Programmatic challenges for this project seem to have been centered on how to provide glazed solar access and airy ventilated spaces without sacrificing interior privacy. The predominantly glass skin was one antagonizing factor. The need to provide two separate homes within the same see-through building scheme was another.
Most of Herzog’s residential-scale work has been met with resistance, and often rejection, by conservative-minded building authorities, a problem he shares with Glenn Murcutt. His response is philosophical: He declares no desire to impress with originality and feels no obligation to conform, further saying that our love for new technology has to be made compatible with our love for our old towns and historic cities. Herzog has, along the way, learned to warn his clients about the bureaucratic challenges of designing solar-oriented prototype buildings in tradition-oriented communities.
Basing the design scheme on the traditional timber frame barn, Herzog adapted a climatically appropriate form and one that was also suitable for the wood framing suggested by the client. This set the challenge of finding suitable transformations of a romantic form into a high-performance building of modern construction.
Appropriate Systems
Alpine barn structures like the Swiss example pictured in Figure 9.21 are well adapted to the cold climate of southern Germany and to construction with indigenous wood timber. Some forms of this building are called spicher, and some are named stoekli; in either case they were once traditionally transformed into cottages for retiring parents when the oldest son took over the farm.
The cantilevering masses of the barn start with a minimal basement, usually excavated into a sloping hillside for direct access to the lowest level and dug deep enough to avoid frost heave. Above this foundation increasingly larger rooms are built, taking advantage of overhanging projections to increase joist spans and floor area where the seeds for next year’s crop are dried and stored. The structural projection also shelters storage for materials and tools outdoors under the overhanging eaves. Surrounding walkways at the upper levels flank the central rooms, providing insulating buffer zones, and these are used for storage of hay, onions, or other goods less susceptible to frost. A steep and broad roof overhangs the building on all four sides, resisting the accumulation of snow and shedding moisture away from the foundation.
All in all, the farm building is an appealing traditional form and a practical means of constructing a climate – appropriate house with minimum materials and resources. Herzog adapted it as both an appropriate historical and functional precedent.
The open site is bordered on both sides by tree-lined fences. This allowed Herzog to press the house against the north property line for protection from the most bitter northerly winter winds and leave it exposed to low angles of winter sun from the south.
The form of the house, a thin pavilion, is worked into the site by indoor/outdoor buffers on all four sides. To the north and south are overhanging balconies and shaded decks. On the east side is a carport whose roof is a terrace accessed from the second floor. Finally, on the west, there is a conservatory greenhouse opening to a tree-covered deck at grade level.
The rich density of conifers and temperate hardwood trees in Bavaria suggest the appropriateness of a wood structure, but heavy timber framing is no longer competitive with engineered wood framing. Adherence to sustainable construction practice would also dictate the use of more reasonable resources. Herzog’s adaptation of the traditional barn building uses laminated wood structure as both an economical and practical material for translation into industrialized construction. The building is essentially a heavy wood frame for glass infill with a great sheltering roof.
The narrow basement in this case is an 11.8 ft X 47.2 ft (3.6 m X 14.4 m) excavation under the center of the house with grade beams extending out to both ends. A 3.9 in. X 15.8 in. (100 mm X 400 mm) beam spans across the basement, cantilevering 2.9 ft (900 mm) past the basement wall on both sides. This structural platform places the first floor level a couple feet above grade and allows for the basement to be daylit and ventilated through panels set between the beams.
Vertical support starts with 5.9 in. X 5.9 in. (150 mm) laminated wood columns set along the basement wall on
11.8 ft centers, which establishes the interior planning grid of seven 11.8 ft X 11.8 ft (3.6 m X 3.6 m) bays. External columns of 2.4 in. X 5.9 in. laminated wood are set on the edge of the floor platform and divide each bay into modules of 2.9 ft, 5.8 ft, and 2.9 ft (900 X 1800 X 900 mm) sequentially. The main floors beams taper to 7.1 in. at their ends and are bound by a 2.4 in. X 7.1 in. (60 mm X 180 mm) edge beam, also of laminated wood.
Beams for the second floor and roof levels do not cantilever past the basement walls but terminate at the interior columns instead. The perimeter area of the second floor and the projecting north and south balconies are balanced on a built up support that spans out 2.9 ft (900 mm) both sides of the external column at the second floor level. The external column continues past this support and is capped by a triangular support member at 5.8 ft (1.8 m) spacing that resembles an inverted and wood clad truss. One leg of this support spans up to the second floor ceiling, another cantilevers horizontally 6 ft out to the eave of the roof, and the sloping top chord supports the roof itself. Beyond the interior columns the roof is glazed in anticipation of replacing them with photovoltaic cells when they are economically viable. The closure from internal column to external column is likewise in-filled with a sloping glass skylight. Purlins of laminated wood run across the inverted trusses to support the glass area of the roof and a more conventional rafter system supports the central opaque roof that covers the 11.8 ft (3.6 m) interior bays. In contrast to the narrow foundation at the 11.8 ft X 47.2 ft (3.6 m X 14.4 m) basement, the outline of the roof measures
31.9 ft X 91.5 ft (9.7 m X 27.9 m).
