At one with nature

nCAVED Holiday Home in Greece

On the rugged Cyclades island of Serifos, in a secluded and rocky cove, there is a very unusual holiday home called nCAVED, built entirely into the earth. The name nCAVED comes from the special feature, “encaved” which literally means “buried”. It is specifically this earth sheltered construction style that protects the building from sun and wind and allows it to become an integral part of the landscape. The green roof rounds it off perfectly with native, drought-resistant vegetation that literally allows the roofscape to disappear into the ground. ZinCo partners, egreen, used the system build-up with Fixodrain® XD 20 on the pitched roofs.

The Greek island of Serifos is one of the Cyclades islands in the Aegean Sea. 33 of these islands are inhabited and Serifos, with a history of mining and metal extraction over a period of five thousand years, is a charming holiday destination today with a craggy landscape, treeless hills, strong winds and wonderfully picturesque strands.

The Athens-based, multi-award winning architectural bureau, MOLD Architects, wanted to create a private house the like of which has never been seen. And, indeed the house still cannot be seen as it’s so perfectly hidden in the earth. The trend in Greece at the moment is towards earth sheltered construction because it makes sense to protect a building in this way from the sun and wind. At the same time, the sloping site provides breathtaking views across the Aegean Sea. In this way, the hilly landscape remains untouched, and the view is unobstructed.

Wedge-shaped architecture

The form of the building follows the soft slope of the 6,000 m² site on the rocky hillside. It becomes evident that clear lines and forms predominate, as the architects have projected a rectangular grid over the hill, producing solids and voids over three levels and an area of about 400 m²: Sleeping area and living area and also a guest area on the lowest level. They are all connected to each other by elegant internal and external stairways. The terraced arrangement of the rooms and the wedge-shaped architecture allow for sweeping views on all levels.

Connecting inside with outside

On the inside, the forward-facing views of the sea help to shape the spatial impact as do the windows to the rear, opening onto the greened atrium.  Together they create an intense, visual connection between the internal and external space. There is also a functional aspect to this as the atrium draws in valuable daylight from above, right down to the bottom of the building where you would expect to find the darkest area.  The play of light and shade is naturally of particular significance in dwellings that are earth sheltered and it has to be taken into consideration with the changing seasons and times of day. The semi-transparent wooden slats in the pergola roofing create striking light and shade patterns.

Natural materials from the locality

MOLD Architects purposely left the stone, fair-faced concrete, oak and steel as natural-looking surfaces, and explained: “The choice of materials and the colour scheme reinforce the impression that the residents are living in an environment that is connected to nature. Because, we believe they should live with and among the elements in an intense and literally touching way.” An additional key concept of the architects is the use of local materials such as natural stone, which was extracted from the site ground, and was re-used for the stone walls and the green roof. Granite and metal were also used, a nod to the island’s mining history.

Protection from heat and wind

The nCAVED house has some excellent bioclimatic features. The arrangement of the rooms with their large seaward and hillside openings provides for natural wind circulation and therefore passive cooling. The building is perfectly protected from the strong North winds and at the same time from overheating as the adjacent earth and the greening of all roof areas operate as an effective climate buffer.  In this way, energy consumption and the operating costs of the building can be kept low.

Doubly helpful

For structural reasons, space-spanning reinforced concrete beams were used for the concrete roof surfaces. In the concrete industry, we refer to downstand beams where these roof members responsible for load transfer project downwards, and upstand beams where they project upwards. Given that the plain internal rooms in nCAVED were to be of the same height, the visible downstand beams on the ceiling were not an option, so upstand beams were used. In this instance, the upstand beams have a second major advantage, namely that they also act as shear barriers for the pitched green roofs. As an integral part of the overall surface, the upstand beams are professionally sealed using a double bituminous, root-resistant roof waterproof membrane, and are clad all round with XPS inverted insulation material.

Multifunctional rolls

The ZinCo system build-up with Fixodrain® XD 20 was chosen for the green roof because not only are the rolls quick and easy to install, but they also combine a number of functions: Protection layer, water storage, drainage, ventilation and the filter sheet is also laminated onto the sheets.

Due to the large contact area and the stable connection, the Fixodrain® XD 20 rolls act directly as a protection layer on the waterproof membrane. The sheets are fixed to each other along the longitudinal side with interlocking studs, resulting immediately in a plate effect. This creates a continuous protective layer that remains in position even on a pitched roof. 

The 2 cm high Fixodrain® elements made of thermoformed recycled polyolefin have cells on their upper side for storing water and a network of channels for drainage. The filter sheet, laminated on and with an overlap of about 10 cm along the longitudinal and head sides, creates a sealed surface which prevents the infiltration of fine particles from the substrate.

Weight-saving build-up

An additional approx. 20 cm insulation layer of EPS hard foam blocks is installed directly onto the Fixodrain® XD 20, hardly making a difference in structural terms. In order to keep the remaining build-up as light as possible, a 15 cm thick layer of pumice stone was used as a sub substrate. Pumice is a purely mineral, porous material of volcanic origin and is therefore particularly light and good for retaining water. 

The next layer is a 15 cm deep extensive green roof substrate specifically chosen for the planned vegetation and which was produced by our Greek partners, egreen, in line with ZinCo specifications. In this case, perlite is added as a water retaining aggregate.

Virtually invisible

The uppermost roof layer is created using 4-5 cm of local soil, so that there is no longer any difference visually to the surrounding earth, and small boulders are dotted around the green roof to enhance this effect.

All in all, therefore, a build-up height of about 60 cm is installed to create a flush connection with the stone walls at the side and the surrounding terrain. It goes without saying that drought-resistant plants were chosen that specifically draw on the local vegetation. A dripline irrigation system ensures that the plants on the roof will thrive in just the same way as those in the surrounding terrain. As a result, the transition from roof to ground is virtually invisible.

Re-discovery

The multi-award winning nCAVED is a house that has been built into the earth and which is simply compelling both architecturally and environmentally. Modern architecture has already created many impressive and innovative living spaces, with its cave, earth-sheltered and earth mound dwellings.

Architects have long re-discovered these archaic origins. Because, the cave as the primal dwelling of mankind, is the epitome of protection and safety and will therefore always unconsciously convey a pleasant sense of well-being.

Author: Oliver Hanna, Export Area Sales Manager, ZinCo GmbH

Site board

Construction project: nCAVED, Agios Sostis, Serifos Island, Greece

Construction year: 2020

Roof area:  approx. 360 m²  

Green roof build-up: ZinCo system build-up with Fixodrain® XD 20 and drought-resistant vegetation

Architect: MOLD Architects, 11852 Athens, Greece

System supplier: ZinCo partner, egreen Hellenic Import Export Enterprises Ltd., 10672 Athens, Greece

System manufacturer:  ZinCo GmbH, 72622 Nuertingen, Germany