Summary and critique of "LEED" 2009 Green Building Design & Construction Reference Guide

Jonathan Ochshorn

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Following is my summary and critique of the Green Building Design & Construction Reference Guide, 2009 Edition. Commentary on the Reference Guide can be found in these red boxes, sometimes within each of the chapter links immediately above, but mostly in my summary and critique of the prior version: Version 2.2 NC.

4. Energy & Atmosphere (EA)

Overview

EA Prerequisite 1 Fundamental commissioning of building energy systems

Intent: Make sure that the energy systems in the building work the way they were designed, according to the owner's project requirements, the basis of design, and the construction documents.

Requirements: There are 6 requirements that apply to energy-related systems (HVAC&R, lighting/daylighting controls, domestic hot water, and renewable energy), as follows:

1. Benefits/issues. Lower costs, less energy used, fewer problems with buildings (contractor call-backs), increased productivity.

2. Related credits. Yes.

3. Referenced standards. None

4. Implementation. Coordinate with possible "enhanced commissioning" EA Credit 3.

5. Timeline and team.

6. Calculations. None

7. Documentation guidance.

8. Examples.

9. Exemplary performance. N/A

10. Regional variations. Climate zones have an impact on which issues may be more critical (e.g., hot humid regions have special issues).

11. Operations/maintenance.

12. Resources.

13. Definitions. Basis of Design, Commissioning [Cx], commissioning authority, commissioning plan, commissioning process, commissioning report, commissioning specification, commissioning team, district energy system (central plant supplying energy to a group of buildings), downstream equipment (stuff inside the building dealing with energy systems connected to a district energy system), enhanced commissioning (best practices), fundamental commissioning, installation inspection (prior to testing, examination of installation), owner's project requirements, systems performance testing (the actual testing to verify whether systems conform to OPR, BOD, and CDs), upstream equipment (part of district energy system, not in the building itself), verification.

EA Prerequisite 2 Minimum energy performance

Intent: Reduce energy use.

Requirements: There are 3 options.

OPTION 1 (Whole building energy simulation): 10% improvement over baseline (or 5% for major renovations). Baseline is per Appendix G, ASHRAE Standard 90.1-2007 (errata, no addenda -- or, in California, option to use Title 24-2005 Part 6), including mandatory sections (5.4, 6.4, 7.4, 8.4, 9.4, 10.4 - see referenced standards) and all energy costs. Assume process energy cost (i.e., "nonbuilding"-energy energy costs such as office equipment, kitchen energy, etc.) of 25% total baseline energy cost (or prove otherwise, but use same values in baseline as in proposal, except when using "exceptional calculation method").

OPTION 2 (Prescriptive compliance): satisfy requirements of appropriate "path" in ASHRAE Advanced Energy Design Guide.

OPTION 3 (Prescriptive compliance, Advanced Buildings): satisfy requirements of New Buildings Institute's "Advanced Buildings Core Performance Guide" if < 100,000 sq.ft. and not health care, warehouse, or laboratory. Must satisfy Sec. 1 (Design process strategies) and Sec. 2 (Core performance requirements).

1. Benefits/issues. Lower costs, less energy used. See overview for rationale.

2. Related credits. Yes.

3. Referenced standards. ANSI/ASHRAE/IESNA Standard 90.1-2007 Minimum requirements for energy-efficiency. "Energy cost budget method" (Sec. 11) allows shifting of boundaries in prescriptive requirements as long as total energy costs are within guidelines, with all "mandatory" provisions still satisfied. [But Implementation section below states that this Section is "no longer an alternative option for compliance..."] The basic ASHRAE energy categories are:

Other ASHRAE Guides: Advanced Energy Guide for Small Office Buildings 2004; Advanced Energy Guide for Small Warehouses and Self Storage Buildings 2008; Advanced Energy Guide for K-12 School Buildings.

New Building Institute, Advanced Buildings Core Performance Guide; Energy Star Program, Target Finder Rating Tool.

Note on computer simulation: Use approved software (e.g., DOE-2, etc.) based on building design. Then modify per ASHRAE 90.1-2007 Appendix G to meet only the minimum prescriptive requirements. Subtract the latter values (use/cost) from the former.

What is striking here is the lack of interest in designing a building that actually makes sense. The only thing measured is the difference between the proposed design and a modified "minimum" proposal, rather than considering alternate proposals that might work even better. That is, if one starts with a bad design, it can still appear "good" when compared to an even less energy-efficient version of the bad design.

