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Conflicting needs of the thermal indoor environment of museums: In search of a practical compromise
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Journal of Cultural Heritage 9 (2008) 125e134 http://france.elsevier.com/direct/CULHER/
Original article
Conflicting needs of the thermal indoor environment of museums: In search of a practical compromise Maria La Gennusa1, Giovanni Lascari2, Gianfranco Rizzo*, Gianluca Scaccianoce1 Dipartimento di Ricerche Energetiche ed Ambientali (DREAM), Universita` degli Studi di Palermo, Viale delle Scienze (Building 9), 90128 Palermo, Italy Received 11 April 2007; accepted 1 August 2007
Abstract Thermal indoor microclimate conditions in museum buildings refer to two important requirements: the preservation of works of art and the comfort of visitors to these buildings and/or those working inside them. Unfortunately, different works of art have different internal parameters which render the management and control of the indoor thermal microclimate difficult. In this work the values proposed by various standards for the thermal environment of museum buildings have been revised. Moreover, the indoor microclimatic conditions relating to people’s comfort have been described, with the aim of singling out possible common ranges for these parameters. With this aim, a useful simultaneousness index has also been introduced. Finally, the proposed approach has been applied to an old Italian building for purposes of clarification. Ó 2008 Elsevier Masson SAS. All rights reserved. Keywords: Cultural heritage; Works of art conservation; Italian standard rules; Comfort indoor; Microclimatic parameters; Simultaneousness index
1. Research aims The first aim of this work is to review the standards and the limit values for typical parameters relating to the indoor environments of museums. Moreover, a comparison will then be proposed between the values referring to the preservation of works of art and those concerning the comfort of visitors or those working inside museum buildings. This paper will point out that the suggested values for both purposes can be at times conflicting. Common ranges for these values are suggested in order to contemporaneously satisfying the needs for people’s comfort and the preservation of works of art. It is also argued that the adoption of the predicted mean vote method, as opposed to the classical temperaturee humidity approach, leads to the highlighting of more realistic
* Corresponding author. Tel.: þ39 091 236210; fax: þ39 091 484425. E-mail addresses: [email protected] (M. La Gennusa), lascari@ dream.unipa.it (G. Lascari), [email protected] (G. Rizzo), scaccia@dream. unipa.it (G. Scaccianoce). 1 Tel.: þ39 091 236225; fax: þ39 091 484425. 2 Tel.: þ39 091 236216; fax: þ39 091 484425. 1296-2074/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.culher.2007.08.003
ranges of indoor parameters and, consequently, to a more effective control of the indoor microclimate of such buildings. 2. Introduction The growing demand for culture, along with improvements in indoor conditions of exhibition spaces, encourages people to spend an increasing amount of time in museums where, together with exhibitions of terracotta objects, sculptures and historical documents, dinners, musical concerts and plays often take place. The different ways in which museums can be enjoyed call for greater attention to be paid to the quality of the indoor environment with the aim of ensuring people’s comfort. But the requirements for the optimal preservation of cultural artifacts do not necessarily coincide with those of thermal comfort. This suggests particular care must be taken when assessing the thermal indoor requirements of such buildings in order to identify a set of parameters capable of satisfying both demands. Such problems are generally addressed [1,2] by means of the appropriate design and management of heating, ventilating and air conditioning (HVAC) systems (thermal and hygrometry
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126
Nomenclature
u0
DR
Dumax var W
fcl hc hr Icl IS M pa PD PPD PMV RH ta tcl tf to Dtpr tr
percentage dissatisfied due to local discomfort from draught (%) clothing surface area factor convective heat transfer coefficient (W/m2 C) radiative heat transfer coefficient (W/m2 C) clothing insulation (m2 C/W) simultaneousness index (%) metabolic rate (W/m2) partial pressure of water vapour (Pa) percentage dissatisfied (%) predicted percentage of dissatisfied (%) predicted mean vote relative humidity of air (%) air temperature referring to people’s comfort ( C) clothing surface temperature ( C) floor surface temperature ( C) operative temperature ( C) radiant temperature asymmetry ( C) mean radiant temperature ( C)
requisites) and by correctly selecting and positioning lighting fixtures (visual requisites). Particularly in countries with a noticeable cultural heritage recognized on an international level, however, very old buildings often function as exhibition spaces devoid of air climatization systems. Indeed, such buildings, which must be considered in many cases as works of art in themselves, do not easily lend themselves to the installation of conventional equipment to avoid the worst excesses of indoor climatic failure. These considerations, therefore, open up the way for a new approach in the design and management of the indoor environment of museums. An accurate analysis of current standards is now necessary. 3. The indoor environment of museums in standards Italy is one of the first countries in Europe which has formulated specific regulations for the conservation of cultural artifacts. For example, various technical standards have been recently specified which refer to the definition and control of microclimates with the specific aim of preserving cultural
relative humidity referring to the works of art preservation (%) daily range of relative humidity of the works of art (%) relative air velocity (m/s) effective mechanical power (W/m2)
Greek symbols q0 air temperature referring to the works of art preservation ( C) qS surface temperature of works of art ( C) Dqmax daily range of air temperature ( C) Subscripts a air ar relative air c convective cl clothing f floor 0 referring to the works of art pr radiant asymmetry r radiative o operative
items in indoor environments. Some of these documents introduce interesting elements that go far beyond their strict application to the Italian context. They will, therefore, be now shortly reviewed in this paper. The UNI 11120 standard [3], issued in May 2004, refers to appropriate protocols for the field measurement of the air and surface temperatures of cultural items, while the UNI 11131 standard [4], of March 2005, refers to field measurements of air humidity. These technical rules can be interpreted as a guideline for the evaluation of the air and surface temperature, and the air humidity of cultural items situated in confined (for example, museums, churches, historical buildings, etc.) or open environments. A previous standard, dating from February 2002, UNI 10969 [5], entitled ‘‘General principles for the choice and the control of the microclimate to preserve cultural heritage in indoor environments’’, contains a list of suggestions for the preservation of works of art. It also points to some guidelines for controlling the indoor microclimates of museums, particularly those operated by means of mechanical HVAC systems.
Table 1 Typical thermal indoor parameters and ranges of measurements in museum buildings Indoor parameter
Symbol
Range of measurements
Mean monthly value of the air temperature Daily range of air temperature Surface temperature of artworks Mean monthly value of the relative humidity of indoor air Daily range of relative humidity of air
q0 Dqmax qS u0 Dumax
Between 30 C and 60 C, with an accuracy of 0.5 C Between 30 C and 60 C, with an accuracy of 1 C þ 0.01 jtair tsurfacej Between 5% and 95%, with an accuracy of 2% (electronic psychrometer)
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
127
Table 2 Suggested values for the optimal conservation of works of art for steady-state indoor climate conditions (UNI 10829 standard and Minister Decree May 2001) q0 ( C)
Dqmax ( C)
u0 (%)
Dumax (%)
18e22 15e24 19e24
1.5
6
<18 21e23
N.S. 1.5 1.5 e 1.5
Water-colours, drawings, pastels
19e24 15e25 21e23 19e24 4e10 15e21 19e24
Ethnographic collections, masks, leather, leather clothes
19e24
1.5
Painting on canvas, oil painting on cloth and canvas, tempera, gouaches
19e24
1.5
Documents, file material Books of great value, leather-bound books, leather bindings, parchment, miniatures
13e18 19e24
e 1.5
Lacquer, inlaid, decorated or lacquer furniture Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wood musical instruments Unpainted wood carvings, wickerwork, wood or bark panels
19e24 19e24
1.5 1.5
19e24
1.5
40e55 50e60 30e50 40e60 N.S. 45e55 40e60 40e60 N.S. 20e35 40e60 30e50 45e60 45e60 50e60 45e60 50e60 40e55 35e50 50e60 45e55 50e60 50e60 50e60 45e65 45e60 40e65
Inorganic materials/objects Porcelain, ceramics, stoneware, terracotta, tiles and demineralised tiles from excavation
N.S.
e
Stones, rocks, ore and stable (porous) meteorites Stone mosaics, stones, rocks, ore, meteorites (non porous), fossils and stone collections
19e24 15e25
e e
Metals, smoothed metals, metal alloys, silver, armour, weapons, bronze, coins, copper objects, tin, iron, steel, lead, pewter Metals with active corrosion sites Gold
N.S.
e
N.S. N.S.
e e
Gypsum and plaster Unstable, iridescent and sensitive glass, sensitive glass mosaics
21e23 20e24
1.5 1.5
e
Ivories, horns, malacological collections, eggs, nests, corals
10e24 6e25 10e24 6e25 19e24
Phonographic records
10e21
e
Man-made fibres Film, colour photograph
e e
Organic material objects coming from damp excavation areas (before treatment)
19e24 0e15 15 to 5 5e15 2e20 19e24
Plastics
19e24
Work of art materials Organic materials/objects Paper, papier maˆche´, paper artwork, tissue-paper, wallpaper, stamp collections, manuscripts, papyri, printings, cellulose materials Fabric, veils, drapery, carpets, fabric tapestry, arras, silk, costumes, dresses, religious vestments, natural fibre materials, sisal, jute Wax, anatomical waxes Herbaria and botanical collections Entomological collections Animals and anatomical organs preserved in formalin Animals, dried anatomical organs, mummies Furs, feathers, stuffed animals and birds
Various objects Murals, frescoes, sinopite (detached) Dry murals (detached)
Film, black and white photograph
N.S. ¼ not significant.
