Several aspects of your building materials have environmental impact: 1)  How will they affect the energy used over the life of your home, e.g. insulation;  2) How much energy did it take to produce the material and get it into your home- “embodied energy”;  and 3) how does the use  of that material affect the environment -  does it cause forest depletion?  Does it off-gas toxic chemicals?

Probably the single biggest factor affecting environmental performance over time is how your building is insulated  Generally, the more the better.  The best kind of insulation depends on where you’re putting it, but the rigid urethane foams give the best R value per inch of thickness, about R7. They’re the most expensive, and are best used wherever space is at a premium. All plastic foams must be separated from the living space by drywall, since they will burn and give off noxious gases in a fire. Polystyrenes, (Styrofoam) give between R3 and R5 per inch.  These are most often used below ground, as they are the easiest to burn and are not affected by water.  Fiberglass, offers flexibility in where you can use it and doesn’t burn, but it must stay dry.  Blown insulations (R=3.5 per inch) can work well either in wall cavities or in attics, and they usually do a good job of filling in voids.  They are available in fiberglass or cellulose, which is recycled paper with fire-retardant treatment.

     “Embodied Energy” refers to all the energy required to get a product to its point of use, and includes energy for extraction of raw materials, transport to processing plants, processing energy, packaging materials, transport to the distribution center, and transport to the job site.  It’s especially high for metals and concrete, lower for wood, and lowest for local stone, rammed earth, or strawbale construction.

    World forests are disappearing fast.  Manufactured products such as plywood,  flakeboard and particleboard use wood much more efficiently because they can use every particle of the tree, without  waste.  They also can be produced from smaller, younger trees.  But they use chemical binders which can outgas into living spaces for years to come.  It’s best to cover them with drywall or other finish material.  Look for more use of Bamboo in coming years, as it grows much faster than other woods.  Bamboo flooring is available now. Some very nice recycled plastic products are now available for use in decks, railings, and paintable trim, using no trees and avoiding the chemicals in treated lumber.

In the final article we’ll look at choices in heating systems which can help  reduce the environmental impact.  See you then.

 

-Bruce Ward