Stained Glass and Climate Change: How are they connected? C. T. Simmons and L.A. Mysak McGill University

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Introduction Inside Ceiling-directed illuminance measurement Relative Transmissivity Measurements Horizontal Daylight Factor (HDF) = ______x 1000 Approximate dates of Blue to White to Approximate dates Total Window Luminance to Given that traditional architecture is fundamentally adapted to regional climate, we investigate sacred windows (A.D.) Red Red of windows (A.D.) Red Luminance Outside zenith-oriented illuminance (fully overcast sky) Chartres Angers Cathedral (Window 30, Virgin ~1180 ~1180 2.2 8.9 - (Window 125) construction in western Europe during the Late Middle Ages (~1100-1450) and Renaissance (~1450- panels) Daylight factors are constant for a CIE standard overcast sky and can be used to predict interior Chartres Cathedral 1205 - 1215 2.1 1600) in Simmons (2008) and Simmons and Mysak (2009a, 2009b). Cathedral 1140 - 1160 4.2 - (Window 39) (Windows XIV and XVII) Chartres Cathedral illuminances for a variety of cloud cover conditions, if we have some measure of exterior Angers Cathedral 1205 - 1215 2.6 ~ 1180 2.6 - (Window 41) (Window 125) illuminance. Chartres Cathedral Chartres Cathedral Interior daylighting depends fundamentally on climate: 1215 - 1220 2.0 - (Window 30, six 13th 1215 - 1220 2.3 (Window 30, six panels) century panels) Chartres Cathedral (2) Luminance Measurements 1205 - 1215 2.0 12.3 Chartres Cathedral (Window 39) ~1235 2.2 (Window 121 lancets) . Mediterranean—sunnier climate--smaller church windows and more coloured (low translucency) Le Mans Cathedral ~1250 1.2 8.5 (Windows 109 and 107) 1200 - 1225 1.8 (Window 200) stained glass. Luminance—point lighting of specific surfaces Évreux Cathedral 1301 - 1310 3.7 21.4 (Windows 10, 12, 14) Le Mans Cathedral ~1250 1.8 (Windows 109 and 107) Cologne Cathedral 1313 - 1322 1.9 - (Window SVI) Cologne Cathedral . Great Britain—cloudier climate, always used whitish GRISAILLE glass extensively, likely to let (Window SVI, coloured 1313 - 1322 4.2 Used HDR Imagery technique documented in Inanici et al. (2006) to transform HDR images into bands only) more light into the interior. .As window sizes expanded in the 1100s and Skt. Kunibert, luminance fields of the scene photographed. Cologne (Central Apse 1215 - 1230 3.7 1200s, darker and more saturated colours were Window) Strasbourg Cathedral 1250 - 1275, 1325 6.0 . Northern and the Holy Roman Empire (HRE) –between the Mediterranean and British (3) Relative Transmissivity used (Gothic vs. Romanesque blue) ( Windows) Évreux Cathedral 1301 - 1310 10.3 climate regimes, first used dark coloured glasses (1190-1260) then much brighter grisaille and high (Windows 10) Évreux Cathedral 1325 - 1330 9.7 .Starting in the late 1200s, a clear and (Window 207) transmissivity glass (1300 -1600). Assumption: the absolute transmissivity of red glass changes little through the Medieval St-Ouen, Rouen 1325 - 1339 7.6 permanent shift to clearer, more transmissive (Window 231) period (rationale: red glass always produced with thin layers of copper substrate on white). windows can be seen in the preferred glazing Troyes Cathedral 1499 6.6 