1.5
1.5 1.5
e 1.5
e e e
N.S. 20e60 40e60 20e60 45e60 <50 <55 <40 N.S. <45 45e55 40e45 55e65 45e60 50e45 45e60 40e60 45e65 40e55 40e60 40e60 30e45 30e50 40e60 20e30 Saturated air 50e65 30e50
6 N.S. 2 6 N.S. e 5 2 6 6 e 6 2 2 2
10 6 10 e e e 2 e
e e 6 2 e e e e e
128
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
Of greater importance is the UNI 10829 standard [6], of July 1999, entitled ‘‘Ambient conditions for the conservation’’. It provides a comprehensive methodology for taking the field measurements of environmental parameters, which are significant for conserving works of art of historical importance. According to this standard, suggested values for parameters relating to the physical environment are provided for each type of objects, assuming a stable (steady-state) climate; reference environmental parameters to be adopted for the correct designing of climatization equipment are also mentioned. Moreover, appropriate measurement procedures, replete with the algorithms necessary for the statistical analysis of the data, are also given. Several categories of materials and objects are highlighted, for which their conservation in stable climate conditions is recommended. These in turn are subdivided into three main groups: materials/objects organic in nature; materials/objects inorganic in nature; and a composite category of objects. The main causes of degradation considered here are the thermal-hygrometer conditions of the air surrounding the objects and the electromagnetic radiation emanating from sources of natural or artificial light. The UNI 10829 standard suggests measuring specific physical parameters, specifying preferred values for these parameters, the maximum daily range, the maximum permissible values and the yearly dose of absorbed energy. According to the values of parameters mainly suggested in these standards, the thermal indoor requirements for the correct conservation of works of art and the thermal comfort of visitors to museum spaces will now be separately reviewed. Finally, a possible compromise will be proposed. 4. Thermal-hygrometer parameters for preserving works of art Typically the thermal-hygrometer indoor environment of exhibition rooms is assessed by measuring and controlling parameters which refer to air temperature and air humidity, as summarized in Table 1. The suggested values of these indoor parameters (with the exception of surface temperature) are reported, for example, in the Italian UNI 10829 standard [6] and the Ministerial Decree of May 2001 [7]. These recommended values for several environmental groups of works of art and materials are reported in Table 2. The values in Table 2 mainly refer to the conditions of preservation and they can be also considered for preventing microbiological damage to works of art with minor alterations [7]. In addition, critical values [7] of relative humidity and air temperature for some particular works of art are also reported in Table 3. Various general observations can be made analyzing these data. First, a lower air temperature value, generally 19 C, seems to apply more to requirements of the HVAC system design than the preservation of works of art. Indeed, in several cases, a minimum air temperature value lower than 19 C is indicated in correctly preserving cultural artifacts.
Table 3 Critical values of relative humidity and air temperature for typical artworks Handcrafts
Relative humidity (%)
Air temperature ( C)
Archaeological bronzes with chloride corrosions Archaeological irons with chloride corrosions Unstable glasses Wet wood
<42
e
<20
e
40e45 100
e <4
Moreover, such values impose very strict limits on the exhibition space where there may also be present works made from different materials. For example, where black and white photographs and books are contemporaneously exhibited, conflicting ranges of air temperature could be found: indeed, the upper suggested temperature value (15 C) for photographs is lower than the minimum temperature value (19 C) suggested for books. And, since similar limit values for these data can be found in several other international standards [8e10], it could be argued that many of them have simply been repeated prior to specific field. These considerations, therefore, suggest a thorough review of standards, even before comparing them with limits relating to the comfort of visitors.
5. Thermal indoor requirements relating to visitors’ comfort in museums The classical approach, which is based on controlling or measuring air temperature and humidity (the so-called ‘‘TeRH’’ method) will be substituted in this paper with a more appropriate method which directly applies to people’s choices. The thermal conditions of comfort relating to people depend on several factors, personal as well as environmental [11], which cannot be confined to a mere evaluation of temperature and relative air humidity. Within this framework, the practical assessment of indoor thermal conditions will refer to various parameters which can be divided into two main categories: temperature and sensation indices. The former express the thermal response of the subject with reference to the so-called ‘‘equivalent temperature’’ (the temperature of an imaginary environment in which the occupants would feel the same thermal sensation as in a real environment). The latter, based on a thermal subjective scale, predict the mean value of the votes expressed by a large
Table 4 Seven-point thermal sensation scale þ3 þ2 þ1 0 1 2 3
Hot Warm Slightly warm Neutral Slightly cool Cool Cold
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134 Table 5 Parameters affecting the local thermal comfort Parameters characterizing the local discomfort
Limit values
Draught, DR Vertical air temperature difference between head and feet, Dta Radiant temperature asymmetry from cold vertical surfaces (cool wall), Dtpr Radiant temperature asymmetry from warm vertical surfaces (warm wall), Dtpr Radiant temperature asymmetry from cold horizontal surfaces (cool ceiling), Dtpr Radiant temperature asymmetry from warm horizontal surfaces (warm ceiling), Dtpr Floor surface temperature, tf
<20% <3 C (PD < 5%)
PD < 5%
129
partial pressure of water vapour, pa; relative air velocity, var; mean radiant temperature, tr ), while two of them are personal (metabolic rate, M, and clothing insulation, Icl). That is [13] PMV ¼ 0:303eð0:036MÞ þ 0:028 ðM WÞ 3:05 103 ½5733 6:99ðM WÞ pa 0:42½ðM WÞ
<10 K
58:15 1:7 105 Mð5867 pa Þ 0:0014Mð34 ta Þ 3:96 4 4 108 fcl ðtcl þ 273Þ ðtr þ 273Þ fcl hc ðtcl ta Þ ð1Þ
<23 K <14 K <5 K
where tcl ¼35:7 0:028ðM WÞ Icl 3:96 4 4 108 fcl ðtcl þ 273Þ ðtr þ 273Þ þ fcl hc ðtcl ta Þ
19 C < tf < 29 C (PD < 10%)
group of people exposed to the same microclimatic conditions. As is well known, the most widely used index for evaluating indoor thermal conditions in moderate environments is the predicted mean vote (PMV) originally introduced by Fanger [12]. It represents the mean value of the votes expressed by a large group of persons on a seven-point thermal sensation scale [13] (Table 4), based on the heat balance of the human body. A neutral thermal balance is reached when the internal heat production in the body is equal to the loss of heat to the environment. In a moderate environment, the human thermoregulatory system automatically attempts to modify skin temperature and sweat secretion in order to maintain heat balance. The PMV index is expressed as a function of six parameters: four of them are environmental (air temperature, ta;
( hc ¼ fcl ¼
0:25
2:38jtcl ta j pffiffiffiffiffi 12:1 var
pffiffiffiffiffi 0:25 for 2:38jtcl ta j > 12:1 var pffiffiffiffiffi 0:25 for 2:38jtcl ta j < 12:1 var
1:00 þ 1:290Icl for Icl 0:078 m2 C=W 1:05 þ 1:645Icl for Icl > 0:078 m2 C=W
ð2Þ ð3Þ
ð4Þ
In these equations some parameters are introduced which require definition: M e metabolic rate (W/m2); W e effective mechanical power (W/m2); Icl e clothing insulation (m2 C/W); fcl e clothing surface area factor (dimensionless); ta e air temperature ( C); tr e mean radiant temperature ( C);
0.016 M = 1.2 met Icl = 1.0 clo
0.014 Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wood musical instruments
Humidity Ratio [kgv/kgda]
0.012
0.01
νar = 0.10 m/s
Murals, frescoes, sinopite
νar = 0.15 m/s
0.008
νar = 0.20 m/s
90% 80%
0.006
70%
0.004
60% 50% 40%
νar = 0.25 m/s
30% 0.002
20% 10% RH
0 10
12
14
16
18
20
22
24
26
28
30
32
34
Operative temperature [°C] Fig. 1. The overlapping zones between people’s comfort and taking care of works of art requisites in typical winter conditions, for selected works of art.
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
130 0.016
M = 1.2 met Icl = 0.5 clo
0.014 Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wood musical instruments
Humidity Ratio [kgv/kgda]
0.012
0.01
νar = 0.10 m/s
Murals, frescoes, sinopite
νar = 0.15 m/s
0.008
νar = 0.20 m/s
90% 80%
0.006
0.004
70%
νar = 0.25 m/s
60% 50% 40% 30%
0.002
20% 10% RH
0 10
12
14
16
18
20
22
24
26
28
30
32
34
Operative temperature [°C] Fig. 2. The overlapping zones between people’s comfort and taking care of works of art requisites in typical summer conditions, for selected works of art.
Table 6 Values of the simultaneousness index, IS, referring to two homogeneous classes of works of art and four typical values of the indoor air velocity in winter conditions, together with the shape (in a TeRH graph) of the common control areas Simultaneousness index IS in winter conditions var ¼ 0.10 m/s Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wooden musical instruments
19.0; 60%
23.5; 60%
var ¼ 0.20 m/s 23.9; 60%
19.6; 60%
var ¼ 0.25 m/s
19.9; 60%
24.0; 60%
23.8; 50%
23.4; 65%
8.9; 65%
19.8; 50%
12.3%
24.0; 50%
23.8; 65%
19.4; 65%
20.2; 50%
11.8%
24.0; 50%
23.8; 65%
19.8; 65%
20.5; 50%
12.6%
19.1; 55%
23.7; 55%
23.5;60%
19.0; 60%
19.7; 55%
19.6; 60%
6.3%
19.1; 55%
24.0; 56%
23.9; 60%
20.0; 55%
19.7; 55%
24.0; 55%
24.0; 60%
20.3; 55%
20.0; 55%
24.0; 55%
24.0; 60%
20.2; 60%
6.2%
6.5% 24.0; 56%
23.7; 55%
12.1%
24.0; 55%
19.9; 60%
23.8; 65% 24.0; 64%
12.6%
12.9%
24.0; 50%
20.1; 65%
24.0; 64%
Both categories
24.0; 60%
20.2; 60%
24.0; 56%
12.9%
12.7%
19.2; 50%
Murals, frescoes, sinopite
var ¼ 0.15 m/s
6.0%
24.0; 55%
20.3; 55%
24.0; 55%
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
var e relative air velocity (m/s); pa e water vapour partial pressure (Pa); hc e convective heat transfer coefficient (W/m2 C); tcl e clothing surface temperature ( C).
