This site plan of the Emeryville Resourceful Building Project shows how a two-story duplex and a two-story single-family house all fit comfortably on a 5,500 ft2 lot.

Table 1. Exterior Wall Assemblies--Cost Comparisons Standard $/Ft2 ERB $/Ft2 2 x 6 @ 16 in OC $3.30 Sustainable 2 x 6 @ 24 in OC $2.75 R-19 fiberglass batts $0.40 R-19 cellulose $0.55 1/2-in OSB $1.10 5/8-in OSB $1.20 Wood fiber cladding $4.50 Cement fiber cladding $5.00 Standard exterior paint $0.55 Recycled exterior paint $0.65 15# building paper $0.15 15# building paper $0.15 1/2-in gypsum board $1.15 5/8-in gypsum board $1.25 Standard interior paint $0.55 Low-VOC interior paint $0.75 Standard caulk $0.05 Low-VOC caulk $0.08 $/ft2 of wall $11.75 $12.38 Total cost this project $74,789 $78,799

Table 2. 50-Year Cost Savings on Siding Hardboard Siding Cement Fiber Siding Cost/ft2 $4.50 Cost/ft2 $5.00 Installed cost $28,642 Installed cost $31,825 Warranty  25 yr Warranty 50 yr Replacement cost at 25 yr $28,642 Replacement cost at 25 yr $0 Replacement cost at 50 yr $57,284 Replacement cost at 50 yr $31,825 Simple expected savings over 50 yr $25,459 Note: These numbers are based on the cost estimate, not on the contractor's pricing.

Table 3. Exterior Wall Assemblies--Gross Energy Requirements in Therms Fuel Fuel Production Fuel Use Transport Feedstock Total Therms Standard ERB Standard ERB Standard ERB Standard ERB Standard ERB Electricity 400 115 203 52 4 3 0 0 607 170 Oil 69 38 193 48 168 113 75 162 508 362 Other 156 129 1,034 620 6 66 2,239 1,552 3,435 2,368 Total th. 625 282 1,429 720 178 182 2314 1,714 4,550 2,900 Savings 55% 343 50% 709 -2% -4 26% 600 36% 1,650 Note: Differences in electrical energy between the two systems result from two key factors: a) differences in energy requirements to manufacture different building products and their related raw materials, and b) differences in types of fuels used to generate electricity in various geographic locations where raw materials are aquired and building products are produced.

Cement fiber lap siding was used on the homes. This material is very durable and more cost-effective in the long run.

Framing in the ERB homes was 24-in on center.

Figure 1. This wall, floor, and roof section shows the variety of green materials selected for the ERB project.

This comfortable, affordable housing project is environmentally sound and fits into the style of the neighborhood.

Table 4. Annual Savings Summary Compared to Title 24 Requirements--Averaged per Residence Energy Efficiency Measures Annual Energy Savings Cost Savings Therms kWh $ R-19 batt insulation 23 9 $16 R-20 spray insulation 61 24 $43 High-efficiency ductwork 23 9 $16 Second-floor mass: Gypcrete 9 4 $7 0.50 U-value windows 41 16 $27 0.35 U-value windows 67 26 $47 High-efficiency condensing furnace 49 0 $32 High-efficiency hydronic heating 90 67 $67 Selected fluorescent lighting 0 88 $11 High-efficiency appliances 0 359 $47 Water heater blanket, low-flow fixtures 50 0 $33 Total of selected measures 250 147 $182 Note: Shaded items are the ones we selected.

Table 5. Annual Emissions from Operating Energy, Averaged per Unit Standard Title 24 Model ERB Model % Savings CO2/unit (global warming) 7,300 kg/yr 5,700 kg/yr 23% SOx/unit (acid rain) 36 kg/yr 30 kg/yr 14% NOx/unit (acid rain) 16 kg/yr 14 kg/yr 18%

Green building principles have not been as widely applied to affordable housing as energy efficiency principles have. The reasons for this include perceived higher construction costs and a reluctance on the part of developers and funders to use new materials and methods for publicly funded projects. Recently my firm, Siegel & Strain Architects, designed a unique residential construction project in a moderately priced neighborhood in the San Francisco Bay Area. With this project, we sought to show how careful selection and installation of mainstream materials--along with judicious use of recent innovations, recycled materials, and alternate construction methods--can create cost-effective, environmentally sound, affordable housing. We also hoped to show that satisfying environmental goals would actually make the housing more affordable.

The Emeryville Resourceful Building (ERB) project consisted of infill housing built on an empty lot in an otherwise developed neighborhood of older homes and apartments. It was completed in February 1999. It consists of three units--a two-story duplex and a two-story single-family house--on a 5,500 ft² lot. The overall massing (that is, the volumetric shape or form) and placement of the buildings was tightly constrained by the size and proportions of the site and the five parking spaces required by local zoning regulations. The project was designed to blend in with the modest surrounding neighborhood housing and to strengthen the urban fabric by using otherwise underutilized land. 

We set ourselves five specific environmental goals:

1. Provide energy-efficient housing.
2. Provide housing that is easy and inexpensive to operate and maintain.
3. Reduce resource consumption.
4. Create a healthy indoor environment.
5. Provide a model for environmentally sound, affordable housing.

