For two United Nations collaborators, home is a holiday house in the hills above Madrid. The husband and wife set their sights on Monte el Pardo, a forested area that is still well connected to the city center. The residence’s location in the Sierra Monte el Pardo mountain range, more than 2,500 feet above sea level, also offers fantastic views of Spain’s capital city.

“The breathtaking vistas and natural surroundings dictated the first sketches of the project, where we sought to maximize the view, the solar orientation, and the integration of the house in the slope of the terrain,” says Jade Serra, partner and cofounder of Slow Studio. The homeowners were drawn to the firm’s focus on sustainability, its commitment to its clients’ quality of life, and its sense of ecological awareness.

The couple live and work abroad, so they use the residence as a refuge for holidays, and they plan to ultimately retire there. Until then, they’d like to be able to rent out the home, while always maintaining a private space for their own use. With flexibility in mind, the team at Slow Studio conceived of a single-family house that’s semi-buried into the terrain and composed of two independent levels with separate entryways.

An internal staircase connects the two levels, although it can be closed by a door when necessary. The upper floor features the primary suite, along with another room and a bathroom, while the ground floor contains the living and dining room, the kitchen, and a small study that can be converted to a bedroom.

Designing a passive house was top of mind for the clients and the firm. In order to achieve zero or near-zero energy consumption all year round, the architects integrated two patios—one at the north end of the house, and one to the south. The south patio is a spectacular double-height space with a glass roof that can opens and close depending on the time of year.

In winter, the patios can be closed to create a greenhouse effect that warms the air within. This air can then be introduced into the house via ventilators. In the summer, the patios can be completely opened to introduce cooling breezes. Air renewal is achieved through a Canadian well that runs under the foundation of the home.

“The interior environment has a comfortable temperature and humidity without the need for energy input,” says Serra. “This, together with the use of noble and warm materials, creates an atmosphere of comfort that can be sensed as soon as one enters the house.”

A view of the lounge from the stairs reveals the couple’s wood stove." layout="" credit="Photo by Salva Lopez" photoUserId="6179228594908954624"/>The cozy lounge is furnished with furniture by Sancal and carpets by Nanimarquina." layout="" credit="Photo by Salva Lopez" photoUserId="6179228594908954624"/>

“The first impression you get when you enter the house is the difference in temperature inside, without having the heat on,” says the client. “The second impression is in relation to the glass—it is so bright, and you have a connection with the outside.”

The interior is composed of natural materials that are free of toxins and volatile organic compounds—and the design team avoided using varnishes, glues, and paints. The palette includes spruce pine, wood fiber insulation, and natural clay finishes—which help to absorb odors and regulate humidity in a natural way.

All of these things combine to form a soothing, sustainable sanctuary for the clients. “The greatest success of the project, and what we are most proud of, is undoubtedly the achievement of an atmosphere of collaboration, respect, and mutual understanding,” says Serra. “The clients trusted our criteria, and allowed us to take risks.”

More from Slow Studio:

A Spanish Family Sets Down Roots With a Cozy, Earth-Toned Passive House

Project Credits:

Architect of Record: Slow Studio / @slowstudio.es

Builder / General Contractor: Arquima

Structural Engineer: Campanya Vinyeta

Civil Engineer: Ecopenta / Maria Peralta

Landscape Design: Serman Construcciones y Decoracion

Lighting Design: Cointec Instalaciones

Interior Design: Matter Barcelona

Cabinetry Design: Carrete Finestres

Technical Architects: Equipo Aparejador

Sustainable Building Cooperative: Societat Organica