to make sure the flyash is replacing cement, not sand and gravel. Compare how many sacks of cement were used to how many are normally used, rather than the percentage of flyash.  A typical mix uses five sacks of cement (500 pounds).

Insulating Concrete Forms (ICFs), are a material that acts as both the form for a concrete wall, but then stays in place to act as insulation.  Using an ICF wall instead of a regular poured wall can use 50% less concrete.  ICFs are typically made of polystyrene foam, and there is a product made with recycled polystyrene and cement, as well as one made with waste wood chips and cement.  More on ICFs is in the construction section.

If a basement isn't needed, the house can be built on a crawlspace instead, using either a post and pier support system or a pin foundation (find out more about these), but since there are other issues in using a crawlspace, these must be considered also (see healthy home section).  When using any kind of post system, larger diameter pieces of wood are used to replace the one piece foundation, so there is a tradeoff between wood and concrete.

A more radical idea to reduce concrete usage it to construct the floor slab out of earth instead.  Cob (a mixture of straw, sand and clay) is the ideal material, because once dry it hardens like concrete.  Because Cob does not set permanently like concrete, it must be protected from water, by a sealer of some kind (eg linseed oil). Given it vulnerability to water, one would think it wise to raise the slab up above the ground somewhat as an added protection against ground water (beyond the usual sand/gravel/polyethylene sheet system). (Find out more about this..check to see if Robert Bolman has a web site).

In any attempt to use less concrete, a creative structural engineer is almost a must, both in getting past the building department and making sure that the building will still last for a long time.

Fiber-cement products have recently become very popular both for siding and roofing. They have the advantage to being relatively rot-proof (although they do wear out, and acid rain would be a significant enemy of these products) and dimensionally stable, which means that paint will typically last much longer on fiber cement siding than it does on wood.

Iron/Steel/Other metals

Metal is both easy to recycle and frequently recycled.  Iron & Steel products in particular often contain a high percentage of recycled content.  The other metals commonly found in homes all have a high value in the scrap yard, and so presumably are often recycled.  Aluminum is made using large quantities of electricity, but much less for recycled aluminum (verify this).  Copper and Brass are the other two common metals.

Steel studs have replaced 2x4s in commercial construction, but are not commonly used in residential construction.  They require a similar amount of energy to produce (see EBN xxx), but the materials otherwise have different environmental impacts.   Steel studs are usually only used in non-load bearing application (ie dividing walls that carry no weight from the upper floor), but have the advantage of being perfectly straight, and pre-drilled for electrical wiring.  Since you can't nail into them (screws are used), you can't attach trim with finishing nails, so special consideration must be given for that situation.

Steel (along with Aluminum) is used for roofing, which comes in both "standing seam" and a variety of shingle type patterns, where a option for the single pattern is "stone coated".  All metal roofing is very durable, and typically will last a very long time. Standing seam roofing is mostly used in light commercial and rural residential applications, as well as in high snow areas because it sheds snow very well.  The shingle type roofing and its stone coated variant are more recent additions and because they are quite expensive are often used on higher end construction.

Plastics and Petroleum derived materials

The use of synthetic material in homes has grown enormously and is responsible for most of the thousands of VOC that can be detected in most new homes (see the section on healthy homes).  Aside from the possible impact on the homes air quality, many plastics produce toxic byproducts during a fire (although that could be a rare enough event to be not relevant to most people), and their manufacture also produces toxic byproducts, some of which seem to inevitable end up in the air and water. In the particular case of PVC, Greenpeace has been on a long term campaign to ban it, and the movie "Blue Vinyl" documents the effect of PVC factories on small communities in Louisiana.

Virtually all synthetic materials are derived from petroleum, which is a non-renewable resource, but recently there has been research into plastics based on alternative sources.  Other than vinyl siding, the total weight of synthetics in a home is only a small percentage, and the embodied energy isn't all that high compared to the energy used to operate the building (verify this--get numbers).