131
temperature of an imaginary black enclosure in which an occupant would exchange the same amount of heat by radiation and convection as in the actual non-uniform environment’’. It is usually defined as follows [15]:
The practical evaluation of PMV is generally made possible through the use of various tables which contain a set of precalculated values for several typical combinations of the six parameters cited. The limit values of PMV for global thermal comfort [13,14] in thermally moderate environments (such as inside museums) are the following:
to ¼
hc t a þ hr t r hc þ hr
ð5Þ
where ta is the air temperature ( C), tr is the mean radiant temperature of the internal surfaces of the room ( C), hc is the convective heat transfer coefficient (W/m2 C), and hr is the radiative heat transfer coefficient (W/m2 C). However, where air velocities are sufficiently low (<0.2 m/s) and where differences between air temperature and mean radiant temperature are limited (<4 C), the operative temperature can be simply calculated as follows:
0:5 PMV 0:5 However, people often linger for a relatively longer period of time the same location in an exhibition space (i.e., in front of a painting). Excluding conditions of ‘‘global’’ thermal comfort, the causes of possible ‘‘local’’ thermal discomfort should also be verified. Table 5 reports the limit values of the parameters characterizing the local discomfort, as suggested by the ANSI/ASHRAE Standard 55 [14]. It is important to note that, regarding the technical standard ASHRAE 55 [14], thermal comfort conditions are expressed in terms of the ‘‘operative temperature’’, that is, a weighed average of air and mean radiant temperatures. In greater detail, the operative temperature is defined [13] as ‘‘the uniform
to ¼
ta þ t r 2
ð6Þ
6. Comparing indoor thermal requisites relating to people’s comfort and preserving works of art On the basis of the aforementioned considerations, various comparisons of indoor thermal requirements relating to people’s comfort and preserving works of art will be described
Table 7 Values of the simultaneousness index, IS, referring to two homogeneous classes of works of art and four typical values of the indoor air velocity in summer conditions, together with the shape (in a TeRH graph) of the common control areas Simultaneousness index IS in summer conditions var ¼ 0.10 m/s Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wooden musical instruments
var ¼ 0.15 m/s 24.0; 60%
22.8; 60%
24.0; 60%
23.4; 60%
4.7%
23.0; 50%
var ¼ 0.20 m/s 23.8; 60%
23.6; 50%
24.0; 60%
0.5%
2.4%
24.0; 50%
var ¼ 0.25 m/s e
24.0; 50% 24.0; 50%
Murals, frescos, sinopite
23.8; 65%
22.7; 65%
23.3; 65%
23.5; 55%
24.0; 60%
24.0; 60%
23.4; 60%
23.9; 55%
24.0; 55%
e
23.5; 55%
24.0; 55%
24.0; 60%
23.8; 60%
0.4%
1.3%
2.5%
22.9; 55%
24.0; 55%
24.0; 55%
22.8; 60%
24.0; 64%
1.0%
2.8%
5.2%
Both categories
23.8; 65%
24.0; 64%
24.0; 64%
22.9; 55%
23.7; 65%
23.8; 65%
24.0; 55% 23.9; 55%
24.0; 55%
e
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
132
in this section. These comparisons refer to the works of art typically present in museums since the optimal thermal and hygrometry values for works of art depend on the kinds of materials used. The tool here utilized for assessing these comparisons is a graphical representation of the ANSI/ASHRAE Standard 55 [14] which reports the thermal comfort conditions in terms of operative temperature and relative air humidity. Starting from the reasonable assumption that air temperature and operative temperature are sufficiently similar in value, indoor thermal conditions for preserving works of art can be represented on the same graph. This enables the singling out of possible common zones where both requirements (people’s comfort and taking care of works of art) are achieved. Figs. 1 and 2 show the optimal zones for both requirements for selected works of art under typical winter and summer conditions, respectively. In these computations the activity level is set to 1.2 met (93 W/m2 e light activity); the effective mechanical power
is set to zero; the desired thermal environment is in accordance with category B (0.5 < PMV < 0.5; PPD < 10%) of the ISO 7730 standard [13]; the clothing level is set to 0.5 clo (0.0775 m2 C/W) during the cooling season and 1.0 clo (0.155 m2 C/W) during the heating season; and the mean radiant temperature is here assumed to be equal to air temperature (consequently, the operative temperature is also equal to air temperature). The calculations can also be applied to various values of air velocity, since this is a parameter which greatly affects the thermal sensation of people and which is typically controlled in confined environments by means of HVAC equipment. It is possible to observe from the figures that increasing air velocity increased the operative temperature of people’s comfort. Moreover, a greater common control zone can be obtained for selected works of art by increasing indoor air velocity in winter and decreasing it in summer. The common area of values relating to air temperature and relative air
Table 8 Simultaneousness index for the presence of different couples of works of art in the same museum room
c) vari ous objects
Pain ting on canv as, oil pain ti ng on cloth and canv as, tempera, gouaches
8
Bo oks of gr eat valu e, leather- bound books, leather bi ndings, parchment, mi ni atures
5
La cquer, in laid , decorated or lacquer furn it ure
3
-
Poly chromati c wood carv in gs, pain ted wood, pain ti ngs on wood, ic ons, wood pendul um-clo cks, wo od mu sical in struments
3
Un pain ted wood carv in gs, wi ckerwork , wood or bark panels Stones, rocks, ore and stable (porous) meteorit es
Plasti cs
Ethnographic colle ctio ns, masks, leather, leather cl othes
Ma n-made fi bres
Wa ter- colo ur s, drawin gs, pastels
Phonographic Records
12
Iv ories, horns, malacolo gi cal coll ecti ons, eggs, nests, corals
3
8
Dr y murals (detached)
3
Entomolo gi cal colle ctio ns
Mu rals, fr escoes, sinopi te (detached)
Herbaria and botani cal colle ctio ns
Un stable, ir id escent and sensit iv e gl ass, sensit iv e gl ass mosaics
12
Gy psum and pl aster
3
Stone mo saic s, stones, rocks, ore, meteorit es (n on porous), fo ssils and stone coll ecti ons
23
Stones, rock s, ore and stable (porous) meteorit es
5
Un painted w ood carv in gs, wi ck erwo rk , w ood or bark panels
Fabric, veil s, drapery, carp ets, fabric tapestry, arras, silk , costumes, dresses, reli gi ous vestment s, natural fi bre materi als, sisal, ju te
Poly chromati c w ood carv in gs, pain ted w ood, pain ti ngs on wood, ic ons, w ood pendul um-clo ck s, wo od musical in struments
8
Lacquer, in laid, decorated or lacquer fu rnit ure
3
B ook s of great valu e, leather- bound book s, leather bi ndin gs, parchment, mi ni atures
Entomolo gical coll ecti ons
5
Pain ti ng on canv as, oi l pain ti ng on cl oth and canv as, temp era, gouaches
Herbaria and botani cal coll ecti ons
8
c) vari ous objects
Wa ter-co lo urs, drawin gs, pastels
Fabric , veil s, drapery, carpets, fabric tapestry , arras, silk , costumes, dresses, reli gi ous vestments, natural fi bre materi als, sisal, ju te
Paper, papi er-mâché, paper artw ork, ti ssue-paper, wallp aper, stamp coll ecti ons, manuscri pts, papyri , prin tings, cell ul ose materi als
b) in or ganic materi al s/objects
Et hnographi c coll ecti ons, masks, leather, leather cl othes
Paper, papi er-m âché, paper artw ork, ti ssuepaper, wall paper, stamp coll ecti ons, manuscri pts, papyri , prin ti ngs, cell ul ose materi als b) in or gani c materi al s/ objects
a) Or gani c materi al s/objects
a) Or gani c materi al s/objects
5
5
8
5
3
3
5
8
8
3
2
-
3
8
3
8
5
12
-
-
12
23
3
-
12
23
2
3
2
12
3
3
18
18
18
12
12
12
18
2
2
5
18
18
18
12
12
12
12
18
18
18
-
18
2
18
5
18
18
18
12
12
12
12
18
18
18
-
18
2
18
18
12
12
18
12
12
18
18
-
18
3
18
12
12
12
12
12
12
12
12
-
12
2
12
3
12
12
12
12
12
12
12
12
3
-
-
12
1
12
-
-
3
12
12
12
12
12
12
12
12
3
-
-
12
1
12
-
5
6
6
18
18
18
12
12
12
12
18
18
18
6
-
6
6
18
2
18
6
8
12
6
24
18
18
18
12
12
12
18
24
24
6
6
6
6
24
3
24
12
Stone mosaic s, stones, rocks, ore, meteorit es (non porous), fossils and stone colle ctio ns
8
23
6
24
18
18
18
12
12
12
18
24
55
6
6
6
6
24
3
24
23
Gy psum and pl aster
3
3
6
6
6
6
6
6
3
3
6
6
6
6
-
-
3
6
-
6
3
Un stable, ir id escent and sensit iv e gl ass, sensit iv e gl ass mosaics
2
6
-
6
-
-
6
-
-
-
-
6
6
-
6
-
-
6
1
6
6
Mu rals, fr escoes, sinopi te (detached)
-
-
-
6
6
6
-
-
6
6
6
6
6
-
-
13
-
6
-
6
-
Dr y murals (detached)
3
6
3
6
6
6
6
6
-
-
6
6
6
3
-
-
6
6
1
6
6
Iv ories, horn s, malacolo gi cal coll ecti ons, eggs, nests, corals
8
12
6
24
18
18
18
12
12
12
18
24
24
6
6
6
6
24
3
24
12
Phonographic Record s
3
2
-
3
2
2
3
2
1
1
2
3
3
-
1
-
1
3
3
3
2
Ma n- made fi bres
8
12
6
24
18
18
18
12
12
12
18
24
24
6
6
6
6
24
3
24
12
Plasti cs
5
23
3
12
6
6
12
6
-
-
6
12
23
3
6
-
6
12
2
12
23
Winter season (basic conditions: 1.2 met, 1 clo, 0.2 m/s).
-
-
2
2
12
-
12
3
-
3
12
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
humidity for people’s well-being and safely preserving works of art represents the zone where the indoor environment of a museum can be controlled. This suggests the introduction of a suitable index for quantitatively assessing the level at which the needs for people’s comfort and preserving works of art are contemporaneously satisfied. For this purpose, a ‘‘simultaneousness index’’, IS, is defined here as the ratio between the (possible) common area for people’s comfort and preserving works of art, and the whole area representing the conditions of comfort. In other words, the IS index represents (in percentages) the level at which the requirements of people’s comfort coincide with the need to safeguard works of art. Typical values of indoor air velocity and two homogeneous (with respect to indoor requirements) classes of works of art
133
and the shape of the common control areas are reported in Tables 6 and 7. Each corner point of these figures is characterized by the twin values of the air temperature and the relative humidity. Since the same museum room could host various works of art, belonging to different homogeneous classes, the shape of the common areas in this case has also been reported. These data can be directly used by designers and museum curators for optimizing the distribution of works of art in various rooms. For example, the data in Tables 8 and 9 report the simultaneousness index (in percentage points) between the requirements for people’s comfort and the preserving of several works of art. Clearly, the higher this index, the easier it is to suitably control the indoor climate of an exhibition space containing works of art, as indicated in Tables 8 and 9.
