© 2007-2009 Jonathan Ochshorn.contact | homepage | index of selected writings |
Following is my summary and critique of the "Materials & Resources" section of the LEED 2.2 New Construction Reference Guide, Second Edition, Sept. 2006 (updated for 2009 version: see comments in blue inserted below). My commentary on the Reference Guide can be found in the red boxes below, and within each of the chapters linked immediately above.
Premise: that aspects of manufacturing and transportation can have negative impacts on the environment.
transportation (of raw materials to processing facility; of finished products to point of use)
The negative impacts include:
using up finite resources
Some of the strategies suggested are:
re-use of existing buildings
use of salvaged materials
use of products with recycled content
use of locally produced materials (less transport impacts)
use of "rapidly renewable" resources, such as fast-growing trees or grasses (match "harvest cycle" with the life of the material when used in a building)
Cost: In the LEED rating system, most of the mitigating measures are determined to satisfy various criteria by measuring the cost of materials used (assumed to be about 45% of total building cost).
All buildings must create a space for storage and collection of recyclables. The area required depends on the size of the building:
0-5,000 sq.ft. of building area requires 82 sq.ft. for recycling
5,001-15,000 sq.ft. of building area requires 125 sq.ft. for recycling
15,001-50,000 sq.ft. of building area requires 175 sq.ft. for recycling
50,001-100,000 sq.ft. of building area requires 225 sq.ft. for recycling
100,001-200,000 sq.ft. of building area requires 275 sq.ft. for recycling
200,001 or more sq.ft. of building area requires 500 sq.ft. for recycling
This points out one of the weaknesses of the LEED system: criteria tend to be organized in discontinuous functions so that, for example, the area needed for recycling almost doubles (from 275 to 500 sq.ft.) when the building size increases from 200,000 to 200,001 sq.ft.
The idea is simple: save existing buildings instead of building new buildings. One doesn't need to save the entire building to get points; instead there are 3 possible points depending upon how much of the exterior (envelope), structure (walls and floors), and interior nonstructural elements are preserved.
1 point for keeping 75% of the existing envelope and structure, measured by comparing the surface areas kept versus the surface areas of the whole building before demolition. Note that this point does not apply if there is an addition to the existing building that is more than twice the size of the existing building.
1 point in addition to the first for keeping 95% of the existing envelope and structure.
1 point for using existing nonstructural interior elements (walls, doors, etc.) in at least half of the project (where the project includes both the existing building and additions).
The idea is to get the contractor to divert 50% (or 75% for an extra point) of waste from disposal (landfill), by finding alternate uses: recycle or reuse somewhere else. Measure by volume or weight. Doesn't count land-clearing debris. Can count the reuse of building materials where there isn't enough surface area to count for CREDIT 1.
Note that comments within the LEED manual suggest that it would be better to focus on "source control" rather than recycling or reuse; that is, try to generate less waste to begin with by more careful planning or more logical design. Yet this credit rewards the opposite. At the extreme, a project that generates only 1 pound of non-recyclable waste (but no recyclable waste) cannot get this credit, whereas a project recycling half of 100 tons of waste does.
The commentary also points out that low landfill costs in the past made recycling or reuse of construction waste "not economically feasible." This is another contradiction within the LEED approach: it suggests that sustainable design features should be implemented on the basis of profitability, it notices the negative historic results of such an attitude (i.e., the current state of the planet), yet it continues to make the profitable exploitation of the environment the "bottom line" criterion for its recommendations.
Similar to the first credit, one gets a point for reusing 5% (or 10% for an extra point) salvaged, refurbished, or reused materials in your project. Since some expensive items are difficult to find used, one is allowed to exclude things like elevators, mechanical systems, plumbing, etc. from the calculation of total building materials.
Note that this calculation is based on cost so that, at the extreme, one could get a point by finding a small quantity of an incredibly expensive object for the building, perhaps a stained glass window salvaged from the Darwin Martin house. Because it might be valued at 5% of the material cost of the building, that single window could generate 1 point.
Here, one gets a point for having 10% (20% for an additional point) of the materials in the project (with the same exclusions for plumbing, mechanical, etc.) consisting of recycled content.
Note that there are two main categories of recycled content:
post-consumer is waste generated by the end-users of the product, whether ordinary people or facilities, that is no longer useable for its original purpose. Such things as newspapers, or plastic bottles are examples.
pre-consumer refers to waste that is diverted from the manufacturing process but cannot be reclaimed as part of that same process. So, if one is making sawdust, and a chip of wood falls into the waste stream, such a chip doesn't count for pre-consumer recycling since it could be sent back to the grinder to make more sawdust. But if that same chip of wood is a byproduct of a milling operation that produces table legs, it cannot be reclaimed in the table-leg manufacturing process, and so becomes eligible for pre-consumer recycling.
The total recycled materials used for this credit are counted based on cost and must comply with the following proportions:
66.7% of the 10% are post-consumer
33.3% of the 10% are pre-consumer
In other words, one needs at least 6.67% post-consumer recycled materials and 3.37% pre-consumer recycled materials, based on cost (double this for the extra point). Where some recycled content is embedded within a product, one prorates its cost according to the weight of the recycled content as a proportion of the total product weight.
