Detailing the Sobek House
This project demonstrates the value of integrating the choice of cladding material with all other design decisions. In this building, structure, enclosure, mechanical, and electrical designs are all interdependent.
The glass panels that envelop the house are triple-glazed, with inert argon gas-filled cavities that provide insulation performance comparable to a 3.94-inch (ten-centimeter) slab of rock wool. The efficiency of these glass panels allows room temperatures to remain comfortable all year round.
All primary construction materials, which include 20 tons (18 metric tons) of glass and 12 tons (11 metric tons) of steel, are recyclable and emission free; no organic compounds are present in the primary structure or enclosure systems.
The building, which took only 11 weeks to construct due to its modular assembly of standardized elements, is an elegant, minimal prismatic solid. It is an archetypal frame, clad with skin that is not visible.
The building is environmentally aware, but the orientation of the building on the site is not critical. The building proportions, design, and details are not adapted to a particular solar orientation.
Argon is an efficient insulator because of its density and poor heat conductivity. It is an odorless, colorless, tasteless, nontoxic gas, six times denser than air; it is used to replace air between glass panes, thereby reducing temperature transfer. This greatly affects the glass's R-value — the value of a material's resistance to heat flow.
The R-value is expressed as the temperature difference that is required to cause heat to flow through a unit of area of material at the rate of one heat unit per hour. In this case, argon gas in triple glazing increases the R-value by approximately 58 percent compared to double glazing.
Another strategy to improve glass insulation is to use low-e glass, a material with a transparent metallic oxide coating applied to the inner glass surface. The coating allows shortwave energy such as light to pass through, but reflects longwave infrared energy such as heat, which improves its thermal resistance.
The interior is open except for a vertical shaft that houses "sanitary installations" that are veiled in translucent glass and aluminum (a movable tub for bathing and relaxing is not within this subspace). The modular accessible floor and ceiling accommodate all horizontal services.
During the summer, heat radiated into the building is absorbed by water-filled ceiling panels and transferred to a heat store. In winter, the heat exchanging system is reversed and hot water circulates through the ceiling system for space heating.
Several glass panels are operable-sash, opening awning-style, providing for natural ventilation. Fixed triplex glass cladding panels are cradled in custom stainless steel "yokes" near each corner. This provides nodal connection to the glass without requiring penetrating bolts. An EPDM (ethylene propylene diene monomer) rubber membrane bounds each piece of glass. Vision glass facades on all elevations offer views to the west over the scenic Stuttgart Basin and in other directions.
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Victoria Ballard Bell is a licensed architect with master's degrees in urban planning and architecture from the University of Virginia. She is a Frederick P. Rose Architectural Fellow and lives in Raleigh, North Carolina.
Patrick Rand is a distinguished professor in the School of Architecture at North Carolina State University's College of Design.
This article is excerpted from Materials for Design by Victoria Ballard Bell, with Patrick Rand, copyright © 2006, with permission of the publisher, Princeton Architectural Press.