Table 9 Simultaneousness index for the presence of different couples of works of art in the same museum room
Fabr ic, veils, dr apery, carpets, fabr ic tapestry , arras, silk , costum es, dr esses, reli gi ou s vestme nt s, natu ral fi br e mate ri al s, sisal, jute
Herbaria and bo tani cal coll ecti on s
E nto mo logi cal coll ecti on s
W ater-colo ur s, dr aw ings, pastel s
E thn og raph ic coll ecti on s, ma sks, leathe r, leather cl ot hes
Pain ti ng on canv as, oil painti ng on cl ot h and canv as, temp era, go uaches
B ook s of gr eat value, leather- bo un d bo ok s, leather bi ndin gs, parc hm ent, mi ni atur es
L acquer, inlaid, decorated or lacquer fu rnit ur e
Poly chroma ti c wo od carv ings, painted wood , painti ng s on wo od, icon s, wo od pend ul um cl oc ks, wo od mu sical instrume nt s
Unpainted wo od carv ings, wi ck erwo rk , wo od or bark panels
Ston es, rock s, or e and stable (por ou s) me teor it es
Ston e mo saic s, stones, ro ck s, or e, me teor it es (non po rous), fo ssil s and stone coll ecti on s
Gy psum and pl aster
Unstable, ir idescent and sensit iv e gl ass, sensit iv e gl ass mo saic s
Mu rals, fr escoes, sino pi te (detached)
Dr y mu rals (detached)
Iv or ies, ho rns, ma lacologi cal coll ecti on s, eggs , nests, corals
Phonog raph ic Records
Ma n- ma de fi br es
Plasti cs
c) va ri ou s objects
Paper, papi er -m âché, paper artw or k, ti ssue-paper, wa llp aper , stam p collections, manu scri pt s, papy ri , pr in ti ng s, cellu lose ma teri al s
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
-
Not
Not
Not
Not
Not
Fabr ic, veils, dr aper y, carp ets, fabr ic tapestry, arras, silk , costum es, dr esses, reli gi ou s vestme nt s, natu ral fi br e ma teri al s, sisal, ju te
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
Not
Not
Not
-
Not
Not
Not
Not
Not
Herbaria and bo tani cal collections
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
-
Not
Not
Ento mo logi cal collections
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
Not
0.
Not
0.5
Not
0.5
Not
Water- colour s, dr awin gs, pastel s
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.
Not
0.5
Not
0.5
Not
E thn ograph ic collections, ma sks, leather, leather cl ot hes
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.
Not
0.5
Not
0.5
Not
Pain ti ng on canv as, oi l painti ng on cl ot h and canv as, temp era, goua ches
Not
Not
Not
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Not
Not
-
Not
0.1
Not
0.1
Not
B ook s of gr eat value, leather- boun d book s, leather bi nd ings, parchm ent, mi ni atur es
Not
Not
Not
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Not
-
-
Not
0.1
Not
0.1
Not
L acquer, in laid, decorated or lacquer furn it ur e
Not
-
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.
-
0.5
Not
0.5
-
Poly chroma ti c wo od carv ings, pain ted wood , painti ng s on wo od , icon s, wood pend ul um -clock s, wo od mu sical in stru ment s
Not
-
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.
-
0.5
Not
0.5
-
Un painted wo od carv in gs, wi ck er wo rk , wo od or bark panels
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.4
Not
0.5
Not
0.5
Not
Ston es, rock s, or e and stable (por ou s) me teor it es
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
Not
0.4
Not
0.5
Not
0.5
Not
Ston e mo saics, ston es, rock s, or e, me teor it es (non po rous), fossils and ston e collections
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
16
No t
Not
0.4
Not
0.5
Not
0.5
Not
Gypsum and pl aster
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
-
Not
Not
Un stable, ir idescent and sensit iv e gl ass, sensit iv e gl ass mo saics
Not
Not
-
Not
-
-
Not
-
-
-
-
Not
Not
-
Not
-
-
Not
Not
Not
Not
-
-
-
0.4
0,4
0.4
-
-
0.4
0.4
0.4
0.4
0.4
-
-
1.0
-
0.4
-
0.4
-
Dr y mu rals (detached)
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
Not
Not
-
-
Not
Not
Not
Not
Not
Iv or ies, horn s, ma lacologi cal collections, eggs , nests, corals
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
Not
0.4
Not
0.5
Not
0.5
Not
Phon ograph ic R ecords
Not
Not
-
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
-
Not
-
Not
Not
Not
Not
Not
Man- ma de fi br es
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
Not
0.4
Not
0.5
Not
0.5
Not
Plasti cs
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
Not
Not
Not
-
Not
Not
Not
Not
Not
Mu rals, fr escoes, sino pi te (detached)
c) vari ou s objects
b) inor ga ni c ma teri al s/ob jects
Paper, papi er-m âché, paper artw or k, ti ssuepaper, wa ll paper, stamp coll ecti on s, ma nu scri pt s, papy ri , pr inti ng s, cell ul ose mate ri al s b) inor ga ni c ma teri al s/ ob jects
a) Or ga ni c ma teri al s/ob jects
a) Or ga ni c ma teri al s/ob jects
Summer season (basic conditions: 1.2 met, 0.5 clo, 0.2 m/s). ‘‘Not’’: denotes not common areas between people’s comfort and works of art saving.
134
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
Table 8 refers to winter conditions while Table 9 refers to summer conditions. In each row, the darkest shading of the cells underlines the condition where the greater common area is found, thereby ensuring more effective management of indoor spaces. It is important to note that seasonal conditions are taken into account not only according to variations in external environmental data but also by varying the personal parameters relating to people. It is clear that the inclusion of one cultural artifact to another in the same exhibition space dramatically reduces the extension of the overlapping area where the indoor environment may be more easily controlled. For example, Table 8 indicates that the common area in winter between people’s comfort and the preservation of paper artwork is only 8% (the first column in Table 8) of the total area where the artwork is preserved. Moreover, when material made of natural fibres is included in the same room, the overlapping area decreases to 5% (the second column in Table 8). Table 9 demonstrates the difficulty of obtaining suitable indoor parameters in museums when comfort is included in the control criteria for summer conditions. However, figures similar to those reported in Tables 6 and 7 and the set of data like those contained in Tables 8 and 9 are very useful to indoor environment designers and museum curators. Thus, suitable works of art can be confidently displayed in the same exhibition space. 7. Conclusions The difficulties involved in balancing the requirements for preserving works of art on display in exhibition spaces and the thermal comfort of visitors to these spaces are here outlined. An extensive review of the optimal indoor microclimatic parameters for preserving works of art, as they appear in current Italian standards, has been carried out. Moreover, an analysis of international standards providing conditions of thermal comfort has been performed and applied to the indoor climate of museum buildings. In order to provide technicians and museum curators with easy and reliable tools of analysis, a simultaneousness index has been introduced. This parameter represents the rate of the control surface (in a temperatureerelative humidity diagram), where both requirements have been satisfied. Finally, useful figures have been introduced that graphically report
the shape of surfaces in a temperatureerelative humidity diagram for a given work of art where both requirements have been satisfied. References [1] M. La Gennusa, G. Rizzo, G. Scaccianoce, F. Nicoletti, The control of indoor environments in heritage buildings: experimental measurements in an old Italian museum and proposal of a methodology, J. Cult. Herit. 6 (2005) 147e155. [2] G. Pavlogeorgatos, Environmental parameters in museum, Build. Environ. 38 (2003) 1457e1462. [3] UNI 11120, Cultural Heritage e Field Measurement of the Air Temperature and the Surface Temperature of Objects, UNI e Ente Italiano di Unificazione, Milano, 2004, (in Italian). [4] UNI 11131, Cultural Heritage e Field Measurement of the Air Humidity, UNI e Ente Italiano di Unificazione, Milano, 2005, (in Italian). [5] UNI 10969, Cultural Heritage e General Principles for the Choice and the Control of the Microclimate to Preserve Cultural Heritage in Indoor Environments, UNI e Ente Italiano di Unificazione, Milano, 2002, (in Italian). [6] UNI 10829, Works of Art of Historical Importance. Ambient Conditions for the Conservation. Measurement and Analysis, UNI e Ente Italiano di Unificazione, Milano, 1999, (in Italian). [7] Ministerial Decree 10 May 2001 Ministry for Arts and Culture, Guidelines on Technical-Scientific Criteria for Application of Standards in Museums e Article 150, paragraph 6, Law by Decree n. 112/1998, Italian Republic’s Official Gazette, 19 October 2001, n. 244 (in Italian). [8] ISO 18911, Imaging Materials e Processed Safety Photographic Films e Storage Practices, International Organization for Standardization, Geneva, 2000. [9] ISO 11799, Information and Documentation e Document Storage Requirements for Archive and Library Materials, International Organization for Standardization, Geneva, 2003. [10] ANSI/NISO Z39.79, Environmental Conditions for Exhibiting Library and Archival Materials, National Information Standards Organization, Bethesda, Maryland, USA, 2001. [11] M. Beccali, A. Nucara, G. Rizzo, Thermal comfort, in: Cutler J. Cleveland (Ed.), Encyclopedia of Energy, vol. 6, Elsevier Inc, 2004. [12] P.O. Fanger, Thermal Comfort, Danish Technical Press, Copenhagen, 1970. [13] ISO 7730, Ergonomics of the Thermal Environment e Analytical determination and Interpretation of Thermal Comfort using Calculation of the PMV and PPD Indices and Local Thermal Comfort Criteria, International Organization for Standardization, Geneva, 2005. [14] ANSI/ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, GA, 2004. [15] ISO 7726, Ergonomics of the Thermal Environment e Instruments for Measuring Physical Quantities, International Organization for Standardization, Geneva, 1998.
