This appendix contains more detailed information about the studies that the committee relied on most heavily in formulating its findings and recommendations related to American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standards 90.1 and 189.1 and of the Leadership in Energy and Environmental Design (LEED) and Green Globes green building certification systems. It also contains information on a literature review (Hunt, 2008) that was not otherwise cited. In all, 26 studies are described. The information provided typically includes the study goals and objectives, the methodology used, characteristics of the sample (e.g., size, location, building types), and the findings that are most relevant to the committee’s statement of task. In most cases, the studies are quoted directly, as indicated by the inclusion of page numbers in parentheses.
The studies are organized into three categories: studies on energy, water, and related factors (subcategories include studies on federal buildings and regional studies); studies on indoor environmental quality and productivity; and studies on the incremental costs to design and construct high-performance or green buildings. Those categories are not, however, exclusive, and findings from some studies could be grouped within more than one category.
STUDIES ON ENERGY, WATER, AND RELATED FACTORS
Lessons Learned from Case Studies of Six High-Performance Buildings
P.A. Torcellini, M. Deru, B. Griffith, N. Long, S. Pless, and R. Judkoff. Technical Report NREL/TP-550-37542. National Renewable Energy Laboratory, Golden, Colo. 2006.
Torcellini et al. conducted field evaluations of six high-performance buildings and compared the energy performance of each of the buildings to each other and to code-compliant base-case buildings. Each of the six new buildings used a design process that included low energy use as a design goal. Computer simulations were used for each building during the design process. (The study does not say whether these buildings were certified under a green building rating system.) After construction, energy flows were monitored for a minimum of 1 year, including lighting loads, heating, ventilation, and air-
conditioning (HVAC) loads, and plug loads. Data were tabulated every 15 minutes and the data were used to calibrate the computer simulation models. Among the study findings were the following:
- All of the buildings used much less energy on an annualized basis than comparable code-compliant buildings. Three of the buildings had net source energy savings of more than 50 percent. Three of the buildings had energy cost savings that exceeded 50 percent. Overall, net source energy savings ranged from 77 to 22 percent, and energy cost savings ranged from 67 to 12 percent.
- Site energy use was 25 to 62 percent less than the baselines. Site energy costs were 12 to 67 percent less than the baselines.
- Each building’s actual energy use was greater than the energy use predicted by models. Factors cited for this included occupant behavior and their acceptance of systems; higher plug loads than modeled; temperature controls set higher in actuality than in modeling; changes between the buildings as they were designed and as they were constructed.
- Creating energy cost goals during design and verifying the costs are difficult due to instability in energy prices.
- Caution must be exercised in comparing the initial predictions, analysis, and actual data because these numbers can vary greatly.
- Measurable goals must be defined that can be used throughout the design process. Setting the goal can drive the project and can result in good performance against that metric.
- Achieving and maintaining high performance of the building requires a constant effort, which is absent in most buildings. Continually tracking building performance is expensive and requires motivated, trained staff. However, advances in metering technology, computerized communications, and automated controls offer hope for the future.
Evaluating the Energy Performance of the First Generation of LEED-Certified Commercial Buildings
R. Diamond, M. Optiz, T. Hicks, B. Von Neida, and S. Herrera. Lawrence Berkeley National Laboratory: Berkeley, Calif. 2006.
This study by Diamond et al. presented an early analysis of the actual energy performance of 21 LEED-certified buildings that were certified between December 2001 and August 2005. The study does not indicate what certification levels had been achieved by individual buildings.
The study compared the modeled energy use for LEED-NC-certified buildings (data taken from the submissions required for LEED certification) against actual utility bills for the first year of operation (utility billing data were collected from 2003 to 2005). Modeled energy data were collected for both the as-designed building and the base-case building. The authors note the study is “only a preliminary guide to how LEED buildings in general are performing as a group” due to a range of issues. The issues included the sample size, the wide variation in building type (libraries, offices, multifamily, mixed use, laboratories) and building size (from 6,100 square feet to 412,000 square feet); 14 buildings were owned by the federal government, certified as LEED-NC, and located across the country; 7 buildings were commercial and concentrated mostly in the Pacific Northwest.
For the 18 buildings for which the authors had both simulated whole building design and actual purchased energy, the actual consumption was 28 percent lower than the base-case. However, there was significant variation among individual buildings, with some being more energy efficient than predicted, and some being less efficient. The actual energy use in the federal buildings was lower than the modeled
use. The authors also concluded that the number of LEED energy-efficiency points did not correlate with actual energy savings.
The authors called for a more comprehensive collection and publication of modeled use versus actual consumption data, noting that a central compilation is needed, as well as consistent applications for how the data are defined, normalized, compared, and reported.
Energy Performance of LEED for New Construction Buildings
C. Turner and M. Frankel. New Buildings Institute, White Salmon, Wash. 2008.
The U.S. Green Building Council, with support from the U.S. Environmental Protection Agency, contracted with New Buildings Institute (NBI) to review the post-occupancy energy performance of 121 LEED-NC-certified buildings. Office buildings were the dominant category in the study, but the sample also included schools, libraries, multi-use, residential, and other types of buildings. One hundred of the buildings were classified as “medium energy use activities,” while 21 buildings were described as “high energy use activities,” such as laboratories, data centers and recreation facilities. The average size of buildings was 110,000 square feet, and about half of the buildings were in the range of 25,000 to 200,000 square feet (p. 11). The results contrast with the size distribution for the national building stock as reported in the Commercial Building Energy Consumption Survey (CBECS), in which 73 percent of all buildings are less than 10,000 square feet and have an average size of 14,700 square feet (p. 12).
The study compared whole building energy use (one full year of post-occupancy energy use) with three different metrics: Energy Use Intensity (EUI) for the LEED-certified buildings to the EUIs derived for the national building stock from the 2003 CBECS; ENERGY STAR® ratings of LEED buildings; and actual energy use for the LEED-certified buildings to initial design and baseline modeling (p. 2). Some of the findings were the following:
- For all 121 LEED-NC buildings the median measured EUI was 24 percent below (better than) the CBECS national average for all commercial building stock (p. 2).
- On all three metrics, average energy use in the total sample of LEED-NC-certified buildings was 25 to 30 percent lower than the CBECS national average. Energy reductions were greater with higher LEED certification levels: LEED-NC-Certified buildings used 26 percent less energy, LEED-NC-Silver buildings used 32 percent less energy, and LEED-NC-Gold/Platinum-certified buildings used 45 percent less energy on average than the CBECS average. However, energy use in individual buildings displayed a large degree of variability: over half of the projects deviated by more than 25 percent from design projections, with 30 percent significantly better and 25 percent significantly worse (p. 5). A “follow-up study of some of the good and poor performers could identify ways to eliminate the worst results and identify lessons to incorporate from the best results” (p. 5).
- For all but the warm-to-hot zones, LEED-NC buildings showed significant improvement over CBECS, with median LEED EUIs between 51 and 64 percent of the CBECS average for those zones (36 to 49 percent lower). For the warm-to-hot zones, the median LEED EUI was virtually the same as CBECS (p. 17).
- Although energy modeling is a good indicator of program-wide (portfolio-based) performance, individual project modeling varies widely from actual project performance outcomes. The ratio of actual to predicted energy use varies widely across projects, even within one LEED certification level (p. 22). “This variability between predicted and measured performance has significant implications for the accuracy of prospective life-cycle cost evaluations for any given building.
