Printer Friendly Format
Commercial Buildings Determinations
Explanation of the Analysis and Spreadsheet
I. Background
The 90_1savingsanalysis.xls worksheet (ZIP 5.8 MB) - (Download Zip Application) - aggregates the results of building energy simulations used in support of the Department of Energy's determination regarding whether ANSI/ASHRAE/IESNA Standard 90.1-1999 Energy Standard for Buildings Except Low-Rise Residential Buildings will improve energy efficiency in commercial buildings. This determination is required by Section 304 of the Energy Policy and Conservation Act .
The Department carried out both a broad quantitative analysis and a detailed textual analysis of the differences between the requirements and the stringencies in the 1989 and the 1999 editions. This spreadsheet only presents the results of the broad quantitative analysis.
II. General Description of the Quantitative Analysis
The quantitative comparison of energy codes was done using whole-building energy simulations of buildings built to each standard. We simulated seven representative building types in 11 representative U.S. climates. Note that only differences between new building requirements were considered in this quantitative analysis. The simulations were based on a 15 zone building prototype used in previous DOE building research. The simulated Energy Use Intensities (EUI) for each zone were scaled to correctly reflect variations in building size and shapes for each representative building type. Energy use intensities developed for each representative building type were weighted by total national square footage of each representative building type to provide an estimate of the difference between the national energy use in buildings constructed to both editions.
The scope of the 1999 edition also addresses additions and renovations to existing buildings, unlike the 1989 edition. While this difference will have a significant energy impact, we found no data available to permit us to accurately quantify this impact.
III. Discussion of the Quantitative Analysis
The analysis methodology is briefly described below. This is followed by a description of the input assumptions.
A. Analysis Methodology
To determine the aggregate impact of changes to the envelope, lighting, and mechanical sections of 90.1, a series of building simulations made using the BLAST (Building Loads Analysis and System Thermodynamics) building simulation software. Seven building types, shown in Table 1, were used in the analysis. These seven building types used represent approximately 80 percent of commercial building energy consumption, according to the Energy Information Administration's 1995 Commercial Building Energy Consumption Survey (CBECS95) data. (The Office building type includes Outpatient Health Care at 76.6 thousand Btu per year.)
Table 1. Energy Consumption by Principal Building Activity (trillion Btu)
| Building Types Simulated | Annual Energy Use | Percent of Total |
|---|---|---|
| Office | 1,095 | 20.6 |
| Mercantile and Service | 973 | 18.3 |
| Education | 614 | 11.5 |
| Lodging | 461 | 8.7 |
| Public Assembly | 449 | 8.4 |
| Food Service | 332 | 6.2 |
| Warehouse and Storage | 325 | 6.1 |
| Total for above Categories | 4,249 | |
| Total for all commercial buildings | 5,323 | 79.8 |
Construction variation within each building category was simulated using four different window to wall area ratios, both mass (such as dense masonry) and light frame wall construction types, and gas and electric heating fuel types. Two scenarios of economizer usage were simulated in each climate to account for the variation of economizer usage requirements in combination with equipment size. The buildings were simulated in 11 different climate locations (Table 2). The climate locations were chosen based on statistical cluster analysis of 234 Typical Meteorological Year weather data tapes and were chosen to be representative of the variation in climate found in the U.S. Several of the more significant climate parameters are shown in Table 2. These include, Heating Degree Days, base 65 degrees Fahrenheit (HDD 65); Vertical Solar radiation, in the North (VSN), East/West (VSEW), and South (VSS) orientations; Cooling Degree Days, base 50 degrees Fahrenheit (CDD 50); minimum recorded outdoor temperatures for 99.6 percent of the time for heating design calculations; maximum recorded Dry Bulb (DB) outdoor temperatures exceeded 1 percent of the time for cooling design calculations; and maximum recorded Wet Bulb (WB) outdoor temperatures exceeded one percent of the time, also for cooling design calculations.