Journal of Cultural Heritage 9 (2008) 125e134 http://france.elsevier.com/direct/CULHER/
Original article
Conflicting needs of the thermal indoor environment of museums: In search of a practical compromise Maria La Gennusa1, Giovanni Lascari2, Gianfranco Rizzo*, Gianluca Scaccianoce1 Dipartimento di Ricerche Energetiche ed Ambientali (DREAM), Universita` degli Studi di Palermo, Viale delle Scienze (Building 9), 90128 Palermo, Italy Received 11 April 2007; accepted 1 August 2007
Abstract Thermal indoor microclimate conditions in museum buildings refer to two important requirements: the preservation of works of art and the comfort of visitors to these buildings and/or those working inside them. Unfortunately, different works of art have different internal parameters which render the management and control of the indoor thermal microclimate difficult. In this work the values proposed by various standards for the thermal environment of museum buildings have been revised. Moreover, the indoor microclimatic conditions relating to people’s comfort have been described, with the aim of singling out possible common ranges for these parameters. With this aim, a useful simultaneousness index has also been introduced. Finally, the proposed approach has been applied to an old Italian building for purposes of clarification. Ó 2008 Elsevier Masson SAS. All rights reserved. Keywords: Cultural heritage; Works of art conservation; Italian standard rules; Comfort indoor; Microclimatic parameters; Simultaneousness index
1. Research aims The first aim of this work is to review the standards and the limit values for typical parameters relating to the indoor environments of museums. Moreover, a comparison will then be proposed between the values referring to the preservation of works of art and those concerning the comfort of visitors or those working inside museum buildings. This paper will point out that the suggested values for both purposes can be at times conflicting. Common ranges for these values are suggested in order to contemporaneously satisfying the needs for people’s comfort and the preservation of works of art. It is also argued that the adoption of the predicted mean vote method, as opposed to the classical temperaturee humidity approach, leads to the highlighting of more realistic
* Corresponding author. Tel.: þ39 091 236210; fax: þ39 091 484425. E-mail addresses: [email protected] (M. La Gennusa), lascari@ dream.unipa.it (G. Lascari), [email protected] (G. Rizzo), scaccia@dream. unipa.it (G. Scaccianoce). 1 Tel.: þ39 091 236225; fax: þ39 091 484425. 2 Tel.: þ39 091 236216; fax: þ39 091 484425. 1296-2074/$ - see front matter Ó 2008 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.culher.2007.08.003
ranges of indoor parameters and, consequently, to a more effective control of the indoor microclimate of such buildings. 2. Introduction The growing demand for culture, along with improvements in indoor conditions of exhibition spaces, encourages people to spend an increasing amount of time in museums where, together with exhibitions of terracotta objects, sculptures and historical documents, dinners, musical concerts and plays often take place. The different ways in which museums can be enjoyed call for greater attention to be paid to the quality of the indoor environment with the aim of ensuring people’s comfort. But the requirements for the optimal preservation of cultural artifacts do not necessarily coincide with those of thermal comfort. This suggests particular care must be taken when assessing the thermal indoor requirements of such buildings in order to identify a set of parameters capable of satisfying both demands. Such problems are generally addressed [1,2] by means of the appropriate design and management of heating, ventilating and air conditioning (HVAC) systems (thermal and hygrometry
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
126
Nomenclature
u0
DR
Dumax var W
fcl hc hr Icl IS M pa PD PPD PMV RH ta tcl tf to Dtpr tr
percentage dissatisfied due to local discomfort from draught (%) clothing surface area factor convective heat transfer coefficient (W/m2 C) radiative heat transfer coefficient (W/m2 C) clothing insulation (m2 C/W) simultaneousness index (%) metabolic rate (W/m2) partial pressure of water vapour (Pa) percentage dissatisfied (%) predicted percentage of dissatisfied (%) predicted mean vote relative humidity of air (%) air temperature referring to people’s comfort ( C) clothing surface temperature ( C) floor surface temperature ( C) operative temperature ( C) radiant temperature asymmetry ( C) mean radiant temperature ( C)
requisites) and by correctly selecting and positioning lighting fixtures (visual requisites). Particularly in countries with a noticeable cultural heritage recognized on an international level, however, very old buildings often function as exhibition spaces devoid of air climatization systems. Indeed, such buildings, which must be considered in many cases as works of art in themselves, do not easily lend themselves to the installation of conventional equipment to avoid the worst excesses of indoor climatic failure. These considerations, therefore, open up the way for a new approach in the design and management of the indoor environment of museums. An accurate analysis of current standards is now necessary. 3. The indoor environment of museums in standards Italy is one of the first countries in Europe which has formulated specific regulations for the conservation of cultural artifacts. For example, various technical standards have been recently specified which refer to the definition and control of microclimates with the specific aim of preserving cultural
relative humidity referring to the works of art preservation (%) daily range of relative humidity of the works of art (%) relative air velocity (m/s) effective mechanical power (W/m2)
Greek symbols q0 air temperature referring to the works of art preservation ( C) qS surface temperature of works of art ( C) Dqmax daily range of air temperature ( C) Subscripts a air ar relative air c convective cl clothing f floor 0 referring to the works of art pr radiant asymmetry r radiative o operative
items in indoor environments. Some of these documents introduce interesting elements that go far beyond their strict application to the Italian context. They will, therefore, be now shortly reviewed in this paper. The UNI 11120 standard [3], issued in May 2004, refers to appropriate protocols for the field measurement of the air and surface temperatures of cultural items, while the UNI 11131 standard [4], of March 2005, refers to field measurements of air humidity. These technical rules can be interpreted as a guideline for the evaluation of the air and surface temperature, and the air humidity of cultural items situated in confined (for example, museums, churches, historical buildings, etc.) or open environments. A previous standard, dating from February 2002, UNI 10969 [5], entitled ‘‘General principles for the choice and the control of the microclimate to preserve cultural heritage in indoor environments’’, contains a list of suggestions for the preservation of works of art. It also points to some guidelines for controlling the indoor microclimates of museums, particularly those operated by means of mechanical HVAC systems.
Table 1 Typical thermal indoor parameters and ranges of measurements in museum buildings Indoor parameter
Symbol
Range of measurements
Mean monthly value of the air temperature Daily range of air temperature Surface temperature of artworks Mean monthly value of the relative humidity of indoor air Daily range of relative humidity of air
q0 Dqmax qS u0 Dumax
Between 30 C and 60 C, with an accuracy of 0.5 C Between 30 C and 60 C, with an accuracy of 1 C þ 0.01 jtair tsurfacej Between 5% and 95%, with an accuracy of 2% (electronic psychrometer)
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
127
Table 2 Suggested values for the optimal conservation of works of art for steady-state indoor climate conditions (UNI 10829 standard and Minister Decree May 2001) q0 ( C)
Dqmax ( C)
u0 (%)
Dumax (%)
18e22 15e24 19e24
1.5
6
<18 21e23
N.S. 1.5 1.5 e 1.5
Water-colours, drawings, pastels
19e24 15e25 21e23 19e24 4e10 15e21 19e24
Ethnographic collections, masks, leather, leather clothes
19e24
1.5
Painting on canvas, oil painting on cloth and canvas, tempera, gouaches
19e24
1.5
Documents, file material Books of great value, leather-bound books, leather bindings, parchment, miniatures
13e18 19e24
e 1.5
Lacquer, inlaid, decorated or lacquer furniture Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wood musical instruments Unpainted wood carvings, wickerwork, wood or bark panels
19e24 19e24
1.5 1.5
19e24
1.5
40e55 50e60 30e50 40e60 N.S. 45e55 40e60 40e60 N.S. 20e35 40e60 30e50 45e60 45e60 50e60 45e60 50e60 40e55 35e50 50e60 45e55 50e60 50e60 50e60 45e65 45e60 40e65
Inorganic materials/objects Porcelain, ceramics, stoneware, terracotta, tiles and demineralised tiles from excavation
N.S.
e
Stones, rocks, ore and stable (porous) meteorites Stone mosaics, stones, rocks, ore, meteorites (non porous), fossils and stone collections
19e24 15e25
e e
Metals, smoothed metals, metal alloys, silver, armour, weapons, bronze, coins, copper objects, tin, iron, steel, lead, pewter Metals with active corrosion sites Gold
N.S.
e
N.S. N.S.
e e
Gypsum and plaster Unstable, iridescent and sensitive glass, sensitive glass mosaics
21e23 20e24
1.5 1.5
e
Ivories, horns, malacological collections, eggs, nests, corals
10e24 6e25 10e24 6e25 19e24
Phonographic records
10e21
e
Man-made fibres Film, colour photograph
e e
Organic material objects coming from damp excavation areas (before treatment)
19e24 0e15 15 to 5 5e15 2e20 19e24
Plastics
19e24
Work of art materials Organic materials/objects Paper, papier maˆche´, paper artwork, tissue-paper, wallpaper, stamp collections, manuscripts, papyri, printings, cellulose materials Fabric, veils, drapery, carpets, fabric tapestry, arras, silk, costumes, dresses, religious vestments, natural fibre materials, sisal, jute Wax, anatomical waxes Herbaria and botanical collections Entomological collections Animals and anatomical organs preserved in formalin Animals, dried anatomical organs, mummies Furs, feathers, stuffed animals and birds
Various objects Murals, frescoes, sinopite (detached) Dry murals (detached)
Film, black and white photograph
N.S. ¼ not significant.