The results of these studies allowed us to make decisions based on environmental performance criteria, initial cost, and long-term costs; when we examined these together, we felt we could make sound decisions based on environmental goals--and stay within budget.

The final analysis identified measurable environmental performance differences between products and assemblies and showed which materials have particular environmental benefits or disadvantages. This allowed the design team to make educated selections. Table 3 is representative of the many comparisons made in this study; it compares the gross energy requirements of the two exterior wall assemblies. The data in Table 3 show that there is a clear environmental advantage to using the ERB assembly.

With the help of the structural engineer, we specified the following measures: 

• frame walls at 24 inches OC; 
• use cut-off ends for blocking;
• use precut studs and joists where feasible;
• use built-up headers instead of solid lumber;
• use the smallest headers allowed by structural drawings; and
• use roof trusses instead of standard framing.

Components that affect energy consumption were computer modeled to compare efficient alternatives to the standard California Title 24 Energy Code requirements. We then selected a package of cost-effective energy-saving materials and systems. These included, among other things: 

• sealed electrical boxes;
• use of foam sill sealer (this was observed during construction to make sure it was used thoroughly);
• high-efficiency ductwork (R-4.2, specified sealant, tested for air infiltration); 
• 0.35 U-value windows with solar insect screens on north- and south-facing windows;
• a high-efficiency condensing furnace;
• a water heater blanket;
• low-flow water fixtures; and
• sprayed cellulose insulation to achieve maximum R-value and to avoid installation defects. 

Our goal was to minimize construction costs so that overall costs were still within an acceptable range for comparable affordable housing projects in the same region. Comparable two- to four- unit custom housing projects in the Bay Area typically run from $95 to $105 per ft² for construction costs alone; the ERB project cost $100 per ft². The greatest benefits and savings were found in: reducing use of resources with optimal framing systems, increasing the durability of materials such as roofing and siding, improving insulation, and saving operating energy with more efficient systems for space heating (the gas furnace was high- efficiency, variable capacity with a 96.6 AFUE, and was properly sized). Benefits also came from an R-11 water heater blanket, heat traps on the water heater, and low-flow fixtures in the homes. The systems or materials that contribute most to operating efficiency, or that far outlast standard materials, resulted in the greatest savings. Figure 1 illustrates the construction systems and finish materials we selected. 

There were a few cases where the contractor's lack of experience did become a problem. In one case, we specified raised heel trusses in order to increase insulation at the edge of the roof; we also specified that these be made out of certified lumber. When the contractor submitted the shop drawings from the truss fabricator, neither of these specifications was shown. We asked for revised drawings showing both specs, but it turned out that the trusses had already been fabricated without our approval of their design. Faced with the prospect of throwing away the nonconforming trusses and using more wood to fabricate another set, we chose to keep the nonconforming trusses. It turned out that, in our mild climate, the improved energy efficiency from the raised heel trusses would have saved the homeowner just $6 per year. 

In another case, we specified formaldehyde-free particle board for the cabinetry. The cabinetmaker's shop drawings didn't indicate the formaldehyde-free product, but we didn't notice! Again, we were faced with sending something to landfill. As a compromise, the cabinets were sealed on all faces to help prevent off-gassing of VOCs.

The experience we gained during the construction phase of this project is not directly quantifiable, but it is extremely useful as a reference for future projects. The design, the products, and the documentation were applied in the most realistic setting possible. We designed the ERB to be built by a typical production house contractor in the affordable housing market, and this approach was largely successful. We did not have a budget allocation to perform postconstruction testing, although it would be very valuable to do so.

Finally, the contractor should be adequately compensated for time spent on tasks that fall outside the scope of standard work. For example, our contractor asked for more money because he had difficulty with the fiber cement siding, which he had never used before. It is heavier than similar wood products and requires different cutting tools, as it is much harder than wood. After the contractor learned some techniques from the manufacturer's representative, things went smoothly, but he requested an additional $6,700 to help offset the extra time he spent. 

Clearly, balancing environmental goals with budget constraints and schedule requires the commitment of the architect, contractor, and owner. However, our findings clearly demonstrate that a thoughtful, interdisciplinary approach can produce competitively priced, environmentally sound, affordable housing and reduce long-term costs to the homeowner or managing agency. We succeeded in the following:

• reducing expected total operating energy (combined gas and electricity consumption) by approximately 33%; 
• reducing emissions from operating energy that contribute to global warming by an estimated 23%; 
• reducing emissions from operating energy that contribute to acid rain by an estimated 16%; 
• reducing the amount of fuel used for materials production by an estimated 50%; and
• reducing wood framing by an estimated 19%. 

Nancy Malone is an architect and researcher with Siegel & Strain Architects in Emeryville, California. She teaches ecological design at the University of California at Berkeley.

Siegel & Strain Architects designed the ERB project for the Emeryville Redevelopment Agency as part of the agency's first-time home buyer program. The project team included Larry Strain, Henry Siegel, and Jaqueline Lange. Additional funding was provided by the Alameda County Source Reduction and Recycling Board and the Alameda County Waste Management Authority. A complete report of the project findings is available from Siegel & Strain Architects. For more information, write to info@siegelstrain.com. 

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