Table 2. Climates Locations Used
| Location | HDD 65 | VSN | VSEW | VSS | CDD 50 | Heating Design 99.6 |
Cooling Design (1% DB) |
Cooling Design (1% WB) |
|---|---|---|---|---|---|---|---|---|
| Denver, CO | 6083 | 428 | 971 | 1321 | 2611 | -3 | 90 | 59 |
| Detroit, MI | 5997 | 390 | 676 | 858 | 3199 | 0 | 87 | 72 |
| Fresno, CA | 2700 | 459 | 1029 | 1199 | 5070 | 30 | 101 | 70 |
| Knoxville, TN | 3818 | 446 | 762 | 898 | 4455 | 13 | 90 | 74 |
| Los Angeles, CA | 1494 | 482 | 962 | 1146 | 4456 | 43 | 81 | 64 |
| Minneapolis, MN | 8060 | 380 | 709 | 972 | 2751 | -16 | 88 | 71 |
| Orlando, FL | 532 | 511 | 881 | 974 | 8288 | 37 | 93 | 76 |
| Phoenix, AZ | 1382 | 488 | 1116 | 1310 | 7830 | 34 | 108 | 70 |
| Providence, RI | 6022 | 393 | 677 | 874 | 2756 | 5 | 86 | 71 |
| Seattle, WA | 5281 | 350 | 621 | 828 | 1683 | 23 | 81 | 64 |
| Shreveport, LA | 2265 | 484 | 843 | 954 | 6022 | 22 | 95 | 77 |
| Tampa, FL | 575 | 518 | 890 | 974 | 7985 | 36 | 91 | 77 |
In addition to simulating buildings that complied with the 1989 and 1999 editions, the changes in envelope, lighting and mechanical requirements were each separately simulated, without changing the 1989 edition's requirements for the other components. Then, because the lighting and envelope requirements impact each other, particularly in the 1989 edition, the combined lighting and envelope requirement differences were analyzed, again without changing the 1989 edition's requirements for the other components. Calculating the difference between this combination and all 1999 edition requirements allowed an assessment of the impact of the mechanical changes after adjusting for this thermal load shift. In all, six separate sets of requirement changes were simulated.
In total, 2464 simulations were performed for each set of requirement changes. A prototypical 48,000 ft2, 15-zone, slab-on-grade building was used for all the simulations. Simulation results for this prototypical building size were then scaled to reflect aggregate energy use in buildings across a wide range of sizes and shapes using CBECS building data. Single zone air-conditioning and heating systems were assumed in the building model to permit this scaling. This simplification should result in a lower-bound estimate of energy savings with the standard as explained in the mechanical system characterization below.
B. Simulation Input Characterization
1. Envelope
The building envelope characteristics examined in the analysis were the opaque wall and roof U-factors, the fenestration U-factors, either the fenestration Shading Coefficient requirements (in the 1989 edition) or Solar Heat Gain Coefficient requirements (in the 1999 edition), and the effective slab U-factors for slab on grade construction. These characteristics were determined for each set of requirement changes, building type, and climate combination simulated.
The 1989 edition's envelope requirements simulated were based on the 1989 edition's Alternate Component Packages (ACP) tables. These tables represent the prescriptive compliance path for the 1989 edition's envelope requirements. Because the 1989 edition's requirements do not necessarily reflect the performance of typical building assemblies, the actual U-factors used in the simulations were chosen to reflect the U-factors of real building assemblies which best approach, without exceeding, the U-factor requirements of the standard. This is expected to be more representative of the real envelope performance resulting from application of the 1989 edition. Note that this procedure provides a lower estimate of the envelope energy savings compared to a more strict requirement-to-requirement characterization of the opaque wall U-factors.
In addition, the 1989 edition's ACP tables represent more stringent envelope requirements than those specified for most climates or buildings, using the equations outlined in Chapter 8 of the 1989 edition. The equations are embodied in the ENVSTD, version 2.4, software. For this reason, the use of the ACP tables as the basis for the 1989 edition's envelope provides a lower bound estimate of energy savings from the building envelope requirements.
2. Lighting
The lighting power density requirements were developed from the whole building lighting requirements for both the 1989 and 1999 editions for comparable building types, where available. The 1999 edition provides single value whole building lighting power density values for 31 different building types. The 1989 edition provides whole building lighting power density values for only 11 different building types. However, it provides different lighting power densities for six different building size categories within each building type. In neither case do the whole building lighting power density values correspond perfectly to the building types simulated. The following procedure was used to develop whole building lighting numbers for each of these categories:
a. Lighting Power - 1989 Edition
For office and warehouse building types, where there is a direct match with the 1989 standard whole building lighting power categories, the lighting power density was estimated by weighting the whole lighting power density across the six building size categories by the fraction of each building type`s floor space in each size category using CBECS95 data.