4. Implementation. Follow appropriate standard, noting climate zones (8 possibilities - map shown below shows only 7 of 8 zones).
climate map based on ASHRAE

Prescriptive enclosure requirements are based on climate zone: window area < 40% wall area; skylights < 5% roof area. These guides can be violated if energy simulation is used in EA Credit 1. Energy Budget Method (Section 11) not allowed as alternative option. There are both mandatory and "performance" requirements for the prerequisite: EA Credit 1 performance documentation can be used for the "performance" portion of this prerequisite. Natural ventilation requires additional documentation.

5. Timeline and team.

6. Calculations. Based on required methodology in ASHRAE 90.1-2007. There are mandatory and either prescriptive or performance requirements as follows:

7. Documentation guidance.

8. Examples.

9. Exemplary performance. N/A

10. Regional variations. Already included in ASHRAE method.

11. Operations/maintenance.

12. Resources.

13. Definitions. baseline building performance; combined heat and power (CHP) = cogeneration; economizer (makes building systems more energy-efficient); energy (simulation) model; energy star rating per energy star portfolio manager (50 = average); interior lighting power allowance (measured in watts); lighting power density (lighting power per unit area); proposed building performance (annual energy cost per ASHRAE Appendix G).

EA Prerequisite 3 Fundamental refrigerant management

Intent: Reduce ozone depletion.

Requirements: Do not use CFCs (chlorofluorocarbons) in HVAC&R equipment, or phase out use in existing equipment.

1. Benefits/issues. CFCs damage the ozone layer, so their elimination is good for stratospheric ozone (and for human health). Note that a building owner is permitted to keep existing CFC-based equipment if the costs of replacement cannot be justified by the savings in energy. For new construction, this cost analysis is moot, since CFC-based equipment is no longer manufactured.

2. Related credits. Yes. See EA Credit 4.

3. Referenced standards. US EPA Clean Air Act, Title VI, Section 608 (Recycling rule for refrigerants).

4. Implementation. If CFC-based equipment is to be kept, reduce leakage to 5% per year per EPA reference. If substitute refrigerants are used, try to find a good alternative (there are none) that not only has low ozone depletion potential (ODP), but also low global warming potential (GWP), and short environmental lifetimes. See Table 1 for "100-year values":

selected productsODPGWPUse
CFCs
CFC-111.04680chillers
CFC-121.010,720refrigerators/chillers
 
HCFCs
HCFC-220.041780ac/chillers
HCFC-1230.0276CFC-11 replacement
 
HFCs
HFC-134a01320CFC-12 or HCFC-22 replacement
HFC-407C01700HCFC-22 replacement
 
Natural
CO201.0 
Ammonia (NH3)00 
Propane03.0 

5. Timeline and team.

6. Calculations. None

7. Documentation guidance.

8. Examples.

9. Exemplary performance. N/A

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions. CFC (chlorofluorocarbons are a type of hydrocarbon); leakage rate; refrigerants (media in refrigeration cycle designed to absorb and reject heat).

EA Credit 1 Optimize energy performance (1-19 points)

Intent: Lower use of energy for all the economic/environmental reasons cited in the overview.

Requirements: There are 3 options. If compliant, then EA Prerequisite 2 is satisfied by default. Note that the big points are only available through Option 1.

OPTION 1 Whole building energy simulation: Create a "whole building" baseline per ASHRAE 90.1-2007 Appendix G (errata but no addenda) and then collect points depending on the energy cost savings achieved for the proposed building based on this formula for new construction: number of points awarded = (% savings - 10) / 2. So, for example, for 12% energy cost saving, we get (12 - 10) / 2 = 1 point.

[From Version 2.2 critique] 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.

For existing building renovation, the formula is: number of points awarded = (% savings - 6) / 2. So, for example, an 8% cost saving results in (8 - 6) / 2 = 1 point.

In any case, the maximum number of points available under this credit is 19, corresponding o 48% savings for new construction, or 44% savings for renovation. Also, round down to the closest integer value of points awarded. All energy costs for the building are included, per ASHRAE 90.1-2007 Appendix G. As in EA Prerequisite 2, mandatory provisions of the standard (5.4, 6.4, 7.4, 8.4, 9.4, 10.4) must be satisfied; and the baseline is defined in the same way.

OPTION 2 Prescriptive compliance path (for 1 point): Satisfy the requirements of the appropriate ASHRAE Advanced Energy Design Guide, same as in EA Prerequisite 2.

