Case
Study: Benavides Residence
Z Works Design Build
Project Goals
In the summer of 2005, Willow and Cesar Benavides commissioned Z Works Design Build to design and build a 2,000 square foot home located in theUniversity Hills subdivision, near the old airport. With three generations living under the same roof, the owners wanted a 2 bedroom/2 bath home with a separate, self-sufficient and fully ADA accessible 1 bedroom/1 bath unit for an aging relative. A home office, with a separate entry, and a small study completed the space requirements for the couple. All these spaces are arranged around a central courtyard, which provides privacy for the apartment as well as the office and study.
The V-shaped courtyard design serves several purposes. It creates a large private outdoor living area, part of which is a covered porch. The courtyard is open on south side to catch the breeze and enhance cross ventilation in the house. The shape of the home and the clerestory windows allow every room to receive natural light from two directions.
Although durability and energy efficiency were the main goals for this project, and the highest priorities for the homeowners, they had no idea that their house would become the most highly rated green home in Austin. The home earned 239 points on the Green Building Program's Single-Family Rating 7.2.
Benavides Residence
Northwest Austin Infill Home
Austin, Texas |
5-Star |
May 2006 |
$145/SQFT |
Project Description
The owners wanted a home that would be practical and livable for their lifetimes and beyond. An important design concept was to create a youth- to elder-friendly home that is safe, accessible, and comfortable for all the occupants
The idea of the house surrounding a courtyard turned out to be rewarding one, especially in terms of energy efficiency. The south-facing, deep overhang became a focus of the home and the roof provides enough space for the 3 Kw photovoltaic system. The house was specifically sited to save the existing trees, which provide shade during the summer months without hindering the performance of the solar panels. The PV system entered the plans in the design phase of the house. The roof was designed so that future PV panels would get optimum exposure but costs for the system were not included in the construction budget. Once construction was complete, and costs stayed within budget, the 3 Kw PV system was purchase and installed. The homeowners received a rebate from Austin Energy for the PV system.
Along with a solar electric system, the homeowners installed a solar hot water heater. The decision to install a solar hot water heater came from a City of Austin code amendment which prohibits the use of electric water heaters in new construction. This left the homeowners with three options for water heating: 1) tie their all-electric home into a gas line; 2) connect a heat recovery unit to the HVAC system; or 3) install a solar hot water heater. Although the solar hot water was a little more expensive up front, it will pay back the investment after about five years.
The home’s exterior walls are 10-inch thick Insulated Concrete Forms (ICF) with total fill insulation and insulated door/window headers in exterior walls. Along with effective insulation, all the ductwork, the high-efficiency 15-SEER HVAC unit, and the attic space are located within a thermal
envelope that includes a SIPs roof deck with an R-33 insulation rating covered by a metal roof.
Project Features
| Energy:
- 3 Kw solar PV system.
- 15 SEER cooling-equipment efficiency.
- All duct work, HVAC unit/equipment and attic space are located within the thermal envelope.
- Programmable thermostat.
- 100+ sq ft covered, usable outdoor area.
- Designed 670 sq ft of living space per ton of cooling.
- Designed to maximize passive solar heating/cooling capabilities.
- All roof overhangs minimum 24 inches to provide shade for windows and walls.
- Total fill insulation and insulated door/window headers in exterior walls.
- Double-pane and low-e glazed windows.
- Fluorescent lights and EnergyStar light fixtures and appliances installed.
- Structural Insulated Panels (SIPs) on roof with R-33
insulation value.
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| Materials:
- Exterior walls are 10-inch thick Insulated Concrete Forms (ICF) with 86% recycled content.
- Roof deck is 8 ½-inch thick SIPs covered by galvalume metal.
- Stained concrete floors throughout the house (slab on grade foundation).
- No solid lumber larger than 2x10’s used.
- All cabinet faces MDF (Medium Density Fiberboard), an engineered lumber product that reduces wood use.
- Lumber longer than 2 feet, concrete and stone rubble, metal scraps, and corrugated cardboard were used or recycled.
- Concrete countertops and shower walls.
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| Water:
- Solar hot water heater for entire house.
- Roof designed to connect to future 2000-3000 gallon rainwater harvesting system for landscape irrigation.
- Existing vegetation retained or landscape plants picked carefully for xeriscaping, no turf grass.
- Low flow toilets.
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| Health and Safety:
- Super-low voc interior paints.
- Exhaust fans venting to the exterior at stove and showers/baths, bathroom fans timers.
- Grab bars and anti-scald valves in baths and showers.
- Doors have lever handles instead of doorknobs.
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| Community:
- Accessibility provided according to COA Barrier-Free Residential Construction Guidelines.
- Public transit system within 1/4 mile.
- Shopping/grocery and park within 1/2 mile radius.
- Home office with dedicated exterior entry.
- Exterior lights designed and installed to prevent up-lighting/ light pollution.
- Homeowners participate in the Austin Energy Power Partner and GreenChoice programs.
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| Commissioning & Testing Results:
The building envelope performance of this home was exceptional. The blower door test, which measures how tightly the home is constructed, showed on of the best results ever seen by the Green Building Program. The GBP requires that air leakage be less than 0.5. This home’s measure leakage was 0.0975, less than 0.1.
A duct leakage test was not conducted because the system is inside the home’s conditioned space.
General Results:
So far, no other rated home includes a PV system and a solar water heater. This home scored 98 points in the Energy category, which is enough to earn it a three star rating on the basis of energy efficiency alone! Because the home is a neighborhood infill and includes a second living unit, it also scored very high in the Community category.
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