In the case of Food Service and Education, the 1989 edition provides lighting power density values for sub categories of these building types. Food Service is composed of Fast Food/Cafeteria and Leisure Dining/Bar subcategories, Education is composed of Preschool/Elementary, Jr. High/High School, and Technical/Vocational subcategories. In these cases, first the lighting power densities for the different building subtypes were averaged together for each building area category. Then, a weighting of these new lighting power densities by building size category was made, using CBECS data for Food Service or Education building types, as appropriate.
In the case of retail type buildings, the 1989 edition has three basic retail building subcategories, Retail, Mall Concourse, and Service. CBECS floor area data is categorized as Enclosed Shopping Center/Mall, Retail (except Mall), Service (except Food), and Strip Shopping. To make a realistic weighting by retail type the following allocation of CBECS retail type floor area was made.
Table 3. Allocation of CBECS95 retail type floor area.
| Retail Building Categories - 1989 Edition | Allocation of CBECS95 Building Category Floor Area |
|---|---|
| Retail | Retail (except Mall) plus Strip Shopping plus half of Enclosed Shopping/Mall |
| Mall Concourse | Half of Enclosed Shopping/Mall |
| Service | Service (except Food) |
Then a weighted average of the allowed lighting power densities was constructed, using the 1989 edition's lighting power density values and the CBEC895 floor area data for each building type and size category.
For Lodging and Public Assembly building types, the 1989 edition has no direct match in the whole building lighting power density tables. For a comparison of these building types, the 1989 edition's whole building lighting power density values were developed by applying the appropriate 1989 edition's space-type lighting power density values (with appropriate Area Factor adjustments) to the building specific space type square footage data used in the development of the 1999 edition lighting power densities. The 1989 edition building specific space type data models the actual weighting of space type square footage, within a specific building type, based on actual current U.S. construction data. The lighting power densities value for the Lodging category is made up of the average of the whole building lighting power densities constructed for the 1999 edition's building categories: Dormitory, Hotel, and Motel. The lighting power densities value for the Public Assembly categories is similarly made up of the average 1999 edition's whole building lighting power densities values for Convention Center, Motion Picture Theater, Performing Arts Theater, Town Hall, Sports Arena, Museum, and Gymnasium.
b. Lighting Power - 1999 Edition
The 1999 edition provides single value, whole building, lighting power densities requirements for Office, Retail, Education, and Warehouse buildings, and these requirements were used in the simulations. The 1999 edition does not provide single lighting power density values for Food Service, Lodging, or Public Assembly buildings. For these cases, the average whole building lighting power density requirements, for building types falling in each category, were taken to form a single lighting power density requirement. In these cases, the same specific building types used to develop the 1989 edition's lighting power density values were used to derive the 1999 edition's lighting power densities for Lodging and Public Assembly building types. The 1999 edition's Food Service value was derived as the average of the 1999 edition's three whole building food service building type values.
Table 4 shows a comparison of Whole Building lighting requirements under both editions.
Table 4. Lighting Power Density (Watts/ft2)
| Building Type | 1989 Edition | 1999 Edition |
|---|---|---|
| Education | 1.79 | 1.50 |
| Food Service | 1.62 | 1.73 |
| Lodging | 1.53 | 1.73 |
| Offices | 1.63 | 1.30 |
| Public Assembly | 1.72 | 1.53 |
| Retail | 2.36 | 1.90 |
| Warehouse/Storage | 0.53 | 1.20 |
3. Mechanical Equipment
Single zone cooling and heating systems were used in the analysis. The choice of single zone system in the analysis is expected to provide a lower bound estimate of cooling energy savings. First, this is because the improvement in the 1999 edition's average efficiency requirements for single zone cooling systems (typically unitary equipment), is relatively small compared to that for typical central system cooling equipment (typically water chillers). This is more obvious when one realizes that shipments of all products to commercial buildings includes residential type cooling products shipped to small commercial buildings. Additionally, modeling single zone systems does not take into account the fact that the 1999 edition has introduced requirements for central system heat rejection equipment, where none existed in the 1989 edition. There is relatively little improvement in heating equipment efficiency requirements in the 1999 edition for equipment used in single zone systems (typically furnaces), or central systems (typically boilers). The impact of the 1999 edition on heating energy use will typically be determined principally by changes in heating loads rather than heating equipment efficiency.
