2.1 Overview

2.1.1Selection of Standard Home (SH)

FIGURE 2-1 The Princeton Home, South Elevation

It was decided to select a home that had been built in the Ann Arbor, Michigan area. This allowed for detailed measurement of the building and examination of area-specific construction methods. After meeting with several local developers who provided blue prints of various home models, the Princeton home (see Figures 2-1 and 2-4) designed and built by the Guenther Building Co., was selected. Throughout this report it is referred to as the Standard Home (SH).

2.1.2 Definition of the Energy Efficient Home (EEH)

This report analyzes the life cycle energy consumption, GWP, and cost of the SH. To understand how the environmental impacts of SH could be reduced, it was redesigned to become a fundamentally more energy efficient home, based on the floor plan of SH. Throughout this report it is referred to as the Energy Efficient Home (EEH). The design changes were reviewed by two architects[14] to ensure technical feasibility.

2.1.3 Functional Units

To provide a base line for objective comparison between SH and EEH, both homes had to be similar. The means for ensuring equivalency between two systems is the definition of functional units that each home must meet. If each home meets certain underlying requirements, or provides the same services in terms of quality and quantity, then they are functionally equivalent.

The functional units adopted and held constant for the SH/EEH comparison were:

Areas where functional equivalency may not hold true include:

FIGURE 2-2 The Princeton Home, Floor Plan, 1st Floor

FIGURE 2-3 The Princeton Home, Floor Plan, 2nd Floor

The design of EEH, while maintaining functional equivalency to SH, did hamper optimization of passive solar heating and cooling strategies. Such strategies include integration of south-facing windows with natural house ventilation [15, 16], design of solar induced air flow through the building, clerestories for increased daylighting, and use of additional thermal storage to balance diurnal temperature swings [17]. Nevertheless, SH architectural style and shape were retained in order to stay within perceived market preferences.

2.1.4 Guidelines on EEH Design

SH life-cycle energy and GWP results were used as guidelines in reducing the overall energy consumption of EEH. The majority of SH primary energy consumption and GWP is generated during the use-phase of the house (i.e., heating, cooling, electricity consumption for appliances). Effort was therefore focused on measures that would reduce the use phase energy consumption (e.g., lowering the thermal conductance properties of the building envelope, reducing energy consumption of appliances, etc.). In addition, building materials were selected that would reduce the embodied or "pre-use phase" energy by either choosing materials with lower embodied energy, or materials that had a significantly lower rate of replacement.

2.2 Description of Princeton Standard Home (SH)

FIGURE 2-4 The Princeton Home, North Elevation

The Princeton SH is a two-story home with 2,450 ft2 of livable space and an internal volume of 26,960 ft3. This is close to the national average of 2,120 ft2 for new homes built in the U.S. [18]. It has an unfinished basement and a two car garage. The first floor has a living room with a vaulted cathedral ceiling, an attached dining room, and a master bedroom with an attached bathroom (shower/bathtub, toilet, two sinks, and two large closets). There is also a kitchen, a laundry room, and a lavatory (sink/toilet). The second floor is comprised of three smaller bedrooms and a bathroom (shower/bathtub/sink/toilet).

FIGURE 2-5 The Basement and Foundation of the SH [from 19]

The floor area of the unfinished basement is 1,675 ft2 which contains the furnace, the water heater, the main fuse-box, and a sump pump. Figure 2-5 provides a cross section of the basement foundation. It has plain concrete walls, a concrete floor and no ceiling drywall. The garage is not insulated. The basement and garage construction materials are included in the SH-materials inventory. It was assumed that the owner would fit out the basement within the first year after purchase, adding drywall to the foundation walls and ceiling, and vinyl tile to the floor. Because this activity takes place soon after construction, the primary energy and GWP were included in the pre-use phase inventories.

The SH has a 2x4 wall construction with 3.5" fiberglass insulation, and 8" of sprayed fiberglass insulation in the ceiling (see Figure 2-6). The house is wired to meet electrical code, and provides the typical amounts of light-switches and outlets. Non-insulated hot and cold water copper piping run throughout the house. The living room has a natural gas fireplace. The kitchen has a sink, electric garbage disposal, stove and stove hood, dishwasher, refrigerator/freezer, and several cabinets. The laundry room features only a plastic sink. Other major energy consuming appliances included in the study, and which must be purchased by the home buyer include a clothes washing machine and a clothes dryer. Except for kitchen and bathroom cabinets, no furniture was included in the study.

The first floor is fully carpeted, except for vinyl tile in the bathrooms, kitchen and garage entrance/hallway, and ceramic tiles in the foyer. The second floor is also fully carpeted with the exception of vinyl tile in the bathroom. Incandescent lighting is used in all rooms except for the closets.

FIGURE 2-6 SH 2x4 Wall Design [from 20]

The home was divided into several systems to allow for easier tracking of materials, energy, green-house gases, and cost. System interaction could then be observed when EEH design changes were made. Table 2-1 below summarizes the eight home systems.

TABLE 2-1 Description of Systems

SystemDescription of System
Walls (interior and exterior)Building structure consisting of lumber construction, fasteners and braces, insulation, drywall, exterior sheathing and siding, brick facing, vapor barriers, trim, adhesives and paint.
FloorsFloor joist lumber, deck lumber, carpet, ceramic and vinyl tiles, mortar, fasteners, and adhesives.
Roof/ceilingWood trusses, fasteners, insulation, roof deck lumber, roof weathering materials, soffit and facia materials, gutters and down-spouts.
Foundation/basementGravel substrate, concrete foundation slab and walls, drainage system
Doors/windowsWood hollow core doors, main entry (insulated) door, garage door. All casement and double hung windows including glazing and frames. Patio sliding door considered to be a window.
Appliances/electricalFurnace, air conditioning unit, water heater, range, range hood, refrigerator/freezer, clothes washing machine, clothes dryer, fireplace, electric garbage disposal, dehumidifier, dishwasher, sump pump, copper wire cabling, switches, plug outlets, lamp fixtures, bulbs, and circuit breakers.
Sanitary/pipingBath tubs, jet pump (for master bath), sinks, pedestals, faucets, toilets and accessories, bathroom tiles. Hot and cold water piping, natural gas piping and PVC drainage and vent piping. Air ducts, registers, grills, air intakes, and exhaust flues.
CabinetsKitchen and bathroom cabinets and countertops