Synthetic materials are ubiquitous in our lives for a good reason: the are cheap, easily mass produced and often out perform all alternative materials.  These materials are commonly found in electrical components, weather stripping, gaskets, plumbing pipe, and caulks and glues, insulation, siding, window frames and decking.  We examine only a few of these:

Foam insulation - this includes polystyrene (Styrofoam), polyurethane, and polyisocyanurate (Polyiso) in both board and blown in varieties.  In each of these cases, a plastic is "blown" with a gas to create a foam that has a large number of voids incorporating the gas, and hence a high insulation value.  The first versions of these were blown with CFCs, and then later with HCFCs.  The current trend is away from all of these materials, and toward more environmentally benign ones.  At the current time, one must know not only the product, but the manufacture to know what blowing agent was used in the product.  All of these products are derived from petroleum, which is not a renewable resource, but they could theoretically be made from alternative sources.

In spite of these issues, foam insulation has some significant benefits.  For use under a concrete slab or other buried locations, foam board is the only material applicable.  Also in situations where there is limited space, the greater insulation value of foam board provides more insulation for the amount of available space.  As part of an SIP, foam board is the only insulation strong and dense enough to make a functional panel.  For more info on insulation materials, see the energy section)

Vinyl windows - although they perform better than aluminum windows and are low cost, their lifetime is not anticipated to be long due to the stress induced into the glass by temperature driven expansion of the vinyl frames.  In addition vinyl is a highly toxic material to manufacture. Paint does not stick well to vinyl.

Fiberglass windows & doors - compared to vinyl, aluminum or wood, fiberglass windows are doors are better performing alternative, because they offer weather resistance, dimensional stability (they don't move much with temperature or humidity), and higher R-value when the hollow frame is filled with insulation (typically blown in foam).  Fiberglass windows are paintable.  Some manufactures are now offering a "wood clad" interior to make them look like wood windows on the inside.

PVC pipe - PVC pipe as a supply line is banned in many locations. ABS?? for drain?

PEX pipe -  PEX is short for Cross-linked Polyethylene, which is polyethylene plastic that undergoes a chemical process that bonds the various molecules within the plastic to each other, making it more chemically stable, and thereby eliminating the "plastic" taste that comes with normal polyethylene containers.  Although it is vulnerable to chemical attack and degradation due to ultraviolet light (ie sunshine), it is not normally exposed to either.  Compared to copper pipes, PEX is much easier to install, and so significantly cheaper.

The main advantage of PEX is due energy savings by reducing the amount of wasted hot water left in the pipes when the faucet is turned off. This is due to the fact that it is installed like electrical wiring, with a main distribution manifold, and a separate pipe run from the manifold to each plumbing fixture in what is refered to as a "home run" configuration.  In copper plumbing, code requires that the shared pipes be large enough so that many faucets can be run at once, but in reality this rarely happens, and the large diameter pipe just leaves more hot water behind wasted.  The difference between the two strategies can easily be a half-gallon to a gallon of hot water every time a faucet is turned on (after the hot water from the previous use has already cooled).  Of course, copper plumbing could also be installed that way, but it would be much more expensive.

Vinyl siding - Vinyl is short for Poly Vinyl Chloride, or PVC, a plastic that is made of toxic materials, and whose manufacture has historically been very polluting (see www.bluevinyl.com).  While vinyl siding is very durable and long lasting, its environmental impact is far beyond acceptable.  Even if it were possible to clean up the vinyl manufacturing plants, the risk to produce vinyl does not seem worth the benefit, since there are undoubtedly alternatives.  PVC by itself is fairly rigid, and in order to make it soft a "softener" is added to the plastic: typically a phthalate of some kind, many of which are deemed to be toxic by various sources.  Vinyl is unfortunately very common in electrical components.  For all these reasons, vinyl siding should be avoided.

Plastic lumber/decking - most of these products are made from polyethylene derived from plastic bag recycling, often combined with sawdust.  Although they are mostly limited to non-structural uses, they perform very well as both decking and landscape timbers, since they are highly rot resistant and surprisingly not slippery.  (do they have UV stabilizers in them, or is polyethylene fairly UV resistant?)