a. Cooling Equipment
Cooling equipment efficiencies were developed by weighting the energy efficiency rating for each of 20 categories of single zone cooling equipment in the standard, by an estimate of shipped cooling capacity for each category. The primary source of shipping data was 1998 U.S. Census Data. In the case of the less than 65,000 Btu per hour unitary air source heat pumps and air conditioners, this census data was augmented by our interpretation of Air-Conditioning and Refrigeration Institute and Lawrence Berkeley National Laboratory data on single phase air-conditioners and heat pumps shipped to commercial buildings. Using the weighting information and equipment efficiencies in each edition, the average unitary equipment efficiency requirement for commercial buildings increased 7.5 percent, from an average energy efficiency ratio of 9.28 to 9.98. This improvement was simulated for all building types except Lodging. For Lodging, it was assumed that the majority of single zone cooling equipment would be packaged terminal equipment. The average efficiency requirement for packaged terminal equipment increased 22 percent, from 8.4 to 10.28, based on a shipped capacity weighting. These efficiencies were used in the Lodging simulations for the respective Standard levels.
b. Space Heating Equipment
No change in heating equipment combustion efficiency is provided in the 1999 edition. However for commercial furnaces, a reduction in casing loss from 1.5 percent to 0.75 percent was modeled. No change in furnace casing losses was assumed where electric resistance heat was assumed.
c. Economizers
Simulations were performed assuming both economizer operation and no economizer operation for each building simulated. Based on the economizer requirements in each edition and the available cooling equipment shipment data, shipped cooling capacity weights were developed for systems requiring economizer usage in each climate.
d. Service Water Heating Equipment
Service water heating equipment efficiencies increased from 78 percent to 80 percent for most tank-type gas fired water heaters. This was reflected in the input assumptions. We did not account for shipments of residential size water heating equipment (regulated by manufacturing standards under Subpart C of 10 CFR 430) to commercial buildings. While these units may be used in some commercial buildings, increased efficiencies are the result of regulatory actions under 10 CFR 430, not Standard 90.1. Nor did we account for the use of tankless instantaneous water heaters in commercial buildings. Correctly accounting for shipped capacity of both the residential size and tankless equipment to commercial buildings would reduce the average efficiency improvement somewhat, but accurate shipment data to commercial buildings is largely unavailable.
No change in water heater standby loss efficiencies was modeled. For fossil fuel fired equipment, the standby loss efficiencies within a given size category are essentially the same. A different formulation of the standby loss equations were used in the 1999 edition and there are both standby loss increases and decreases in any given product category, no overall impact is well established. For electric water heaters, there appears to be a reduction in standby loss efficiency in the 1999 edition. However, the Energy Policy and Conservation Act, as amended, does not permit the manufacture or sale of these lower efficiency products. Therefore, there is no predicted impact on actual buildings.
4. Aggregation of results
Aggregation to a national estimate of energy use is based on energy use intensities (EUI) developed from simulations under each edition. Aggregation of energy use intensity from the simulations was done as follows: 1) extract zone-based energy use intensities from simulations; 2) aggregate results by required economizer usage in each climate; 3) map simulation results by climate to 11 geographical areas (augmented census divisions); 4) scale simulation results to existing building stock floor area by building type and census region; 5) weight results for frame and mass wall construction by appropriate building type and census region weights for these types of construction; 6) weight results for heating fuel by augmented census division weights for electric resistance heating usage in commercial buildings (CBECS data); 7) convert energy use intensities by fuel type to site energy, source energy, and energy cost intensities, by building type and augmented census division; 8) weight energy use intensity results by building construction floor area estimates, by building type and in each augmented census division. The building construction data was derived from the Energy Information Administration's National Energy Modeling System data sets.
Tables 5, 6 and 7 show the aggregated energy use and associated energy savings by building type.