OPTION 3 (Prescriptive compliance, Advanced Buildings for 1-3 points): As in EA Prerequisite 2, satisfy requirements of New Buildings Institute's "Advanced Buildings Core Performance Guide" if < 100,000 sq.ft. and not health care, warehouse, or laboratory. Must satisfy Sec. 1 (Design process strategies) and Sec. 2 (Core performance requirements).

1. Benefits/issues. The same economic and environmental issues described in the Overview apply here.

2. Related credits. Yes. See EA Credit 4.

3. Referenced standards. ASHRAE 90.1-2007 (Option 1 and EA Prerequisite 2 rely on Appendix G for computing energy cost savings that are over and above the baseline values permitted in the standard). See EA Prerequisite 2 for other references and information.

4. Implementation.

The special case of CHP (combined heat and power, or cogeneration) is developed in detail.

5. Timeline and team.

6. Calculations. Option 1 requires modeling (energy use simulation); whereas Options 2 and 3 are prescriptive.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. For Option 1 only, 1 ID point possible for an additional 2% cost savings (i.e., 50% for new construction or 46% for renovations).

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions. baseline building performance; daylighting; downstream equipment; district energy system; energy (simulation) model; energy star; lighting power density; percentage improvement; plug load (receptacle load); proposed building performance; upstream equipment.

EA Credit 2 On-site renewable energy (1-7 points)

Intent: Lower use of fossil-fuel based energy.

Requirements: Use on-site renewable energy, calculating the cost savings as in EA Credit 1 (or EA Prerequisite 2). The number of points awarded = (% savings +1) / 2. Also, round down to the closest integer value of points awarded. For example, a savings of 6% corresponds to (6 + 1) / 2 = 3.5 or, rounding down, 3 points. The maximum number of points awarded is 7, corresponding to a savings of 13%.

1. Benefits/issues. The same economic and environmental issues described in the Overview apply here. Some discussion of wind and biomass as helping economic development in rural areas.

2. Related credits. Yes, but small effect.

3. Referenced standards. ASHRAE 90.1-2007. Note that for this credit, on-site renewable energy is considered to be "free" in the calculation of energy costs. This is an implicit admission that the calculation of sustainability based on cost is flawed (since the actual cost of using on-site renewable energy may well be greater than the cost of using conventional power).

4. Implementation. Renewables include: solar, wind, geothermal, water, bio-based energy for either electricity generation, or direct heating/cooling of spaces or of water. Selling excess electricity to the grid seems to be OK (i.e., you can count it when calculating savings), but if the electricity is produced on-site in order to sell it to the grid (i.e., it is not intended for the building), it is not counted for this credit. This is a bit confusing. Passive solar or daylighting cannot be used for this credit. Renewable energy certificates (RECs) can be sold by owners of buildings meeting this credit if RECs equivalent to twice the energy output of the owner's system are purchased from a "Green-e eligible source. This section remains puzzling to me.

5. Timeline and team.

6. Calculations. Energy use can be calculated based on the calculations in EA Credit 1, or on standards correlated to building type (Commercial Buildings Energy Consumption Survey).

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Additional credit possible by achieving a savings of 15% or more.

10. Regional variations. Availability of renewable on-site energy varies by region: solar in the South West, wind along coasts, biomass in agricultural areas.

11. Operations/maintenance.

12. Resources.

13. Definitions. biofuel (wood by-products, agricultural waste); biomass (plant material that can be converted to heat energy for electric generation); district energy system; downstream equipment; geothermal energy (uses hot water or steam below grade??); green-e (Center for Resource Solutions, identifies green electricity); life-cycle cost analysis; net metering; on-site renewable energy; renewable energy; upstream equipment.

EA Credit 3 Enhanced commissioning (2 points)

Intent: Like Prerequisite 1, but starting earlier and ending later; with additional requirements to verify that systems are working properly, as intended and designed.

Requirements: There are 6 requirements that apply to energy-related systems (HVAC&R, lighting/daylighting controls, domestic hot water, and renewable energy), as follows:


1. Benefits/issues. Lower costs, less energy used, fewer problems with buildings (contractor call-backs), increased productivity.

2. Related credits. Yes.

3. Referenced standards. None

4. Implementation. Coordinate with EA Prerequisite 1.

5. Timeline and team. See Table 1 for summary of commissioning steps (for both EA Prerequisite 1 and EA Credit 3). Owner's Project Requirements: basic program, costs, quality levels, sustainability goals, energy use goals, IEQ goals, O&M requirements. Basis of Design: design assumptions for energy/IAQ systems including applicable standards and performance requirements.

