Thoughts on Sustainable Construction
The range of 'Green" or 'sustainable' construction practices is a continuum. As we design projects, we're always asking the question "How green is it really?" We find that the following little system of categories is helpful in order that we can be talking about the same thing.
1. Energy-efficient construction
Most people and U.S. building codes now recognize at least some elements of energy-efficient construction.
Some examples: careful thermal envelope design, including good windows and exterior doors; air-tight detailing and construction; heat-exchange ventilation; superinsulation; careful selection, design and sizing of energy-efficient heating, cooling and lighting equipment.
At the outer edge, this category also includes passive solar design with thermal mass; solar panels for space heating, electrical generation and/or water heating,; wind generation, etc.
2. Resource-efficient construction
The construction industry and building-materials manufacturers ~~ under pressure from consumers, rising costs and government regulators ~~ are slowly becoming more resource-efficient
Some examples: 'just-enough' design, avoiding excessive size and complexity; construction with re-used materials; use of products made in part or wholly from recycled materials; timber only from sustainably-harvested sources; minimization of construction waste; design for low water use, etc.
3. Low-toxin construction - 'healthy house'
In it's pure form this is specialized construction. It's appropriate for a small, but growing, percentage of the population with chemical sensitivities, persons with a specific disability. Of course, EVERYONE benefits from healthy construction.
Some examples: specially selected paints, adhesives and sealants; extensive use of hard-surface materials such as tile or wood floors instead of carpet; elimination or isolation of plastic-containing products and VOC's; use of steel framing to avoid turpines in wood; rigidly controlled construction site practices; low-EMF (electromagnetic fields) wiring and appliances; etc.
4. 'Natural' or low-impact construction
A goal of 'natural' construction is near zero-pollution and low embodied energy. The goal is elusive, of course, but the principle guides the search.
Some examples: alternative building technologies -- when climate-appropriate -- such as light-clay, adobe, rammed earth, straw bale; use of only locally-made and renewable 'least-processed' materials; plant-based (not chemical-based) coatings; little or no petrochemical-based materials; no PVC; use of native plant species in landscaping; safeguarding of natural water systems; integration of natural systems within the buildings, such as 'living machines' for waste water treatment; natural building cooling and ventilation; substantial indoor plantings and so on.
Generally speaking and as currently practiced, each step forward on the continuum includes the ones before it. Each step yields more sustainable results and takes you farther from today's building norms in the U.S. That is, 1. is closest to conventional practice and 3. and 4. are the farthest.
These broad categories are not rigid, of course; some of the techniques cross over. For example, imagine the wall of a house built using 10" deep Larsen trusses (instead of studs) made of recycled lumber, sheathed in low-toxin fiberboard, with recycled cellulose insulation to produce high-performance superinsulated construction using less wood and no petrochemical plastic. It should be mentioned that although 1. through 4. are all viable as construction approaches, the techniques don't necessarily all go together. Some techniques will have negative implications for affordability, at least until they become more common. Some will have a steeper learning curve, or face more code resistance, than others.
'Sustainable' building takes more.
One thing is clear however: a more sustainable project is more demanding, of everyone involved. More research must be done, more care exercised in sourcing materials, more thought given to the design phase to examine new details and materials, more care in communication exercised among the disciplines involved to integrate new techniques, more care taken during construction.
When you're planning to build, you need to decide where your project will be on the continuum of sustainability. The whole project team - the owner, the designer, the builder and tradespeople, the consultants, the materials suppliers - all must be communicating to decide how far the project is to go down the path of innovation and sustainability. To do this you must examine the skills, money, time and the will that are available for this project. There's much to talk about...
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