Better feedback to the design community is needed to help calibrate energy modeling results to actual performance outcomes” (p. 32). Follow-up investigations into reasons for measured-to-design deviation and for the wide variations in modeled baseline performance could improve future modeling and benchmarking (p.5).
- Project types with high process loads, such as laboratories, are problematic because energy use of high-energy building types is not well understood by designers. “Neither the LEED program nor the modeling protocol address[es] these projects well” (p. 32).
For this study, the participating owners were given the opportunity to survey the perception of occupants. The brief online survey used was modeled after the Buildings in Use (BIU) work, which includes a database of post-occupancy evaluations for more than 1,000 buildings (Vischer and Preiser, 2005). Occupants were asked to rate the key indoor environmental factors of acoustics, lighting, temperature, and air quality as well as overall building satisfaction. For each factor, the majority of LEED building ratings were positive and exceeded BIU normative scores. The lowest-rated area was acoustics (pp. 30-31). The authors noted that “such results are typical for office occupant surveys and often felt to be a result of open floor space plans, common in green and nongreen buildings alike” (p. 31).
Do LEED-Certified Buildings Save Energy? Yes, But …
G.R. Newsham, S. Mancini, and B. Birt. National Research Council Canada. 2009.
Newsham et al. reanalyzed the data used in the Turner and Frankel (2009) study for the 100 buildings categorized as “medium energy use activities.” Of these buildings, 38 were certified as LEED-NC-Certified, 35 as LEED-NC-Silver, and 27 as LEED-NC-Gold/Platinum. Newsham et al. added statistical rigor to the original analysis by conducting a series of t-ests. In the t-ests, each LEED-NC-certified building was paired with a single matched building (matched on the basis of activity type, size, age, and climate zone) from the CBECS database (p. 6). Multiple t-ests were conducted involving differing numbers of buildings based on the quality of the matching criteria. The authors’ conclusions were the following:
- On average, LEED-NC-certified buildings used 18 to 39 percent less energy per floor area than the CBECS averages.
- Twenty-eight to 35 percent of LEED-certified buildings used more energy than their matched counterparts from the CBECS database.
- There was no statistically significant relationship between LEED-NC certification level and energy use intensity or percent energy saved versus the baseline (pp. 14-15). LEED-NC-Silver buildings did not exhibit better energy performance than LEED-NC-Certified buildings, and LEED-NC-Gold/Platinum buildings did not exhibit better energy performance than LEED-NC-Silver buildings.
- The measured energy performance of LEED-NC buildings has little correlation with the certification level of the building or the number of energy credits achieved by the building during the design phase (p. 18). The results suggest the energy credit scheme needs to be refined so that it delivers more reliable performance at the individual building level.
The authors noted that “these results also highlight the importance of investigating the post-occupancy performance of buildings. There is clearly no meaningful way to refine green building rating schemes so that they become more reliable without measured performance data” (p. 18).
A Re-Examination of the NBI LEED Building Energy Consumption Study
J.H. Scofield. Energy Program Evaluation Conference, Portland, Ore. 2009.
Scofield reexamined the data in the Turner and Frankel (2008) study for the 100 LEED-certified buildings classified as “medium energy use activities.” Scofield took exception to Turner and Frankel’s comparison of the mean of one distribution to the median of another and stated that “to compare the mean of one with the median of the other introduces bias by compensating for skew in only one distribution” (p. 765). He also defined mean energy intensity differently, using a gross square foot averaging method, and conducted statistical tests of the data for several subsets of the Turner and Frankel database. Scofield compared data from some of the LEED-certified buildings to the CBECS database and also to a subset of buildings from CBECS constructed between 2000 and 2003. His conclusions included the following:
- LEED-NC-certified medium-energy buildings, on average, used 10 percent less site energy, but no less source (or primary) energy, than did comparable conventional buildings whether restricted to new vintage (constructed between 2000 and 2003) or not.
- LEED-NC-Certified buildings used slightly more site energy than the CBECS comparison group, while LEED-Silver and LEED Gold/Platinum buildings used 23 percent and 31 percent less site energy, respectively, than the CBECS comparison group.
- LEED office buildings used 17 percent less site energy than that of the CBECS comparison group of all vintages; there was no significant reduction in primary (source) energy use relative to non-LEED office buildings
Do LEED-Certified Buildings Save Energy? Not Really …
J.H. Scofield. Energy and Buildings 41(12):1386-1390. 2009.
Scofield later published a direct rebuttal to Newsham et al. in which he reanalyzed the Turner and Frankel (2008) data for a subset of 35 LEED-certified office buildings using a different methodology. Scofield focused on source energy (which accounts for both on-site energy and off-site energy losses associated with the generation and distribution of electricity), whereas the Turner and Frankel (2008) and Newsham et al. (2009) studies used site-energy only. Scofield weighted the energy intensity of each building by its gross square feet, whereas Turner and Frankel (2008) and Newsham et al. (2009) weighted the energy intensities of each building. Scofield states that these “different averaging methods yield different means, and correspondingly, give rise to significantly different conclusions when comparing mean energy intensities of various building sets” (p. 1387). He noted that the CBECS data set is dominated by the energy used by large buildings in the set. Many smaller LEED buildings do outperform non-LEED buildings of similar size, but this may be less important when looking at the total energy footprint of the building stock, simply because these smaller buildings do not contribute nearly as much in total energy used. Scofield described his concern with using building-weighted averages as used in the CBECS data set as follows:
The fallacy of using “building-weighted” averaging to characterize the energy intensity of a collection of N buildings is readily apparent when you take it to a smaller extreme. Suppose you were to divide a single building up into N rooms, some big and some small. You could calculate the energy intensity of each room separately. There are two ways to calculate the mean room energy intensity. The “gsf-weighted” method yields a mean energy intensity identical to that of the building. The “room-weighted” or unweighted average does not. It is clear that only the former makes physical sense. The same is true when considering a collection of N buildings (p. 1390).
Despite the differences in methodologies, Scofield found that LEED-NC-certified office buildings used, on average, 10 to 17 percent less site energy than comparable non-LEED buildings. He also found the following:
- LEED-NC-certified conventional buildings, on average, showed no significant primary [source] energy consumption. For this reason, he concluded that LEED certification “is not delivering reduction in greenhouse gas emissions associated with building operation” (p. 1387).
- Smaller buildings tend to out-perform (i.e., use less site energy) CBECS more than do larger LEED buildings (p. 1389). Scofield speculated that “energy consumption in larger buildings is dominated by plug loads and operating practices, which are not addressed by LEED” (p. 1390).
Scofield did not provide any data about differences in LEED building performance by level of certification.
Greening Our Built World: Costs, Benefits, and Strategies
G. Kats. Island Press, Washington, D.C. 2010.
The author analyzed data for 170 green buildings (defined as certified or anticipating LEED certification, or certification under another similar rating system). Approximately 15 percent of the 170 buildings were certified under systems such as the Massachusetts green schools guidelines, Enterprise Green Communities, or the Green Guide for Healthcare Facilities.
Data were gathered directly from building owners, architects, and developers for buildings completed between 1998 and 2009. A range of building types was included in the sample—schools, offices, healthcare, academic facilities, and others—located in 33 states and eight countries. The author synthesized the results of his 170-building survey with findings from other studies to develop estimates of net present value (NPV) benefits (p. 3).