Table 5. Estimated energy use intensity by building type - 1989 edition
| Building Type | Floor Area Weight | Whole Building Energy Use Intensity (kBtu/sf-yr or $/sf-yr) |
||||
|---|---|---|---|---|---|---|
| Electric | Gas | Site EUI | Source EUI | $UI | ||
| Assembly | 0.068 | 61.55 | 32.18 | 93.73 | 231.78 | 1.48 |
| Education | 0.218 | 35.65 | 18.86 | 54.50 | 134.47 | 0.87 |
| Food | 0.027 | 101.60 | 35.52 | 137.12 | 363.04 | 2.32 |
| Lodging | 0.079 | 42.80 | 17.61 | 60.41 | 155.88 | 1.00 |
| Office | 0.190 | 49.85 | 5.61 | 55.45 | 165.00 | 1.09 |
| Retail | 0.246 | 57.14 | 3.95 | 61.09 | 186.39 | 1.23 |
| Warehouse | 0.173 | 10.43 | 8.19 | 18.62 | 42.32 | 0.27 |
| National | 43.36 | 12.09 | 55.44 | 151.52 | 0.99 | |
Table 6. Estimated Energy Use Intensity by Building Type - 1999 edition
| Building Type | Floor Area Weight | Whole Building Energy Use Intensity (kBtu/sf-yr or $/sf-yr) |
||||
|---|---|---|---|---|---|---|
| Electric | Gas | Site EUI | Source EUI | $UI | ||
| Assembly | 0.068 | 55.71 | 33.88 | 89.59 | 215.04 | 1.37 |
| Education | 0.218 | 31.59 | 20.05 | 51.64 | 122.88 | 0.79 |
| Food | 0.027 | 102.78 | 34.91 | 137.69 | 366.12 | 2.35 |
| Lodging | 0.079 | 42.71 | 18.76 | 61.47 | 156.86 | 1.00 |
| Office | 0.190 | 44.56 | 6.32 | 50.88 | 148.95 | 0.98 |
| Retail | 0.246 | 48.14 | 5.17 | 53.31 | 159.08 | 1.05 |
| Warehouse | 0.173 | 17.91 | 9.11 | 27.02 | 67.15 | 0.43 |
| National | 40.17 | 13.13 | 53.31 | 142.54 | 0.93 | |
Overall, considering those differences that can be reasonably quantified, the 1999 edition will increase the energy efficiency of commercial buildings. However, this is not true for all new buildings of all building types. In the case of the Food Service, Lodging, and particularly the Warehouse building categories, the 1999 edition will allow increased energy usage. This is primarily due to an increased lighting power allowance for each building category under the 1999 edition.
Table 7. Estimated Percent Energy Savings with 1999 edition - by Building Type
| Building Type | Building Type Floor Area Weight |
Whole Building Energy Use Intensity (kBtu/sf-yr or $/sf-yr) |
||||
|---|---|---|---|---|---|---|
| Electric | Gas | Site EUI | Source EUI | $UI | ||
| Assembly | 0.068 | 9.5 | -5.3 | 4.4 | 7.2 | 7.5 |
| Education | 0.218 | 11.4 | -6.3 | 5.2 | 8.6 | 9.0 |
| Food | 0.027 | -1.2 | 1.7 | -0.4 | -0.8 | -0.9 |
| Lodging | 0.079 | 0.2 | -6.5 | -1.7 | -0.6 | -0.5 |
| Office | 0.190 | 10.6 | -12.7 | 8.2 | 9.7 | 9.8 |
| Retail | 0.246 | 15.7 | -30.7 | 12.7 | 14.7 | 14.9 |
| Warehouse | 0.173 | -71.6 | -11.3 | -45.1 | -58.7 | -59.7 |
| National | 1.000 | 7.3 | -8.6 | 3.9 | 5.9 | 6.2 |
A comparison of energy savings by building type for each of the different standard scenarios modeled is shown in Table 8.