Transverse bracing is provided by several solid partition walls across the internal columns that divide the house into minor pavilions facing east and west. At the west end of the structure is a two-story-high bay that serves as a conservatory, and its north and south walls are secured with tubular steel X-bracing to aid in longitudinal stiffness. The east end of the house terminates in a covered carport, with its roof serving as a large terrace accessed from the second floor balcony. To the north there is a 41.3 ft X 5.9 ft (12.6 m X 1.8 m) storage building with connecting canopies to both dwellings.
External cladding of the house is typical of passive heating schemes, with extensive glass to the south and opaque insulated construction to the north. Herzog uses 5.9 in. (150 mm) insulation blankets in all the opaque walls with cement-bound chipboard on both sides. The primary vertical glazing is insulated clear glass, and the skylights are insulated with a laminated inner light. The glazed portion of the roof is tempered single pane.
An experimental solar collector was built into four of the 5.8 ft (1.8 m) bays of the south wall. These resemble unvented Trombe wall construction, except that they are filled with translucent insulation fibers inspired by the light – transmitting hairs of the well-insulated polar bear. Glass is used as the panel’s outside covering, and a 4.0 in. (100 mm) thick precast concrete slab with a black painted surface is placed behind the insulation to absorb sunlight and store heat. The collectors total only 194 ft2 (18 m2) but succeed in providing 10 percent of the annual heating requirement.
In the summer, shade from the high sun is provided at the ground floor by the overhanging balconies, and sunlight at the upper floor is screened by the roof purlins below the glass canopy. Two-story-high trellises are planted in front of three bays of the south wall. The plants grow from wood decks outside the middle bays to the bottom of the eave line. For air, a great number of exterior doors on the house accommodate the separate occupancies, and these can also be used for natural ventilation in warmer weather. No less than 27 doors open to decks and balconies, and the end wall of the conservatory has an additional pair of sliding doors. The attic space above the center bay width is ventilated at both ends by louvers sheltered beneath the projecting roof gable. A continuous roof ridge vent provides ample exhaust for hot air from the attic.
Backup mechanical heating is a necessity in the 6701 annual degree-day heating climate of Munich. The winter dry-bulb design temperature is a frigid 10°F (-12.5°C), and the summer design conditions are a mild 78°F dry – bulb and a 63°F wet-bulb temperature (25.5/17.4°C). Supplemental heat is provided by a conventional boiler in the basement and distributed by radiators. In addition, there is a wood-burning stove in each dwelling.
While the house is closed tight in winter, indoor air quality is maintained by an air-to-air heat exchanger that reclaims warmth from exhausted indoor air and passes it to incoming outside makeup air. These simple devices pass the two air streams by each other with lots of high-con – duction surface area separating them. Usually some 90 percent of the heat can be reclaimed from kitchen, toilet room, and other exhaust air streams. Ideally, slightly more outdoor air is brought in than indoor air is exhausted to keep the house positively pressurized relative to the outdoors and thereby reduce infiltration of cold air.
The one-room-deep pavilion plan of the Pullach House is not unlike that of Glenn Murcutt’s Magney House. Even the quasi-division into two independent living units expresses a similarity of scheme. These affinities are largely due to the shared goals of blending interior rooms with the outdoors, both for environmental reasons—sun and ventilation—and for communion of interior space with its natural setting. Herzog’s scheme is quite different, though, in its sectional qualities and in the arrangement of circulation at the perimeter of occupied space rather than through a central axis as in the Magney House. The two – story construction of the larger Pullach House obviously makes for a different kind of section as well.
The seven bays of the interior are planned in three major sections, from east to west, as two bays for a small one-bedroom dwelling with an internal stair, two bays for a double-height gallery with an open stair and two guest rooms, and two bays for a grander one-bedroom dwelling opening onto the gallery on one side and terminating in the extra third bay of the double-height conservatory on the other. From south to north the plan is layered into a
2.9 ft (884 mm) wide sunlit circulation path, the 11.8 ft (3.6 m) wide center bays, and another 2.9 ft (884 mm) boundary to the north, where the insulated walls are supplemented by an assortment of storage compartments, closets, and other built-in buffers.