© 2007 Jonathan Ochshorn.contact | homepage | index of selected writings |
Following is my summary and critique of the "Energy & Atmosphere" section of the LEED 2.2 New Construction Reference Guide, Second Edition, Sept. 2006. My commentary on the Reference Guide can be found in the red boxes below, and within each of the chapters linked immediately above.
Some of the rational for energy conservation in buildings that appears in the Introduction is repeated, although the numbers cited differ: buildings use 37% of the energy (30% in the Introduction) and 68% of the electricity (60% in the Introduction) produced in the U.S. Additionally, LEED becomes suddenly — and selectively — concerned about the working conditions of coal miners ("Mining is a dangerous occupation..."), presumably because such work makes possible atmospheric pollution associated with the burning of coal (which produces 1/3 of the anthropogenic nitrogen oxide in the U.S., a key smog ingredient; 2/3 of the sulfur dioxide in the U.S., a component of acid rain; as well as more fine particulate matter than any other activity in the U.S.).
The initial commentary also points out that the "rate of return on energy-efficiency measures improves" as fuel costs increase, something likely to happen because of global competition for finite supplies.
This notion of always measuring the usefulness of sustainability by checking its "rate of return" is typical of the LEED approach.
It is not enough to specify energy-conserving equipment and design energy-efficient buildings: one must also make sure that such designs and equipment are actually installed and operating as intended. That a properly functioning building is not necessarily the outcome of an ordinary design process is itself a remarkable admission; in any case, "commissioning" involves the following operations concerning the main energy-using building systems (i.e., HVAC&R, lighting and daylighting controls, domestic hot water, and any renewable energy systems):
First, a so-called "commissioning authority" (CxA) must be designated with experience in such things.
This CxA reviews the two documents that define the project objectives: the "Owner's Project Requirements" (OPR) and the "Basis of Design" (BOD), the latter of which is prepared by the design team.
These requirements (for commissioning) must be included in the construction documents, so they are an official, contractual, obligation of the owner and contractor. Most of the commissioning details end up in a section of the General Conditions of the specifications as well as in the specific specification sections (also bid forms and drawings where applicable) related to the particular commissioned items.
A specific commissioning plan must be developed.
Adequate installation and performance of the main energy-using systems must be verified, per commissioning plan.
Finally, a commissioning report summarizing the findings must be produced.
Note that the building envelope itself is excluded from the commissioning requirements, although the LEED commentary suggests that "significant financial savings and reduced risk of poor indoor air quality" can be achieved by voluntarily including it within this prerequisite. Also note that a more rigorous commissioning exercise can be undertaken as part of EA CREDIT 3 (see below).
This prerequisite prevents projects from obtaining LEED certification without at least meeting minimum guidelines for energy efficiency established by ASHRAE/IESNA Standard 90.1-2004. Included are requirements for the building envelope, HVAC, service water heating, power, lighting, and other equipment that are adjusted according to climate zone.
Note that these "minimum" requirements are already embodied in many state building codes.
Mandates zero use of chlorofluorocarbon (CFC) -based refrigerants in new HVAC&R systems; phase-out and conversion within 5 years for existing systems; or, where a connection is envisioned to some sort of existing central chilled water plant and "system replacement or conversion is not economically feasible," at least control of CFC leakage per Title VI of the EPA Clean Air Act, Rule 608. CFCs have great ozone depletion potential (ODP) and, per Montreal Protocol, are "no longer available in new equipment." Alternative refrigerants should be selected based not only on ODP but also GWP (global warming potential). This is not required in the prerequisite, but shows up in EA CREDIT 4 below.
Like prerequisite 2, this is something automatically complied with in most cases, as CFCs are no longer included as refrigerants in new HVAC&R equipment.
This is the big one, and can generate up to 10 LEED points, depending on the degree of energy savings. There are actually 3 compliance paths, as follows:
Energy cost savings, computed by comparing "Prerequisite 2" (ASHRAE 90.1-2004) baseline energy costs with projected costs based on a "whole building energy simulation," translate into 1 point for 10.5% cost savings, and up to 10 points for 42% savings (smaller savings percentages apply to renovations: 3.5% for 1 point; 35% for 10 points). One may indeed wonder how a building proposal can be compared to a "baseline" condition that doesn't actually exist: in fact, the ASHRAE 90.1 Standard (specifically Appendix G, Performance Rating Method) is meant to be applied to a "typical" or standard design with light framing and insulation, orientated in various ways with windows equally distributed around all 4 sides. Computer simulations are used to find an average "baseline" value (energy cost) for these presumably standard (i.e., thoughtless) designs that is then compared with the proposed (i.e., thoughtful) design.
Here, cost is explicitly made the basis of the design's sustainable "value": if it costs less, it must be more sustainable (and we'll give you more points). The LEED commentary states: "The intent is to encourage simulations that provide owners value, and help them minimize their energy costs." Of course, the idea of making environmental decisions based on cost rather than on actual environmental impact is what contributed to environmental damage in the first place. The history of energy use, and consequent environmental damage, from the abuse of timber to coal to oil, is set in motion by the same calculation of cost and profitability advocated in the LEED guidelines.