1.5
1.5 1.5
e 1.5
e e e
N.S. 20e60 40e60 20e60 45e60 <50 <55 <40 N.S. <45 45e55 40e45 55e65 45e60 50e45 45e60 40e60 45e65 40e55 40e60 40e60 30e45 30e50 40e60 20e30 Saturated air 50e65 30e50
6 N.S. 2 6 N.S. e 5 2 6 6 e 6 2 2 2
10 6 10 e e e 2 e
e e 6 2 e e e e e
128
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
Of greater importance is the UNI 10829 standard [6], of July 1999, entitled ‘‘Ambient conditions for the conservation’’. It provides a comprehensive methodology for taking the field measurements of environmental parameters, which are significant for conserving works of art of historical importance. According to this standard, suggested values for parameters relating to the physical environment are provided for each type of objects, assuming a stable (steady-state) climate; reference environmental parameters to be adopted for the correct designing of climatization equipment are also mentioned. Moreover, appropriate measurement procedures, replete with the algorithms necessary for the statistical analysis of the data, are also given. Several categories of materials and objects are highlighted, for which their conservation in stable climate conditions is recommended. These in turn are subdivided into three main groups: materials/objects organic in nature; materials/objects inorganic in nature; and a composite category of objects. The main causes of degradation considered here are the thermal-hygrometer conditions of the air surrounding the objects and the electromagnetic radiation emanating from sources of natural or artificial light. The UNI 10829 standard suggests measuring specific physical parameters, specifying preferred values for these parameters, the maximum daily range, the maximum permissible values and the yearly dose of absorbed energy. According to the values of parameters mainly suggested in these standards, the thermal indoor requirements for the correct conservation of works of art and the thermal comfort of visitors to museum spaces will now be separately reviewed. Finally, a possible compromise will be proposed. 4. Thermal-hygrometer parameters for preserving works of art Typically the thermal-hygrometer indoor environment of exhibition rooms is assessed by measuring and controlling parameters which refer to air temperature and air humidity, as summarized in Table 1. The suggested values of these indoor parameters (with the exception of surface temperature) are reported, for example, in the Italian UNI 10829 standard [6] and the Ministerial Decree of May 2001 [7]. These recommended values for several environmental groups of works of art and materials are reported in Table 2. The values in Table 2 mainly refer to the conditions of preservation and they can be also considered for preventing microbiological damage to works of art with minor alterations [7]. In addition, critical values [7] of relative humidity and air temperature for some particular works of art are also reported in Table 3. Various general observations can be made analyzing these data. First, a lower air temperature value, generally 19 C, seems to apply more to requirements of the HVAC system design than the preservation of works of art. Indeed, in several cases, a minimum air temperature value lower than 19 C is indicated in correctly preserving cultural artifacts.
Table 3 Critical values of relative humidity and air temperature for typical artworks Handcrafts
Relative humidity (%)
Air temperature ( C)
Archaeological bronzes with chloride corrosions Archaeological irons with chloride corrosions Unstable glasses Wet wood
<42
e
<20
e
40e45 100
e <4
Moreover, such values impose very strict limits on the exhibition space where there may also be present works made from different materials. For example, where black and white photographs and books are contemporaneously exhibited, conflicting ranges of air temperature could be found: indeed, the upper suggested temperature value (15 C) for photographs is lower than the minimum temperature value (19 C) suggested for books. And, since similar limit values for these data can be found in several other international standards [8e10], it could be argued that many of them have simply been repeated prior to specific field. These considerations, therefore, suggest a thorough review of standards, even before comparing them with limits relating to the comfort of visitors.
5. Thermal indoor requirements relating to visitors’ comfort in museums The classical approach, which is based on controlling or measuring air temperature and humidity (the so-called ‘‘TeRH’’ method) will be substituted in this paper with a more appropriate method which directly applies to people’s choices. The thermal conditions of comfort relating to people depend on several factors, personal as well as environmental [11], which cannot be confined to a mere evaluation of temperature and relative air humidity. Within this framework, the practical assessment of indoor thermal conditions will refer to various parameters which can be divided into two main categories: temperature and sensation indices. The former express the thermal response of the subject with reference to the so-called ‘‘equivalent temperature’’ (the temperature of an imaginary environment in which the occupants would feel the same thermal sensation as in a real environment). The latter, based on a thermal subjective scale, predict the mean value of the votes expressed by a large
Table 4 Seven-point thermal sensation scale þ3 þ2 þ1 0 1 2 3
Hot Warm Slightly warm Neutral Slightly cool Cool Cold
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134 Table 5 Parameters affecting the local thermal comfort Parameters characterizing the local discomfort
Limit values
Draught, DR Vertical air temperature difference between head and feet, Dta Radiant temperature asymmetry from cold vertical surfaces (cool wall), Dtpr Radiant temperature asymmetry from warm vertical surfaces (warm wall), Dtpr Radiant temperature asymmetry from cold horizontal surfaces (cool ceiling), Dtpr Radiant temperature asymmetry from warm horizontal surfaces (warm ceiling), Dtpr Floor surface temperature, tf
<20% <3 C (PD < 5%)
PD < 5%
129
partial pressure of water vapour, pa; relative air velocity, var; mean radiant temperature, tr ), while two of them are personal (metabolic rate, M, and clothing insulation, Icl). That is [13] PMV ¼ 0:303eð0:036MÞ þ 0:028 ðM WÞ 3:05 103 ½5733 6:99ðM WÞ pa 0:42½ðM WÞ
<10 K
58:15 1:7 105 Mð5867 pa Þ 0:0014Mð34 ta Þ 3:96 4 4 108 fcl ðtcl þ 273Þ ðtr þ 273Þ fcl hc ðtcl ta Þ ð1Þ
<23 K <14 K <5 K
where tcl ¼35:7 0:028ðM WÞ Icl 3:96 4 4 108 fcl ðtcl þ 273Þ ðtr þ 273Þ þ fcl hc ðtcl ta Þ
19 C < tf < 29 C (PD < 10%)
group of people exposed to the same microclimatic conditions. As is well known, the most widely used index for evaluating indoor thermal conditions in moderate environments is the predicted mean vote (PMV) originally introduced by Fanger [12]. It represents the mean value of the votes expressed by a large group of persons on a seven-point thermal sensation scale [13] (Table 4), based on the heat balance of the human body. A neutral thermal balance is reached when the internal heat production in the body is equal to the loss of heat to the environment. In a moderate environment, the human thermoregulatory system automatically attempts to modify skin temperature and sweat secretion in order to maintain heat balance. The PMV index is expressed as a function of six parameters: four of them are environmental (air temperature, ta;
( hc ¼ fcl ¼
0:25
2:38jtcl ta j pffiffiffiffiffi 12:1 var
pffiffiffiffiffi 0:25 for 2:38jtcl ta j > 12:1 var pffiffiffiffiffi 0:25 for 2:38jtcl ta j < 12:1 var
1:00 þ 1:290Icl for Icl 0:078 m2 C=W 1:05 þ 1:645Icl for Icl > 0:078 m2 C=W
ð2Þ ð3Þ
ð4Þ
In these equations some parameters are introduced which require definition: M e metabolic rate (W/m2); W e effective mechanical power (W/m2); Icl e clothing insulation (m2 C/W); fcl e clothing surface area factor (dimensionless); ta e air temperature ( C); tr e mean radiant temperature ( C);
0.016 M = 1.2 met Icl = 1.0 clo
0.014 Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wood musical instruments
Humidity Ratio [kgv/kgda]
0.012
0.01
νar = 0.10 m/s
Murals, frescoes, sinopite
νar = 0.15 m/s
0.008
νar = 0.20 m/s
90% 80%
0.006
70%
0.004
60% 50% 40%
νar = 0.25 m/s
30% 0.002
20% 10% RH
0 10
12
14
16
18
20
22
24
26
28
30
32
34
Operative temperature [°C] Fig. 1. The overlapping zones between people’s comfort and taking care of works of art requisites in typical winter conditions, for selected works of art.
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
130 0.016
M = 1.2 met Icl = 0.5 clo
0.014 Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wood musical instruments
Humidity Ratio [kgv/kgda]
0.012
0.01
νar = 0.10 m/s
Murals, frescoes, sinopite
νar = 0.15 m/s
0.008
νar = 0.20 m/s
90% 80%
0.006
0.004
70%
νar = 0.25 m/s
60% 50% 40% 30%
0.002
20% 10% RH
0 10
12
14
16
18
20
22
24
26
28
30
32
34
Operative temperature [°C] Fig. 2. The overlapping zones between people’s comfort and taking care of works of art requisites in typical summer conditions, for selected works of art.
Table 6 Values of the simultaneousness index, IS, referring to two homogeneous classes of works of art and four typical values of the indoor air velocity in winter conditions, together with the shape (in a TeRH graph) of the common control areas Simultaneousness index IS in winter conditions var ¼ 0.10 m/s Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wooden musical instruments
19.0; 60%
23.5; 60%
var ¼ 0.20 m/s 23.9; 60%
19.6; 60%
var ¼ 0.25 m/s
19.9; 60%
24.0; 60%
23.8; 50%
23.4; 65%
8.9; 65%
19.8; 50%
12.3%
24.0; 50%
23.8; 65%
19.4; 65%
20.2; 50%
11.8%
24.0; 50%
23.8; 65%
19.8; 65%
20.5; 50%
12.6%
19.1; 55%
23.7; 55%
23.5;60%
19.0; 60%
19.7; 55%
19.6; 60%
6.3%
19.1; 55%
24.0; 56%
23.9; 60%
20.0; 55%
19.7; 55%
24.0; 55%
24.0; 60%
20.3; 55%
20.0; 55%
24.0; 55%
24.0; 60%
20.2; 60%
6.2%
6.5% 24.0; 56%
23.7; 55%
12.1%
24.0; 55%
19.9; 60%
23.8; 65% 24.0; 64%
12.6%
12.9%
24.0; 50%
20.1; 65%
24.0; 64%
Both categories
24.0; 60%
20.2; 60%
24.0; 56%
12.9%
12.7%
19.2; 50%
Murals, frescoes, sinopite
var ¼ 0.15 m/s
6.0%
24.0; 55%
20.3; 55%
24.0; 55%
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
var e relative air velocity (m/s); pa e water vapour partial pressure (Pa); hc e convective heat transfer coefficient (W/m2 C); tcl e clothing surface temperature ( C).