2.3 System Boundaries of Life Cycle Analysis

2.3.1 Processes Included

Primary energy consumption and GWP gas emissions were accounted for in the following processes:

a) raw material extraction, and production of engineered materials (e.g., steel plates, wood studs, copper slabs)
b) manufacturing of building components (e.g., windows, siding, carpet), and appliances
c) transportation of materials from raw material extraction to part fabrication, and from there to the construction site
d) construction of the home at the building site, including site earthwork
e) energy consumed during the use-phase of the home (utility-provided energy)
f) embodied energy of maintenance and improvement materials (as in a, b, and c)
g) demolition of the home after its useful life
h) transportation of demolished materials to recycling centers or landfills (except the concrete foundation and basement floor, which was assumed to remain in the ground)

In order to adequately account for the additional energy and material requirements caused by manufacturing and construction losses, efficiency factors for these two life cycle steps were employed. For the manufacturing of building products and appliances, a 95% efficiency factor (by mass) was assumed for all materials, except for secondary aluminum (88%) [21], ceramic tiles (98%) [22], mortar for ceramic tiles (88%) [23], and vinyl (99.6%) [24]. This 95% efficiency factor reflects waste generated during the various manufacturing processes, such as steel stamping, plastics molding, machining of metal parts, or gypsum board manufacturing.

An additional 5% was used to account for construction losses, which are losses of materials on site due to cutting and fitting (i.e., roof underlayment, copper wire, concrete). For the following house components, the on-site losses were included in total building quantities; the exact percentage of the losses however, could not be identified:

All efficiencies during the material production phase are accounted for in the data sets used for this life cycle step (i.e., raw material production before parts manufacturing).

2.3.2 Processes and Factors Not Included

In an effort to focus on those architectural systems that directly influence energy use and GWP of a residential home, some components that are part of a home and some external factors were not addressed. The following is a list of those issues not included in this study:

It is important to note that, because wood is a renewable resource, its feedstock energy (combustion fuel energy) was not accounted for according to EPA LCI guidelines [25]. However, for materials made from non-renewable resources (e.g., plastics), feedstock energy has been included in the energy inventory.

The environmental burdens associated with the ultimate treatment of the demolished building materials, such as landfilling, recycling, and reuse were not evaluated. Attempting to determine the nature and efficiency of the recycling industry in 50 years would be conjectural. Moreover, attempting to determine which industrial products might be recovered and recycled at that time was deemed beyond the scope of this study. Such information, if available, would have allowed for assignment of material production burden credits to EEH, based on lowered future material production energy requirements.

2.4 Life Cycle Materials Data Base

Energy and GWP data sets were supplied by the DEAM software database [26], which has information for a wide range of materials. DEAM data sets were available for 94.5 % of the materials in the building, by mass. Data sets (accounting for 5.2 % of the building mass) were taken from a study published by the Western Wood Products Association [27]. AIA's Environmental Resource Guide [28] and the Swiss publication Ökoinventare für Verpackungen [29] provided the remaining data sets (accounting for 0.3 % of the building mass). For the majority of materials, complete material production and manufacturing data sets could be located, with gaps only occurring in the manufacturing process of some materials. However, complete data were available for the primary energy consumption of the building's materials, which includes raw material extraction and manufacturing of prefabricated materials, (e.g., cold-rolled steel). Data sets were available (approximately 90% of the building by mass) for manufactured components and assembled items (e.g., windows, roof shingles).This does not introduce significant error since component fabrication burdens are generally far lower than material production burdens. A typical example is the production of high-density-polyethylene (HDPE) pipes. While it takes about 78.5 MJ (fuel and feedstock) to produce HDPE polymer, only 9 MJ are estimated to be required for the manufacturing of the pipe [30].

GWP data sets from this report are a composite measure of many different gases that have varying levels of global warming potential. It is standard convention to convert non-CO2 gases into equivalent CO2. Many gases have a much higher global warming potential, pound for pound, than CO2. Table 2-2 below provides global warming potentials for different gases used in this study, and by many practitioners in the Life-Cycle-Assessment community worldwide.

TABLE 2-2 Global Warming Potentials (20 year time horizon) [31]

Global Warming Gas
GWP Factor

CO2 = 1
Global Warming Gas
GWP Factor

CO2 = 1
Carbon Dioxide (CO2):
CFC 12 (CF2Cl2):
Methane (CH4):
CFC 13 (CF3Cl):
Nitrous Oxide (N2O):
CFC 14 (CF4):
Halon 1301 (CF3Br):
CFC 114 (C2F4Cl):
CFC 11 ( CFCl3):
HCFC 22 (CHF2Cl):

Table 2-3 provides energy consumption/GPW data for all major materials used in this study. Primary energy includes both resource extraction/processing energy and component fabrication energy except where marked (data not available). The major processes associated with component manufacturing are given for those materials where that have manufacturing primary energy data.

TABLE 2-3 Primary Energy and Global Warming Potential of Materials

Fabrication Process
Primary Energy (MJ/kg)

(Material Production and Fabrication)

kg CO2 equiv./kg
acrylonitrile butadiene styrene (ABS)
aluminum, primary
asphalt shingle
shingle mnfg
shredding, treating
ceramic **
mixing, firing
facing brick
felt underlayment #15
general mfg
fiber glass
high density polyethylene (HDPE)
latex **
mineral spirits
oriented-strand board
polyamide resin (PA)
polyethylene (PE)
plastic-wood composite *
shredding, molding
cutting, pressing
formaldehyde resin
polymethylmethacrylate (PMMA)
polypropylene (PP)
polystyrene (PS)
polyvinyl chloride (PVC)
rubber ++
styrene butadiene rubber (SBR) ++
stainless steel
steel cold rolled
extruding, galvanizing
water-based paint

* according to manufacturer [32] 50% post-industrial vinyl, 50% recycled post-industrial wood
** For materials where specific primary energy and GWP data were not available, similar materials with complete data sets were substituted (for ceramic sinks "ceramic tile" data were used, and for latex in carpet and paint, "SBR" was used)
*** fabrication primary energy not included
+ data not available
++ Other contradictory values for SBR and rubber were found: Rubber 67.7 MJ/kg [33], SBR 145.1 MJ/kg [34]

Several building materials were composites. Carpet, for example, was assumed to be 58% nylon (PA6), 10% Polypropylene (secondary backing) and 32% Latex (binder) [35].