Some typical construction materials can have high scores here: much structural steel can be over 90% post-consumer recycled material, as it is made from junked American cars; while concrete "fly ash" is considered a pre-consumer product, as it is generated during the production of coal to produce electricity (a notorious source of global warming gases).
Fly ash is given a bit of a boost in the LEED rating system, by allowing its recycled content within concrete to be based on cement weight, rather than on the much heavier total weight of the concrete. This promotes the use of fly ash because cement is the pricey component of concrete (the heavy aggregate is basically free); since one gets points based on cost, having the fly ash computed as a fraction of the cement weight and cost produces a much higher valuation for the fly ash as a recycled component of concrete. To see why this is so, examine the calculations of fly ash value computed both ways (the numbers are made up so that the calculations are easy to follow, but the basic ramifications of considering only the cement show up clearly):
The weight of fly ash, measured as a fraction of cement weight = 1/2 = 0.5.
The weight of fly ash, measured as a fraction of concrete weight = 1/10 = 0.1.
The value (cost) of fly ash, prorated according to cement weight and cost = 0.5(18) = $9.
The value (cost) of fly ash, prorated according to concrete weight and cost = 0.1(20) = $2.
In other words, the value of the fly ash is taken as $9, computed per LEED according to its weight as a fraction of the total cement weight; on the other hand, it would be valued at only $2 if computed as a component of the entire concrete, while it's actual cost is $6. Go figure…
Also note that inefficiencies in the manufacturing process are rewarded (since they would tend to generate more pre-consumer recycling material); and bad habits in the production of other goods, for example, over-packaging, are also rewarded, for the same reason.
One point is awarded for having 10% (an extra point for 20%) of materials (also excluding the tough stuff as above) extracted, processed, and manufactured within 500 miles of the project site.
Again the 10% (or 20%) is based on cost so that a single diamond of sufficient value used as decorative embellishment for a building in Lichtenburg, South Africa, would presumably qualify for 2 LEED points, in spite of its dubious relationship to sustainability.
Note that the LEED rationale for using regional materials is not only to reduce the environmental costs of transportation over long distances, but also to support "the use of indigenous resources" for its own sake. The claim that "the local economy is supported..." seems specious, since local manufacturers who sell beyond the 500 mile radius would lose out to the same extent that manufacturers who sell only locally would gain. That "money paid for these materials is retained in the region, supporting the regional economy..." is questionable for the same reason, as well as for other reasons. This is an idealization of a profit-driven, global economic system that knows no national boundaries, let alone artificial boundaries defined by a 500-mile radius. It is also worth noting that, unlike other credits, the value of this credit is not measured by comparing costs of using local/regional materials to the costs of other options. It is also clear that projects that happen to be near manufacturing facilities for products that would have been used in any case get these points "for free."
This credit encourages the use of materials that are harvested from plants having a 10-year (or smaller) cycle of growth, and requires that 2.5% of the total material value (i.e. cost), excluding the tough stuff, comes from such plants.
Examples are: bamboo, wool, cotton (insulation), agrifiber, linoleum, wheatboard, strawboard, cork.
This credit only makes sense in a context where the destruction of ecosystems is considered a natural outcome of doing business; otherwise, it cannot be rationally explained. The point here is not that one should be surprised that such a relationship exists between competition and profitability, on the one hand, and ecological disasters on the other hand; but only that, once again, the LEED guidelines seem oblivious to the contradiction built into their underlying strategy: specifically, that the drive for profit, responsible for the innumerable negative impacts on the environment underlying the guidelines, is then referenced as both rationale for implementing, and criterion for judging, proposed remediation measures. What this credit points to, without actually requiring it, is scientific ("responsible") management of renewable plant-based materials, whatever their growth cycle might be. Suggesting instead that the use of plants with a short growth cycle should be rewarded makes no sense. Should we also require that the grains we eat every day have a corresponding growth cycle of 1 day? The point would be to organize the production of grain so that its use is consistent with its production cycle. One would expect a similar stipulation for products used in construction.
Note that the LEED commentary suggests that because "rapidly renewable resources may be harvested more quickly, they tend to give a faster payback on investment for manufacturers." First, this makes no sense from an economic standpoint, since "payback" is concerned only with the return on the investment, not the growth cycle of the material (especially since it's not necessary to wait 50 years for a hardwood forest to grow when it already exists); second, what does this have to do with sustainability? The commentary goes on to suggest that such rapidly-renewable resources take up less space since they can be harvested at a more rapid pace, and that this is somehow advantageous: "The land saved [?] from the production requirements of rapidly renewable resources may be used for a variety of other uses..." as if slow-growth forests are not a legitimate use of real estate?
This point is awarded when half the wood products used in the building come from responsibly-managed forests, as certified by the Forest Stewardship Council's [FSC] Principles and Criteria.
The concept of "chain-of-custody" [COC] is important here, since wood that has been obtained from forests and then used in all sorts of products cannot easily be identified as "responsible" merely by observation: it must have a "birth certificate" of sorts that proves it comes from the right family. The fraction of good wood is based on cost, which helps, since such wood is invariably more expensive. Where the wood is embedded in some other product, prorate its value using any consistent measure (weight, volume, or cost).
In the 2009 version, no substantial changes.
First posted Nov. 2, 2007; last updated 18 September, 2009 (updated for 2009 version)