Could a climate transition have partly motivated the ‘Grisaille Revolution,’ i.e., the increasing selection of (Window 232) palette. Troyes Cathedral 1500 4.7 overcast-adaptive grisailles and high transmission glazing in France and the HRE? Compare total window luminance to the transmissivity of the window’s red pieces (panels) of glass (Window 231) St-Nizier, Troyes 1613 7.7 in the following way: (Window 100) .The traditionally lighter colour palette in HRE Toledo Proxy Evidence for a Climate Shift in Northwestern Europe during the Thirteenth and N (Rhineland churches) may account for delayed (Four Clerestory and 1439 - 1513 3.5 i where i is an index representing an individual panel (a rectangular Windows) Fourteenth centuries  subsection of the larger window), N the total number of separate transition to grisailles until the mid-late 1300s. i1 i ,red panels analyzed in the window, μ the mean luminance of panel i, and Proxy evidence from peat bogs (Barber et al. 2004) and speleothems (Proctor et al. 2000) suggest a i μ the mean luminance of red pane samples from panel i. Conclusions transition to wetter and/or cooler conditions in northwestern Europe during the Thirteenth and Fourteenth N i,red . Given proxy-established trends in centuries. Horizontal Daylight Factors Sunny Illuminances Interiors with Coloured Glazing vs. Grisaille Glazing 25-50 lux (Le Mans Choir, summer and winter) precipitation and the NAO index, northwestern 15-60 lux (Bourges Ambulatory, summer and winter) Full-Colour 0.02-0.05% (Angers, Bourges, Chartres, Le Mans, 2-8 lux (Chartres , spring/summer) continental Europe likely experienced a sharp Furthermore, historical precipitation and North Atlantic Oscillation proxies suggest a transition to wetter Interiors Strasbourg, Tours) 15 lux (Strasbourg Nave, spring) and likely cloudier conditions over western continental Europe by the end of the Thirteenth century. 8-30 lux (León, Winter) change to increasingly cloudy conditions in the

0.05-0.06% (Cologne Choir) 34 lux (Beauvais Choir, summer) late Thirteenth and Fourteenth centuries. Grisaille 0.10-0.20% (Évreux Choir) 45-54 lux (St-Serevin Nave, winter) Revolution 0.10-0.17% (Bourges Nave) 39 lux (Evreux Nave, summer) Interiors 0.15-0.40% (Évreux Ambulatory) 0.08-0.35% (Chartres South Ambulatory) .Grisailles and Renaissance glazing show a 5-

0.18-0.23% (Troyes Nave) 39 lux (Troyes Nave, Summer) 10x increase in ambient illumination (HDFs) 0.16-0.25% (Bourges Ambulatory Chapels) 140-200 lux (Bourges Ambulatory Chapels, Winter) 0.20-0.40% (Évreux Lady Chapel) 80-202 lux (St-Gervais-St-Protais Chapels, Winter) compared to the earlier coloured programs. 0.08-0.22% (St-Gervais-St-Protais, Paris, Nave/S. 20-131 lux (St-Gerv.-St-Prot. Nave/Choir, upper limit) Renaissance Ambulatory) 0.10-0.20% (St-Romain, Rouen, crossing and transepts) 238 lux (St-Nizier Choir, Troyes, upper limit) Interiors 0.33-0.43% (St-Étienne-du-Mont Choir and Ambulatory, Paris) .Interior lighting gains associated with lighter- 0.20-0.45% (St-Ouen Nave, upper limit) 0.07-0.15% (St-Serevin, Nave) coloured stained glasses (Grisaille Revolution) 0.30-1.00% (St-Pantaléon and St-Nicolas, Troyes, upper limit) are greatest under overcast sky conditions.