2.5 Home Maintenance and Improvements

To determine the contributions of maintenance and home improvements on life cycle energy consumption, a schedule of activities was created. It determines the interval of those maintenance activities that are needed to keep the home in good repair (e.g., repair of broken windows, or changing of light bulbs), as well as those of major home improvements (e.g., replacement of siding, carpet, roofing). Materials needed for these activities were quantified, and their life cycle energy and GWP added to the total. Table 2-4 provides an overview of home maintenance and improvement assumptions, based on a home life of 50 years. Data on the replacement rate of many items could not be found, and replacement frequencies were therefore estimated. Other sources are shown.

TABLE 2-4 Maintenance and Home Improvement Schedule for SH and EEH


(based on home life of 50 years)
Years occurring after Construction
Inside walls and door repair
1st & 2nd floor internal re-painting
10, 20, 30, 40
Exterior re-painting
10, 20, 30, 40
PVC siding
Astro Building Prod.[36]
New roofing (asphalt shingles) for SH
20, 40
DEAM Data Base [37]
New refrigerator
15, 30, 45
New garbage disposal
15, 30, 45
New sump pump
15, 30, 45
New water heater
15, 30, 45
New range
15, 30, 45
New range hood
New A/C central unit
20, 40
New dishwasher
20, 40
New cloths washer
15, 30, 45
New cloths dryer
15, 30, 45
Kitchen and bathroom cabinet replacement
Changing of all incandescent light bulbs for SH
every 3 years
Changing of all compact florescent light bulbs for EEH
every 5 years
Replacement of all vinyl floor tiles in house
20, 40
Replacement carpet
every 8 years
Interface Inc. [38]
Replacement of all windows (includes breakage)

* calculated using bulb life and annual hours of light usage

2.6 Life-Cycle Inventory of SH

2.6.1 Construction Phase

Material quantities for SH were determined by taking blue-print dimensions and performing field cross-checks. The Princeton home studied was a finished model home, with a similar unit under construction adjacent to it. By using these two sites, it was possible to verify all dimensions. Mass was determined by using material density data. When published data were unavailable, field weighing established material densities. Local vendors, subcontractors and product representatives were of great assistance in providing information (e.g., product dimensions, weights, material compositions).

Because many appliance manufacturers do not provide the weight of their products, appliance mass was determined by contacting local distributors and inquiring for shipping weight. Appliance material composition was checked against material composition data taken from a life cycle inventory study of a kitchen range [39]. Percentages of various materials (e.g., steel, aluminum, glass, plastic) in that study were used in estimating the percentage of materials in other appliances.

The database used to inventory material production and component manufacturing energy and GWP, accounted only for transportation to the manufacturer. Modes of transportation, and the distance from part/component manufacturer to the construction site had to be determined. Table 2-5 shows transportation data summarizing information provided by local suppliers. Due to the nature of the lumber data sets employed in this study [40], it was not possible to separate wood transportation energy from total energy. However, the figures do reflect the "average transportation distance and mode" [41] for wood from western states to all other states.

TABLE 2-5 Transportation Distance and Mode Data

MaterialDistance from Source Mode of Transportation
Concrete50 miles (80 km) 100% truck
Gravel30 miles (48 km) 100 % truck
All Other400 miles (640 km) 50 % truck, 50 % rail
Disposal of Demolished Materials100 miles (160 km) 100% truck

2.6.2 Use Phase

Building energy consumption can be determined by taking measurements of the actual fuel and electricity consumed over an extended period, or by modeling simulations. Use of modeling software was selected for several reasons:

  1. The project time limitations did not allow for actual site measurement. A full year of measurements would be needed. A survey of randomly selected Princeton home owners was taken, however (see Section 2.6.7).
  2. Employing simulation software eliminates distortions from seasonal variations, calibration errors of heating/cooling control equipment, irregular occupant behavior, and abnormal weather conditions.
  3. Modeling of SH with software made design of EEH easier. Parameters where established by running numerous scenarios to determine the energy consumption of various building envelope configurations.

2.6.3 Modeling of SH

The Energy-10 software was used to model use-phase energy consumption. This software was developed in partnership by the Passive Solar Industries Council, the National Renewable Energy Laboratory, Lawrence Berkeley National Laboratory, and the Berkeley Solar Group, and distributed by the Passive Solar Industries Council [42].

Actual SH building characteristics modeled in Energy-10 were:

2x4 wood frame construction, 16" on center
3.5" of rolled bat glass wool insulation
0.5" drywall finishing on interior walls (0.75" for garage)
0.5" Orient strand board (OSB) and polyisocyanurate sheathing
PVC exterior siding
overall R-value of polyisocyanurate wall section = 14.9 (hr ft² F/Btu)
overall R-value of OSB wall section = 12.2

prefabricated 2x4 wood trusses

8" of sprayed glass wool insulation ("E")
drywall finishing on interior ceiling ("F")
OSB sheathing on roof ("C")
asphalt roof shingles ("A")
#15 felt underlayment ("B")
overall R-value of ceiling = 22.9

2x10 floor joists on 12" centers
0.75" OSB
carpet, vinyl and ceramic tile floor covering

double-glazed double-hung windows with PVC frames
overall R-value (including frame) between 2.0-2.1
window glass thickness 1/8"

f-factor for basement walls = 1.3 Btu/hr ft F (used to calculate heat loss through the walls in an unheated basement)

effective leakage area (ELA) = 153 in²
0.67 house air changes per hour
fan air flow rate [44] = 302 cfm (ft3/min)

occupancy: four people
South-East Michigan climate (Detroit, MI)
heating set point at 70°F with set-back point at 65°F,
cooling set point at 75°F with set-up point at 79°F
heating and cooling set-back/set-up occur between 11 pm and 7 am

2.6.4 SH Heating/Cooling Energy Use

Both heating and cooling energy were determined with Energy-10 for SH as well as for EEH. The program calculates the heat required to maintain the internal building temperature based on the following factors:

2.6.5 Internal Heat Gains

Internal heat gains from lights, electrical appliances, hot water and occupants were determined separately and imported into Energy-10. These additional internal heat gains lower the natural gas heating requirement (but increase summer cooling energy requirements). Calculating internal heat gain was done in two steps:

1) Peak internal heat gains were calculated in W/ft2 (as required by Energy-10). The peak load occurs when a specific source (e.g., stove or hot water heater) is operating at its highest "level" of performance, thus emitting the largest amount of waste heat.

2.)The magnitude of internal heat radiating from different sources varies according to the time of day. Energy-10 timetables were used that allocate internal heat released into the building thermal envelope as a fraction of peak load. Lower daytime and continuous weekend occupancy was assumed.

