Engel-Schon'S House, a large passive house

What architectural solutions are needed to make a large passive house possible, on a steep north-facing slope?
This was the first challenge that architect Nico Engel set himself for his house located in the heart of the town of Esch sur Alzette, on a former mining site that has been converted.

Dare to reconsider the traditional interior organization of the house.
In view of the constraints of the exposure, the first choice was to create the living spaces (living room, kitchen, dining room) on the 3rd level, on the same level as the garden, to open them widely towards the South and the forest.
Obviously the distance of this space from the street side entrance is a disadvantage, especially for the reception of visitors who have to climb 2 levels. This arrangement led the architect to conceive the staircase ascent as a walk that gives the visitor the opportunity to discover the house. The ascent takes place in the middle of a large central void that connects the spaces on all levels, making them closer both visually and acoustically. The staircase railing is the guiding thread of the route, a wide metal ribbon sometimes treated as a simple protective wall, sometimes as library shelving.
This central space is also a real breathing space for the house, allowing cooling through natural ventilation from the ground floor to the upper floors.

Sculpting the house with the land to find the sunshine
The building would have been completely embedded in the ground, with blind rooms, if the architect had not found the architectural solution of the day wells. Dug into the slope on the sides of the building, they generously let light into the living rooms. They bring sunshine from east and west, contributing to passive solar energy and shape the general volume of the house while leaving it a certain compactness.
Finally, these daylight wells, at the interface with the natural terrain, contribute to better integrating the building into the slope, through the play of the supports.
On the ground floor, the guest bedroom and the fitness room benefit from the West and East orientations. They each open, through large bay windows, onto an intimate patio where the vegetation and the mass of the walls help to regulate the house's temperature and humidity.
On the intermediate floor, which includes the bedrooms, the laundry room and an office; Several bedrooms benefit from a double orientation with beautiful corner windows. The parents' bedroom, set back from the street, opens to the east through large picture windows.

Imagining an architectural expression for a north facade overlooking the street
On the north side, to limit wastage, the openings are limited to the maximum: the entrance, the garage door, the staircase lighting and corner windows for 2 bedrooms. These openings are integrated into a resolutely modernist composition of the facade. The garage door disappears, integrated into a wooden cladding that forms the base up to the entrance. A vertical slit, very sculptural, a sort of crack in the cubic volume, making one forget the scale of the 3 floors, marks the entrance.
What technical choices can be made to meet the requirements of a low environmental impact project?
This is the second challenge to which the architect wished to bring concrete solutions.
The choice of simple and efficient technical systems, coupled with an architectural design adapted to the site, is the second challenge to which the architect wished to provide concrete solutions.
The architectural design has created the right conditions for passive solar operation. It took into account user comfort but also energy savings, by favouring natural lighting and temperature regulation through natural ventilation and thermal inertia (generated by the buried walls).
After having limited the potential sources of energy consumption, the technical choices were made for 3 complementary systems: an air-to-air heat pump for heating and hot water, double flow ventilation with an energy exchanger and photovoltaic panels, installed on the roof, covering the needs of the heat pump.

A choice of reusable or recyclable quality materials
The choice of materials favours environmentally sound materials, common applications for local businesses and possible reuse or recovery.
Thus, only the main structure of the house is made of concrete, for a solid anchorage in the ground, but its configuration may allow for other development arrangements in the future.
The walls of the house are like a skin that dresses this structure and gives it its volume: the laminated wood walls are insulated with cellulose wadding and are made either of wood fibre board with brushed coating (traditional material on the street side) or with a wooden lathing that supports a wooden cladding (natural material on the garden side).
The flat roofs are treated with Frigolite thermal insulation and Alwitra Evalon V waterproofing, recoverable because they are not sealed.
These devices allow an easy deconstruction with recovery of materials.
The frames are made of recyclable aluminium, and the windows are triple-glazed with external solar protection by means of wide slat blinds.
Rainwater recovery and use
The retention of rainwater is treated here, not in technical works, but in ornamental ponds with a poetic dimension.
The water from the roof passes through several basins, distributed on the slope, which are filled gravitationally by overflow effect. From an architectural point of view, they provide a horizontality that allows the project to sit in the slope. From a functional point of view, they are useful for watering the garden and for cooling the atmosphere through evaporation.