Composition (asphalt) roofing -  traditionally made from natural fibers impregnated with asphalt, most of the better composition roofing is now made with fiberglass fibers (verify this!), and as a result composition roofing is now offered in 40 and 50 year warranties.  Old composition roofing is "recyclable" but its unlikely that it is used for new roofing (where does it go?  does the asphalt degrade in the sun?  reference to EBN article?)

Carpeting - most carpeting is the synthetic variety, typically made of Nylon.  Large quantities of carpet end up in the landfill every year, although carpet manufacturers are making great strides in recycling old carpets.  Many carpets have a significant number of additives, such as stain blockers and can be a large source of VOCs  (what is the typical "curing" time?).  An alternative synthetic carpet is made from PETE, sometime from recycled pop bottles, and typically produces a lower amount of VOCs (verify this).  Also available are natural fiber carpets, which have their own set of problems (NOTE: get some references and more details info.. try EBN, EPA or just google carpet.  Also check Carpet and rug institute web site).

No matter what type of carpet you choose, all carpets are havens for dust and dust mites and will absorb and re-emit odors and other VOCs.  Even if the carpet itself is benign the backing can be a source of VOCs, and the underlayment is often the worst offender.  In general, healthy house experts recommend that you avoid permanently installed carpet completely and use area rugs instead, sending them out to be cleaned.  (but what about the cleaning fluid?  If carpet doesn't really get clean, then why would rugs get any cleaner?)

Laminate countertops - (what are these things made out of?).  They're very low cost, but they don't last long, and aren't recyclable, so as a result they all end up in the landfill.  Because of their low cost, laminate counters are by far the most popular choice.  

Paints - paints consist of a pigment (which is typically a powder), a binder (which is typically resinous or plastic) and a solvent which keeps the paint liquid until it evaporates.

Pigments are either an inorganic material that is mined (typically some kind of ground up rock, or a metallic compound), or an organic material (derived from a plant, or more typically from coal tar or petrochemical based).  Older paints were often made with lead and other heavy metals, and so can be quite toxic.  These pigments are benign as long as they stay encased in the oil binder, but when the flake or are scraped or sanded they can easily release heavy metal dust into the air, with potentially serious health consequence.

Until the discovery of latex paint, the only choice was oil paint (?except what about lime washes and milk & egg based paints?), which uses linseed oil (from the flax plant) as the binder and solvent.  These original oil paints dried very slowly, taking two or more days to dry to the touch. Modern oil paint contains alkyd resin as an additive, and produces a relatively fast drying  paint (dry to the touch in just a couple of hours). Unfortunately along with the alkyds came additional VOCs, some of which are quite toxic.  It should be noted that simple oil paint is not free of VOCs, as the linseed oil emits VOCs as part of the oxidation reaction that causes it to harden.

In latex paint the binder is a polymer and the solvent is mostly water, so as it dries most of what evaporates is water.  Unfortunately additional solvents are often needed to get the paint to stick better and to work with some kinds of pigments.  (more info?).

clear finishes - this category includes varnishes, waxes, shellac, lacquer, drying oils and plastics such as polyurethane, and typically consist of a resinous material dissolved in a solvent.  Most traditional clear finishes are derived from plants (e.g. varnish is from tree sap), and contain a fairly high level of VOCs.  Newer polyurethanes use water as a solvent, and so have lower amount of VOCs.  Unfortunately clear finishes are not interchangeable, as they have different hardness's and  water resistance.  In addition, some sit on the surface of the wood, and some are absorbed into the wood.

caulks - latex, silicone, many others.

glues - urea formaldehyde, phenol formaldehyde, MDI, woodworkers (aliphatic resin?)

Other Materials

Tile/Stone/brick -  Tile is made from clay and typically glazed with a glass like mixture colored with pigment, of which some pigments are heavy metals.  All the materials are relatively abundant, and with the exception of glazes that contain radioactive elements, tile is environmentally benign.  Old tile all ends up in the landfill, and probably the only reason its not recycled is that its probably much cheaper to mine new material than separate the glazes from the tiles.

Brick is also made from clay (and sand?), but unlike tile, old bricks come loose from their mortar fairly easily and can be reused as is (sometimes with a lot of mortar chipping!).