Peak internal loads were determined by calculating the radiative energy from the total number of heat emitters at the time of maximum use. This was usually between 7-11 PM. This corresponds with maximum family usage of lights, electrical appliances, hot water, and with the maximum number of occupants in the building. These combined heat sources help heat the building. Consumption data for hot water usage, typical home electrical appliances and plug loads were based on Household Energy Consumption and Expenditures 1993 [45]. The heat gain value used for occupants was 100 W/person [46].

2.6.6 SH Electrical Energy Use

Electrical energy consumption was determined independently from Energy-10. A list of appliances used in the building was determined, which consisted of standard household appliances and entertainment equipment. Appendix D-1 provides a list of those appliances modeled, and their annual energy use. Actual SH appliance manufacturers and model numbers were recorded. Those manufacturers were contacted and average annual energy consumption information collected. Other sources were used to determine annual energy use when model types were not known [47].

2.6.7 Survey of SH Heating Energy Consumption

To check Energy-10 generated results, seven survey forms were mailed to Princeton home owners in the subdivision studied. A sample of the survey form is given in Appendix A-1. Only one household responded to the survey. Visits to those homes not returning the survey were then conducted. It was revealed that most were renters, or had not lived in the home for more than one year. An Energy-10 calculation was performed and the results normalized for actual heating-degree days (HHD) in 1997-98 [48]. Table 2-6 compares the Energy-10 calculation to the single survey result.

TABLE 2-6 Summary of Princeton Natural Gas Energy Use Survey

Annual Natural Gas Costs
Survey #1
$667.40 (HDD Normalized)
$637.00 (Actual)

The Energy-10 result was only 4.8% lower that the field survey result. The variation could be due to one or several of the following reasons:

2.7 Life Cycle Inventory of EEH

EEH was modeled for greater energy efficiency to determine by what degree environmental impacts could be reduced, and at what incremental cost. It was also modeled to have the same floor plan and internal dimensions as the SH. The guiding principle in the design of EEH was to minimize life cycle energy. As reported in Section 3.2, 93.7% of SH life cycle energy consumption occurs in the use-phase. Thus, EEH design changes focused on minimizing use phase energy. Measures to reduce the material fabrication/construction (pre-use phase) energy by choosing materials with lower embodied energy were also taken.

Reductions in heating and cooling loads also allow for downsizing of furnace and A/C equipment which reduce overall cost. This is a secondary, but nevertheless significant benefit of a higher performance thermal envelope.

2.7.1 EEH Construction Phase

SH effective leakage area (ELA) was measured to be 153 square inches [49] (see Section 3.5.2). EEH was estimated to be 20 square inches [50]. This is based on thorough use of caulking, and the effects of sprayed-in cellulose insulation.

Building materials with lower embodied energy or higher durability were identified to replace SH materials with high embodied energy or with high replacement frequencies. In terms of embodied energy over the life cycle of the home, the major targets for reduction were polyamid (PA), concrete, asphalt shingles, steel, and polyvinylchloride (PVC). GWP reductions concentrated on concrete and steel because they make up a significantly high percentage of the building's mass.

Attention was given to those materials which effect both, use-phase and the embodied energy. Substitution of glass fiber heat insulation with cellulose insulation (made from 100% recycled newspaper [51]) is an example of this dual approach. Cellulose insulation has 87% less embodied energy per kg installed than fiberglass insulation. In addition, the R-value of sprayed-in cellulose insulation is 10% higher than that of fiber glass insulation. The life cycle inventory data sets used reflect both, the change in insulation mass, and embodied energy per kg. Based on the application technique, cellulose insulation also creates a tighter air infiltration barrier by filling in more voids in the wall cavity.

Careful consideration was given to wall design. Pierquet, et al. [52] evaluates the embodied energy of 12 different wall systems and compares them to annual energy savings based on varying R-values. Pierquet, et al. used a standard 2x4 stud wall with fiberglass insulation as the base case, and compared it with wall sections made of strawbale, structural insulated panels (SIPs), I-beam studs, 2x6 studs, autoclaved cellular concrete, and varying combinations of 2x4 construction and rigid foam insulation. Walls with very high R-values included the strawbale and double 2x4 walls. The strawbale wall had the lowest embodied energy. When the fiberglass insulation in the double 2x4 wall was replaced with cellulose, its embodied energy dropped to be almost equal with that of the strawbale wall.

Strawbale walls are not commonly used in northern climates. Special efforts must be made to protect the straw from moisture, and were therefore not considered. SIPs are relatively easy to build with and form a tight air seal. There is considerable embodied energy in the extruded polystyrene (EPS) foam insulation however. For this reason, SIPs were not considered. The double 2x4 wall with cellulose insulation was selected based on embodied energy and R-value criteria.

The concrete basement walls, having a high embodied energy due to their mass, were replaced with wood walls having a lower embodied energy. The wood walls also have a higher R-value. A bare 10" thick concrete basement wall has an R-value of 12 when the thermal insulating effects of the earth are included. A 2x8 wood frame wall (with CCA-treated studs and plywood to resist decay), insulated with cellulose, has an R-value of 39. There is also a net reduction of overall embodied energy of 2.5%. Wood basements are built in Michigan, and at least one local architect [53] uses them. One company in Detroit [54] specializes in wood basements, and has built them for many years.

It must be noted that the chromated copper arsenate (CCA) used to treat the wood is toxic. Manufacturing, use, and disposal of this product may generate serious environmental problems. Alternatives to CCA have showed only moderate success [55]. Another alternative to both cast-in-place concrete, and pre-treated wood foundation walls are pre-cast foundation blocks. These blocks may have lower life cycle energy characteristics. This study did not pursue this alternative.

Except for color (affecting solar absorptivity and reflectivity), roof cover materials have little or no effect on the heat gain or loss through the building envelope because the roof is un-insulated and the attic space is ventilated. However, the asphalt shingles used on SH, have a very high embedded energy per unit of mass. The BEES [56] database indicated that after 20 years, a second layer of asphalt shingles are placed on top of the original layer. At year 40, both shingle layers and the original felt underlayement are removed, and a new layer of shingles and felt underlayment applied. This makes the roof a very energy intensive part of the house. As an alternative, a product consisting of 50% post-industrial vinyl and 50% recycled post-industrial wood [57] was selected. It is similar in appearance to wood shingles. The manufacturer gives a 50 year warranty. This approach reduced the life cycle embodied energy of the roofing materials by 98 %. Another alternative with potentially lower embodied energy are sheet metal based roofing materials. This study did not examine the cost or life cycle energy of this building material.

