Coastal homes along the Mediterranean face a specific challenge: properties with exceptional sea views often sit behind small, closed-off facades built decades earlier. When a multi-generational house in Denia, Spain, was converted from a dark compartmented building into a single residence, the design team started from the opposite of what existed. Small openings became large ones, cramped rooms became open volumes, and a dark interior was replaced with light pouring in from every direction. Passive house architecture principles show that transforming an existing building envelope is often more complex than building new, because the load-bearing structure and party walls impose fixed constraints.
The original house sat on a flat coastal plot with direct sightlines to the sea. Multiple families had occupied separate units, creating a fragmented layout with small individual windows that barely acknowledged the waterfront. The renovation combined these units into one dwelling while maintaining the existing footprint. No expansion of the building envelope was possible under local zoning. Every gain in light and space had to come from reworking the interior and the openings within the existing perimeter walls.
From Dark Compartments to Open Volumes
The existing structure imposed a floor plan with load-bearing walls dividing the interior into small rooms. Each former unit had its own entrance, kitchen, and living space, resulting in redundant walls and corridors throughout the building. The renovation strategy removed every non-structural partition and inserted steel beams where needed to support the floors above after interior walls came down.
This approach mirrors the spatial reorganization found in modern barnhouse transformations, where existing structural bays define the limits of open-plan living. The difference is that coastal renovations must also prioritize views, meaning the orientation of the open space must align with the waterfront facade.
Opening the Window Openings
The most dramatic change was the enlargement of window openings. Where the original house had narrow punched windows typical of 1970s Mediterranean construction, the renovation cut openings as wide as the structural grid allowed. Each window was extended vertically to the floor slab and horizontally to the adjacent column line. The result was a ground floor living area where the glass-to-wall ratio on the sea-facing facade exceeds 70 percent.
Structural engineering calculations must account for the reduction in lateral stiffness when removing large portions of masonry or concrete walls. In this project, a reinforced concrete frame around each new opening transferred loads to the foundation while keeping the visual profile minimal. Aluminum framing with thermal breaks was specified to maintain energy performance despite the large glazed areas.
| Element | Original Condition | Post-Renovation | Improvement Factor |
|---|---|---|---|
| Window-to-wall ratio (sea facade) | 15-20% | 70%+ | 3.5x |
| Interior volume, ground floor | ~180 m3 (divided) | ~280 m3 (open) | 1.6x |
| Daylight penetration depth | ~3 m from facade | ~8 m from facade | 2.7x |
| Natural ventilation paths | Single-sided, 1-2 per room | Cross-flow, 3-4 paths | 2-3x |
The daylight penetration depth increase is particularly significant. With the original 15-20 percent window coverage, usable daylight stopped about 3 meters from the facade. After the renovation, open-plan volumes and enlarged windows push daylight 8 meters deep, reaching the rear of the ground floor without artificial lighting during daytime.
Material Contrast as a Design Tool
A notable feature of this coastal transformation is the deliberate use of color and material contrast. The front of the house, facing the sea, is finished in white. The rear elevation uses black. This is not arbitrary. White represents light, the sea, and infinity in the design logic. Black relates to the mountain visible in the distance from the rear of the property.
Front vs. Rear Material Strategy
The white front facade uses a light-reflecting exterior cladding system that bounces additional daylight into the interior through the enlarged windows. Window selection for coastal environments must account for salt spray exposure, wind loads, and solar heat gain. The white cladding reduces heat absorption by reflecting up to 80 percent of incident solar radiation, lowering the cooling load on the sea-facing side.
The black rear elevation uses dark-toned metal panel cladding that recedes visually against the landscape. This dark finish absorbs heat during winter months, warming the rear circulation spaces. The combination of a cool white front facade and a warm black rear facade creates a passive solar gradient across the house.
| Property | White Front Facade | Black Rear Facade |
|---|---|---|
| Solar reflectance | ~80% | ~5-10% |
| Heat absorption | Low | High |
| Visual effect | Recedes, merges with sky/sea | Recedes, merges with mountain |
| Seasonal benefit | Summer cooling | Winter passive heating |
| Cladding material | Porcelain tile system (Xlight) | Metal panel or dark mortar |
The contrast extends indoors through the staircase core and floor finishes. Natural wood flooring in the living areas adds warmth against the white walls and dark-framed glazing.