Benefit-cost analyses and simple payback models were developed to compare life-cycle benefits with the initial cost of green design and construction. NPV benefits were calculated using a 20-year time period, a 7 percent discount rate, and 2 percent annual inflation. It was noted that the discount rate was equal to or higher than the rate at which states, the federal government, and many corporations have historically borrowed money and “thus provides a reasonable basis for calculating the current value of future benefits” (p. 4). To allow comparability of financial impacts over time, costs and benefits were expressed in terms of dollars per square foot (p. 3).
For calculating energy and water savings, the contacts for each building relied on industry standards to create a baseline for conventional buildings, against which green building savings could be measured. The building architect provided the cost premiums to allow a comparison between green building costs and the baseline. The study modeled benefits that accrued (1) directly to building owners and occupants and (2) indirectly to the surrounding communities and society at large. The author noted the limitations of the study, including the potential for bias created by the data-gathering methodology and the fact that the sample of buildings was not precisely representative of the actual inventory of green buildings nationally. In estimating long-term costs and benefits, modeled costs and projected energy and water savings data were used where actual data were not available (p. 7). Among the study findings were the following:
- For the 170 (U.S.) buildings in the data set, owners or owner’s representatives reported that it cost 0 to 18 percent more to build a green building compared to a conventional building. The median additional cost was 1.5 percent, with the large majority of premiums reported between
0 and 4 percent. The author concluded that most green buildings cost slightly more than similar conventional buildings to construct.
- Generally, the greener the building, the greater the cost premium, but all LEED levels can be achieved for minimal additional cost. Of the buildings in the data set with a cost premium of 0 to 2 percent, 29 buildings were LEED-Gold and 5 were LEED-Platinum. Nine green buildings (one Silver, four Gold, four Platinum) reported a green premium of 10 percent or more (p. 10).
- Twenty projects in the data set were major renovations. The median green premium was 1.9 percent and the average was 3.9 percent (p. 13).
- Buildings in the data set reported a range of projected and actual reductions in energy use, from less than 10 percent to more than 100 percent (meaning that the building generated more power than it used), with a median reduction of 34 percent and a mean reduction of 35 percent (p. 15). The author concluded that, based on the median savings from the data set and national data on baseline energy expenditures, the present value of 20 years of energy savings in a typical green building ranges from $4 per square foot to $16 per square foot, depending on building type and LEED level of certification (p. 14).
- Projected energy savings generally increased with the level of greenness, and there was a range of projected savings at each LEED level. “When compared with an ASHRAE 90.1 baseline building, LEED-Certified buildings in the data set reported median savings of 23 percent; for Silver the figure was 31 percent; for Gold, 40 percent; and for Platinum, 50 percent” (p. 16).
- Of the 170 buildings in the data set, 119 reported or projected reductions in indoor potable water use when compared to conventional buildings; reductions ranged from 0 percent to more than 80 percent, with a median of 39 percent. Water savings generally increase with LEED level of certification. The present value of water savings in typical green buildings ranged from $.50 per square foot to $2 per square foot, depending on building type and LEED level of certification.
Studies for Federal Buildings
Assessing Green Building Performance: A Post Occupancy Evaluation of 12 GSA Buildings
K.M. Fowler and E.M. Rauch. Pacific Northwest National Laboratory, Richland, Wash. 2008.
Fowler and Rauch looked at 12 General Services Administration (GSA) buildings designed to be LEED-certified or otherwise designated as “green.” The sample included 6 office buildings, 4 courthouses, and 2 combination office/courthouse buildings located in half of GSA’s national regions. Eight of the 12 buildings were LEED-certified (6) or LEED-registered (2). (As of the summer of 2007, GSA had 19 LEED-certified buildings, so the sample represented one-third of its LEED inventory.) Of the LEED-certified buildings, 2 were LEED-NC-Certified, 2 were LEED-NC-Silver, 1 was LEED-EB-Silver, and 2 were LEED-NC-Gold (1 building was LEED registered but the level of certification was not available).
Building performance measures that were collected, normalized, and analyzed included water, energy, maintenance and operations, waste generation and recycling, occupant satisfaction, and occupant commute. The data sources for these analyses included utility bills, maintenance budgets, and an occupant survey. Twelve consecutive months of data were collected for each performance metric and then normalized using the building and site characteristics (p. ix).
Fowler and Rauch (2008) calculated aggregate operating costs (energy and water utilities, general maintenance, grounds maintenance, waste and recycling, and janitorial costs per rentable square foot) for 12 GSA green buildings and compared those costs to industry baselines. The baselines were devel-
oped from a number of sources, including data from BOMA and the International Facility Management Association (IFMA).
The occupant survey was based on the Center for the Built Environment (CBE) survey, for which there were baseline data from which to make comparisons.
Fowler and Rauch found the following:
- Regarding energy use, on average the GSA office buildings in this study performed 29 percent better (used 29 percent less energy) than office buildings in the CBECS national database. All of the buildings performed 29 percent better than the CBECS regional averages. All performed 14 percent better than the GSA energy goal for its portfolio of facilities (p. xi).
- Aggregate operating costs on average were 13 percent lower than average costs reported in industry sources. However, several of the buildings had consistently higher operating costs in each category (p. xii). Regarding water use, domestic water use was estimated as the base water load revealed from the monthly water use data. Given these estimates, the average use of the 12 GSA green buildings was 3 percent less than the calculated water indices baseline (p. xii).
- All of the GSA buildings scored above the CBE median for general occupant satisfaction with the building. On average, the buildings scored 22 percent higher than the CBE median.
Re-Assessing Green Building Performance: A Post-Occupancy Evaluation of 22 GSA Buildings
K.M. Fowler, M. Rauch, J.W. Henderson, and A.R. Kora. Pacific Northwest National Laboratory, Richland, Wash. 2010.
Fowler et al. included updated data from the 12 GSA green buildings included in Fowler and Rauch (2008) plus data from 10 additional green buildings. In all, the study included 8 courthouses, 12 federal buildings (office space), and 2 courthouse/federal buildings. Thirteen of the buildings were LEED-certified, 3 were LEED-registered (1 of these buildings did not specify the proposed level of certification), while the others emphasized energy efficiency during the design phase. These buildings accounted for approximately one-third of the 40 GSA buildings that were LEED-certified as of late 2009. The methodology used was generally the same as Fowler and Rauch (2008). The results were generally consistent with those of Fowler and Rauch (2008). Specifically, the authors found that for the GSA buildings:
- Energy performance was better than or equal to the baseline for all of the buildings. The energy performance average of the buildings was 25 percent better than CBECS national baseline, 10 percent better than GSA regional averages for fiscal year (FY) 2009, 13 percent better than FY2009 GSA Target values (goal for energy performance across GSA), and 18 percent better than CBECS regional averages (p. x). The CBECS national average used was for office buildings constructed between 1990 and 2003, while the regional averages were for all building types.
- Two-thirds of the green buildings used less water than the GSA baseline, with the average being 11 percent lower. Of the 6 green buildings with higher water use than the baseline, 5 had cooling towers or evaporative cooling, 2 had exterior fountains in a hot, dry climate, and 3 had non-typical operating schedules (p. xi).
- On average, aggregate operating costs were 19 percent lower than the baseline (the aggregate operating cost metric included water and energy utilities, general maintenance, grounds maintenance, waste and recycling, and janitorial costs). Seventeen of the 22 green buildings had costs that ranged from 2 to 53 percent lower than the baseline. Five of the 22 green buildings
had higher costs than the baseline, ranging from 1 to 27 percent higher. The higher costs were attributed to higher general maintenance costs and higher energy costs.
- The occupant survey indicated that, on average, occupant satisfaction with the green buildings in general were 27 percent higher than the CBE baseline, except for lighting, where it was the same as the baseline.