6. Calculations. None

7. Documentation guidance.

8. Examples. Chart shows typical percentages of the various recyled materials: LEED requires only paper, glass, plastics, cardboard, and metals (59%).

9. Exemplary performance. Possible for building envelope commissioning in addition to the requirements listed here.

10. Regional variations. Climate zones have an impact on which issues may be more critical (e.g., hot humid regions have special issues).

11. Operations/maintenance.

12. Resources.

13. Definitions. Basis of Design, Commissioning [Cx], commissioning authority, commissioning plan, commissioning process, commissioning report, commissioning specification, commissioning team, district energy system (central plant supplying energy to a group of buildings), downstream equipment (stuff inside the building dealing with energy systems connected to a district energy system), enhanced commissioning (best practices), fundamental commissioning, installation inspection (prior to testing, examination of installation), owner's project requirements, systems performance testing (the actual testing to verify whether systems conform to OPR, BOD, and CDs), upstream equipment (part of district energy system, not in the building itself), verification.

EA Credit 4 Enhanced refrigerant management (2 points)

Intent: Reduce ozone depletion.

Requirements: Two options (in either case, exclude small HVAC units and other small refrigeration units): Either do not use refrigerants at all (Option 1) or...

OPTION 2. Use refrigerants with a low combined ODP and GWP (ozone depletion and global warming potential); specifically: LCGWP + LCODP x 100,000 <= 100; where


where:


1. Benefits/issues.

Because some refrigerants are bad for ozone depletion, while others are bad for global warming, the best advice is as follows:


2. Related credits. Yes.

3. Referenced standards.

4. Implementation. See Prerequisite 3. "Table 1" for "100-year values" is repeated here:


selected productsODPGWPUse
CFCs
CFC-111.04680chillers
CFC-121.010,720refrigerators/chillers
 
HCFCs
HCFC-220.041780ac/chillers
HCFC-1230.0276CFC-11 replacement
 
HFCs
HFC-134a01320CFC-12 or HCFC-22 replacement
HFC-407C01700HCFC-22 replacement
 
Natural
CO201.0 
Ammonia (NH3)00 
Propane03.0 

The commentary points out a dilemma in refrigerant selection: HCFCs have smaller ODP than CFCs, but are still problematic in that regard. HFCs have virtually no ODP, but worse GWP than HCFCs. And HFCs are not as efficient refrigerants as HCFCs, so more electricity is needed for a given amount of cooling, releasing more CO2 into the atmosphere to produce the power. In other words, "ozone-friendly" refrigerants may be worse for climate change when their inefficiencies are taken into account.

[From Version 2.2 critique] 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."

Refrigerant charge (Rc) = "ratio of refrigerant required (pounds) to gross cooling capacity provided (tons) for a given piece of HVAC&R equipment." [p.309]. Low values correspond to more efficient equipment using less refrigerant and therefore having less impact on the atmosphere. Maximum 10-year life values for selected refrigerants are listed in Table 2: R-22 (presumably the same as HCFC-22) = 0.57; R-123 = 1.60; R-134a = 2.52; R-407c = 1.95. Note that absorption chillers are assumed to last 23 years.

Halon (fire suppression chemical that has large ODP) has been phased out per 1994 Montreal Protocol. Replacement fire suppression chemical systems cannot use halons, CFCs or HCFCs.

5. Timeline and team.

6. Calculations. See equations above. For multiple HVAC&R units, take weighted average based on cooling capacity (tons).

7. Documentation guidance.

8. Examples. For an office building with several HVAC&R units of different types, the calculations are as follows:

Number of unitsQ (tons)R-typeGWPrODPrRc (lb/ton)Life (years)Lr (%)Mr (%)
Type A = 1500R-134a13200223110
Type B = 210 x 2R-2217800.042.415210
Totals520

Type A:

  1. Total leakage = Lr x Life + Mr = 33%

  2. LCGWP = Lifecycle global warming potential = [GWPr x (33%) x Rc] / Life
    = (1320 x 0.33 x 2) / 23 = 37.9 lb CO2/Ton-Year

  3. c) LCODP = Lifecycle ozone depletion potential = [ODPr x (33%) x Rc] / Life
    = (0 x 0.33 x 2) / 23 = 0 lb CFC 11/Ton-Year

  4. d) Atmospheric impact = LCGWP + LCODP x 100,000 = 37.9 + 0 = 37.9


Type B:

  1. Total leakage = Lr x Life + Mr = 40%

  2. LCGWP = Lifecycle global warming potential = [GWPr x (33%) x Rc] / Life
    = (1780 x 0.40 x 2.4) / 15 = 113.9 lb CO2/Ton-Year

  3. LCODP = Lifecycle ozone depletion potential = [ODPr x (33%) x Rc] / Life
    = (0.04 x 0.40 x 2.4) / 15 = 0.00256 lb CFC 11/Ton-Year

  4. Atmospheric impact = LCGWP + LCODP x 100,000 = 113.9 + 256 = 369.9


Weighted average = [(Type A impact)(500 tons) + (Type B impact)(20 tons)] / (520 tons)
= (37.9 x 500 + 369.9 x 20) / 520 = 50.7 which is no greater than 100, so OK.

9. Exemplary performance. N/A

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions. CFC (chlorofluorocarbons are a type of hydrocarbon); leakage rate; refrigerants (media in refrigeration cycle designed to absorb and reject heat).

EA Credit 5 Measurement and verification (3 points)

Intent: Make sure that systems are operating as intended over time.

Requirements: There are 2 options, both based on strategies for measurement and verification (M&V) developed in the International Performance Measurement & Verification Protocol (IPMVP) Volume III (Concepts and Options for Determining Energy Savings in New Construction, 4/2003), and both requiring a minimum M&V period of 1 year after occupancy and a process to correct any problems found.

Either comply with the protocol's "Option D" (Calibrated simulation, savings estimation method 2) ; or comply with the protocol's "Option B" (Energy conservation measure isolation).

1. Benefits/issues. Clearly, all the intentions of prior energy credits are contingent upon on-going performance which these credits measure and verify (at least for 1 year).

For buildings that may last 50 years or more, it isn't clear why only 1 year of monitoring is sufficient to be awarded these 3 points.

The economics of such M&V are justified by balancing the costs of M&V against the "risks" of wasting money on inefficient energy systems.

2. Related credits. Yes.

3. Referenced standards. International Performance Measurement & Verification Protocol (IPMVP) Volume III

4. Implementation. Comparison of Options B and D. Option B appropriate for small projects, with each energy system isolated and monitored (metered). A baseline building is also determined so that "savings" can be calculated. Option D is appropriate for large, complex systems where interactions make isolated metering difficult. So this is a "whole building" M&V process, using computer simulation to compare actual energy consumed with predicted (calibrated computer-based) consumption. The calibration fine-tunes the model to conform to reality; then a baseline is created by subtracting the advanced features, i.e., those not required by basic ASHRAE standards.

5. Timeline and team.

6. Calculations. The referenced standard (IPMVP) provides calculation guidelines.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. N/A

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions. district energy system; downstream equipment; energy conservation measures; upstream equipment; verification.

EA Credit 6 Green power (2 points)

Intent: Help encourage renewable energy delivered through the electric "grid" that have zero pollution impacts.

Requirements: There are 2 options, each requiring that 35% of the building's electricity comes from renewable sources per the Center for Resource Solutions Green-e certification. For Option 1, the baseline annual electric use is determined from EA Credit 1 calculations; for Option 2, electric use can be estimated using the US DOE (Department of Energy) Commercial Building Energy Consumption Survey database.

1. Benefits/issues. Electric generation is a significant polluter (acid rain, smog, GWP). Avoid nuclear or large-scale hydro, as these have negative impacts. Biomass, wind can help economic development in rural areas (good for farmers, Native Americans, etc.). Easy to implement, since the power still comes via the grid.

2. Related credits. Yes.

3. Referenced standards. Center for Resource Solutions, Green-e product certification requirements. Three products are certified: REC (renewable energy certificates), utility green-pricing programs, and competitive electricity products.

4. Implementation. Buy power from a Green-e certified provider (in "open" markets), or sign up for a Green-e accredited program (in "closed" markets). Otherwise, buy RECs ("green-tags") to subsidize production of "green" electricity elsewhere, without changing anything about the local electricity provided.

5. Timeline and team.

6. Calculations. As described above.

7. Documentation guidance.

8. Examples.

9. Exemplary performance. Possible if 100% of electricity is purchased from renewable sources.

10. Regional variations.

11. Operations/maintenance.

12. Resources.

13. Definitions. biomass; geothermal energy/heating systems; green power; hydropower; photovoltaic (PV); renewable energy; RECs; solar thermal systems; wave and tidal power systems; wind energy

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