Environmental Valuation & Cost-Benefit News

* Location: San Diego, CA
* Building type(s): Commercial office
* Renovation of a 1981 building
* 78,000 sq. feet (7,250 sq. meters)
* Completed 1995
* Rating: Green Building Challenge

The Ridgehaven Building is a relatively nondescript 1981 commercial office building that was renovated for the City of San Diego's Environmental Services Department. The renovation provided an opportunity to showcase cost-effective energy efficiency improvements, resulting in a remarkably efficient building for a very reasonable price.

Environmental Aspects

Goals for the project were healthy indoor air quality, resource efficiency, and efficient building operations. The following criteria to address these goals were ultimately included in the project specifications: minimize the environmental impact of selected materials, systems, and construction; create a healthful work environment by minimizing material chemical emissions; improve indoor air quality through mechanical systems selection and construction; maximize resource conservation and recycling in both material selection and construction; and maximize energy conservation through mechanical and electrical system efficiency.

Healthy indoor air quality was a primary goal since some of the EDS employees had chemical sensitivities. Additionally, the city wanted to avoid any issues with sick building syndrome and wanted to create a healthful work environment.

Cost data in U.S. dollars as of date of completion.
* Total project cost (land excluded): $2,700,000
* Property cost: $3,000,000

The project cost approximately $37/ft2 ($398/m2) for renovation, on top of the $41/ft2 ($441/m2) purchase price.

The city saved approximately $76,000 in energy expenses after the first year of operation. With the specified energy management system now in place, the Environmental Services Department (ESD) can expect to save well over $80,000 in annual energy costs. The ESD estimates an average payback period of 4 years on the energy-saving systems.

On average, the environmentally friendly building materials used in this project cost more than conventional materials. To lower the overall project costs, creative use of the materials was necessary, such as forgoing more expensive wall coverings. Other tradeoffs included sealing or painting the cabinetry in place of costlier laminating, and using cellulose insulation rather than fiberglass batts.

Another method of addressing building costs included a life-cycle analysis approach to building materials cost. For instance, carpet tiles in general cost more than broadloom carpet. However, worn carpet tiles can be moved from high-traffic areas to low-use areas, thus extending the useful life of the material. In addition, the perlite acoustical ceiling tiles have a longer estimated useful life than conventional ceiling tiles. Linoleum is extremely durable and also has a longer life expectancy than conventional resilient flooring. By averaging the cost of the material over the extended life of the product, specifying durable products was another way to lower material costs.

By diverting over 186 tons (170 tonnes) of debris from the landfill, the city saved approximately $93,050 ($1.27 per ft2) by avoiding landfill tipping fees. Since the owner, ESD, also runs the landfill, this helps the city meet requirements of California Law AB939.

Energy-saving lighting and controls were specified based on the DOE2 computer analysis of the lighting engineer's recommendations. Energy-efficient mechanical heating, ventilation, and air-conditioning (HVAC) systems and controls were also specified based on the DOE computer simulation of the mechanical engineer's recommendations.

Energy-efficient T-8 fluorescent lamps and 2x4-foot (0.6 x 1.2 m) parabolic fluorescent light fixtures were installed. These fixtures are considerably more efficient than the original building lighting. Daylight sensors and occupancy sensors were installed to control the lighting and reduce energy consumption. Occupancy sensor plug strips were installed at computer workstations for added energy savings.

Although the original building facade had recessed windows, solar control film was installed on the east-, south-, and west-facing window elevations to further reduce solar heat gain. At the upper-level corner offices, overhead, sloped glazing of the original structure created a greenhouse effect. Awning shades were installed to minimize solar heat gain at these locations.

The entire existing mechanical HVAC system was replaced with high-efficiency water-source heat pumps (14.9 EER), adjustable-speed condenser pumps, variable-air-volume boxes for outside air, and an energy-efficient cooling tower. Direct digital computer (DDC) controls were installed to balance the system for additional energy savings. (A substitute system was installed the first year that was not as effective as the specified system, yet still surpassed the annual energy consumption goal of 9 kWh/ft2 [97 kWh/m2]. The building has been operating more efficiently since the specified system was installed in March 1997; however, the system has increased the building's energy consumption.)

Currently, the building uses approximately 60% less energy in building operation than the original structure. In addition, the building surpasses Energy Efficiency Standards (California Title 24 requirements) by over 50% through the installation of state-of-the-art energy-saving electrical and mechanical systems. The actual energy consumption of the renovated building is now 8.2 kWh/ft2 (88.3 kWh/m2) per year compared to 21 kWh/ft2 (226 kWh/m2) per year that the conventional office building used prior to energy upgrades.

The Ridgehaven Office saves over 60% in energy consumption compared to a nearly identical office building, with no energy-efficient systems upgrades, on adjacent property.

Added to Database February 5, 2007

U.S. Department of Energy Energy Efficiency and Renewable Energy Division www.eere.energy.gov
Building Technologies Program
http://www.eere.energy.gov/buildings/database/overview.cfm?projectid=41