Case Study: Holt Residence Addition
Smith L Holt, Architect

Project Goals
Set in a neighborhood built in the 1950s, this project is a good example of the integration of new construction with old while respecting the surroundings. The design of the house stays true to the neighborhood and the concepts of green building without conflict with the desired aesthetic or the special requirements that drove the need of the addition. The project embodies some key ideas: it was planned green from the start, contains highly efficient systems, is beautiful, and maintains respect for and integrity with the original house design and the community around it.

Project Name/Location	Rating	Completion Date	Cost/ft2 (excludes land)
Holt Addition Central Austin addition to existing 1955 residence.	5-Star	March 2006	not available

Project Description
This project combines a variety of green materials and strategies. The use of new technology with correct home orientation creates a harmonious integration of sustainable features in the living spaces. This makes the house more efficient and reduces the impact on the environment. Configuration and material choices were key to the success of achieving a five-star rating from the Green Building Program. The original house remains intact, updated and integrated into the project when it could have easily been demolished. This was a key sustainable choice.

In the new portion of the house, windows are situated to gather light and breeze while overhangs help block out the sun in the summer.  High windows in the addition draw heat out of the house and cool air is drawn in through windows on the first floor.  The entire house is covered by a metal roof.  Metal roofs are more energy-efficient because they release heat very quickly after sunset, which allows the house to stay cooler.  A majority of the new walls utilize insulated concrete forms, composed of recycled polystyrene and concrete.  This eliminates the need for additional steps and materials in construction because the insulated concrete form makes up the interior and exterior wall surfaces.  Wood materials removed from the existing house during construction, as well as finger-joined studs and metal studs, were put to use in the few areas where conventional construction was needed.  Bio-based spray foam insulation, which uses soybean oil to replace petroleum products, was used in the attic, common to the existing house and the new addition.  Where spray insulation was not appropriate, recycled cotton batt insulation was utilized.  Integral color stucco and stained concrete floors minimized the need for additional finish materials, while no VOC paints along with other water based and non-toxic finishes helped complete the project with few air pollutants.  With all of these elements thoughtfully combined, the house integrates into the neighborhood and has received a five-star rating from the Austin Energy Green Building program.

Project Features

Energy:

• Sealed combustion, on-demand water heater
• Sealed combustion furnace
• All appliances are Energy Star rated
• T-8 fluorescent fixtures used for indirect lighting
• 1.8 KW photovoltaic system installed

Materials:

• The project uses a mixture of Insulated Concrete Forms (Rastra), finger jointed studs, and metal studs
• Stained concrete floors
• Recyclable polycarbonate panels for car port
• Reuse of wood reclaimed from demolished portion of the existing house

Water:

• Low flow toilet
• High efficiency clothes washer
• On-demand water heater

Health and Safety:

• No VOC paint used
• Sealed combustion appliances
• Formaldehyde free insulation

Community:

• Integrated into neighborhood by being sensitive to the existing architecture
• Developed in concert with the City of Austin Neighborhood Plan for the area
• Large front porch

Commissioning and Testing/Results:

• Supply and return ductwork located in the conditioned envelope negating the need for duct testing.
• Blower door test resulted in .4 ACH.
• HVAC sized at 618 sf per ton of air conditioning.

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