Some years back, architect Ignacio G. Galán was walking through the woods outside Madrid with his client, who paused to point out frogs hopping through the trees. As a child visiting his grandparents there, he used to catch frogs like these in the same woods, he tells Galán, which is a mix of native holm oaks and pines imported for resin extraction. Today, industry has since vacated, but the client has returned to the foothills of the Sierra de Guadarrama with his children to bike, run, and catch frogs once again—and build a home of their own.

The frogs sparked an idea for New York–based Galán and his partners, Madrid-based Álvaro M. Fidalgo and Arantza Ozaeta, whose collaborations often answer unique architectural questions. In addition to designing a spacious family retreat, they envisioned a pond to honor the family’s bond with the forest’s aquatic life—and a home that would help sustain it. “We wanted the house to be part of the ecosystem rather than extracting from it,” says Galán.

In Avila, Spain, a family with ties to the area built a home that harmonizes with a forest recovering from industrial resin extraction. It has a graywater pond that doubles as a habitat. “We came up with the idea of the pond, but Ambient Paisajismo, the landscape architects, taught us so much—how to rebuild the ecosystem with compatible species that favor both biodiversity and beauty,” says Ignacio G. Galán." layout="wide" credit="Photo by Imagen Subliminal (Miguel de Guzmán + Rocío Romero Rivas)" photoUserId=""/>

Without city plumbing, a home typically requires a septic tank, but the architects devised a system they call “un-tanking.” Instead of burying a tank underground, they developed an open setup that separates black and graywater, channels clean runoff into ventilated filters, and reintroduces it into the environment through the new pond.

Now, just down the hill from the house, descendants of the frogs from the client’s childhood also enjoy a new home. “The frog became the protagonist,” says Galán. “It links their memories to the site and symbolizes the return of life to a recovering ecosystem.”

The six-bedroom, 4,300-square-foot house was designed to minimize disruption to the terrain—no deep foundation was dug and no trees were removed. Downstairs, two bedrooms are tucked behind a generous open-plan living space that includes the kitchen, dining, and lounge spaces, all opening to a large veranda that connects directly to the forest. Upstairs, four bedrooms and a small living room provide private space.

It’s big enough for the client’s family, including grandparents and friends, when they want to escape Madrid. When the client and their partner come alone, as they sometimes do to work remotely, they can use a section of the second floor like a one-bedroom apartment. This “nested” space can be independently heated and incorporates a study, bathroom, and a kitchenette in the living room.

Designed to minimize its use of natural resources and be as efficient as possible, the house doesn’t have a central air or heating system. Instead, it maintains a comfortable temperature through central Spain’s hot summers and chilly winters with a combination of natural ventilation and a radiant heating and cooling system beneath ceramic floors. Two wood fireplaces with a shared chimney provide additional warmth through colder months, while solar panels power a heat pump that drives the radiant system.

The facade is clad in trans-ventilated ceramic and zinc siding, which features an air cavity between the exterior walls that acts like the home’s skin, protecting it from heat in the summer and cold in the winter, explains Fidalgo.

asymmetrical metal roof, aids in the home’s natural climate control." layout="wide" credit="Photo by Imagen Subliminal (Miguel de Guzmán + Rocío Romero Rivas)" photoUserId=""/>

To reduce the building’s surface volume and minimize heat gain and loss, the architects designed the roof with multiple asymmetrical pitches at varying heights. An added feature of the unique geometry, “each room has access to windows on at least two facades to ensure multiple sources of light and facilitate natural ventilation,” explains Galán.

Connected to memories and mindful of the land with its off-grid, biophilic features, this forest retreat enables both human and amphibian life to flourish in harmony. "We looked to architecture that supports the residents,” says Galán, “and builds alliances amongst the forms of life that share the site with them.”

A Panoramic Passive House Rises in the Mountains Above Madrid

Project Credits:

Architect of Record: Ignacio G. Galán / @nachoglezgalan and Ozaeta-Fidalgo / @ozaetafidalgo

Builder/General Contractor: Construcciones Maganto Martín S.L.

Structural Engineer: Alfredo Lafuente

Civil Engineer: Jorge Chico

Landscape Design: Ambienta Paisajismo

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A Graywater Pond Doubles as a Frog Habitat at This Forest Retreat Outside Madrid