The Quinlivan Net-Zero Energy House is a privately-funded design research project. The project’s goals center on testing and evaluating the Passive House Building Energy standard for use in hot and humid climates. The research team sought to reconcile the requirements of a high-performance super-insulated building envelope with more porous vernacular building models common in tropical and sub-tropical climates. The project work is centered on the design of a single-family residence in Gainesville, Florida.

The project site is located at the intersection of NW 10th Street and NW 34th Avenue in the City of Gainesville, Florida, in Section 29, Township 9, and Range 20. The site consists of two parcels, both currently owned by Garrett Quinlivan. The two combined parcels total approximately 37,600 square feet, or 0.86 acres, of land area.

In direct contrast to loose and porous building envelope strategies, the Passive House building standard aggressively targets energy performance through the design and construction of air-tight and super-insulated envelopes, designed to eliminate or minimize thermal bridges. It differs from other rating systems in that it is centered on specific quantitative energy performance metrics. While it has only been formalized in the United States since 2007, the earliest research on these strategies dates from the 1970s. The Passive House Alliance United States (PHA-US) notes that “The Passive House standard is the most stringent building energy standard in the world: buildings that meet the standard use 80 percent less energy than conventional equivalent buildings, and provide superior air quality and comfort.” This claim appears to be validated by published test data from houses constructed to meet the standard.

The basic principals of Passive House design and construction are relatively clear and straight-forward:

• Superinsulate the entire envelope continuously.
• Eliminate thermal bridges.
• Create a continuous air barrier.
• Provide mechanical ventilation with heat or energy recovery.
• Use high-performance windows and doors.

The Quinlivan House has been designed to meet these criteria on a site in Gainesville, Florida. As designed, the thermal envelope includes a 2×6 wood frame bearing wall, cavities filled with dense-pack fiberglass insulation, two layers of 1 ½ inch thick continuous board insulation, and a foil radiant barrier. The thermal resistance of the exterior walls is in excess of R 35 hr-ft2-°F/BTU.

Within this exterior envelope, a continuous air barrier was created with a layer of oriented strand board, where all seams and joints were taped to avoid air exfiltration/infiltration. In addition, a continuous liquid-applied air barrier was used. Special attention was required at the foundation, at door and window openings, and at the juncture with the roof to avoid thermal bridges.

Because of the site’s location in a warm, humid climate, the vapor barrier is pushed outward in the wall assembly to prevent the migration of moisture-laden air into the wall assembly and/or into the conditioned space of the structure. This helps avoid condensation within the wall cavity.

Project Data

• Completion: July 2016 
• Construction cost: $243,702 ($135.39/sf x 1,800 gsf)