Steel is a major component of SH GWP. The majority of the steel in the home is found in the duct system, appliances and assorted fasteners. No suitable alternatives to these steel products were identified.

Electrical appliances are complex systems containing many components and materials. A developing body of work in the Life Cycle Design community is dedicated to reducing the life cycle environmental impacts of such products. Because the pre-use phase energy of appliances contribute only a small fraction to the overall environmental burdens of the home, this study did not pursue strategies to reduce them. Determination of the material composition of EEH appliances used the same approach taken in Section 2.6.1 for SH appliances. Appliance mass was determined by requesting shipping weight information from local distributors and product manufacturers. Appliance material composition was checked against material composition data taken from a life cycle inventory study of a kitchen range [58]. Percentages of various materials (e.g., steel, aluminum, glass, plastic) in that study were used in estimating the percentage of materials in other appliances.

The effort to select appliances with lower life cycle energy consumption focused on the use phase. Appliances were selected that conserve electricity by being more efficient. The range and the clothes dryer were switched to run on natural gas because of the overall higher primary energy utilization of natural gas over electricity. About 30% of the power generated by burning fossil fuel in power plants actually reaches the home. This is because of accumulated energy conversion losses of fuel to heat, electrical generation and transmission.

2.7.2 Use Phase

To reduce energy consumption, efforts concentrated on reducing building envelope heat loss, increasing solar heat gain, reducing summer overheating, and employing higher efficiency heating/cooling equipment and appliances. Tables 2-7 through 2-21 list the various design scenarios considered, and detail the advantages and reductions in embodied energy, and state whether they were employed or not.

TABLE 2-7 Energy Efficient Strategy Walls/Insulation

Strategy: substitute fiberglass insulation with cellulose, and increase thickness by creating a double 2x4 wall (See sketch of Saskatchewan wall section Figure 2-7)
Advantage: improve thermal performance of envelope, reduce embodied energy of insulation per kg, increase recycled content
SH materials deleted: fiberglass bat insulation
SH Mass, wood/fiber glass (50 yr.): 12,297 kg
SH Embodied energy (50 yr.): 78,027 MJ
EEH materials added: additional wood studs, cellulose insulation
EEH Mass, wood/cellulose (50 yr.): 18,807 kg
EEH Embodied energy (50 yr.): 108,577 MJ
Increase of Embodied Energy (50 yr.) 39%
Comments: EMPLOYED A major cause for use-phase energy consumption reductions

FIGURE 2-7 EEH Saskatchewan Wall System [from 59]

TABLE 2-8 Energy Efficient Strategy Walls/Infiltration

Strategy: reduce infiltration from average of 0.67 ACH, to 0.35 [60] with caulking, sprayed-in cellulose, (see Figure 2-8)
Advantage: reduce use-phase energy consumption
SH materials deleted: n/a
SH Mass (kg for 50 yr.): n/a
SH Embodied energy (MJ) n/a
EEH materials added: negligible (caulking)
EEH Mass (kg for 50 yr.): negligible
EEH Embodied energy (MJ) negligible
Reduction of Embodied Energy (MJ) n/a

FIGURE 2-8 Typical Air Leakage Spots [from 61]

1-joints between joists and foundation
2-joints between sill and floor
3-electrical boxes
4-joints at windows
5-joints between wall and ceiling
6-ceiling light fixtures
7-joints at attic hatch
8-cracks at doors
9-joints at interior partitions
10-plumbing-stack penetration of ceiling
11-chimney penetration of ceiling
12-bathroom and kitchen ventilation fans
13-air/vapor barrier tears
14-chimney draft air leaks
15-floor drain

TABLE 2-9 Energy Efficient Strategy Walls/Sheathing

Strategy: replace polyisocyanurate with oriented strand board (OSB)
Advantage: reductions in life cycle energy, increased use of renewable resources, additional structural strength
SH materials deleted: polyisocyanurate, steel wind bracers
SH Mass OSB, polyisocyanurate, steel wind bracers (50 yr.): 1,660 kg
SH Embodied energy (50 years) 10,430 MJ
EEH materials added: OSB
EEH Mass OSB (50 yr.): 2,536 kg
EEH Embodied energy (50 years) 8,622 MJ
Reduction of Embodied Energy (50 years) 17%

TABLE 2-10 Energy Efficient Strategy Walls/Exterior Siding

Strategy: substitute PVC siding with wood
Advantage: reduces embodied energy over the life cycle of the house
SH materials deleted: PVC siding panels (77.4 MJ/kg for PVC)
SH Mass (kg for 50 yr.): 1,098 kg
SH Embodied energy (MJ) 93,210 MJ
EEH materials added: wood siding board (6 MJ/kg), water-based paint (77.6 MJ/kg)
EEH Mass (kg for 50 yr.): 1,041 kg (including paint)
EEH Embodied energy (MJ) 28,120 MJ (including repainting every 5 years)
Reduction of Embodied Energy (MJ) 65,090 MJ
NOT EMPLOYED because of higher maintenance requirements, and low amount of wood suitable for recycling

TABLE 2-11 Energy Efficient Strategy Roof/Insulation

Strategy: substitute fiberglass insulation with cellulose, and increase thickness (attic), modify roof truss to accommodate for additional ceiling insulation (see Figure 2-9)
Advantage: SH ceiling is R-23, EEH ceiling is R-49. Cellulose has better air infiltration properties and lower EE.
SH materials deleted: blown-in fiberglass
SH Mass (50 yr.): 476 kg
SH Embodied energy (50 yr.): 11,735 MJ
EEH materials added: blown-in cellulose
EEH Mass (50 yr.): 1,506 kg
EEH Embodied energy (50 yr.): 5,599 MJ
Reduction of Embodied Energy (50 yr.): 52%
EMPLOYED (although there may be added construction difficulties)

FIGURE 2-9 Raised Roof (to accommodate sufficient ceiling insulation) [from62]

TABLE 2-12 Energy Efficient Strategy Roof/Shingles

Strategy: substitute asphalt shingle roofing with recycled plastic/wood fiber shingles [63]
Advantage: lower embodied energy
SH materials deleted: asphalt shingles and No. 15 Felt underlayment
SH Mass (50 yr., 2 replacements): 8,862 kg
SH Embodied energy (50 yr. 2 replacement): 142,587 MJ
EEH materials added: recycled-plastic/ wood composite shingles
EEH Mass (50 yr., no replacement): 441 kg
EEH Embodied energy (50 yr., no replacement): 3,023 MJ
Reduction of Embodied Energy (50 yr.): 98%