Data were available for 15 LEED-certified buildings: 2 LEED-NC-Certified, 1 LEED-EB, 6 LEED-NC-Silver, 1 LEED-EB-Silver, and 5 LEED-NC-Gold. For 5 of the 7 LEED-Silver buildings, energy use was lower for all three baselines (CBECS regional, GSA target, GSA regional). The energy use in 2 LEED-Silver buildings was higher than the CBECS regional average. For 5 of the 7 LEED-Silver buildings, water use was lower than the industry and GSA baselines. Two LEED-Silver buildings (1 with a cooling tower and 1 with evaporative cooling) had significantly higher water use than the industry average (p. xi). For 6 of the 7 LEED-Silver buildings, the aggregate operating cost was 10 to 44 percent lower than the baseline; for 1 building it was 9 percent higher than the baseline.
The LEED-Gold buildings performed consistently better than the baseline for all buildings and all metrics with one exception: one of the buildings used significantly more water than the baseline in both the 2008 and 2010 studies.
Among the authors’ conclusions were the following:
- “One of the important lessons learned with respect to whole building performance measurement and assessment is that the baselines selected for performance comparison are what define the study findings” (p. 83).
- “Examining building performance over multiple years could potentially offer a useful diagnostic tool for identifying building operations that are in need of operational changes. Investigating what the connection is between building performance and the design intent would offer potential design guidance and insight into building operation strategies” (p. 75).
- “Operations and maintenance data are being tracked by more building managers, but the quality of the data varies by buildings. Additionally, there is no consistent level of detail collected at each building because of the flexibility of the tracking systems … makes comparisons between buildings a challenge” (p. 82).
Energy Consumption Evaluation of U.S. Navy LEED-Certified Buildings
C. Menassa, S. Mangasarian, M. El Asmar, and C. Kirar. Journal of Performance of Constructed Facilities 26(1):46-53. 2012.
This study was undertaken to establish if the U.S. Navy’s LEED-certified buildings had achieved the 30 percent energy reduction required by EISA 2007 and other mandates, when compared to other buildings with similar functions and locations (p. 46). The study looked at the energy and water performance of 11 buildings operated by the Naval Facilities Engineering Command that had achieved various levels of LEED certification (3 Certified, 5 Silver, 3 Gold) by 2008. The study compared their site energy and water use to 11 NAVFAC buildings of similar size, function, and location that had not been LEED certified (p. 48). It was assumed that the comparison buildings had similar exterior facades and construction materials (p. 48). The analysis also involved comparing the electrical consumption for the LEED-certified buildings to those of the commercial building national average available from the 2003 CBECS database.
The sample of 11 buildings included a drill hall, 3 maintenance facilities, a laboratory, a child care center, 2 bachelor enlisted quarters, a golf course clubhouse, and 2 administrative buildings. The study found that:
- Seven of 11 LEED-certified buildings used less electricity, with the reductions ranging from 3 to 60 percent less energy. However, 4 of the 11 LEED-certified buildings used more energy than their non-LEED counterparts, ranging from 11 to 200 percent more energy.
- Four of 5 LEED-Silver buildings had energy savings ranging from 3 to 49 percent greater than their non-LEED counterparts, while 1 LEED-Silver building used 128 percent more energy than its non-LEED counterpart. Two of the 3 LEED-Gold buildings had energy savings of 6 and 15 percent greater than their non-LEED counterparts, while the third used twice as much energy as its non-LEED counterpart.
- Only 3 of the 11 LEED-certified buildings used less energy than the CBECS baseline (p. 51).
- Seven of 9 LEED-certified buildings reduced their water consumption from 18 to 72 percent. For the 4 LEED-Silver buildings for which water data were available, water savings ranged from 18 to 61 percent better than their non-LEED counterparts (p. 50). Two of the 3 LEED-Gold-certified buildings showed water savings of 56 percent and 60 percent, while the third used 90 percent more than its non-LEED counterpart.
LEED Building Performance in the Cascadia Region: A Post Occupancy Evaluation Report
C. Turner. Cascadia Region Green Building Council, Portland, Ore. 2006.
This study looked at measured energy and indoor water usage (at least 1 year of utility bills) of 11 LEED-certified buildings for three metrics: actual use compared to the initial model predictions; actual use to baseline (approximate to code); and actual use compared to the ENERGY STAR® median. The study sample included 7 offices or libraries and 4 multifamily residential buildings, with a range of LEED certifications (3 LEED-NC-Certified, 4 LEED-NC-Silver, 3 LEED-NC-Gold, 1 LEED-EB-Gold). Energy and water use was measured as gross conditioned square feet (p. 3).
Initial modeling results of projected energy and water use came from the building’s LEED submittal for energy optimization and indoor water use reduction (p. 4). Savings estimates were made by comparing the actual (measured) data to the modeled usage data without further adjustment or calibration (p. 4). Savings estimates were made by comparing actual energy and water use to the modeled use levels. Baseline referred to modeled usage from the LEED Energy Cost Budget or Water Use baseline case, approximately a building similar to the initial design but constructed just to meet code requirements (p. 3). The author also calculated net present value cost savings for energy and water, assuming a 25-year time period, a discount rate of 3 percent, and constant use of energy, and assuming that utility rates increase only at the rate of inflation.
An online survey was distributed to occupants in 10 of the 11 buildings. The survey sought to determine perceptions of building indoor environmental quality in terms of temperature, air quality, lighting, noise, and plumbing fixtures.
Results of the study included the following:
- All of the buildings used less energy than their initial baseline modeling (approximate to code), averaging nearly 40 percent below baseline. All but two showed energy savings when compared
- to an average similar building in the region. The author estimated that the cost savings per year for energy would range from $0 to $26 per square foot (p. 9).
- Six of the 11 buildings were using less total energy than was suggested by the initial design models (p. 5). “No single building’s actual performance was within 20 percent of its design model” (p. 5).
- Of the 7 buildings for which water use projections (models) were available, 4 were using 8 percent less water than predicted (p. 12). “At the level of current water and sewer billing rates, the dollar value of these water volume savings per square foot is minimal” (p. 13).
- Four LEED-NC-Silver buildings used 39 to 57 percent less energy than their approximate to-code baseline model (p. 6). The 2 LEED-NC-Gold buildings for which data were available used 43 to 86 percent less energy than the baseline. For the 4 LEED-NC-Silver buildings, the savings would be $7 to $26 per square foot; for the 3 LEED-Gold buildings, the savings would range from $0 to $8 per square foot (p. 9).
- Data on water use were available for 7 buildings only. Five of the 7 buildings used 5 to 36 percent less water, 2 buildings used 4 to 6 percent more water than the approximate to-code baseline (p. 12). Of the 4 LEED-Silver buildings, 3 used 27 to 36 percent less water, while 1 used 4 percent more water. The 1 LEED-Gold building for which data were available used 5 percent less water than the approximate to-code baseline (p. 12).
The report summary states that:
Most buildings in this study are experiencing real energy savings in relation to their original baseline modeling. Most buildings are also performing well in relation to general commercial space…. The average 25-year present value of dollar savings for buildings in this study, when compared to the regional median, is $2 per square foot. However, there is a large variation in estimated savings, depending on the calculation method used (p. 15).
The majority of buildings also show some savings for indoor water usage in relation to original baseline modeling. As with the energy results, the baseline projections were not calibrated for actual occupant behavior, and wide differences between design and actual results limits the accuracy of these savings estimates (p. 15).