Table 8. Percent energy savings from 1989 edition(national figures, all building types)
| Standard Scenario | Electric EUI | Gas EUI | Site EUI | Source EUI | $UI |
|---|---|---|---|---|---|
| 1989 edition | 0 | 0 | 0 | 0 | 0 |
| 1989 edition with 1999 edition envelope requirements | -0.2 | -6.3 | -1.6 | -0.8 | -0.7 |
| 1989 edition with 1999 edition lighting requirements | 5.9 | -8.3 | 2.8 | 4.6 | 4.9 |
| 1989 edition with 1999 edition lighting and envelope requirements | 5.7 | -12.0 | 1.8 | 4.1 | 4.4 |
| 1989 edition with 1999 edition mechanical requirements | 2.2 | 3.0 | 2.4 | 2.3 | 2.2 |
| 1999 edition compliant buildings | 7.3 | -8.6 | 3.9 | 5.9 | 6.2 |
IV. General Description of the Spreadsheet
The analysis spreadsheet (90_1SavingsAnalysis.xls) is composed of 13 separate spreadsheet tabs. These tabs are described in the tab titled Instructions, the details of which are repeated here.
For each of the standard scenarios, 2464 individual building permutations were run. The simulations represent all possible combinations of the following:
- Eleven specific climate weather tapes (Denver, Detroit, Fresno, Knoxville, Los Angeles, Minneapolis, Phoenix, Providence, Seattle, Shreveport)
- Seven different building types (Office, Retail, Education, Public Assembly, Food Service, Lodging, and Warehouse)
- Electric or Gas heating system
- Four different window area fractions (7, 18, 38, and 45 percent)
- Economizer and No-Economizer Runs
- Mass or Steel Frame Wall Construction
Each simulation was carried out using the three story, 15 zone, scalable building model used in previous 90.1 analysis work. For each simulation completed for each scenario, we extracted the following data: whole building lighting and plug energy use intensity (EUI), electric system energy use intensity (fan, condensing unit, and any electric heating) for each of 15 zones, gas HVAC system energy use intensity (gas heating) for each zone, whole building hot water energy use intensity (electric), and whole building hot water energy use intensity (gas). Data in these latter columns are mutually exclusive as buildings simulated were allowed either electric or gas hot water use, but not both. All values are reported in thousands of Btu per square foot (kBtu/ft2).
A. Aggregation Process
The aggregation process is easily followed by reviewing the Aggregation spreadsheet tab starting at the upper left hand corner of that spreadsheet. As discussed on the Instructions tab, the viewer is first allowed to select the set of results being aggregated using the buttons shown in Column B, rows 5 - 19. Selection of any button populates the aggregation spreadsheet with results data from that selected set of simulations. The raw results data for each scenario is shown in Table 9.
Table 9. Spreadsheet tabs and associated analysis scenario for raw simulation outputs
| Tab | Analysis Scenario |
|---|---|
| 1989SimData | 90.1-1989 scenario |
| 1999SimData | 90.1-1999 scenario |
| 1989SimData_99lighting | 90.1-1989 with 90.1-1999 lighting requirements |
| 1989SimData_99mechanical | 90.1-1989 with 90.1-1999 envelope requirements |
| 1989SimData_99mechanical | 90.1-1989 with 90.1-1999 equipment efficiencies and economizer requirements |
| 1989SimData_99lighting_99envelo | 90.1-1989 with 90.1-1999 lighting levels and 90.1-1999 envelope requirements |
Conversely, the user can select the button labeled "Save Results" which will run all six scenarios, and populate the "OutputResults" tab with the results of the simulations by building type and location. In addition it will provide a comparison of the output for each scenario against a baseline 90.1-1989 standard. If this is selected, the user will be asked to provide a new spreadsheet name to store the results in a separate file. In naming this new spreadsheet, please omit the .xls extension.
All aggregation steps are taken in the Aggregation spreadsheet tab. For each step of the aggregation, the weighting data used in that step is identified, and its location in the workbook shown in the Aggregation tab. The remainder of this document walks the user through the Aggregation tab from building simulation data to final national Energy Use Intensity (EUI) estimates for a given scenario.
When a scenario is selected in the Aggregation tab, the raw simulation results from the selected scenario populate columns B-AS in the Aggregation tab. These results are converted to nine "metazone" electric and gas EUI data shown in columns BB-BS. The metazones represent the EUI for three metazones (building core, perimeter and perimeter "corner") on each of the bottom floor, middle floor, and top floor of the simulated building. The perimeter corner and perimeter cross represent the average of all perimeter orientations (North, West, East, and South), making the aggregations orientation neutral.