TABLE 2-13 Energy Efficient Strategy Basement/Walls

Strategy: replace 10" concrete foundation wall with 2x8 wood frame wall with cellulose insulation
Advantage: increases thermal insulation and reduces embodied energy
SH materials deleted: 10" concrete basement walls, drywall inside
SH Mass concrete foundation wall/floor slab, damp proofing (50 yr.): 172,060 kg
SH Embodied energy (50 yr.): 285,641 MJ
EEH materials added: 2x8 wood studs (12" on center), 8" thick sprayed-in cellulose, plywood, PE foil, and drainage gravel outside, drywall inside
EEH Mass wood structure, cellulose, drainage gravel, concrete footing/floor slab (50 yr.): 190,075 kg
EEH Embodied energy (50 yr.): 276,001 MJ
Reduction of Embodied Energy (50 yr.): 3.4%

TABLE 2-14 Energy Efficient Strategy Basement/Insulation

Strategy: insulate foundation
Advantage: Reduces heat losses through basement walls
SH materials deleted: 10" concrete basement walls
SH Mass concrete foundation wall/floor slab, damp proofing (50 yr.): 172,060 kg
SH Embodied energy (50 yr.): 285,641 MJ
EEH materials added: Foam board insulation
EEH Mass (50 yr.): not calculated
EEH Embodied energy (50 yr.): not calculated
Reduction of Embodied Energy (50 yr.): not calculated
NOT EMPLOYED (Wood basement used)

TABLE 2-15 Energy Efficient Strategy Floors/Tiling & Thermal Mass

Strategy: install tile floors and specify limited use of throw-down rugs
Advantage: create thermal storage mass, reduce embodied energy consumption of carpet
SH materials deleted: 2x10 floor with carpet
SH Mass carpet first floor (50 yr.): 3,284 kg
SH Embodied energy (50 yr.): 403,972 MJ
EEH materials added: 2x12 rafters, 12" on center, OSB, 3" concrete, 0.75" tiles, (carpet only in bedroom and closet/closet hallway)
EEH Mass concrete/tiles/mortar (50 yr.): 27,445 kg
EEH Embodied energy (50 yr.): 134,736 MJ
Reduction of Embodied Energy (50 yr.): 67%
Comments: NOT EMPLOYED heating energy actually increased with the above arrangement at an additional cost for concrete/tile floor of about $19,000. Only when insulation was put underneath the concrete, did the heating energy decrease to the value of a 2x10 floor with fiberglass insulation.

TABLE 2-16 Energy Efficient Strategy Floors/Alternate Covering Material

Strategy: replace carpet with material with lower embodied energy
Advantage: lower embodied energy
SH materials deleted: carpet
SH Mass carpet entire home (50 yr.): n/a
SH Embodied energy (50 yr.): n/a
EEH materials added: e.g., cork
EEH Mass (50 yr.): n/a
EEH Embodied energy (50 yr.): not available
Reduction of Embodied Energy (50 yr.): n/a
Comments: NOT EMPLOYED best alternative appeared to be cork, but was considered to be too expensive (although provides large savings in embodied energy). Initial installation cost were approximately 2.5 times higher than carpet, although life cycle cost was 10% lower, due to a lower replacement rate and less maintenance.

TABLE 2-17 Energy Efficient Strategy Windows/Glazing Area

Strategy: Increase window area from 337 ft2 (using double lowE/argon in EEH) to 490 ft2 (double lowE/argon in EEH)
Advantage: Increases solar gain while reducing heating (and possibly cooling loads)
EEH original Mass (50 yr.): 923 kg (from glazing area of 337 ft2)
EEH original Embodied energy (50 yr.): 36,603 MJ
EEH materials added: LowE glass, argon, (additional 153 ft2)
EEH new Mass (50 yr.): 1,342 kg
EEH new Embodied energy (50 yr.): 23,559 MJ
Increase of Embodied Energy (50 yr.): 7,356 MJ

INCREASED GLAZING AREA NOT EMPLOYED Additional glazing area is not effective because of increased annual primary energy consumption. See section 3.5.1 for additional explanation.

TABLE 2-18 Energy Efficient Strategy Appliances

Strategy: Where feasible, replace appliances using electricity with appliances that use natural gas. Install highest-efficiency appliances everywhere else
Advantage: Using natural gas reduces primary energy consumption by a factor of about 3, Higher efficiency appliances lower use phase energy
SH Appliances: Refrigerator, Garbage Disposal, Water Heater, Range, A/C Central Unit, Dishwasher, Clothes Washer and Dryer, and Furnace
Appliances not used in EEH anymore: Garbage Disposal (composting or vermiculture assumed)
Appliances in EEH with increased efficiency: Refrigerator, Furnace, Water Heater, Range, A/C Central Unit, Dishwasher, Clothes Washer and Dryer
Reduction of Embodied Energy (50 yr.): no change assumed
Reduction of Use-Phase Energy 40%

TABLE 2-19 Energy Efficient Strategy Lighting

Strategy: Replace all incandescent bulbs with florescent bulbs.
Advantage: Reduces use phase energy
SH materials deleted: All incandescent bulbs
EEH materials added: Compact and tube florescent bulbs
Reduction of Use-Phase Energy (50 yr.): 686 kWh/year reduction (73% reduction)

TABLE 2-20 Energy Efficient Strategy Building-Integrated Shading

Strategy: Provide for optimum overhang on all windows (see Figure 2-10), based on Ann Arbor's latitude
Advantage: Allows full winter sun access but cuts out significant amounts of summer sun, reducing summer heat gain
SH materials deleted: None
SH Mass (50 yr.): None
SH Embodied energy (50 yr.): None
EEH materials added: roof truss lumber, OSB roof sheathing, shingles
add'l EEH Mass OSB, 2x4 lumber, plastic/roof roof shingles (50 yr.): 260 kg
EEH Embodied energy (50 yr.): 17,872 MJ
Increase of Embodied Energy (50 yr.): 17,872 MJ

TABLE 2-21 Energy Efficient Strategy Hot Water Heat Exchanger

Strategy: Recover waste heat from disposed-of hot water, utilizing a heat transfer coil that passes collected waste hot water around the hot water intake supply line.
Advantage: Reduces the natural gas consumption for water heating by 40% (preheating water to the hot water heater)
SH materials deleted: None
SH Mass (50 yr.): None
SH Embodied energy (50 yr.): None
EEH materials added: copper tubing, solder
EEH Mass (50 yr) not calculated
EEH Embodied energy (50 yr.): not calculated
Increase of Embodied Energy (50 yr.): not calculated
Comments: EMPLOYED reduces annual consumption of natural gas by 211 kg/yr.