Occupancy surveys show high satisfaction with office buildings overall and generally positive averages for all categories other than noise conditions (p. 15).
Green Buildings in Massachusetts: Comparison Between Actual and Predicted Energy Performance
J.L.B. Sacari, U. Bhattacharjee, T. Martinez, and J. Duffy. American Solar Energy Society, Cleveland, Ohio. 2007.
Sacari et al. compared the predicted energy use (estimated during the pre-construction, design phase) to the actual energy use (utility bills for electricity and natural gas) in 19 new or renovated “green” buildings in Massachusetts compared to the Massachusetts baseline building code. They found that “most green buildings are consuming on an average 40% more energy than predicted” but “are still consuming less than a building designed to Massachusetts baseline building code” (p. 1).
The “green” buildings included 12 school buildings that were certified under the Massachusetts Collaborative for High-Performance Schools and 6 other buildings certified under the LEED rating system. The study does not provide information about the certification levels of the green buildings. Prediction data were obtained primarily from applications for funding to the Massachusetts Collaborative Technology.
Reasons given for large discrepancies between the predicted energy use and the actual energy use included the following:
- Energy modelers appear to use incremental energy savings resulting from the proposed energy efficiency measures adopted in the building and the on-site renewable energy generation, according to several modelers interviewed. Therefore, the predicted energy use does not capture the characteristics of the building in its entirety.
- Limitations in the building modeling cannot predict the human behavior in the buildings related to the use of plug loads, levels of occupancy, and building operation hours.
- Modifications in the original design made in the buildings during the construction phase due to limitations in the budget and/or changes in the type of materials used.
- Some buildings have experienced high rates of energy consumption in their first months of operation due to not all the systems installed being completely operative or commissioned. The delay in the task of contractors and subcontractors, the correct settings of the systems, and the process of learning and adaptation by the users have influenced the energy consumption (p. 4-5).
The average energy consumption of most of the buildings is less than the “base case,” or the same building designed according to the minimum requirements of the energy code, but energy consumption is higher than predicted. Other factors that have attributed [sic] to the increase in energy include: budget problems, changes in end use, increase in occupancy, building modifications, energy management systems not being maximized, and selection of materials (p. 8).
In general, based on the results of this study, green buildings are contributing in very positive ways to reducing the energy and environmental impacts relative to existing buildings and minimum code buildings. But the frustration in stakeholders based on the difference between predicted and actual paid-for-energy use should be addressed mainly by communicating uncertainties in design predictions, by better training in the use of the technologies in the buildings, and by commissioning (p. 8).
Comparison of Commercial LEED Buildings and Non-LEED Buildings Within the 2002-2004 Pacific Northwest Commercial Building Stock
D. Baylon and P. Storm. Published in ACEEE Summer Study on Energy Efficiency in Buildings. 2008.
Baylon and Storm compared the performance of 24 LEED-certified buildings constructed between 2002 and 2005 in the Pacific Northwest (Washington, Oregon, and Idaho) to a larger sample of contemporary buildings built to local codes. The LEED system at that time incorporated ASHRAE 90.1-1999 as the base for energy performance. Most of these buildings had been occupied for at least 2 years, and the researchers compared actual site energy use for the two samples. The authors note that “whereas typical LEED comparisons focus on differences between LEED building features and national code (or building performance and initial modeling, this paper is focused on the regional relevance of the LEED standard and implementation” (p. 4-1).
The LEED buildings in the sample saved 12 percent more energy than the comparison group. The authors noted that energy codes in Washington and Oregon were more stringent than ASHRAE 90.1-1999 (p. 4-1). The sample of LEED buildings included 9 different building types; the study did not provide information about the certification levels.
Regional Green Building Case Study Project: A Post-Occupancy Study of LEED Projects in Illinois
D. Widener. U.S. Green Building Council, Chicago Chapter, Chicago, Ill. 2009.
Widener analyzed the post-occupancy performance and costs and benefits of 25 LEED-certified projects related to measured site energy and greenhouse gas emissions, water, commute transportation, construction and operating costs, green premium, health and productivity impacts, and occupant comfort. The study collected multiple years of post-occupancy data. The 25 projects represent projects certified at all LEED levels and programs: new construction; existing buildings; commercial interiors, and core and shell. The projects ranged in size from 3,200 square feet to 4.2 million square feet and included buildings used for education, lodging, mixed use, office public assembly, public safety, and other (p. i). Most participating projects had been certified under LEED versions 2.0 or 2.1. The study did not identify specific LEED-certification levels (i.e., Certified, Silver, Gold, or Platinum).
Two types of site energy analysis—whole project energy use and partial energy use projects—were conducted. The metric used was site energy use intensity and was measured as kBtu/square foot/per year for all fuels. Seventeen projects classified as whole project energy use projects—those where complete site energy data were provided for a building or project space, including heating/cooling, lighting, and load attributed to the building occupants—were analyzed. Eight projects where only partial site energy data were provided were also analyzed. The study found that the median EUI was 94 kBtu/square foot/year for whole energy projects, which was approximately 5 percent lower than the regional CBECS Midwest average. The median EUI for partial projects was 38 kBtu/square foot/year, which was 7 percent lower than the CBECS Midwest average.
Among the conclusions of the study were the following:
Specifically related to energy performance, many Illinois LEED projects perform better than conventional commercial interiors and buildings, but as with conventional buildings there is a large variation amongst projects. A significant finding is that the Illinois LEED whole project energy use projects that achieved a higher number of EA Credit 1 (LEED-NC) points performed better. This finding makes sense; projects that prioritize energy efficiency as a key LEED strategy are likely to perform better than those projects that do not focus on energy efficiency or choose to prioritize points in other LEED categories (p. v).
Since every building is unique in its use, occupancy, operations, maintenance, and systems, actual post-occupancy measured performance that reflects actual operating conditions of the specific building will be the best benchmark. Other benchmarks, such as comparisons to other buildings (LEED and non-LEED, including CBECS and ENERGY STAR®) or any modeled predictions are temporal or limited in use, even as methodologies and data sets evolve to provide more accurate comparisons (p. v).
Regularly collecting and analyzing building performance post-occupancy is a critical component in operating a green, high-performance building (p. v).
Postoccupancy Energy Consumption Survey of Arizona’s LEED New Construction Population.
D. Oates and K.T. Sullivan. Journal of Construction Engineering and Management 138:742-750. 2012.
This technical paper examines 47 percent of Arizona’s 53 LEED-NC-certified buildings in an effort to determine if Arizona’s LEED-NC-certified buildings achieve expected energy performance, how they compare with the existing building population, and whether either system or managerial variables demonstrate efficiency correlations.
Oates and Sullivan (2012) conducted post-occupancy energy consumption surveys for 25 LEED-NC-certified buildings in Arizona. The sample included seven types of buildings that had been certified under LEED versions 2.0, 2.1, and 2.2 and that had been in operation for at least 1 year as of October 2009. Areas of analysis included total site and source energy use intensity, standard mean and gross square foot weighted mean, and comparisons by climate zone. Actual energy performance of those buildings as measured by EUI for source and site energy was compared to national averages from the CBECS database. The CBECS data were normalized to match the gross square feet weights for each building type in the LEED sample.
The LEED building sample was also characterized principal building activity to separate medium-energy-intensity (19) and high-energy-intensity (6) structures. Medium-energy-intensity buildings included office buildings, education structures, and the like. The high-energy-intensity structures were all laboratories. The authors noted that two buildings accounted for 40 percent of the total data set’s gross square footage and 51 percent of the gross square footage in the medium-energy-intensity subset, which would skew the results.
