Obsolescence of Function
By the mid-1950s, the invention of drug therapy rendered sanatoria obsolete. Zonnestraal was converted to a general hospital in 1957.5J The open balconies of the first residential pavilion became fully enclosed between 1955 and 1958, drastically altering its lightness and transparency. Around 1976, the main building went through a radical renovation. The main entrance was moved to the former location of the kosher kitchen, and almost all interior partitions were removed and reconfigured.60 The slender steel window frames were replaced with wide, aluminum-framed double glazing. In the 1980s the second residential pavilion stood relatively unaltered, but glass had fallen out, either through vandalism or deterioration of the frames and structures that supported the curtain walls (Figure 2.16). Broken windows exposed the concrete and rebars to the elements and caused them to corrode.61 When the general hospital joined another hospital in town in the early 1990s, the complex was largely vacated. Photographs of Zonnestraal from the 1980s and 90s, with double glazing framed in wide aluminum mullions, show the building robbed of its buoyancy and dignity. The striking disparity between the original and the renovated building further underscores the significance of material and detail choices in the reading of glass transparency. The renovation from this period demonstrates how architectural vision can be violated when materials are updated with little consideration for significance of original materiality.
FIGURE 2.16 Deteriorated Dresselhuys Pavilion in 2000, prior to renovation. In the early 1990s the buildings were largely vacated.
Photograph: Hans Hoogenboom. Streekarchief Gooi en Vechtstreek (early 2000s).
Restoration and Preservation of a Building Designed for Brevity
As seen in Zonnestraal, the contemporary restoration of an early modem building allows a comparative analysis of a restored building against the original. How are changes in glass technology reflected in decisions and ideologies of earlier buildings? In 1994, the Dutch government decided to restore Zonnestraal.62 The restoration was undertaken by architects Hubert-Jan Henket and Wessel dejonge, co-founders of Docomomo (Documentation and Conservation of Buildings, Sites and Neighborhoods of the Modem Movement) International.63 Their work followed extensive research into the original construction at Delft University of Technology. De Jonge reflects that the restoration of Zonnestraal “proved an unprecedented source of knowledge and hands-on experience with early modem building technology and its preservation.”64 The restoration indeed revealed how the readings of Zonnes-traal’s glass transparency were dependent upon changes in materials and construction details.
During the restoration, De Jonge and Henket faced critical questions regarding the preservation of a modern glass building. Examining their preservation process reveals Zonnnestraal’s glass as exclusive to a particular place and culture in Dutch history. When the original architects’ intent was to amplify transparency, does it violate the design to replace the windows with today’s insulated or laminated float glass, in order to meet thermal efficiency for current standards? Furthermore, how should qualities of glass at the time of construction in the 1920s be preserved during restoration? In maintaining the original qualities of glass, the specification of glass is critical.65 The architects carefully assessed whether to follow as closely as possible the original specification of single-lite glass, or to replace with present-day insulated glass panels. As a result, the glass used in the restoration is not the same everywhere as it was in the original building (Figure 2.17). In consultation with building physics consultants DGMR, the architects decided to install single glazing in areas that did not require careful climate control, primarily the hallways and the main hall upstairs, where there are no occupants immediately adjacent to the curtain walls.66
The details and physical properties of glass radically alter a building’s transparency. De Jonge notes that the Zonnestraal would read completely different had the glazing been replaced with all insulated units with today’s standard float glass.67 Drawn glass like that from 1928 was made using sand with a lower iron content, which resulted in purer, colorless glass. In contrast, today’s standard glass has a greenish tint from iron oxide, which is added to accelerate melting rate in the manufacturing stage.68 In addition to the color, today’s less flawed, machine-made float glass would have eliminated the vertical ripples of the original building. For the restoration, low-iron drawn glass was imported from Lithuania to stay true to the original color and patterns from the 1920s. The cross-axial layout of the main building creates places, such as the entrance vestibule, where one looks
Origna
- 1 partiton plastered wire mesh
- 2 steel INP80 at 1500 mm centre to centre
- 3 steet window casing 25 mm
- 4 single sheet glass
New facade
- 1 light brick
- 2 mneral plaster
- 3 new steel INP80
- 4 condensation gutter
- 5 single sheet glass 5 mm
- 6 new steel window casing 32 mm
- 7 joint 3 mm with sealant
FIGURE 2.17 Top: plan details of a comer of original 1928 single-lite glass. Bottom: plan detail of the same corner in 2001 renovation, in which the corner is turned with two sheets of low-iron, single-lite drawn glass. The adjacent panel to the right is an insulated glass unit with low-iron drawn glass for outside light only.
Wessel de Jonge Architecten BNA (2001).
through four layers of glass as a time (Figure 2.18). In these locations, the attention to glass color was particularly important,69 as the tint becomes amplified with multiple layers of glass.
In such space as the offices, where single glazing is insufficient for today’s thermal comfort, the architects specified a custom assembly: an 11 mm thick double-glazing unit fabricated in a Belgian factory, with a gray uPVC spacer made in Italy. Where the single and double glazing are adjacent to each other, the windows have the Lithuanian low-iron, drawn glass on the outside to maintain consistent appearance.70 To keep the cost down, instead of using the custom glass on both the inside and the outside, the inner pane is a single layer, low-iron Starphire Ultra-Clear™ float glass — a readily available product manufactured in the US by Pittsburg Plate Glass (PPG).71
FIGURE 2.18 A view through multiple sheets of glass at a corner in the main building, where clear, colorless glass is particularly important.
Photograph: Author (2018).
FIGURE 2.19 Dresselhuys Pavilion’s window-lined corridor with patient rooms along the right-hand side. During the renovation, these windows were replaced with insulated glass, allowing more possible functions of the building in the future.
Photograph: Author (2018).
When Zonnestraal was designed, healthcare standards advocated keeping windows open at all times, including the winter; it was the opposite of a tightly sealed building. Energy efficiency upgrades to meet today’s standards are impossible without losing the essential architectural character of Zonnestraal.72 In the Dresselhuys Pavilion (the second residential pavilion), all the patient rooms received the double-glazed units used in the main building (Figure 2.19). The reason was twofold. This building has rows of private patient rooms arranged so that one does not look through multiple layers of glass walls as in the main building. Second, the building did not have an occupant type specified at the time of restoration. To allow many possible uses in the future, therefore, the Pavilion was restored with insulated glass walls.73
