Lowtech high tectonics

Andrea Deplazes

Camouflaged energy concept

One example for energy-saving construction within the costs framework of conventional building methods: What was originally intended as a conventional school design at the tender stage changed during the planning phase to a concept complying with the Swiss "Minergie" Standard. In doing so it was possible to avoid delegating the energy problem to the building services and instead to achieve a synthesis with the tectonics of the structure.

A visitor to the school in Vella would be unable to discover anything that could be deemed unusual in a school. The buildings employ a solid form of construction, with fair-face concrete walls internally and solid timber wall panelling for the classrooms and the sports and assembly halls. The buildings are enclosed in a layer of thermal insulation 12 cm thick, which in turn is protected by a layer of render about 3 cm thick - exactly as used in the traditional timber houses not far from the school, which are clad with a thin render "membrane". The internal layout corresponds exactly with typical school requirements.

But upon closer inspection our attentive visitor would make a few discoveries: no radiators in the rooms, no centralised heating plant in the basement, no solar collectors anywhere in the building or on the roof! Instead, a mechanical ventilation system ensures a supply of fresh air with a low air change rate (0.5) and is intended to prevent uncontrolled ventilation losses (e.g. windows left open unintentionally). A heat exchanger has been installed downstream from this system to introduce waste heat from the exhaust air into the incoming fresh air. That is it, the only technical component in the school; this belongs to the - in architectural terms - less interesting part of the concept. More conspicuous are the ribbed concrete floors, the solid floor finishes of Vals quartzite stone slabs (also in the classrooms) and the large-format windows with their hopper-shaped reveals whose timber frames are screened externally by the thermal insulation. This is where the inconspicuous energy concept begins - with the use of passive solar energy.

A technical problem?

Soon after beginning the planning it was discovered that the location of the new school would be really ideal for exploiting solar energy. Although nothing of this kind had been allowed for in the budget, the local authorities approached us, the architects, with the wish to integrate solar collectors into the roof surfaces. ("However, it mustn't cost more.")

We were not impressed by the idea of the "badge of enlightened energy consciousness", which all too often is placed conspicuously in the foreground. After all, the addition of technical equipment to the building would have disturbed not only the architectural surroundings of this mountain village with its splendid, archaic houses. To greater extent it disturbed our understanding of our role as architects - trying to combine diverse, often conflicting parameters in the design process - in that we would have to come to terms with an aesthetically successful integration of collectors into roof and other surfaces.

A tectonics solution

We therefore developed the concept of storing the solar energy in solid components. The appealing notion here is that we can use the same wall thicknesses and floor depths as in a conventional design - provided that the components are of solid construction so that they can absorb the incoming solar radiation (through the windows) as quickly as possible and thus prevent overheating in the interior. However, as the walls in the classrooms would be needed for all sorts of blackboards, magnetic notice boards, cupboards and showcases, and hence would not be available as a storage medium, we opted for ribs on the absorption surfaces and the optimisation of the floor mass distribution in line with the recognition that the dynamic penetration of heat radiation into solid components is about 10 cm (primary storage). During periods of good weather lasting a few days in the winter the storage media can be continually charged (secondary storage).

Multiple use strategy

This is coupled with additional, satisfying multiple uses. Provided with ribs, the floors easily span the 7.5 metres across the classrooms with little material consumption. At the same time, the profiled soffits create an extremely effective acoustic diffusion so that other acoustic measures (absorption) are unnecessary. Inexpensive energy-saving

Figs 20 and 21: School building and multipurpose hall (left), south facade with large area of glazing (right)

Bearth & Deplazes: school complex, Vella (CH), 1997

Figs 20 and 21: School building and multipurpose hall (left), south facade with large area of glazing (right)

Bearth & Deplazes: school complex, Vella (CH), 1997

Project

Energy concept Building services

School complex with mul purpose hall, Vella (CH) Local authority of Vella, Lugnez (CH) Valentin Bearth, Andrea Deplazes, Chur Andrea Ruedi, Chur Nold + Padrun, Chur

Key parameters

Recommendations of SIA 380/1 "Energie im Hochbau", 1988 edition; target value : 260 MJ/m2a

SIA brochure D 090 "Energiegerechte Schulbauten";

standard target value: 150 MJ/m2a optimised target value: 76 MJ/m2a

Value calculated for Vella according to "Handbuch der passiven Sonnenenergienutzung", SIA/BEW document D 010: 24 MJ /m2a Measured results for Vella (IBT diploma thesis 98/99): 34 MJ/m2a

The deviation of the measured energy consumption values from the calculated ones for the school complex in Vella lies within the tolerances of the method of calculation

Storage capacity (reserve for poor weather) During a period of poor weather lasting 4 days, an outside temperature of -5°C and decreasing solar gains the storage media discharges from an average 21°C to 19°C. At this point the descending temperature gradient intersects with the preheated (with the heat exchanger) air temperature curve of the mechanical ventilation system such that the value can be maintained. (Measured values from 12-15 Jan 1999, measurements taken in winter 1998/99)

lights are easily installed between the ribs without creating any glare. And finally, the ribbed floors create a rich architectural motif which can certainly be regarded as a transformation of the Baroque ceilings in the aforementioned houses of this district. Just one last component was missing in order to redirect the maximum amount of solar radiation up to the soffit - light-redirecting louvres on the inside of the window panes.

But as specially designed light-redirecting systems would have been too expensive, we made use of conventional aluminium louvres which we threaded onto the operating cords and rotated 180°. These louvres are let down in winter just enough so that the pupils nearest the windows are not disturbed by the shallow, intense in coming sunlight, which is heightened by snow on the ground. However, the foremost one-third of the floor surface directly adjacent to the windows can still absorb heat and correspondingly "charge up" like a sheet of blotting paper across the depth of the room. The louvres can be rotated into position to reflect the sunlight over the heads of the pupils and up to the underside of the ribbed floor slab. This allows not only the heat absorption of the floor slab to be exploited to best effect, but also improves the natural lighting across the depth of the room, which in turn reduces the amount of electrical energy required for lighting. And the fact that in this position the louvres are still "open" and thus permit a view of the surrounding countryside should not be underestimated.

Versatile concept

As a concept for the use of solar energy through storage in solid components such as floors and walls, which have to be constructed anyway, this method is not confined to schools. The multiple use strategy of components is the condition that must be fulfilled in order to remain competitive - in terms of price - with conventional methods of building. It could be the right time to switch from the modernistic understanding of complementary architectural systems comprising monofunctional individual parts to synthetic, complex, polyfunctional components. That is what we call holistic thinking. Only in this way can we achieve added value in economic, energy, and cultural terms "in one fell swoop", which is nothing other than "sustainability". The entire energy concept with solid storage media would have been architecturally meaningless for Vella if the necessary massiveness could not have been combined with the theme of plasticity and the "monolithic mass" of the building, in the play of the surfaces, interior depth, and thin-wall facade skin, both in the corporeal expression of the building and in the motifs of the detailing, and with the urbanistic structure of this mountain village and its powerful, cubic, stocky houses.

Excerpt from

Bulletin, Magazin der Eidgenössischen Technischen Hochschule Zurich, issue No. 276, "Energie - im Umbruch", January 2000, pp. 32-33.

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