The 19 building medium-energy-intensity group was analyzed separately from the high-energy group of 6 buildings. The high-energy-intensity subset was not analyzed because the sample size was too small.) Variables tested for the medium-energy-intensity group included site EUI, source EUI, gross square feet, occupants per square foot, total number of awarded LEED credits, total number of LEED Energy and Atmosphere Credits, the facility manager’s years of experience, the number of buildings managed by the facility manager, and others.
The authors found that the 19 medium-energy-intensity LEED-certified buildings used 13 percent less site energy and 1 percent less source energy than the CBECS comparison group. Of the 19 buildings for which the design and baseline model simulations were available, only one used less energy than had been predicted in the design case and only four used less energy than the baseline simulation.
Other findings were the following:
- Energy consumption was not tracked in most LEED NC-certified buildings. Possible factors contributing to this shortcoming included: no dedicated facility manager; a lack of communication between the business office that processed utility bills and the facility manager; not having a dedicated meter; the building manager simply choosing not to track performance metrics (p. 749).
- The research identified a significant facility management deficiency within the LEED buildings. A lack of education at start-up and commissioning operations may partially explain the operational knowledge gap for some managers. In fact, a majority of survey participants were unfamiliar with their building’s heating, ventilation, and air conditioning system (p. 749).
STUDIES RELATED TO INDOOR ENVIRONMENTAL QUALITY AND PRODUCTIVITY
Occupant Satisfaction with Indoor Environmental Quality in Green Buildings
S. Abbaszadeh, L. Zagreus, D. Lehrer, and C. Huizenga. Proceedings of Healthy Buildings, Lisbon. Volume III, pp. 365-370. 2006.
Abbaszadeh et al. looked at occupant satisfaction in green office buildings in comparison to occupant satisfaction in conventional buildings. They asked the occupants directly (through Center for the Built Environment (CBE) surveys) about their satisfaction with indoor environmental quality (IEQ) in their workspace.
The CBE database as of 2005 contained 181 buildings and 33,285 respondents (average 46 percent response rate). Within the CBE database, 15 office buildings were identified as LEED-certified and 6 additional buildings were reported as green, based on the receipt of national or local green building or energy efficiency awards. Together, those 21 buildings comprised one comparison group. The other comparison group consisted of the remaining buildings in the database, referred to as non-green buildings.
The study focused on occupant satisfaction with thermal comfort, air quality, lighting, and acoustics. The authors noted that “self-reported productivity scores follow the same pattern as those of satisfaction— productivity scores are high where satisfaction is high, and low where satisfaction scores are low” (p. 366).
Among the findings, were the following:
- On average, occupants in LEED-rated/green buildings were more satisfied than occupants of conventional buildings when it came to thermal comfort, air quality, and overall satisfaction with workspace and building.
- The mean overall satisfaction score in LEED-rated/green buildings (1.47) was significantly higher than that for conventional buildings (0.93).
- Occupants in LEED-rated/green buildings were more satisfied with thermal comfort (.36) compared to −0.16 for occupants in conventional buildings and more satisfied with air quality in their workspace (1.14 versus 0.21). Even when considering only non-green buildings that were less than 15 years old, the mean satisfaction score with air quality was significantly higher for LEED-rated/green buildings (1.14 versus 0.52) (p. 366).
- The authors found that when including only buildings 15 years old or newer, no statistically significant relationship was found for the IEQ categories of lighting and acoustics. “Complaint profiles of those dissatisfied with their lighting point to problems with daylighting and electric lighting levels—at its source this could be due to inadequate provision of controls over lighting” (p. 370). “Complaint profiles of those dissatisfied with the acoustic quality in their workspace point to problems with sound privacy and distracting noise from people’s conversations and telephone rings” (p. 370).
- The data showed that a higher percentage of people in LEED-certified/green buildings work in cubicles with low or no partitions; common strategies to maximize daylight, views, ambient lighting opportunity, personal control, flexibility, and equality of workspace allocation in green offices result in more open space and fewer enclosed private offices.
Green Buildings and Productivity
M.G. Miller, D. Pogue, Q.D. Gough, and S.M. Davis. Journal of Sustainable Real Estate 1(1):65-89. 2009.
Miller et al. summarized a literature search on various aspects of productivity (e.g., health and productivity, telecommuting and productivity, productivity gains from technology or economic pressure). They also outlined some of the difficulties of measuring productivity, especially for people performing knowledge-intensive work where the inputs and outputs are not easily quantifiable. “This is because direct measurement for professionals in an office environment requires the monitoring of (1) the ability to focus and think, synthesize, and add value to the firm; (2) the ability to measure the contribution of individuals that likely work in a team environment; and (3) the ability to monitor the quality of work as well as the efficiency and output” (p. 66).
Miller et al. also summarized the results of an empirical study. For that study, they hypothesized that green buildings (ENERGY STAR® label or LEED certification, any level) provided more productive
environments for workers than conventional buildings. Two measures of productivity were used: sick days and the self-reported productivity percentage after moving to a new building. The authors noted that the survey and its results were preliminary.
The survey was conducted in 154 buildings that contained more than 2,000 tenants. Some 534 tenant responses were collected from buildings located across the United States. Miller et al. found that 55 percent of the respondents agreed or strongly agreed that employees in green buildings were more productive, while 45 percent suggested no change (p. 81). They also found that 45 percent of the respondents agreed that workers were taking fewer sick days than before moving to a green building, while 45 percent found it was the same as before and 10 percent reported more sick days (all in ENERGY STAR®-labeled buildings).
Miller et al. also calculated the economic impacts of those tenants who claimed an increase in productivity. Economic impacts were “based on salaries that approach the cost of rent using a very conservative square foot per worker assumption” (p. 81).
A Comparison of the Performance of Sustainable Buildings with Conventional Buildings from the Point of View of the Users
G. Baird, A. Leaman, and J. Thompson. Architectural Science Review 55(2): 135-144. 2012.
Baird et al. sought to determine whether users perceived sustainable buildings to perform differently from conventionally designed buildings. The questionnaire used was the standard two-page questionnaire developed by the Buildings in Use (BIU) study for office buildings. The questionnaire included 45 questions grouped into several categories, including environmental (temperature, noise/acoustics, lighting) and overall satisfaction (design, needs, comfort overall, productivity, and health). The questions typically asked occupants to rate a factor on a scale of 1 to 7, with 1 being unsatisfactory and 7 being ideal.
The set of sustainably designed buildings included 31 commercial and institutional buildings located in 11 different countries. All of the buildings were either recipients of national awards for sustainable design or highly rated in terms of their country’s building sustainability rating tool(s) or had pioneered some aspect of green architecture. The buildings ranged in size from 1,000 to 20,000 square meters and were occupied by 15 to 350 staff. Fifteen of the buildings were predominantly office use, 10 were academic teaching buildings, 4 housed laboratories or research organizations, and 2 contained a combination of light industrial and administrative functions. Surveys were gathered from 2,035 staff members.
The comparison set consisted of 109 conventional buildings selected from the BIU database that had been surveyed during a similar time period as the sustainable buildings. Included were buildings occupied by 15 to 1,100 occupants and office, light industrial, visitor center, and academic activities. The independent t-test was used to determine whether differences between the mean values for the various aspects were statistically significant. Among the authors’ findings were the following:
- “In the case of the four environmental subcategories, the scores were not universally more favourable [sic] for the sustainable building set” (p. 140).
