Visitors to the hilltop neighborhood of Travessa do Patroc'nio in Lisbon come screeching to a halt (even if on foot) when they first glimpse a three-story house whose walls pulsate with lush vegetation. The vertical gardens of the Patroc'nio House bring a new meaning to 'picturesque,' the adjective often used to describe this city of low-rise, white- or pastel-stuccoed buildings with red-tiled roofs. In this single-family residence, two living exterior walls, angled slightly outward and supporting 4,500 plants, cause the narrow structure to look more like a tree than a townhouse. 'That's what I wanted'a tree!' exclaims the architect Lu's Rebelo de Andrade of RA\\Architecture and Design Studio in Lisbon, who completed the house with his son Tiago in 2012.

Lavender, rosemary, and saffron are only some of the fragrant flora sprouting from the effulgent walls installed by ADN Garden Design. The client, BWA'Building With Art, a developer specializing in custom residential projects, had acquired a worse-for-wear building on the tiny, 1,075-square-foot corner site. In discussing its replacement with BWA, the senior Andrade argued that the new spec house should look completely different'without being too unsettling'to attract a buyer. 'Architects have a responsibility to add to the views of others,' he explains. 'We need to be guardians of that.'

Andrade had incorporated a living wall as part of the elegant Aquapura Douro Valley hotel he designed in northern Portugal in 2008. But here was a chance to do it in a tightly knit city neighborhood. The parti for the Modernist, poured-in-place-concrete structure reflects its close abutment to a taller building next door. A skylit, three-flight stair on the west party wall skims past a study and a garage on the ground floor, ascending to second-level sleeping quarters, then to the third-level living and dining spaces. The stair ends at the roof, where the skylight opens like a hatch to allow the future residents and visitors to clamber onto the wood deck and take a swim in the 4-foot-wide, 40-foot-long pool. A projecting canopy for the rooftop elevator cabin supports photovoltaic panels that capture solar energy for hot water. There may not be room for a backyard garden and pool in this diminutive site, but that's OK. Both features come as an integral part of an energy-efficient house where the thick, leafy walls retain warmth in the winter and help cool the house in the summer.

Since the rooms in this shiplike dwelling are compact, the architects deftly contrived to suffuse the interiors with daylight and a sense of borrowed space. The living and dining areas open off the stair landing like alcoves, and glazed bands carved out of the planted wall facing east introduce daylight to both the living and the bedroom floors. Portholes in the bottom of the rooftop pool also admit light into the living areas, while glass balustrades add to the interior's sense of transparency and reflectivity. The architects even enhanced daylight in the master bedroom by enclosing the shower in translucent glass on three sides, and increased outdoor space with small rear balconies that open off the master bedroom and kitchen.

Working with ADN Garden Design, a Lisbon firm known for its aquariums, the architects emulated the work of Patrick Blanc, who developed vertical gardens for Ateliers Jean Nouvel's Mus'e du Quai Branly in Paris (2006) and Herzog & de Meuron's CaixaForum in Madrid (2008).

The effect is a rich floral quilt emanating seasonal scents, which requires only a full day with the gardener two or three times a year. Fortunately, Lisbon's mild climate lends itself well to living walls, although the architects and consultants say it's best to stick to local plants. 'So far we only had to replace 5 percent of them,' says Tiago Rebelo de Andrade. 'We were told to expect 20 percent.'

The 2,650-square-foot house, which cost $780,000 to build, including the 1,240 square feet of planting, has become something of a living landmark since its completion last August'the first time a house has been designed with an exterior vertical garden in Lisbon, the team notes. While the downturn in the Portuguese economy 'created a challenge,' says BWA's head, Louis Soares Franco, he says that prospective buyers from abroad have been showing interest. Lu's and Tiago Rebelo de Andrade, gratified by the reaction, hope to do it again.

On a recent sunny winter day, the architects, the client, and the living-wall consultants sat with a journalist in the ground-floor study, peering unseen through the wood louvers as passersby came up to the house, pointed, and started to smile. Did we hear 'ador'vel'? That would be Portuguese for 'adorable.'

Completion Date: August 2012

Size: 2,650 square feet

Total construction cost: $780,000

Architect:
RA\\Architecture and Design Studio

People Client: BWA—Building With Art Architect RA\\Architecture and Design Studio Personnel in architect's firm who should receive special credit: Principal(s) in charge: RA\\Architecture and Design Studio — Luís Rebelo de Andrade, principal; Tiago Rebelo de Andrade, Manuel Cachão Tojal, architects; Madalena Rebelo de Andrade, Raquel Jorge, team ADN GARDEN DESIGN Photographer(s): Fernando Guerra/Fg + Sg Photography

Products Glass and metal framing: Reynaers Aluminium Doors: Dierre; VitroChaves (glass upswinging door) Photovoltaic system: Vulcano