4 points are awarded for projects complying with ASHRAE Advanced Energy Design Guide for Small Office Buildings (2004). Obviously, this only applies to office occupancy and small floor areas (less than 20,000 sq.ft.).
One to three LEED points can be awarded by obtaining 2.5%, 7.5%, or 12.5% of the building's energy (measured in units of cost rather than in units of energy) on-site (e.g., from solar, wind, geothermal, biomass, bio-gas, or low-impact hydro sources). Systems can be either electrical (e.g., wind, hydro, photo-voltaic, etc.); geo-thermal (deep-earth water or steam generating either thermal or electrical energy); or solar-thermal (active solar).
In the "compared to what?" category, the LEED commentary suggests that "biomass can divert an estimated 350 million tons of woody construction, demolition, and land-clearing waste from landfills each year." The question not asked is whether the practices that result in this mass of waste ought to be changed.
This credit is an extension of Prerequisite 1 (Fundamental Commissioning...), adding the following commissioning steps:
The "commissioning authority" (CxA) must be hired prior to the construction documents phase, must be independent of the design/construction teams, and experienced in at least two building projects.
The CxA must review the owner's project requirements (OPR), the basis of design (BOD), and the design documents no later than the mid-point of the construction documents phase, rechecking later.
The CxA must review contractor submittals.
A "systems manual" must be produced, and a process for training building occupants and operating staff must be created.
CxA must review building operations 8-10 months after substantial completion (handover) or the project, and a plan must be developed to resolve anything within the commissioning scope that is unsatisfactory.
This credit is an extension of Prerequisite 3, to support "early compliance" with the Montreal Protocol. It basically adds a concern with global warming potential (GWP) to the concern with ozone depletion potential (ODP) found in Prerequisite 3. To do this, the weighted average annual "life cycle" potentials of the proposed refrigerant in terms of both global warming and ozone depletion, accounting for expected annual leakage, end-of-life loss, and refrigerant charge, must not exceed 100 (where the units combine weight of CFC and carbon dioxide in pounds for OPD and GWP respectively). Note that small units (window AC or small refrigerators) are excluded. Also note that not using refrigerants at all is another option for compliance.
Again in the "compared to what?" category, the LEED commentary notes that the "indirect" GWP of HVAC&R equipment, due to the generation of electricity off-site to power the equipment, is much greater than the actual impact of the HVAC&R refrigerants. While it is possible to lower the requirements for electricity by using more efficient equipment (and get points through EA Credit 1), there is no mechanism in LEED to measure the project's actual contribution to global warming.
The difficulty with this credit is that the most efficient refrigerants with low ODP generally have high GWP. The "natural" refrigerants" (i.e., water, ammonia, hydro-carbons, and carbon dioxide) potentially offer options, but are not problem-free (according to the Natural Refrigerants Fund: "The main barriers to the use of ammonia are its toxicity and flammability in particular concentrations in the air. For hydro-carbons the concern is their high flammability. CO2 has low energy efficiency and very high working pressures in cycles with transcritical parameters. Systems with water require turbocompressors that can pass the large volume flows. Air systems have a very good energy efficiency only at large temperature lift making them suitable for heat pumps and very low temperature refrigeration applications. The safety barrier can be surpassed using technical standards and regulations, coupled with proper maintenance and training of personnel." The LEED commentary offers no solutions to this dilemma, only the acknowledgment that "selecting the appropriate refrigerant for any given project and HVAC system may be impacted by available equipment, energy efficiency, budget, and other factors."
This credit is earned by making a plan to measure and verify energy use for at least one year, post-occupancy, using simulation or analysis methods based on the following options found in the International Performance and Verification Protocol (IPMVP):
Option "B" typically involves whole building metering for small buildings where the main energy systems can be isolated and monitored.
Option "D" is for more complex buildings where the individual energy conservation measures are difficult to isolate; it involves simulations that are "calibrated" based on actual energy use.
This credit requires that at least 35% of "grid-source" electricity is from renewable sources and is produced on a "net zero pollution" basis, for a period of two years. The "green-ness" of the energy is measured per the Center for Resource Solutions (CRS) "Green-e" certification, and includes solar, wind, geothermal, bio-mass, and low-impact hydro.
The actual power purchased need not be "green," if one uses instead renewable energy certificates (RECs), tradable renewable certificates (TRCs), etc.
According to the LEED commentary, Green-e certification means that the electricity is "greener and cleaner than the average retail electricity product sold in that particular region." The Green-e.org web site PDF (p.6, as of 10/20/07) states that "offerings must offset at least 25% of a residential customer's electricity usage with new renewables…" to be certified.
First posted Nov. 2, 2007; last updated 14 February, 2008 [natural refrigerants]