Cells BV14-BW20 allow the user to select the economizer weighting used in the aggregation. The default weighting aggregates the metazone EUI for each combination of parameters for both an economizer simulation, and a no-economizer simulation. These separate simulations are weighted by the fraction of shipped cooling tonnage of DX cooling equipment whose size would require having an economizer under the Standard simulated. The economizer weighted metazone EUI results are shown in columns BV-CP.
The results for each climate simulated are mapped to a set of 11 augmented geographic census divisions in the U.S. This is done using mapping data relating the fundamental climate constituents with the climates in a given region of the country. This mapping is shown in the tables in cells CU3-DG13. Using these climate location weights, the electric and gas EUI estimates for the simulation results by climate are mapped to each augmented census division. They are shown in columns CV-DM. Column DO shows details about the remaining building permutations.
The zonal EUI for these remaining building permutations are then aggregated by the fraction of floor space for each of the nine metazones, corresponding to each building type, in each augmented census division. The data used to produce this mapping was developed from building floor area, number of stories, and aspect ratio data. It was derived from the 1992 CBECS microdata files, at the census region level. The user selectable option buttons in cells DP16-DT19 can allow the user to choose between scaling or not scaling the EUI data from the simulation model to match the detailed building population data.
The user selectable option buttons in cells DX12-EA19 allow the user to choose to aggregate the simulation results for the range of window wall ratios (WWR) from 0-50 percent (the WWR Range All option), or to look at the results by a single window wall ratio range. The representative WWR values for the different WWR ranges are
| WWR Range | WWR simulated |
|---|---|
| 0-10% | 7% |
| 11-25% | 18% |
| 26-50% | 38% |
| 51-100% | 45% |
Both standards require a building trade-off option for window wall ratios higher than approximately 45-50 percent. There is no clear mechanism to determine what U-factor and solar heat gain coefficient would be required for these buildings, however, to provide some approximation we did develop simulation of the energy use for a 45 percent WWR. This 45 percent WWR is the midpoint for the top WWR ratio range for which 90.1-1999 has prescriptive requirements and a level at which prescriptive requirements are available for most of the ACP tables. This allows the user to explore the approximate baseline energy use expected to be used in a trade-off procedure for higher WWR levels.
The user selectable option buttons in cells EF14-EH19 allow the user to present results for lightweight or mass wall combinations, or a CBECS weighted national average of the two basic wall constructions. The lightweight wall scenario is represented by metal frame wall construction for the 1999 edition, with the exception of lightweight warehouse construction, in which metal building walls and roof were assumed.
Columns EL-EO aggregate the remaining building EUI data by Heat Fuel type using CBECS data. The user can select to look at Heating Fuel equals gas or Heating Fuel equals electric resistance. Or, the user can select to aggregate the simulation for fossil fuel and electric resistance heating, using electric resistance weighting data from CBECS1995. If the user selects to use the weighted heating fuel type data, two options for weights have been provided - either by CBECS census division, or by census region and building type.
In columns EQ-ET, the building and augmented census division fuel usage EUI data is converted to building site EUI, primary (source) EUI, and dollar cost intensity data. The primary (source) energy use conversions used are shown in ER14-ET16.
Finally, regional and national estimates of the fraction of the predicted building construction for each building type and by augmented census division for the period from 2001-2010 were used to provide national weighting of the EUI estimates. The weighting information was extracted from DOE/EIA National Energy Modeling System (NEMS) and is shown in columns EV-EY, and the resulted weighted EUI data is shown in columns FB-FH by building type and columns FJ-FP by augmented census division. Cells FB11-FF19 show the user selectable options used for the aggregation. For either breakdown, a national site EUI, source EUI, and energy cost intensity ($UI) are shown for the selected standard scenario. As discussed, when the user selects to "Save results", the spreadsheet cycles through the 6 available standard scenarios, and for each scenario, saves these final results by building type and augmented census division in the OutputResults tab and subsequently the user's own identified spreadsheet for the saved results.
The output in the OutputResults tab shows the final results for each selected Standard scenario, as well as the savings over the baseline ASHRAE 90.1-1989 standard by building type and augmented census division, as well as nationally. These relative savings estimates can be seen in rows 50-80 of the OutputResults spreadsheet tab.