Fig. 4 HDFs in the north ambulatory of during two different rounds of . Illumination contrasts in between sunny and cloudy conditions is greatest in winter measurements. Numbers shaded in black indicate a highly precise average Fig. 5 HDFs in the Grisaille (white glass-dominated) Fig. 3 Horizontal daylight factors (HDF) for Tours Cathedral, where (within 0.015% of both observations) of the two daylight factor calculations. . the numbers are an average based on two rounds of highly precise Medium grey represents averaged daylight factors that fall just outside of Évreux Cathedral (choir and ambulatory), based on two (NAO trends would be important). measurements. Measurements in the western choir are influenced this precision range, and pink values represent calculated daylight factors rounds of data collection. based on only one round of observations. The windows associated with strongly by clear modern glazing grisailles or otherwise white-dominated glass are numbered according to . Under sunny conditions, grisailles afford small lighting gains compared to Thirteenth century their bay number as represented in the Corpus Vitrearum Medii Aevi (Grodecki et al., 1981). Fig. 1 Historically-based precipitation proxy developed in Zhongwei et al. (1995) as a 30- Fig. 2 Figure modified from Brutckner and Mackensen (2006, their figure 6), with full-colour glazing, and for low sun angles (mornings, evenings, and winter), they also produce year running annual mean for continental Europe. Two statistical methods (hatched curves) the northwest Scotland precipitation record from Proctor et al. (2000) portrayed on much more significant window backlighting that disrupts the broader cathedral’s iconographic given in Zhongwei et al. (1995), relating meteorological station data to the narrative top and Skagerrak deep water temperature from Brutckner and Mackensen (2006) accounts, are averaged to give the resulting mean precipitation trend (solid curve). The on the bottom. Low (high) values of Skagerrak deep water temperature and program. vertical axis represents the number of seasons (yearly quarters) experiencing markedly drier Scotland precipitation both correspond to a lower (higher) NAO phase index. (negative) or wetter (positive) than normal conditions. Figure provided courtesy of Gaston Demarée. .Climate changes operating in tandem with trends in aesthetic tastes likely motivated a Methodology permanent shift in architectural daylighting strategy. This has important implications for understanding thresholds between climate and architectural design, an increasingly important For the first time, an extensive analysis of interior lighting and glazing transmissivity was conducted in a concern as we undergo a period of rapid climate change. variety of European churches and cathedrals using several Extech 407026 illuminance meters and a Canon Digital Rebel XTi SLR camera. References Barber K, Chambers F, & Maddy D (2004). Boreas 33: 132–144. Three analysis strategies: Brutckner S, & Mackensen A (2006). Holocene 16: 331-340. (1) Daylight Factors and Illuminance Measurements Grodecki, L., Perrot, F., & Taralon, J (1981). CVMA Recensement France II (Paris). Proctor, C., Baker, A., Barnes, W., & Gilmour, M. (2000). Climate Dynamics: 16, 815-820. Illuminance—ambient illumination (integration of visible light over a half-hemisphere) Simmons, C.T. (2008). MSc. Thesis, McGill University, August 2008. Fig. 6 Clear sky luminance profile (0-50 cd/m2) for the Fig. 7 The choir overcast luminance profile Fig. 8 Cologne Cathedral choir luminance profile (0-5 cd/m2) at Simmons C.T., & Mysak L.A. (2009a). Accepted Arch. Sci. Rev. (August 2009). . illuminance measurements under clear skies at different times of the year choir clerestory of Le Mans at 1007 GMT on 30 June, (0-5 cd/m2) of Tours Cathedral at 955 GMT 1211 GMT on 14 January, 2008, under an altostratus overcast sky 2008. Note the luminane scale range is 10 times that in on 29 January, 2008, under a low-base with horizontal exterior illuminance of 9600 lux. The white-painted . illuminance measurements to calculate daylight factors (a constant) Figs. 7 and 8. stratus overcast with an exterior horizontal vault luminance values have been multiplied by a factor of 0.764 to Simmons C.T., & Mysak L.A. (2009b). Re-submitted to Clim. Change (August 2009). illuminance of 8610 lux. account for the higher reflectance of the white paint compared to TEMPLATE DESIGN © 2008 www.PosterPresentations.com the original limestone surface, assuming that the paint and limestone have a similar reflective diffusivity. Zhongwei, Y, Alexandre, P, & Demarée, G (1995). Roy. Meteor. Inst.of Belgium, Brussels, 20p.