FIGURE 2-10 Optimum Window Overhang Design [from 64]

Solar orientation was also considered. The Princeton (SH) was built with the greatest amount of windows facing north (see Figures 2-1 and 2-4). In an Energy-10 simulation, the SH with true orientation was compared with an SH rotated 180°. Rotating the building reduced annual energy heating by 8/10 of a percent. Because this incremental increase in solar gain was obtained at no additional material cost, the EEH was modeled with a 180° rotation.

2.7.3 EEH Electrical Energy Use

EEH electrical energy consumption was determined in an identical fashion to SH. Appendix D-1 provides a list of those appliances modeled and their annual energy use.

2.8 Life Cycle Cost Analysis

The life cycle cost of SH was determined by adding the accumulated home finance payments (down and mortgage payments), annual utility payments, and scheduled maintenance and improvement costs. These represent all costs borne by the homeowner excluding items outside the study scope (e.g., furniture, landscaping, home insurance, property taxes).

The mortgage down-payment was assumed to be 15% of the home purchase value. Monthly mortgage payments were determined using an annual interest rate of 7% over a mortgage period of 30 years, payable at the first of the month. No refinancing was assumed, and these costs did not vary over the 30 year period.

The cost of EEH was calculated by:

  1. determining the constructed cost of SH by dividing out the developers profit first, assumed to be 20% [65], and then subtracting the cost of the property, $55,000 [66]. This gives the construction value of SH,
  2. determining appropriate material and labor unit rates and contractor overheads for Michigan [67]; adjusting cost data (if more that one year old) using a 3% annual escalation rate,
  3. defining which SH systems were to be replaced by more energy efficient systems, determining material quantities and installed cost; subtracting this cost from the construction value of SH in step 1,
  4. defining new EEH systems and determining material quantities and installed costs; adding this cost to the result of step 3,
  5. adding back property cost, and then the developer's profit used in step 1.

EEH annual mortgage costs were then determined using the same finance assumptions for SH.

Yearly home maintenance and improvement costs for both SH and EEH were based on the replacement timetable given in Table 2-4. Material quantities were determined for each task, and future labor and material unit rates calculated using a 3% annual escalation factor.

Year-one annual energy costs for SH were determined by first calculating annual natural gas usage (from energy-10 modeling) and electricity usage based on annual consumption data for home appliances (refer to Appendix D), and then multiplying by Ann Arbor utility rates of $0.462/therm and $0.08/kWh (residential rates [68]). Year one annual energy costs for EEH were determined by using the same approach except that energy consumption data for electrical appliances was selected from a list of most energy efficient equipment on the market [69].

Annual utility rates vary over time depending on numerous economic and political factors and have traditionally defied prediction. The task of estimating future natural gas and grid electric unit rates for the next 50 years was therefore not attempted. Instead, four energy rate scenarios were used to determine sensitivity of changing rates over time. The scenarios are summarized in Table 2-22 below:

TABLE 2-22 Utility Rate Escalation Scenarios

Description of Scenario
Natural gas rates remain constant for 50 years
Electricity rates remain constant for 50 years
Base Case
Natural gas rates decline 1.1 %/yr. from 1998 up to 2010, rises 0.03% /yr. up to 2020. Does not change from 2021 to 2048
Electricity rates decline 1 %/yr. From 1998 up to 2010, declines an additional 0.58%/yr. until 2020. Does not change from 2021 to 2048
EIA DOE [70]

Natural gas rates escalate 4.2 %/yr. from 1998 until 2010. This gives an increase of 63% at year 2010. Annual escalation between 2011 and 2048 assumed to be 1%.
Electricity rates escalate 4.2 %/yr. from 1998 until 2010 This gives an increase of 63% at year 2010. Annual escalation between 2011 and 2048 assumed to be 1%.
Wefa Inc. [71]
Natural gas costs $0.721/therm in 1998 and increase annually 1% until 2048.
Electricity costs $0.127 $/kWh in 1998 and increase annually 1% until 2048.
German [72]


