Large-format units in combination with the latest energy-controlling technology is revolutionising contemporary cladding
Who says contemporary East Coast architecture is staid and dreary? Completed in consecutive years, KieranTimberlake’s glass pavilions at Dilworth Park, Philadelphia and Renzo Piano Building Workshop’s new Whitney Museum in Manhattan are as bold as the pioneering work of the Chicago School. They also invite comparison with one another as cladding projects. Their main point of divergence is compositiaon. The roof profile of the twin glass pavilions is set out in the arc of a circle, the locus of which coincides with the apex of City Hall which stands behind them. It’s the type of visual conceit Eisenstein delighted in. On another level, as all-glass construction, the pavilions also pay homage to the City Hall as an exemplar of all-masonry architecture. Both are noteworthy as unusually tall single-material structures.
The Whitney, on the other hand, rampantly defies analysis as a 2D composition, it is completely a 3D animal. More to the point, its exterior is the outcome of combining five very different external envelope concepts. Its more detailed tectonic configuration is driven by what is possible where these conceptual systems and their skew planes meet. John Pachuta, a partner at the project’s facade consultant Heintges & Associates, identifies these envelope types as ribbons of 8mm thick steel-sheet cladding, curtain walling with steel mullions, precast-concrete panels which clad the cores, glass walls at ground-floor level with tension cables, and sawtooth roofing.
Case study: Aktivhaus B10, Stuttgart by Werner Sobek (2014)
The model for this project was car manufacturing, which prefabricates individual elements independent of the production process and later builds them into the vehicle as complete modules, increasing efficiency.
‘Glass panes are vacuum glass, meaning the cavity is not gas-filled, creating a much better thermal insulation than the ordinary, high-performance IGUs,’ says Werner Sobek general manager Thomas Winterstetter: ‘The roof is covered with PVs, and external walls with a special seamless vertical flat membrane facade.’ The house has a predictive, self-learning building control system.
Industrial prefabrication and the suitability of the structure for transport underpin the concept. Four modules were designed and prefabricated independent of the remaining building to increase the degree of prefabrication and to facilitate maximum flexibility for planning tasks. These modules offer space to install the electrics, building services equipment, kitchen and bathroom.
Despite its compositional and tectonic narratives, the Dilworth Park pavilions seem closer to the Chicago frame spirit portrayed by Colin Rowe’s eponymous essay. To use a Christopher Alexander term which parallels the entrepreneurial spirit Rowe captures, the design is unselfconscious in its pursuit of technical goals. These technical aims are very close to consultant engineer Eckersley O’Callaghan’s heart: nearer to the macrocosmic end of the spectrum, its glass panel components are very large and are the only structural elements, and on a more detailed level there are no metallic fixings.
Precast-concrete technology is central in the drive towards larger cladding units and panels. It is particularly effective where projects require fast installation, often involving road closure on inner-city sites, and crafted finishing materials such as stone or brickwork, with handset construction and special work such as soldier coursing which are problematic at high levels. The York Handmade Brick Company has worked closely with precast fabricator Marble Mosaics to achieve hand-crafted quality on demanding projects such as the Carmelite building in London, designed by Fletcher Priest, which has reticulated convex brick slips laid with stretcher bond for a basket-weave effect, with a fine creased texture and neat edges.
Source: Zooey Braun
Unitised precast construction, rather than on-site installation of smaller panels, might seem an obvious approach to high-rise, fast-track inner-city projects, but tends not to be more cost effective. Also, where large expressed joints between units are unwanted, a panelised approach might be more suitable, although there are ways of concealing these junctions by allowing layered vertical planes to slide past each other. Complex interlocking junctions between units may also help to minimise the impact of movement and construction joints. Putting these problems to one side, it is worth investigating the different types of precast facade construction available: Dutch specialist Hurks Precast, for example, manufactures precast sandwich panels where insulation can be installed between inner and outer concrete leaves.
Turning to glass facade products, older readers may have missed transformations in the performance of Profilit glass planks which in Britain are now marketed under the name Reglit. Like patent glazing, they acquired a reputation for elegance and low performance, but are now available with high thermal insulation and low air permeability. There is also plenty of choice in the planks’ wind resistance, colour and finish.
Case study: Dilworth Park, Philadelphia by Kieran Timberlake (2014)
At Kieran Timberlake’s Dilworth Park pavilions, the glass panel components are very large and are the only structural elements, and on a more detailed level there are no metallic fixings. Connections between wall and roof panels have sillicone joints with backer rods and, where required, setting blocks. There is also shop-applied sillicone battering, and the roof panels have 15mm overhangs for weathering.
As semi-enclosed entrances to a below-ground transit interchange, the pavilion’s American-manufactured panels are single-glazed units, with five heat-strengthened laminations in vertical conditions and seven on the roof, which spans over 5m. The walls are captured in stainless-steel shoes at ground level and cantilever vertically up to 5.5m. This is by no means the first all-glass architectural structure, but examples on this scale are rare and it is noble in its deceptive simplicity.
Again on the subject of environmental performance as distinct from structure and construction, German multidisciplinary Werner Sobek has designed and completed an Aktivhaus which aims to show the sustainable benefits of innovative materials and technology. This is part of the B10 research project, which takes its name from its address, Bruckmannweg 10, on Stuttgart’s 1920s Modernist Weissenhof Estate. Werner Sobek claims this is the world’s first active house, generating twice as much energy as it uses.
‘We are seeing an interest in pushing the limits on the size of glass and cladding panels while minimising or concealing the means of support, and this approach requires innovation in engineering, fabrication, shipping and installation of the components,’ says Heintges’s John Pachuta. ‘At the Whitney, these elements provide a wow factor, adding scale and monumentality while creating a unique identity for the building.’
Eckersley O’Callaghan director James O’Callaghan has spoken of his love affair with glass, demonstrated in his practice’s ultra-transparent, fixing-averse Apple outlets. But he is also acutely conscious of energy. ‘We face an increasing challenge with how much glass can be used in the building skin while meeting energy compliance’, he says. ‘The road to large format glass has been paved, it is time to focus on the energy-controlling technologies to marry them with the large-format glass: size mattered, now energy governs.’
Dilworth Park, Philadelphia (2014) by KieranTimberlake: The glass pavilions stand in stark visual contrast to the all-masonry City Hall, but parallel its use of a single material.