131
temperature of an imaginary black enclosure in which an occupant would exchange the same amount of heat by radiation and convection as in the actual non-uniform environment’’. It is usually defined as follows [15]:
The practical evaluation of PMV is generally made possible through the use of various tables which contain a set of precalculated values for several typical combinations of the six parameters cited. The limit values of PMV for global thermal comfort [13,14] in thermally moderate environments (such as inside museums) are the following:
to ¼
hc t a þ hr t r hc þ hr
ð5Þ
where ta is the air temperature ( C), tr is the mean radiant temperature of the internal surfaces of the room ( C), hc is the convective heat transfer coefficient (W/m2 C), and hr is the radiative heat transfer coefficient (W/m2 C). However, where air velocities are sufficiently low (<0.2 m/s) and where differences between air temperature and mean radiant temperature are limited (<4 C), the operative temperature can be simply calculated as follows:
0:5 PMV 0:5 However, people often linger for a relatively longer period of time the same location in an exhibition space (i.e., in front of a painting). Excluding conditions of ‘‘global’’ thermal comfort, the causes of possible ‘‘local’’ thermal discomfort should also be verified. Table 5 reports the limit values of the parameters characterizing the local discomfort, as suggested by the ANSI/ASHRAE Standard 55 [14]. It is important to note that, regarding the technical standard ASHRAE 55 [14], thermal comfort conditions are expressed in terms of the ‘‘operative temperature’’, that is, a weighed average of air and mean radiant temperatures. In greater detail, the operative temperature is defined [13] as ‘‘the uniform
to ¼
ta þ t r 2
ð6Þ
6. Comparing indoor thermal requisites relating to people’s comfort and preserving works of art On the basis of the aforementioned considerations, various comparisons of indoor thermal requirements relating to people’s comfort and preserving works of art will be described
Table 7 Values of the simultaneousness index, IS, referring to two homogeneous classes of works of art and four typical values of the indoor air velocity in summer conditions, together with the shape (in a TeRH graph) of the common control areas Simultaneousness index IS in summer conditions var ¼ 0.10 m/s Polychromatic wood carvings, painted wood, paintings on wood, icons, wood pendulum-clocks, wooden musical instruments
var ¼ 0.15 m/s 24.0; 60%
22.8; 60%
24.0; 60%
23.4; 60%
4.7%
23.0; 50%
var ¼ 0.20 m/s 23.8; 60%
23.6; 50%
24.0; 60%
0.5%
2.4%
24.0; 50%
var ¼ 0.25 m/s e
24.0; 50% 24.0; 50%
Murals, frescos, sinopite
23.8; 65%
22.7; 65%
23.3; 65%
23.5; 55%
24.0; 60%
24.0; 60%
23.4; 60%
23.9; 55%
24.0; 55%
e
23.5; 55%
24.0; 55%
24.0; 60%
23.8; 60%
0.4%
1.3%
2.5%
22.9; 55%
24.0; 55%
24.0; 55%
22.8; 60%
24.0; 64%
1.0%
2.8%
5.2%
Both categories
23.8; 65%
24.0; 64%
24.0; 64%
22.9; 55%
23.7; 65%
23.8; 65%
24.0; 55% 23.9; 55%
24.0; 55%
e
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
132
in this section. These comparisons refer to the works of art typically present in museums since the optimal thermal and hygrometry values for works of art depend on the kinds of materials used. The tool here utilized for assessing these comparisons is a graphical representation of the ANSI/ASHRAE Standard 55 [14] which reports the thermal comfort conditions in terms of operative temperature and relative air humidity. Starting from the reasonable assumption that air temperature and operative temperature are sufficiently similar in value, indoor thermal conditions for preserving works of art can be represented on the same graph. This enables the singling out of possible common zones where both requirements (people’s comfort and taking care of works of art) are achieved. Figs. 1 and 2 show the optimal zones for both requirements for selected works of art under typical winter and summer conditions, respectively. In these computations the activity level is set to 1.2 met (93 W/m2 e light activity); the effective mechanical power
is set to zero; the desired thermal environment is in accordance with category B (0.5 < PMV < 0.5; PPD < 10%) of the ISO 7730 standard [13]; the clothing level is set to 0.5 clo (0.0775 m2 C/W) during the cooling season and 1.0 clo (0.155 m2 C/W) during the heating season; and the mean radiant temperature is here assumed to be equal to air temperature (consequently, the operative temperature is also equal to air temperature). The calculations can also be applied to various values of air velocity, since this is a parameter which greatly affects the thermal sensation of people and which is typically controlled in confined environments by means of HVAC equipment. It is possible to observe from the figures that increasing air velocity increased the operative temperature of people’s comfort. Moreover, a greater common control zone can be obtained for selected works of art by increasing indoor air velocity in winter and decreasing it in summer. The common area of values relating to air temperature and relative air
Table 8 Simultaneousness index for the presence of different couples of works of art in the same museum room
c) vari ous objects
Pain ting on canv as, oil pain ti ng on cloth and canv as, tempera, gouaches
8
Bo oks of gr eat valu e, leather- bound books, leather bi ndings, parchment, mi ni atures
5
La cquer, in laid , decorated or lacquer furn it ure
3
-
Poly chromati c wood carv in gs, pain ted wood, pain ti ngs on wood, ic ons, wood pendul um-clo cks, wo od mu sical in struments
3
Un pain ted wood carv in gs, wi ckerwork , wood or bark panels Stones, rocks, ore and stable (porous) meteorit es
Plasti cs
Ethnographic colle ctio ns, masks, leather, leather cl othes
Ma n-made fi bres
Wa ter- colo ur s, drawin gs, pastels
Phonographic Records
12
Iv ories, horns, malacolo gi cal coll ecti ons, eggs, nests, corals
3
8
Dr y murals (detached)
3
Entomolo gi cal colle ctio ns
Mu rals, fr escoes, sinopi te (detached)
Herbaria and botani cal colle ctio ns
Un stable, ir id escent and sensit iv e gl ass, sensit iv e gl ass mosaics
12
Gy psum and pl aster
3
Stone mo saic s, stones, rocks, ore, meteorit es (n on porous), fo ssils and stone coll ecti ons
23
Stones, rock s, ore and stable (porous) meteorit es
5
Un painted w ood carv in gs, wi ck erwo rk , w ood or bark panels
Fabric, veil s, drapery, carp ets, fabric tapestry, arras, silk , costumes, dresses, reli gi ous vestment s, natural fi bre materi als, sisal, ju te
Poly chromati c w ood carv in gs, pain ted w ood, pain ti ngs on wood, ic ons, w ood pendul um-clo ck s, wo od musical in struments
8
Lacquer, in laid, decorated or lacquer fu rnit ure
3
B ook s of great valu e, leather- bound book s, leather bi ndin gs, parchment, mi ni atures
Entomolo gical coll ecti ons
5
Pain ti ng on canv as, oi l pain ti ng on cl oth and canv as, temp era, gouaches
Herbaria and botani cal coll ecti ons
8
c) vari ous objects
Wa ter-co lo urs, drawin gs, pastels
Fabric , veil s, drapery, carpets, fabric tapestry , arras, silk , costumes, dresses, reli gi ous vestments, natural fi bre materi als, sisal, ju te
Paper, papi er-mâché, paper artw ork, ti ssue-paper, wallp aper, stamp coll ecti ons, manuscri pts, papyri , prin tings, cell ul ose materi als
b) in or ganic materi al s/objects
Et hnographi c coll ecti ons, masks, leather, leather cl othes
Paper, papi er-m âché, paper artw ork, ti ssuepaper, wall paper, stamp coll ecti ons, manuscri pts, papyri , prin ti ngs, cell ul ose materi als b) in or gani c materi al s/ objects
a) Or gani c materi al s/objects
a) Or gani c materi al s/objects
5
5
8
5
3
3
5
8
8
3
2
-
3
8
3
8
5
12
-
-
12
23
3
-
12
23
2
3
2
12
3
3
18
18
18
12
12
12
18
2
2
5
18
18
18
12
12
12
12
18
18
18
-
18
2
18
5
18
18
18
12
12
12
12
18
18
18
-
18
2
18
18
12
12
18
12
12
18
18
-
18
3
18
12
12
12
12
12
12
12
12
-
12
2
12
3
12
12
12
12
12
12
12
12
3
-
-
12
1
12
-
-
3
12
12
12
12
12
12
12
12
3
-
-
12
1
12
-
5
6
6
18
18
18
12
12
12
12
18
18
18
6
-
6
6
18
2
18
6
8
12
6
24
18
18
18
12
12
12
18
24
24
6
6
6
6
24
3
24
12
Stone mosaic s, stones, rocks, ore, meteorit es (non porous), fossils and stone colle ctio ns
8
23
6
24
18
18
18
12
12
12
18
24
55
6
6
6
6
24
3
24
23
Gy psum and pl aster
3
3
6
6
6
6
6
6
3
3
6
6
6
6
-
-
3
6
-
6
3
Un stable, ir id escent and sensit iv e gl ass, sensit iv e gl ass mosaics
2
6
-
6
-
-
6
-
-
-
-
6
6
-
6
-
-
6
1
6
6
Mu rals, fr escoes, sinopi te (detached)
-
-
-
6
6
6
-
-
6
6
6
6
6
-
-
13
-
6
-
6
-
Dr y murals (detached)
3
6
3
6
6
6
6
6
-
-
6
6
6
3
-
-
6
6
1
6
6
Iv ories, horn s, malacolo gi cal coll ecti ons, eggs, nests, corals
8
12
6
24
18
18
18
12
12
12
18
24
24
6
6
6
6
24
3
24
12
Phonographic Record s
3
2
-
3
2
2
3
2
1
1
2
3
3
-
1
-
1
3
3
3
2
Ma n- made fi bres
8
12
6
24
18
18
18
12
12
12
18
24
24
6
6
6
6
24
3
24
12
Plasti cs
5
23
3
12
6
6
12
6
-
-
6
12
23
3
6
-
6
12
2
12
23
Winter season (basic conditions: 1.2 met, 1 clo, 0.2 m/s).
-
-
2
2
12
-
12
3
-
3
12
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
humidity for people’s well-being and safely preserving works of art represents the zone where the indoor environment of a museum can be controlled. This suggests the introduction of a suitable index for quantitatively assessing the level at which the needs for people’s comfort and preserving works of art are contemporaneously satisfied. For this purpose, a ‘‘simultaneousness index’’, IS, is defined here as the ratio between the (possible) common area for people’s comfort and preserving works of art, and the whole area representing the conditions of comfort. In other words, the IS index represents (in percentages) the level at which the requirements of people’s comfort coincide with the need to safeguard works of art. Typical values of indoor air velocity and two homogeneous (with respect to indoor requirements) classes of works of art
133
and the shape of the common control areas are reported in Tables 6 and 7. Each corner point of these figures is characterized by the twin values of the air temperature and the relative humidity. Since the same museum room could host various works of art, belonging to different homogeneous classes, the shape of the common areas in this case has also been reported. These data can be directly used by designers and museum curators for optimizing the distribution of works of art in various rooms. For example, the data in Tables 8 and 9 report the simultaneousness index (in percentage points) between the requirements for people’s comfort and the preserving of several works of art. Clearly, the higher this index, the easier it is to suitably control the indoor climate of an exhibition space containing works of art, as indicated in Tables 8 and 9.