[14] John Barrie of John Barrie Associates (Ann Arbor, MI), and Kurt Brandle, AIA, Emeritus Professor for Architecture, University of Michigan (Ann Arbor, MI)
[15] Jones, Robert W., Balcomb, D., Yamaguchi, K., "Convective Heat Transfer Inside Passive Solar Buildings", LA UR-83-2545, Los Alamos National Laboratory, Los Alamos, NM, 1983
[16] Miller, B., "Solar Home with a View", Solar Today, May/June 1997, pg. 24
[17] Balcomb, D., "Advanced Passive Solar Design", A Workshop Presented at the SOLAR '98 Conference of the American Solar Energy Society, Albuquerque, NM, June 14, 1998, pg. 93-129
[18]"Housing Facts and Figures: Characteristics of New Single Family Homes, 1971-1994", National Association of Home Builders Economics Department, <>, 5/12/98
[19] Strother, E., Turner, W., "Thermal Insulation Building Guide", Robert A. Krieger Publishing Company, Inc., Malabar, FL, 1990, pg.402
[20] Nisson, J.D. Ned., "The superinsulated home book", John Wiley & Sons, Inc., New York, 1985, pg.32
[21] DEAM Database, Ecobilan
[22] DEAM Database, Ecobilan
[23] DEAM Database, Ecobilan
[24] DEAM Database, Ecobilan
[25] EPA publication EPA/600/R-92/245, "Life-Cycle Assessment: Inventory Guidelines and Principles", February 1994
[26] DEAM Database, Ecobilan
[27]"Eco-Profile of Lumber Produced in the Western United States, Life Cycle Inventory of WWPA Western Lumber", Western Wood Products Association and Scientific Certification Systems, Inc., Oakland, California, August 1995
[28] AIA Environmental Resource Guide, American Institute of Architects, Washington, DC, 1992-1998
[29]"Ökoinventare für Verpackungen, Schriftenreihe Umwelt Nr. 250/I", Bundesamt für Umwelt, Wald und Landschaft, Bern, Switzerland, 1996
[30] DEAM Database, Ecobilan
[31] Heijungs, R. et al., "Environmental Life Cycle Assessment of Products, Guide-October 1992", Centre of Environmental Science, Leiden, Netherlands, 1992
[32] Product name : "Eco-shake", Re-New Wood, Inc., 104 N.W. 8th, PO Box 1093, Wagoner, OK, 74467, 1-800-420-7576
[33] Sullivan, J.L. and J. Hu. Life Cycle Energy Analysis for Automobiles, SAE paper 951829 1995
[34] Boustead, I., Hancock, G.F., ìHandbook of Industrial Energy Analysisî, Ellis Horwood Publishers, Chichester, UK, 1979
[35] Personal communication with sales representative of local carpet store, June 1998
[36] Phone conversation with Steve Cook, Astro Building Products, Ann Arbor, Michigan, on June 22, 1998
[37] DEAM Database, Ecobilan
[38] Phone conversation with Rob Glancy, Intern at Interface Inc., on June 24, 1998
[39] Jungbluth, N., "Life Cycle Assessment for Stoves and Ovens, UNS Working Paper No. 16", Umweltnatur- und Umweltsozialwissenschaften, Zürich, Switzerland, 1997
[40]"Eco-Profile of Lumber Produced in the Western United States, Life Cycle Inventory of WWPA Western Lumber", Western Wood Products Association and Scientific Certification Systems, Inc., Oakland, California, August 1995
[41] Personal communication with a representative from Scientific Certification Systems, Inc., Oakland, California, July 10th 1998
[42]"Energy-10, Release 1.2" - January 1998, Passive Solar Industries Council, 1511 K Street, NW, Suite 600, Washington DC 20005
[43] Blower door test report, 7/30/98, 2355 Foxway, Ann Arbor, MI, issued by D.R. Nelson and Assoc., Inc.Lake Orion, MI
[44] Based on 0.67 air changes per hour
[45]ìHousehold Energy Consumption and Expenditures 1993î, DOE/EIA-0321 (93), October 1995, US Department of Energy, Washington, DC, pg. 18
[46] According to "Energy-10, Release 1.2" - January 1998, Passive Solar Industries Council, 1511 K Street, NW, Suite 600, Washington DC 20005
[47]ìHousehold Energy Consumption and Expenditures 1993î, DOE/EIA-0321 (93), October 1995, US Department of Energy
[48] Dennis F. Kahlbaum, Meteorology Department, University of Michigan, Ann Arbor, MI
[49] Blower door test report, 7/30/98, 2355 Foxway, Ann Arbor, MI, issued by D.R. Nelson and Assoc., Inc. Lake Orion, MI
[50] Personal communication with Kurt Brandle, AIA, Emeritus Professor for Architecture, University of Michigan (Ann Arbor, MI), and LeRoy Harvey, Executive Director, Urban Options, East Lansing, MI, July 1998
[51]"Cocoon Cellulose Insulation Specifications", product information sheet for Cocoon (TM), Greenstone Co. (6500 Rock Spring Dr., Suite 400, Bethesda, Maryland), 1998
[52] Pierquet, P., Bowyer, J., Huelman, P. "Thermal Performance and Embodied Energy of Cold Climate Wall Systems", Forest Products Journal, June 1998, Vol. 48, No. 6, pp. 53-60
[53] John Barrie of John Barrie Associates (Ann Arbor, MI)
[54] 21st Century Superior, Wood Basements, 17131 Gore Street, Detroit, MI 48219, (313) 534-4272
[55] Wilson, A., "Disposal: The Achilles' Heel of CCA-Treated Wood", Environmental Building News, Vol. 6, No. 3, March 1997, pp. 1, 10-13.
[56] Based on DEAM™ modules
[57] Product name : "Eco-shake", Re-New Wood, Inc., 104 N.W. 8th, P.O. Box 1093, Wagoner, OK, 74467, 1-800-420-7576
[58] Jungbluth, N., "Life Cycle Assessment for Stoves and Ovens, UNS Working Paper No. 16", Umweltnatur- und Umweltsozialwissenschaften, Zürich, Switzerland, 1997
[59] Nisson, J.D. Ned., "The super-insulated home book", John Wiley & Sons, Inc., New York, 1985, pg.96
[60] Personal communication with Kurt Brandle, AIA, Emeritus Professor for Architecture, University of Michigan (Ann Arbor, MI), LeRoy Harvey, Executive Director, Urban Options, East Lansing, MI, and Kristine Anstead, Technical Support Director, Energy-10 consultant, July 1998
[61] Nisson, J.D. Ned., "The super-insulated home book", John Wiley & Sons, Inc., New York, 1985, pg.37
[62] Nisson, J.D. Ned., "The super-insulated home book", John Wiley & Sons, Inc., New York, 1985, pg.145
[63]"Eco-shake", Re-New Wood, Inc., 104 N.W. 8th, P.O. Box 1093, Wagoner, OK, 74467, 1-800-420-7576
[64] Strother, E., Turner, W., "Thermal Insulation Building Guide", Robert A. Krieger Publishing Company, Inc., Malabar, FL, 1990, pg.125
[65] Phone conversation with Tod Griffin, Guenther Homes, on July 15, 1998
[66] Phone conversation with Tod Griffin, Guenther Homes, on July 15, 1998
[67] Kiley, M.D., Allyn, M., "1997 National Construction Estimator, Labor & Material Costs, Manhours and City Cost Adjustments For All Residential, Commercial and Industrial Construction", Craftsman Book Company, Carlsbad, CA, 1996
[68] residential electricity and heating bills 1998, Ann Arbor, MI
[69] Wilson, A., Morrill, J. ìConsumer Guide to Home Energy Savingsî, Sixth Edition, The American Council
[70]"Annual Energy Outlook 1998, With Projections To 2020, December 1997", Energy Information Administration, Office of Integrated Analysis and Forecasting, U.S. Department of Energy, Washington, D.C. 20585, DOE/EIA-0383(98), pg. 78
[71]"Annual Energy Outlook 1998, With Projections To 2020, December 1997", Energy Information Administration, Office of Integrated Analysis and Forecasting, U.S. Department of Energy, Washington, D.C. 20585, DOE/EIA-0383(98), pg. 78
[72] Energy bill July 1998, Reppe family residence in Langebrück, Germany

End of section 2.0 Methods

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0.0 Abstract and Executive Summary
1.0 Introduction

3.0 Results
4.0 Conclusions

Last updated November, 16th '98, National Pollution Prevention Center