The design of this detached single-family house was
commissioned to us by a couple with the dream of retirement living in the
middle of nature. The site is characterized by Mediterranean vegetation
typical of the area and includes olive trees, pines, mastic trees, and palm
hearts on calcareous soils. The plot, of about 900 m2, is located at
the end of small urbanization on the edge of the Garraf Natural Park, on
the coast south of Barcelona.
A construction that would allow contemplating the
landscape and would entail low energy consumption was the main requirement of this
commission. At the same time, the project presented multiple challenges: a
steeply sloping, north-facing plot, and a limited budget.
The urban planning regulations place the built
occupation in the center of the plot, allowing to construct up to three levels. The proposal
interprets this provision of the planning and strategically renounces the third storey
in favor of integration with the topography and the natural environment. The project is
interpreted as an opportunity to demonstrate that it is possible to build passive
buildings, designed bioclimatically and built with healthy materials at an affordable cost.
The house was conceived with the vocation of
respectfully integrating with its natural context and of being a passive building. Based on
simplicity and sustainability, the proposal offers a creative response to the initial
complexities. The house is embedded in the terrain to adapt to the topography and
blend into the landscape. At the same time, it takes advantage of the ground’s insulating
power and accompanies the natural slope by stepping the interior spaces into
two levels.
The geometry of the house is explained by the purpose
of leaving nature as the protagonist and at the same time offering its
inhabitants a protected and welcoming space from which to contemplate the landscape. The two
arms of the built volume open to the North, the mountain of Montserrat, and the
immensity of the natural park. The house is organized in a single volume articulated on
two floors. The facades facing the street and towards the neighbours are intentionally
devoid of openings. The day area and a bedroom are located on the ground floor; on the
first floor there is a second bedroom and a large terrace with solarium and garden.
Each room in the house allows the contemplation of the forest from a different
perspective.
The choice of materials responds to criteria of health
for people, respect for the environment and constructive and economic efficiency.
For the exterior walls, aerated concrete blocks have been used due to their lightness
and high insulating power; thermo-treated natural cork panels for the exterior
finish of the façades and their insulation to blend into the natural environment too.
For the interior finishes, lime and silicate paints have been applied. The upper face of
the floor slab, finished with quartz crystals, has been used as flooring. Solid pine wood
treated with natural stains has been used for the exterior carpentry.
Before the challenge of achieving a passive building,
the project adopts multiple bioclimatic design strategies that respond to a
detailed study of the climate and the topography of the site. The building is designed by
orienting it along the north-south axis so that it takes full advantage of the
contribution of solar radiation in winter and natural ventilation is thereby more effective in
summer.
The following Bioclimatic strategies have been adopted to heat the
building during the cold months.
1) The South façade, in its glazed part, works as a
solar heater due to the greenhouse effect.
2) The Trombe-Michel walls located on the South wall
function as hot chambers that reach high temperatures during the day and transfer it
by convection and radiation to the house’s interior.
3) On the North face the openings have been reduced to
a minimum.
4) On the coldest days, on the North side, a
high-efficiency stove can be lit.
The following Bioclimatic strategies have been adopted to cool the building during the warm months.
1) The façade openings have been calculated so that
they can safely ventilate during the night with natural cross ventilation.
2) Trombe-Michel walls work as “solar chimneys;” by
heating up more than the house’s interior spaces.
3) The deciduous trees planted in front of the South
façade protect it from intense summer solar radiation.
4) The eaves of the South façade prevent the solar rays
from heating up the glazed area of the façade.
5) The natural pond located below the building favors
the air cooling.
Throughout the year, the excellent insulation of the
entire enclosure, the high-quality carpentry and the elimination of air infiltrations
manage to keep the temperature inside the house stable. Green spaces and grey and rainwater
treatment are integrated into the project design as part of the same
bioclimatic strategy. Rainwater from the roofs is collected in a tank
located below the parking space and is used for watering the garden and for the natural pond
at the lower end of the site. The natural pond contains a plant filter that acts as a
photo-purifier and promotes biodiversity in the local fauna. Grey water has been separated from waste water for
later recycling and recovery.
The heating demand for this building is 5.4 KWh/m2
year and the cooling demand 14.5 KWh/m2 year. No active air conditioning system is
used, except for the wood stove. Photovoltaic panels have been installed on the roof to
cover internal electrical needs.
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