The Staircase as a Sculptural Core
The staircase in this coastal renovation was designed as the visual anchor of the interior. Positioned at the center of the floor plan, it is visible from the entrance and from multiple points throughout the open living area. The design team opened all the spaces surrounding the staircase so that it reads as a freestanding sculptural element rather than a utilitarian connection between floors.
Visibility and Circulation
A stair that is visible from the entry creates a stronger arrival experience. When the staircase also receives natural light from above, it becomes a landmark inside the house. In this project, a skylight was positioned directly above the staircase, sized to match the stair footprint. Overhead light changes throughout the day, casting shifting shadows on the treads and risers.
Skylight-to-Staircase Sizing Ratio
Design guidelines for overhead lighting of interior staircases recommend a skylight area equal to 80 to 120 percent of the stair plan area. A staircase measuring 2 meters by 3 meters at its base (6 square meters) should have a skylight of 4.8 to 7.2 square meters directly above. This ratio ensures that the entire stairwell receives direct or diffused light throughout the day, not just at midday when the sun is directly overhead.
Overhead Lighting Strategy for Deep Plans
Even with enlarged windows, the center of a deep coastal house may not receive enough daylight. The Mirma House addresses this with a skylight positioned at the top-right corner of the staircase core, providing overhead illumination that reaches down to the ground floor. Showcase home designs often use similar strategies, combining perimeter windows with central roof penetrations to eliminate dark zones in deep floor plans.
Skylight selection for coastal zones must account for salt fog, high humidity, and wind-driven rain. Fixed skylights with a 15-degree minimum pitch shed water effectively. Double-glazed units with low-E coatings and argon fill provide U-values of 1.1 to 1.4 W/m2K, comparable to high-performance windows. The frame should be aluminum with a thermal break, powder-coated for corrosion resistance.
Structural Adaptations for Large Openings
Cutting large window openings into existing load-bearing walls requires careful structural sequencing. The typical process involves installing temporary shoring, cutting the opening with a diamond-blade saw, placing a steel or reinforced concrete lintel above the opening, and pouring concrete columns on each side if the opening extends to the floor. Wall openings in passive house projects follow similar sequences but also require careful attention to the air barrier continuity around the new frame.
- Step 1: Install temporary shoring on both sides of the wall section to be removed. Supports must extend to the foundation or a load-bearing floor below.
- Step 2: Cut the opening 50 mm oversize on each dimension to allow space for the structural frame.
- Step 3: Install the steel lintel or transfer beam at the top of the opening. Grout the gaps between beam and existing wall.
- Step 4: Cast reinforced concrete columns or install steel posts at the opening edges if the opening is wider than 1.5 meters.
- Step 5: Waterproof the rough opening, install the window frame, and seal the air barrier with flashing tape or liquid membrane.
- Step 6: Remove temporary shoring after all structural elements have achieved full strength.
The total cost for enlarging a typical window opening from 1.2 meters to 2.4 meters width in a concrete or masonry wall runs between $1,800 and $4,500 depending on the structural reinforcement required. This cost is typically recovered through increased property value, as rooms with floor-to-ceiling glazing and sea views command a premium of 15 to 25 percent over similar units with standard windows in coastal markets.
Coastal home transformations like this one demonstrate how existing buildings can be reimagined without expanding their footprint. The key moves, removing internal partitions, enlarging existing openings, adding overhead skylights, and using material contrast strategically, are applicable to any house with good orientation and an existing structure worth keeping. Passive house remodeling projects show that even the most constrained building envelope can be transformed into a light-filled, energy-efficient home through careful sequencing and integrated design.