A Net-Zero Home in Colorado Raises the Bar for Indoor/Outdoor Living

Atop the footprint of a 1940s ranch house, architect Renée del Gaudio designs a family residence that intimately connects to its site.

A decade ago, interior designer Stephanie Waddell moved with her husband and young son into an aging ranch house in the foothills of Colorado’s Rocky Mountains. Located on a leafy road in the city of Boulder, the single-story house, which dates to 1948, was rather dark and cramped, but the family made the most of it. By 2017, however, the time had come to update the 1,750-square-foot dwelling. "We definitely needed a little more space," says Stephanie, who leads local studio Istoria Interior Design.

Mariposa Garden House lies low to the ground, much like the 1940s ranch house that formerly occupied the site.

For help in creating her new family home, she turned to close friend Renée del Gaudio of Renée del Gaudio Architecture, a Boulder-based firm that focuses on site-specific design. Among the firm’s award-winning projects is del Gaudio’s own home, Sunshine Canyon House, a rustic yet modern abode that embraces the natural landscape. 

For her friend’s dwelling, del Gaudio wanted to create "a house of gardens and light." To achieve this, she conceived a drastic plan: raze the original house, but preserve its irregular, blocky footprint, which steps around little pockets of greenery. "The redeeming quality of the house was its footprint—the twists and turns the exterior walls took in relation to the landscape on the property," says del Gaudio. "The original foundation was not so much a constraint as a real opportunity."

Shade is provided by overhanging roofs with cedar eaves.

A pathway leads from the main dwelling to a detached art studio in the backyard.

The home’s "twists and turns" are driven by the landscaping on the property, says architect Renée del Gaudio.

And so, the 70-year-old ranch house came down, and atop the existing concrete foundation rose the Mariposa Garden House: a two-level, 3,150-square-foot building comprising rectilinear volumes with ample glazing, flat roof planes, and a series of surrounding gardens with outdoor spaces. (The materials from the tear down, it should be noted, were donated to recycling organizations.) 

To build the home, del Gaudio implemented a new timber frame and membrane roof, and installed energy-efficient walls. In the rear of the building, the team erected a tall brick "chimney volume" to accommodate two fireplaces, one for each level. The vertical masonry form also holds a compact mudroom on the first floor. 

A 16-foot-wide sliding door connects the main living area to a covered patio.

The dining area features an oak table with metal legs, created by local company Double Butter. The chairs are by Arhaus, and the light fixture is by Hammerton Studio. The living room is filled with vintage chairs.

A brick volume houses a fireplace on each of the two levels, and a mudroom on the lower level. 

In the kitchen, the team installed walnut cabinetry, slate countertops, and a backsplash made of tiles from New Ravenna. The bar stools are from Sossego.  

The facades are clad in ebony-stained cedar, a material that further grounds the house to the land, del Gaudio explains. Cedar was also used for the roof eaves. A variety of glazed apertures—from generous picture windows to long clerestories—usher in daylight and open the home up to its surroundings. 

Inside are lofty rooms and a fluid layout. The main level encompasses an office, two bedrooms, and an open-plan living area, along with a separate art studio to the back of the lot. The upper level, envisioned as a "nest in the trees," holds a master suite. Despite having a partial second level, the residence appears low to the ground, much like the original house. "We didn’t want to build anything massing-wise that would obstruct views," says del Gaudio.

Providing opportunities for indoor/outdoor living was an important aspect of the project. In turn, the design team incorporated a 16-foot-wide sliding glass door in the living room, which enables the space to seamlessly merge with a large covered patio. 

Tucked just off the kitchen is a breakfast nook with a round table from CB2, chairs from Arhaus, and an upholstered bench. Hanging overhead is a spherical pendant from Restoration Hardware.

In the main living area, the team built a custom shelving unit made of walnut and steel that’s fitted with brass hardware.

In the entryway is wooden cabinetry with perforated metal webbing. The vintage bench is from Mid Century Møbler, and the pendant is by DCW Editions.

The lower and upper levels are connected by a slender staircase with white oak treads.

Stylish patio furniture and a built-in grill help establish the perfect setting for the family to entertain guests or have a casual dinner. Beyond the patio is a fire pit, which sits among quaking aspen trees and other native vegetation.

The home’s upper level also affords the family a strong connection to the outdoors. The master bedroom flows onto a glass-lined terrace overlooking the backyard; a fireplace permits year-round use of the open-air space. "Stephanie has these heated chairs out there that we’ve been sitting in throughout the winter," says del Gaudio. "It’s just this really cozy, private space."

On the second floor, a master suite flows out onto a terrace with a ribbon fireplace.

Creating a comfortable and inviting atmosphere was Stephanie’s guiding principle for the house, but especially the interiors, where she put her professional talents to work in spite of the challenges. "Working on my own house was very stressful," she laughs. "I don't know if I'd ever do it again."

Throughout the dwelling are contemporary and vintage pieces in a range of hues, textures, and patterns. Earthy elements—like walnut cabinetry, stone tile, slate countertops, and leather upholstery—help the home feel warm and approachable.

"I hate the idea of anyone being intimidated by my home, or worried that they’re going to break something," says Waddell. "It’s one of the reasons I purchase vintage decor: If it gets bumped, or if there’s a spill on the rug, it becomes part of the piece’s history."

The master bathroom features terra-cotta wall tiles from Tabarka, round mirrors from CB2, and faucets from Kohler. The vanity was made by Wedgewood, a local company.

A powder room features wallpaper from Wall Shoppe.

Exposed Douglas fir rafters traverse a corridor in the timber-framed house.

Another key concern for Stephanie and her was environmental responsibility. Beyond a super air-tight building envelope, the house has an abundance of sustainable elements. These include a high-efficiency boiler, in-slab radiant heating, charging outlets for electric vehicles, and LED lighting throughout.

The residence is net-zero thanks to an eight-kilowatt photovoltaic array (with inverters) on the roof. The preservation of the former home’s footprint, which helped reduce material usage and waste, also counts among the project’s environmental merits. 

Plus, the footprint helps connect the new home to its predecessor, where Stephanie and her family lived happily for years."They loved living in the original house," said del Gaudio. "By using its foundation, we’ve tied the house to its past." 

On the second level, a glass-lined terrace overlooks the backyard.

The backyard features low-water plantings and a cozy fire pit.

Floor plans for Mariposa Garden House


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