- An overall improvement in temperature and air quality was statistically significant. The sustainable buildings were perceived to be colder on average in winter but much the same (still on the hot side) in summer, whereas their air was perceived to be both fresher and less smelly year round (p. 140).
- Users also perceived a considerable improvement in lighting in the sustainable buildings in comparison to the conventional buildings that was statistically significant (p. 140).
- The users’ perception of differences in noise levels was not statistically significant. Users in both samples of buildings perceived of slightly too much noise from various internal sources (e.g., conversations, telephones) (p. 140).
- For the sustainable buildings, all of the factors in the satisfaction category showed a significant improvement over the conventional buildings. Occupants of sustainable buildings perceived that they were 4 percent more productive than did occupants of conventional buildings. The improvement in perceived health among occupants in conventional buildings (3.29 on the 7-point scale) in comparison to occupants in sustainable buildings (4.25) was also statistically significant (p. 143).
STUDIES ON THE INCREMENTAL COSTS TO DESIGN AND CONSTRUCT HIGH-PERFORMANCE OR GREEN BUILDINGS
Costing Green: A Comprehensive Cost Database and Budgeting Methodology
L.F. Matthiessen and P. Morris. Davis Langdon Company, Los Angeles, Calif. 2004.
Matthiessen and Morris undertook a study with the goal of comparing construction costs of buildings where LEED certification was a primary goal to the costs of similar buildings where LEED was not considered during design. The authors studied 93 non-LEED and 45 LEED-seeking buildings for which data were gathered from the database of the Davis Langdon Company. All costs were normalized for time and location to ensure consistency for the comparisons. They noted that the non-LEED buildings all would have earned some LEED points by virtue of their basic design, but sustainability had not been the intent. Among their conclusions were the following:
- Many projects achieve sustainable design within their initial budget or with very small supplemental funding. This suggests that owners are finding ways to incorporate project goals and values, regardless of budget, by making choices.
- Each building project is unique and should be considered as such when addressing the cost and feasibility of LEED. Benchmarking with other comparable projects can be valuable and informative but not predictive.
- There was no statistically significant difference [in cost per square foot] between the LEED and the non-LEED seeking buildings. The cost per square foot for the LEED-seeking buildings was scattered throughout the range of costs for all buildings studied, with no apparent pattern to the distribution. This was tested statistically using the t-test method of analyzing sample variations.
- Cost differences between buildings are due primarily to program type.
- There are low-cost and high-cost green buildings.
- There are low-cost and high-cost non-green buildings.
- Comparing the average cost per square foot for one set of buildings does not provide any meaningful data for any individual project to assess what—if any—cost impact there may be for incorporating LEED and sustainable design. The normal variations between buildings are sufficiently large that analysis of averages is not helpful.
- Closer examination of the non-LEED and LEED buildings suggests that for any building there are usually about 12 points that can be earned without any changes to design, due simply to the building’s location, program, or requirements of the owner or local codes. Up to 18 additional points are available for a minimum of effort and little or no additional cost required.
Cost of Green Revisited: Reexamining the Feasibility and Cost Impact of Sustainable Design in Light of Increased Market Adoption
L.F. Matthiessen and P. Morris. Davis Langdon Company, Los Angeles, Calif. 2007.
This study compared the construction costs of 83 buildings seeking LEED 2.1 and 2.2 New Construction certification to 138 non-LEED-seeking buildings. The building types included academic classroom buildings (17 LEED-seeking, 43 non-LEED seeking), laboratories (26/44), libraries (25/32), community centers (9/9), and ambulatory care facilities (9/8). The costs were normalized for time and location. Some of the findings from the study were the following:
- Many projects are achieving LEED certification within their budgets and in the same cost range as non-LEED projects.
- Construction costs have risen dramatically but projects are still achieving LEED.
- While there appears to be a general perception that sustainable design features add to the overall cost of the building, the data do not show a significant difference in the average costs of LEED-seeking and non-LEED-seeking buildings.
The Economics of LEED for Existing Buildings for Individual Buildings
Leonardo Academy, Inc., Madison, Wis. 2008.
The authors presented survey data for 11 to 13 buildings certified under the LEED-EB program. The data were provided by the owners or managers of the buildings for 2006-2007. The white paper focused on the certification, implementation, and process costs for LEED-EB certification and an operating cost comparison.
In terms of the costs to certify, implement, and process LEED-EB certifications, data from 13 buildings were available. The authors found that the average cost for LEED-EB implementation and certification was $1.58 per square foot, while the median was $1.52 per square foot. However, the certification costs varied significantly from building to building, from $0.02 per square foot to $5.01 per square foot (p. 5). The authors note that “the results do not follow expectations of higher costs for higher certification levels, but this may be due to the very small sample size at this time” (p. 7).
In this study, operating costs included cleaning expenses, repair and maintenance expenses, roads/grounds expenses, security expenses, and administrative and utility expenses. Data for 11 buildings, all of which had a significant component of office space, were collected and compared to the operating costs in the Building Owners and Managers Association’s (BOMA’s) Experience Exchange Report. The authors found that “in all categories of operating costs, more than 50% of the LEED-EB buildings have expenses less than the BOMA average for the region. Total expenses per square foot of the LEED-EB buildings are less than the BOMA average for 7 of the 11 buildings” (p. 21).
GSA LEED Cost Study
Steven Winter Associates. 2004.
This study was undertaken to estimate the costs to develop “green” federal buildings using LEED 2.1. The report provides a detailed and structured review of both the capital and soft cost implications of achieving Certified, Silver, and Gold LEED-ratings for the two building types most commonly constructed by the GSA: a five-story courthouse and a mid-rise federal office building.
For both building types, baseline construction costs were developed to reflect federal design requirements. An analysis was performed to identify the incremental costs associated with green building measures that would likely be implemented to meet the specific LEED prerequisite and credit requirements.
Individual LEED credit assessments and cost estimates were completed for six scenarios to create a cost range for LEED-Certified, -Silver, and -Gold certification levels. The study indicated that there was an inherent degree of variability to LEED construction cost impacts, based on the following findings:
- There was no correlation between the point value of a LEED credit and its cost.
- A range of different strategies can often be used to earn the same individual LEED credit.
- The cost of some credits varied significantly based on the building type and building program.
- Some credit costs varied based on region-specific or project-specific issues.
The authors concluded that many Silver-certified projects could be built at a cost that was within 4 percent of the cost for a similar non-LEED-certified courthouse or office building, as well as occasional LEED-Gold-certified projects (p. 8).
LEED Cost Evaluation Study
Indian Health Service. Department of Health and Human Services. 2006.
The U.S. Indian Health Service (HIS) conducted this study to evaluate the potential cost impacts of achieving LEED-NC and LEED-NC-Silver certification on its facilities, which are primarily hospitals and other healthcare-related buildings. They evaluated both initial capital cost investments and life-cycle costs (using a 20-year life). The purpose was to develop realistic cost factors for the implementation of LEED certification in the IHS budget estimating system so that projects could be adequately funded up-front for this purpose. For the study, LEED credits were evaluated against standard practices of the Indian Health Service as outlined in the agency’s design guide.
Among the study findings were the following:
- Initial capital construction costs (design and construction) would require a 1 to 3 percent increase in the budget to meet the Certification level, and a 3.5 to 7.6 percent increase in the budget to meet LEED-Silver certification.