Stone, including granite, marble and travertine is a relatively inert material, although some stone (particularly granites) have a relatively high level of radioactive impurities.  When mined locally stone is a good environmental choice, but most granites and marbles come from far away.

Sheetrock - sheetrock is a sandwich of gypsum and paper, sometimes (always?) reinforced with fiberglass fibers.  The materials in it are relatively abundant, and the gypsum is easily recycled.  Gypsum is a naturally occurring deposit that is mined in many locations, and is considered non-toxic.  The main problem with sheetrock is that it absorbs many VOCs and so can be highly contaminated. 

Sheetrock is used in virtually all houses because it is the cheapest available product and gives a look that is generally pleasing to most people.

Insulation
A comparison of insulations can be found in the energy section.

Reused/Recycled Materials

There are many uses for reused materials in construction, although most typically they are high value finish materials.  Some materials are very easy to use, and others require a lot of effort.  The biggest difficulty is that many of them require a lot of time to gather and a lot of space to store them.   Unlike new materials, reused materials often come in weird sizes, and often are one of a kind (or at least not in the quantify you want), so you typically don't go looking for a specific thing.  Rather you find something you like, and try to find a place to put it.  

Of course, the best reused material is one that is left in place and just refinished.  Assuming that isn't practical, there are three classes of reused materials, each one with its own level of difficulty.

Reclaimed & Re-manufactured

These are products that someone else has reclaimed and is selling in a form ready to use. Common products in this category include re-milled timbers and re-milled flooring.    Another example is finger jointed wood, which comes both as 2x4's and in moldings. In general these products are drop in replacements for the equivalent new product.

Salvage

These are products that someone else has removed, but they are typically in the "raw" state and need some cleaning up to be used.   You find these materials at salvage yards, and sometimes at antique stores.  Example materials include flooring, doors and their hardware, windows, cabinets and their hardware, moldings, high value wood, lighting fixtures and plumbing fixtures. It is usually in pretty good shape, but often tarnished in some way.  These materials will need some work to be usable: for example wood flooring might have a stray nail or staple and probably needs to have the excess old finish scraped off its edges.  Odd size materials is the norm.  Some of the materials, like toilets and windows can't be used as replacements for new one, because they don't perform as well.  Old toilets use too much water and old single pane windows are best used only in decorative situations.  Finally, when using any old material with paint on it, there is a high chance it contains lead, so you need to sand/cut it with caution.

Trolling

These are materials that no one has processed at all: you find them on your own site or maybe at someone else's.  You have to do all the work to remove the material as well as the work to make it useful.  This is the hardest thing to do, but also the most fun because it encourages you to be very creative.  Finding useful material in your own scrap pile is highly rewarding.

Recycled content

When you can't find anything to re-use, there is always recycled content material.  Some standard building materials like MDF already use post-industrial waste, but not many use post-consumer waste.  Most iron and steel has some recycled content, and fiberglass insulation is starting to use some also. One good example is cellulose insulation, which is often 100% post-consumer.

One dilemma that often comes up with recycled content products is that they are a composite of materials, and so many of them are difficult to recycle.

Final thoughts

In the best of worlds, when the house needs remodeling, you want your house to be easily adaptable to its new owners by keeping it in a simple shape.  You also want to make it easy to be able to reclaim the materials that have to be removed. 

For information on building systems (SIP, ICFs, strawbale etc), and a comparison of building materials, see the construction section.

Resources:

Building With Vision: Optimizing and finding Alternatives to Wood, Watershed Media, 2001

How buildings learn, Stewart Brand

Guide to Resource Efficient Building Elements, Tracy Mumma, 
Center for Resourceful Building Technology, 1997

See the material section on buildinggreen.com

"Forest Certification Growing Fast", Environmental Building News V12#4 (Apr 2003)

"Cement and Concrete: Environmental Considerations", Environmental Building News V2#2 (Mar/Apr 1993)

"The Fly Ash Revolution: Making Better Concrete with Less Cement", 
Environmental Building News V8#6 (June 1999)