El Paso, Texas: Net-Zero Energy Housing for Seniors

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El Paso, Texas: Net-Zero Energy Housing for Seniors

 

A 73-unit affordable housing development for very low-income seniors in El Paso, Texas is helping establish a new standard for sustainable affordable housing in Texas and throughout the United States. Developed by the Housing Authority of the City of El Paso (HACEP), the Paisano Green Community combines passive and active design to help the building attain net-zero energy consumption and a Leadership in Environmental and Energy Design (LEED) Platinum certification for Building Design and Construction in the New Construction category. The project, which was funded through the American Reinvestment and Recovery Act (ARRA), is one of the first public housing projects in the country to meet these standards and was recognized in 2013 with an Award of Excellence from the National Association of Housing and Redevelopment Officials.

Background and Context

Located in western Texas just north of the Mexican border, El Paso is one of the hotter and sunnier cities in the United States. The community of approximately 674,400 residents receives more than 300 days of sunshine each year, with average monthly high temperatures approaching 95 degrees in the summer. In 2010, HACEP launched a national design competition to inform the development of a new affordable senior community in this desert climate on a 4.2-acre parcel that it owned. Armed with an $8.25 million ARRA grant awarded through HUD’s Capital Fund Recovery Competition program, HACEP challenged architects to submit designs for innovative, high-quality housing that would set a new standard for energy efficiency in El Paso. Prepared by Boulder, Colorado-based WORKSHOP8, the winning design incorporates a combination of passive strategies, such as building orientation and building envelope performance, and active strategies, including highly efficient lighting and mechanical systems, that allow the project’s renewable energy systems to generate nearly all of the energy demand for the 73 housing units.

Designing for the Local and Regional Context

The design for the Paisano Green Community responds to the challenges of the site and the broader desert environs. Surrounded by civic and industrial uses, the project consists of a series of buildings organized along the length of the rectangular-shaped parcel’s north-south axis (see site plan). A community building, with two large meeting rooms, residents’ mailboxes, a communal kitchen, and a rooftop terrace, frames the northern edge of the site. Forming the western side are 4 three-story buildings with one- and two-bedroom apartments. The site’s eastern edge consists of a linear townhouse building with two stories containing 9 single-room occupancy units and 9 one-bedroom apartments.

The buildings’ arrangement creates a series of outdoor spaces in the interior of the site, screening the neighboring properties and improving energy efficiency by optimizing passive solar design strategies. Buildings are oriented to minimize solar heat gain, with few east- and west-facing windows and with southern facades shaded by deep roof overhangs. The four multifamily buildings — sited parallel and oriented along an east-west axis — are connected by a partially enclosed structure with steel screens to allow air circulation through the site, shield the adjacent truck facility from view, and limit the exposure of the buildings’ west-facing walls to the sun.

The buildings have a highly efficient envelope to minimize heat loss in the winter and heat gain in the summer. The building walls are insulated to R-28, exceeding the minimum recommendations for the climate, and the roofs are insulated to R-30. The building envelope includes air-sealing measures such as caulking and vapor barriers to minimize energy losses through infiltration. The mechanical systems, including hot water and heating, ventilation, and air conditioning, were also specified with energy efficiency in mind. Each apartment is equipped with a ductless mini-split air source heat pump with a seasonal energy efficiency ratio (SEER) of 16 — more efficient than the SEER 13 minimum for air conditioners established by the U.S. Department of Energy. An air-source heat pump water heater that uses renewable energy meets the community’s full demand for hot water.

The project’s other renewable energy systems include a roof-mounted, 182-kilowatt photovoltaic array and two 10-kilowatt wind turbines. This onsite production capacity, coupled with the building’s energy-efficiency features, will help Paisano achieve net-zero energy performance measured over the course of the year. A model of the buildings’ energy consumption before occupancy estimated that the annual energy demand for a one-bedroom unit at Paisano would be only 14.9 percent of that of a one-bedroom unit built to meet the standards of the 2009 International Energy Conservation Code (IECC); the estimated energy cost of $191 per year is nearly $700 less than the cost for a comparable IECC unit. For a very low-income household of two people in El Paso earning 50 percent of the area median income of $44,800, this $700 savings represents 3.5 percent of annual income. Because estimating electricity use related to plug loads and other resident behaviors is challenging, Paisano has been designed to accommodate additional solar panels in the future to help bring annual utility costs to zero.

Financing and Cost Considerations

The $14.8 million project was made possible by a substantial capital grant through HUD’s Capital Fund Recovery Competition program (table 1). The $8.25 million ARRA grant was matched by $2.78 million from HUD’s Capital Fund Program, $3.3 million in HACEP reserve funds, and a $500,000 loan provided by the city of El Paso.

Although the per-unit cost of approximately $203,150 was nearly twice the construction cost of a typical El Paso apartment, a life-cycle analysis showed that over a 50-year lifespan, the full cost of the Paisano Green units is 20 percent less than that of typical El Paso apartments when utility and building maintenance costs are considered along with capital costs. The $1.22 million invested in the renewable energy systems is expected to save $1.45 million in operating costs over a 30-year timeframe and $3.7 million over a 50-year span.

Lessons Learned

Since opening in August 2012, the Paisano Green Community has received extensive recognition for its comprehensive approach to sustainability. The LEED Platinum-certified project received a Home Energy Rating System (HERS) Index score of 10 by integrating passive and active energy-efficiency features. Energy consumption data for the fully leased complex show that these investments are paying off. The energy cost for each unit averages approximately $18.30 per month in the apartment buildings and $21.11 for each townhouse unit. These costs are in line with the estimated modeled cost of $15.92 per month. With consumption varying widely among the units, the potential exists to further reduce energy use. At Paisano, HACEP demonstrated a creative approach to soliciting exemplary and innovative designs while expanding its capacity to incorporate green building strategies into future projects.