Tom Székely, P.E., LEED AP

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May 16, 2007

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Doing the Right Thing, Part Four



In closing last time I wrote about LEED-NC’s concern with minimum energy performance, but what was left unstated was the fact that its primary reliance is on computer modeling of the energy consumption of the proposed building.  This primary method awards from 1 to 10 points, dependent upon the percentage improvement when compared to the ASHRAE Standard’s baseline building performance.  LEED-NC also recognizes an alternate prescriptive compliance path which awards only 4 points, for office buildings up to 20,000 square feet in size, and finally recognizes a third alternate awarding only one point for partial prescriptive compliance of any type building of any size.


Computer modeling of energy consumption, while rather involved (to the point of adding $50K in consulting fees to a reasonably large commercial building) should revolve around the proposed use of such energy efficient systems so as to pay back both the differential cost of the equipment and the extra fees within 2 to 5 years, and this has actually been happening more and more of late.


The next metric in the Energy and Atmosphere rating area is Renewable Energy, with LEED-NC awarding from 1 to 3 points dependent upon what percentage of the building’s energy comes from on-site renewable sources. LEED-EB awards up to 4 points and allows for purchase of green power from off-site energy sources, with these differences again reflecting the relatively greater difficulty in trying to make an existing building energy efficient.  In both LEED-NC and LEED-EB, however, while the guidance refers to non-polluting sources, it also allows for biomass and biogas sources; i.e., combustion, which must result in the formation of CO2, which, since it’s used by green plants, is not so bad as the carbon monoxide and oxides of nitrogen resulting from the incomplete combustion in pre-EPA automobiles and industry.


This reflects the reality that, wind, solar, and geothermal sources are neither sufficiently widespread nor sufficiently high in specific power capacity to supply power to commercial or industrial users. You have to burn something, or go to nuclear power, or decide modern technological society is a net negative, and turn away from it if you expect to get energy only from sun, wind, or geothermal sources.

Green Building methods exist because modern technological society has in fact been a net positive, and the idea is to do what one can to keep it that way. LEED-NC reinforces this via the awarding of one additional point for off-site green power, separate from the 3 on-site renewable power points.  LEED-NC closes out this rating area with one point each for enhanced commissioning, enhanced refrigerant management, and measurement and verification of energy consumption over time, which completes the 17 points of a “perfect” score in the LEED-NC Energy and Atmosphere rating area.

All of the difference, and more, between that score and the 23 points of a “perfect” LEED-EB score in the Energy and Atmosphere rating area is comprised by a building operation and maintenance metric worth up to 3 points, and a performance measurement metric worth up to 4 points.

This makes all the sense in the world.  If there’s one area in which things seem to go downhill at lightspeed, it’s in the actual operation and maintenance of a building‘s mechanical systems.  The three operations and maintenance points are awarded as one point for staff education (24 hours per person per year), one point for systems maintenance, and one point for systems monitoring.

While the one point for monitoring is awarded for simple alarming to indicate out of spec conditions, the performance measurement metric awards 3 of its 4 points for continuous data gathering at the rate of one point per 4 data items, from a list of 14 such items. You don’t get the points for just measuring and reporting, however. You have to use the data in a performance improvement program, providing a quarterly report card of each item metered.  This brings us to the last LEED-EB performance measurement point, which is awarded for a measured 10% reduction in environmental emissions.

The next rating area, Materials and Resources, because it has to do with the components of construction materials, construction and operational waste products, and, in the case of LEED-EB, the use of non-toxic biodegradable cleaning products, particularly lends itself to negotiated contract and design-build projects, which, by definition, have a construction team on board while still in the design process.

The next to last rating category, Indoor Environmental Quality (22 points EB, 15 points NC), is what very often is the deciding factor in convincing a building owner-occupant to go after LEED certification. Green Building seminar lately, you’ve heard over and over again how the largest part of a building’s operating cost is the salary and benefits paid to the people who work there.

Simple math shows that small increases in employee productivity and retention have a huge effect on the operating cost of a building, with one case purporting to have generated enough savings to have paid for the entire project (not just the premium for sustainable design and construction) in two years.

The particulars of this rating area have to do with lighting, thermal comfort control, and removal of indoor pollutants, which leads to one of the “gotchas” of sustainable design.  Indoor pollutant removal is effected by outdoor air being injected into the building’s HVAC system, and the NYS Energy Conservation Construction Code in some cases calls for more outside air than is presently called for in New York City’s Building Code. A similar situation exists vis-à-vis the NYC Building Code, ASHRAE 90.1, and LEED.


That is, the cooling and dehumidification of summertime outside air is a very large part of the air conditioning load, is rather more difficult and costly than mitigation of solar heating load, and it would thus be counterproductive to increase a system’s outside air fraction. ASHRAE 90.1 continues to wrestle with this, and has thus reduced recommended outside air amounts since it was first issued in 1975.

The last rating area, Innovation, awarding 4 points in both LEED-EB and LEED-NC, also awards a final point for having a LEED Accredited Professional (soon to be me?) on the design team.

OK, that’s LEED.

Any suggestions on what I should write about next?

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