A Modern-Day Chapel that Brings the Outside In
Using DuPont™ SentryGlas® structural interlayer in laminated SGG Stadip safety glass from Saint-Gobain Glass helped lighten the structure of the Chapelle des Diaconesses in Versailles. The chapel opens itself up to the environment through the subtle interplay of glass and wood.
A new setting has been created for the most important services of the Protestant parish of the Diaconesses de Reuilly in Versailles (Yvelines, France). The sisters wanted to place the chapel project firmly in the 21st century and "offer modern people an interior that combines beauty, intimacy and celebration, inviting them to reflect and find peace".
To replace the tent structure that previously served as a chapel and showed considerable wear after being in use for 20 years, French architect Marc Rolinet came up with a lightweight structure consisting of two units in wood and glass. It follows the uneven topography of the site and creates access at two levels. An upturned wooden shell forms the oblong contemporary chapel, built of superimposed pine strips that were individually steam-curved on site. This organically shaped chapel curls up inside a voluminous glass structure with a triangular base that is protected from hot sunlight by a horizontal roof, also made of wooden strips. The walking space between the chapel and its transparent envelope is meant to invite meditation and offer a direct link with the surrounding park dotted with tall trees. This bioclimatic envelope filters and exploits the natural daylight entering through 360 degrees.
The transparency and ethereal character of the building were enabled by integrating laminated safety glass with the DuPont™ SentryGlas® structural interlayer for the two façades and the roof. "I soon realised how useful this material would be and insisted on using it right from the start," explains Marc Rolinet. The work was performed well in advance to derive maximum benefit from the mechanical properties of this structural interlayer. "The structural calculations performed by DuPont in cooperation with the Austrian branch of Saint-Gobain Glass enabled us to reduce the glass thickness, increase the pitch and lighten up the supporting structure".
In this project, DuPont certainly demonstrated the benefits of SentryGlas® as compared with the conventionally used material polyvinyl butyral (PVB). The SentryGlas® structural interlayer offers three times less deflection than laminated PVB safety glass and induces half the inherent stress within the glass layers at the same glass thickness (glass and interlayer). "Only the deflection resistance of SentryGlas® made it possible to realise such long trapezoidal panels on the roof (2.2 metres in length)", says Michel Gallizia from the Glass Laminating Solutions division of Du Pont de Nemours France.
This choice also had a positive effect on the overall construction costs, because to offer the same mechanical strength, glazing of the same size without the DuPont™ SentryGlas® structural interlayer would have had to be thicker. That would have meant additional costs both for the glazing and the structural elements, since they would have had to bear the correspondingly heavier load. The architectural benefit is also obvious, because this solution enables optimum glazing sizes without any influence on the supporting structure.
The horizontal roof panels consist of five layers of glass. The first is made of 10mm thick tempered SGG Securipoint safety glass with high mechanical strength. It is provided with a reinforced heat insulation layer and an SGG Cool-Lite sun screen. The following layers consist of a 12mm air layer,
a 12mm layer of SGG Securipoint tempered glass, a 1.52mm SentryGlas® structural interlayer and an 8mm layer of SGG Securipoint tempered glass. The façades have an 8mm thick layer of tempered glass, the 1.52mm SentryGlas® structural interlayer, followed by 8mm tempered glass, a 16mm insulating air layer and 10mm tempered glass. All three glass layers are made of SGG Securipoint grade. The fixing devices were integrated directly into the laminated inner glass layer of the vertical panels. This tasteful fixing system was enabled by the interlayer, which adds strength and provides more reliable framing for this large-scale application.
Apart from this inherent strength, the interlayers offer better edge stability and excellent optical properties. The open-edged sheets are insensitive to edge discoloration and delamination. What is more, SentryGlas® enhances the safety and strength of the entire assembly. Thanks to its impact strength which is higher than that of PVB, the interlayer holds the glass sheets in place even if they are shattered.
Another benefit in terms of optical appearance and maintenance of the chapel's horizontal surfaces is that the SentryGlas® interlayer greatly reduces the deflection of the laminated glass. This phenomenon may be caused in the long term by high temperatures linked to solar radiation. Since the roof has no curved surfaces, this also prevents streaks of dirt deposited by the weather.
The architect also likes using this material for its optical effects. "This material is much more attractive than conventional laminated glass. The planarity of the glass combined with DuPont™ SentryGlas® gives the façades a mirror-like effect". The transparency is durably maintained, as shown by many architectural applications for DuPont™ SentryGlas® since the mid-1990s.
The Chapelle des Diaconesses de Marc Rolinet won the jury's special prize at the 3rd Lauriers de la Construction Bois competition in April 2008. The projects and structures nominated for this national architecture competition, which focuses on wood construction, were on exhibition during the Salon européen du bois et de l'habitat durable wood construction fair, held in Grenoble (Isère, France) from 3 to 6 April 2008.