Table 9 Simultaneousness index for the presence of different couples of works of art in the same museum room
Fabr ic, veils, dr apery, carpets, fabr ic tapestry , arras, silk , costum es, dr esses, reli gi ou s vestme nt s, natu ral fi br e mate ri al s, sisal, jute
Herbaria and bo tani cal coll ecti on s
E nto mo logi cal coll ecti on s
W ater-colo ur s, dr aw ings, pastel s
E thn og raph ic coll ecti on s, ma sks, leathe r, leather cl ot hes
Pain ti ng on canv as, oil painti ng on cl ot h and canv as, temp era, go uaches
B ook s of gr eat value, leather- bo un d bo ok s, leather bi ndin gs, parc hm ent, mi ni atur es
L acquer, inlaid, decorated or lacquer fu rnit ur e
Poly chroma ti c wo od carv ings, painted wood , painti ng s on wo od, icon s, wo od pend ul um cl oc ks, wo od mu sical instrume nt s
Unpainted wo od carv ings, wi ck erwo rk , wo od or bark panels
Ston es, rock s, or e and stable (por ou s) me teor it es
Ston e mo saic s, stones, ro ck s, or e, me teor it es (non po rous), fo ssil s and stone coll ecti on s
Gy psum and pl aster
Unstable, ir idescent and sensit iv e gl ass, sensit iv e gl ass mo saic s
Mu rals, fr escoes, sino pi te (detached)
Dr y mu rals (detached)
Iv or ies, ho rns, ma lacologi cal coll ecti on s, eggs , nests, corals
Phonog raph ic Records
Ma n- ma de fi br es
Plasti cs
c) va ri ou s objects
Paper, papi er -m âché, paper artw or k, ti ssue-paper, wa llp aper , stam p collections, manu scri pt s, papy ri , pr in ti ng s, cellu lose ma teri al s
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
-
Not
Not
Not
Not
Not
Fabr ic, veils, dr aper y, carp ets, fabr ic tapestry, arras, silk , costum es, dr esses, reli gi ou s vestme nt s, natu ral fi br e ma teri al s, sisal, ju te
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
Not
Not
Not
-
Not
Not
Not
Not
Not
Herbaria and bo tani cal collections
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
-
Not
Not
Ento mo logi cal collections
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
Not
0.
Not
0.5
Not
0.5
Not
Water- colour s, dr awin gs, pastel s
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.
Not
0.5
Not
0.5
Not
E thn ograph ic collections, ma sks, leather, leather cl ot hes
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.
Not
0.5
Not
0.5
Not
Pain ti ng on canv as, oi l painti ng on cl ot h and canv as, temp era, goua ches
Not
Not
Not
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Not
Not
-
Not
0.1
Not
0.1
Not
B ook s of gr eat value, leather- boun d book s, leather bi nd ings, parchm ent, mi ni atur es
Not
Not
Not
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Not
-
-
Not
0.1
Not
0.1
Not
L acquer, in laid, decorated or lacquer furn it ur e
Not
-
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.
-
0.5
Not
0.5
-
Poly chroma ti c wo od carv ings, pain ted wood , painti ng s on wo od , icon s, wood pend ul um -clock s, wo od mu sical in stru ment s
Not
-
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.
-
0.5
Not
0.5
-
Un painted wo od carv in gs, wi ck er wo rk , wo od or bark panels
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
-
0.4
Not
0.5
Not
0.5
Not
Ston es, rock s, or e and stable (por ou s) me teor it es
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
Not
0.4
Not
0.5
Not
0.5
Not
Ston e mo saics, ston es, rock s, or e, me teor it es (non po rous), fossils and ston e collections
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
16
No t
Not
0.4
Not
0.5
Not
0.5
Not
Gypsum and pl aster
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
-
Not
Not
Un stable, ir idescent and sensit iv e gl ass, sensit iv e gl ass mo saics
Not
Not
-
Not
-
-
Not
-
-
-
-
Not
Not
-
Not
-
-
Not
Not
Not
Not
-
-
-
0.4
0,4
0.4
-
-
0.4
0.4
0.4
0.4
0.4
-
-
1.0
-
0.4
-
0.4
-
Dr y mu rals (detached)
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
Not
Not
-
-
Not
Not
Not
Not
Not
Iv or ies, horn s, ma lacologi cal collections, eggs , nests, corals
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
Not
0.4
Not
0.5
Not
0.5
Not
Phon ograph ic R ecords
Not
Not
-
Not
Not
Not
Not
Not
Not
Not
Not
Not
Not
-
Not
-
Not
Not
Not
Not
Not
Man- ma de fi br es
Not
Not
Not
0.5
0.5
0.5
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Not
Not
0.4
Not
0.5
Not
0.5
Not
Plasti cs
Not
Not
Not
Not
Not
Not
Not
Not
-
-
Not
Not
Not
Not
Not
-
Not
Not
Not
Not
Not
Mu rals, fr escoes, sino pi te (detached)
c) vari ou s objects
b) inor ga ni c ma teri al s/ob jects
Paper, papi er-m âché, paper artw or k, ti ssuepaper, wa ll paper, stamp coll ecti on s, ma nu scri pt s, papy ri , pr inti ng s, cell ul ose mate ri al s b) inor ga ni c ma teri al s/ ob jects
a) Or ga ni c ma teri al s/ob jects
a) Or ga ni c ma teri al s/ob jects
Summer season (basic conditions: 1.2 met, 0.5 clo, 0.2 m/s). ‘‘Not’’: denotes not common areas between people’s comfort and works of art saving.
134
M. La Gennusa et al. / Journal of Cultural Heritage 9 (2008) 125e134
Table 8 refers to winter conditions while Table 9 refers to summer conditions. In each row, the darkest shading of the cells underlines the condition where the greater common area is found, thereby ensuring more effective management of indoor spaces. It is important to note that seasonal conditions are taken into account not only according to variations in external environmental data but also by varying the personal parameters relating to people. It is clear that the inclusion of one cultural artifact to another in the same exhibition space dramatically reduces the extension of the overlapping area where the indoor environment may be more easily controlled. For example, Table 8 indicates that the common area in winter between people’s comfort and the preservation of paper artwork is only 8% (the first column in Table 8) of the total area where the artwork is preserved. Moreover, when material made of natural fibres is included in the same room, the overlapping area decreases to 5% (the second column in Table 8). Table 9 demonstrates the difficulty of obtaining suitable indoor parameters in museums when comfort is included in the control criteria for summer conditions. However, figures similar to those reported in Tables 6 and 7 and the set of data like those contained in Tables 8 and 9 are very useful to indoor environment designers and museum curators. Thus, suitable works of art can be confidently displayed in the same exhibition space. 7. Conclusions The difficulties involved in balancing the requirements for preserving works of art on display in exhibition spaces and the thermal comfort of visitors to these spaces are here outlined. An extensive review of the optimal indoor microclimatic parameters for preserving works of art, as they appear in current Italian standards, has been carried out. Moreover, an analysis of international standards providing conditions of thermal comfort has been performed and applied to the indoor climate of museum buildings. In order to provide technicians and museum curators with easy and reliable tools of analysis, a simultaneousness index has been introduced. This parameter represents the rate of the control surface (in a temperatureerelative humidity diagram), where both requirements have been satisfied. Finally, useful figures have been introduced that graphically report
the shape of surfaces in a temperatureerelative humidity diagram for a given work of art where both requirements have been satisfied. References [1] M. La Gennusa, G. Rizzo, G. Scaccianoce, F. Nicoletti, The control of indoor environments in heritage buildings: experimental measurements in an old Italian museum and proposal of a methodology, J. Cult. Herit. 6 (2005) 147e155. [2] G. Pavlogeorgatos, Environmental parameters in museum, Build. Environ. 38 (2003) 1457e1462. [3] UNI 11120, Cultural Heritage e Field Measurement of the Air Temperature and the Surface Temperature of Objects, UNI e Ente Italiano di Unificazione, Milano, 2004, (in Italian). [4] UNI 11131, Cultural Heritage e Field Measurement of the Air Humidity, UNI e Ente Italiano di Unificazione, Milano, 2005, (in Italian). [5] UNI 10969, Cultural Heritage e General Principles for the Choice and the Control of the Microclimate to Preserve Cultural Heritage in Indoor Environments, UNI e Ente Italiano di Unificazione, Milano, 2002, (in Italian). [6] UNI 10829, Works of Art of Historical Importance. Ambient Conditions for the Conservation. Measurement and Analysis, UNI e Ente Italiano di Unificazione, Milano, 1999, (in Italian). [7] Ministerial Decree 10 May 2001 Ministry for Arts and Culture, Guidelines on Technical-Scientific Criteria for Application of Standards in Museums e Article 150, paragraph 6, Law by Decree n. 112/1998, Italian Republic’s Official Gazette, 19 October 2001, n. 244 (in Italian). [8] ISO 18911, Imaging Materials e Processed Safety Photographic Films e Storage Practices, International Organization for Standardization, Geneva, 2000. [9] ISO 11799, Information and Documentation e Document Storage Requirements for Archive and Library Materials, International Organization for Standardization, Geneva, 2003. [10] ANSI/NISO Z39.79, Environmental Conditions for Exhibiting Library and Archival Materials, National Information Standards Organization, Bethesda, Maryland, USA, 2001. [11] M. Beccali, A. Nucara, G. Rizzo, Thermal comfort, in: Cutler J. Cleveland (Ed.), Encyclopedia of Energy, vol. 6, Elsevier Inc, 2004. [12] P.O. Fanger, Thermal Comfort, Danish Technical Press, Copenhagen, 1970. [13] ISO 7730, Ergonomics of the Thermal Environment e Analytical determination and Interpretation of Thermal Comfort using Calculation of the PMV and PPD Indices and Local Thermal Comfort Criteria, International Organization for Standardization, Geneva, 2005. [14] ANSI/ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, GA, 2004. [15] ISO 7726, Ergonomics of the Thermal Environment e Instruments for Measuring Physical Quantities, International Organization for Standardization, Geneva, 1998.