- Energy savings over 20 years of operation have the potential to significantly mitigate the initial capital cost impacts. “Given the potential margin of error inherent in these types of calculations, and the uncertainty of future energy prices, life-cycle cost savings may completely offset or even exceed initial capital costs” (p. ES-3).
The authors of the study made the following recommendation:
It is advisable for IHS to adopt LEED certification in pursuit of sustainable design and adjust project budgets accordingly. Doing so provides a measurable benchmark for determining success. LEED is widely known, has significant credibility within the private and public sectors, provides third-party validation and provides recognition for the agency, affiliated tribes, and communities. Flexibility in the LEED process facilitates multiple avenues for achieving a basic certification under disparate circumstances, site conditions, and geographic locations…. a 3.0% increase to the project budget is appropriate to pursue a basic [Certified level] certification (p. ES-3).
MILCON Energy Efficiency and Sustainability Study of Five Types of Army Buildings
D.M. Caprio and A.B. Soulek. U.S. Army Corps of Engineers, Washington, D.C. 2011.
This study investigated current building features and construction methods and materials that will optimize energy reduction and sustainability for new construction standard designs in FY2013. The standard designs were for the five most commonly constructed Army building types: unaccompanied enlisted personnel housing (barracks); tactical equipment maintenance facility; company operations facility (government office and other public assembly); brigade headquarters (government office and data center); and dining facility. Among the goals for the study were the following:
- Determine the difference in initial investment or “first” cost of the proposed baseline buildings with energy enhancements to meet the energy and sustainability mandates as compared to the original baseline buildings without energy enhancement.
- Determine compliance with the energy performance option of ASHRAE Standard 189.1.
- Reduce both indoor and outdoor potable water usage.
- Account for the impact on operations and maintenance by energy systems.
- Comply with the Guiding Principles for Federal Leadership in High-Performance and Sustainable Buildings.
The selected standard designs were required to meet all applicable energy reduction and sustainable design mandates (e.g., LEED Silver, Energy Policy Act of 2005, EISA 2007, and Executive Orders 13423 and 13514). The requirements were to “optimize the mission, function, quality, and cost” of each building design type. The baseline designs were amended and supplemented to include antiterrorism and force protection and select Department of Defense Unified Security Criteria, among other factors, and the designs were evaluated for full mission scope and full energy and sustainability compliance.
The authors noted difficulties in establishing a clearly defined baseline for determining energy performance because “these buildings do not have equivalent building categories within CBECS” and because of initial confusion over the different energy baselines found in ASHRAE standards (modeled building energy), and Section 433 of EISA 2007, which is based on measured building and plug load energy (p. v).
Energy simulations were completed using Energy Plus version 5.0 (DOE, 2010). Each energy-efficiency measure (EEM) was modeled independently; packages of energy-efficiency improvements were also modeled because the savings from each individual measure are not additive (p. 3). EEMs were modeled for each building type across 15 locations representative of the climate zones that serve as the basis for the development of ASHRAE standards.
The authors note that “the study was able to show the energy effectiveness of a range of efficiency measures, but it was not able to show the cost effectiveness of individual measures, nor was it able to optimize the designs for the highest energy performance at the lowest costs. This typically is done early in the design phase.” The results were based on total energy use as opposed to the fossil-fuel-based portion of total energy use alone (p. 1).
Among the study conclusions were the following:
- Significant energy savings are possible for all climates.
- Cost increases for the recommended Low Energy Packages for the five building types ranged from 2 to 10 percent, with a high of 28 percent.
- It is very difficult to reach the EISA 2007 target for the 2015 goal of 65 percent fossil fuel reduction with building-specific efficiency measures alone.
- Buildings achieving 25 to 35 percent energy savings yield the maximum energy savings for the lowest cost.
- For buildings achieving 35 to 60 percent energy savings, each increment of energy saved comes at an increasingly higher cost (plug load reduction, small-scale renewable energy, building orientation, site-specific design).
- It may be cost prohibitive to design and construct buildings with energy savings of greater than 60 percent without looking beyond the building (significant plug load reduction, clustering, renewable energy, cogeneration, etc.)
- Some facility types in certain regions will never achieve the 65 percent energy target through energy-efficiency measures alone (p. vi).
- There is a high level of confidence that the five building types would meet or exceed the goal of ASHRAE 189.1 to achieve a 30 percent reduction in energy use compared to an ASHRAE 90.1-2007 building, including plug loads (p. vii).
- Assuming proper construction and commissioning, energy savings in these buildings would be immediate. In terms of renewable energy however, their cost is over six times higher than the current investment in energy-efficiency measures in today’s dollars (p. vii).
Incremental Costs of Meeting ASHRAE Standard 189.1 at Air Force Facilities
Logistics Management Institute, Reston, Va. 2011.
The authors sought to determine the incremental up-front construction cost to the Air Force (AF) of adhering to ASHRAE Standard 189.1 for High-Performance Green Buildings Except Low Rise Residential. Their purpose was to identify aspects of ASHRAE Standard 189.1 that could be included in Air Force Construction Criteria. Case studies for four different types of facilities in four different climate zones were conducted. Among the study findings were the following:
- Because AF buildings already are constructed to meet the Guiding Principles for High-Performance and Sustainable Buildings and meet at least LEED-Silver requirements and other federal sustainable building requirements, the added initial cost of meeting ASHRAE 189.1 as a percentage of total building construction costs was 1 to 2.8 percent for three of the four building types and 7.1 percent for the fourth type.
- Some of the requirements listed in ASHRAE Standard 189.1 would require fundamental changes to the implementation of the AF energy and metering programs.
- One part of the standard requires being able to reduce a building’s energy demand by 10 percent at peak load times. However, if an AF building provides mission-critical functions, the building would be excepted from base-wide load shedding management.
- The standard requires that electricity, gas, and water meters have remote reading requirement. The AF requires advanced meters for new construction, but it has ordered a strategic pause in connecting new meters to existing remote meter reading systems due to security concerns and the pursuit of a standardized platform.
- The AF currently does not have the ability to manage the data collected by the meters (or sub-meters on some systems).
- Some of requirements overlap with what AF is already doing; others, like renewable energy, drive a very large capital investment that may not align with the AF corporate renewable energy strategy, and still others may be in conflict with how individual programs are implemented in the AF.
- The U.S. Army took exception to the renewable energy requirement because it makes more sense for military bases to use their size and footprint to tackle the problem rather than looking at individual building applications where the numbers simply are not life-cycle cost effective (p. v).
Literature Review of Data on the Incremental Costs to Design and Build Low-Energy Buildings
W.D. Hunt. PNNL-17502. Pacific Northwest National Laboratory, Richland, Wash. 2008.
Hunt conducted a literature review on the incremental costs to design and build low-energy buildings as opposed to green or sustainable buildings. For this review, a low-energy building was defined as one that “achieves 30 to 50 percent energy savings when compared to a building built to ASHRAE Standard 90.1-2004.”
Among the findings were the following:
- Objectively developed and verifiable data on the cost premium for low-energy (high-efficiency) buildings are very limited. Most of the literature focused on green or sustainable buildings, not low-energy buildings.
- In cases where energy efficiency costs were available, the cost premiums ranged from 1 to 7 percent. In most cases, the cost premium was less than 4 percent. A notable exception is small warehouses in cooler regions (climate zones 5 through 7), which carried estimated cost premiums of between 5.9 and 7 percent.
- Technology solutions are available right now to achieve savings on the order of 30 percent and more over ASHRAE Standard 90.1-2004; however, cost effectiveness of these technology standards is often not addressed (p. 2).