The BIM approach (Building Information Modelling) is all around Architecture, Engineering and Construction professionals, but when it comes down, very few companies are founding their daily work on this paradigm and applications are really far from being homogeneous. BIM is many times (let’s say “usually”) incorrectly identified as a specific software package or a type of 3D digital model. However, BIM is much more than a newer version of CAD or a 3D visualisation tool.
The BIM approach provides a digital featuring of a building or infrastructure throughout its whole life-cycle, adding extra information to help making better and more-timely decisions upon a 3D model that allows a multidimensional analysis: 4D (evolution); 5D (costs); 6D (sustainability -including energy efficiency-); 7D (maintenance).
Although there is still a lack of knowledge on how BIM and associated digital innovations are applied across European countries, the European Directive 2014/24/EU imposes BIM Level 2 for government centrally procured projects. Level 2 refers a collaborative process of producing federated discipline specific models, consisting of 3D graphical data (those visually represented) and semantic data (those significant additions) as well as associated documentation (for instance: master plans). Information is exchanged using non-proprietary formats, such as Industry Foundation Classes (IFC).
Consequently the built heritage is subject to BIM for the purposes of documentation, conservation and dissemination, but the distinctiveness and sensitivity to meet heritage demands requires technological and methodological particularizations leading to the concept of Heritage-BIM (H-BIM). The purpose of H-BIM is to provide a 3D parametric model as a “container” of information generated all over time by different procedures, by different people, and from different sources (hw & sw). The model would capture the multidisciplinary nature of Heritage, far away from the simplicity and modularity of conventional construction, and would be very useful to study, evaluate the state of conservation and plan interventions on the assets in a profitable way. It is quite a challenge for a sector where digitization is a pending issue.
This technologically means facing many challenges, starting with the minimum amount of graphical and semantic data that would be adequate to support the activities of the sector. Two of the most important are:
The combination of 3D data with different types of images (thermography, high resolution photographs or multispectral recordings) to produce a really useful H-BIM model for exhaustive assessment.
The photorealistic texturing of 3D models for a rigorous representation of reality.
Both aspects are being worked by CARTIF to decisively help companies, managers and public administrations in the digitization of Cultural Heritage.
In two previous posts [When the Historic Buildings Talk (I) and (II) apart from making clear the importance of the conservation of the built heritage as long as describing the environmental factors that influence such conservation, we have already faced the temperature and the humidity as the two key factors to be monitored. Anyway, and in case you forgot about it, there are other aspects that also must be monitored to avoid deteriorations resulting in expensive and time consuming restorations:
Lighting (natural and artificial).
In this post we are going to get involved with lighting, which mainly affects the movable goods that decorate or treasure the historic buildings. Be patient, pollutants are left for the next (and last) delivery.
Illumination can be of natural origin (coming from the sun) or artificial (coming from electrical sources), but in any case is an electromagnetic radiation that covers three ranges: infrared (IR), visible (VIS) and ultraviolet (UV). We usually call “light” the visible part to human eyes. UV radiation has a smaller wavelength than VIS and is the one with the highest associated energy. IR radiation has a longer wavelength than VIS radiation and is less energetic. Both UV and IR radiations are not necessary “to see”, but they do influence the deterioration of the materials.
When a work of art is illuminated, whether it is a painting, a polychrome, a tapestry or a parchment, the whole range of radiation (IR, VIS and UV) is absorbed by the materials of which it is composed. This radiation is associated with energy capable of altering and degrading the molecular structure of many materials, especially the most “perishable”, such as those of organic origin (textiles, pigments, leather and paper).
The UV component (highest energy), is the one with the greatest capacity to alter the materials, disintegrating and weakening, producing their yellowing. The VIS component is able to decolorize the most sensitive pigments. On the other hand, the IR component produces a heating effect that accelerates certain chemical reactions.
Thinking about this, it seems that for the assets we keep in museums, churches, hermitages, castles, palaces, archives and libraries, it would be best to preserve them in the dark. However, for study, conservation, and especially for exhibition purposes, some kind of illumination is required. Following the criteria of the IPCE, which establishes the Spanish National Preventive Conservation Plan (PNCP), these are the parameters to evaluate the risks derived from illumination:
Intensity of artificial and natural sources.
Exposure time to the illumination.
Spectrum (range) of emission of the artificial light sources, knowing if they emit in not-visible radiation bands.
Incidence of natural illumination, its orientation, and whether the radiation is direct or diffuse.
What lighting control measures exist on-site.
In turn, the assessment of the damage caused by lighting must take into account the following aspects:
Since this damage is cumulative, we should flee from high levels of illumination, but maintaining a commitment for adequate vision. By giving concrete values: 50 lux for the most sensitive materials and 150-200 lux for medium-sensitivity cultural assets.
Damage is determined by the amount of illumination, i.e. the intensity of illumination during the time an asset is exposed (lux / h). Thus, keep in mind that the damage in the case of high illumination levels with short exposures would be the same as with low levels and longer exposures.
The degradative effect of lighting also depends on other environmental factors such as humidity and air pollution.
Therefore, where we place our cultural assets, how natural light affects them, and with what kind of lamps we focus on, are critical aspects for their proper conservation (see Figure). CARTIF offers advice and tailored solutions based on a proven experience of more than 20 years in applied research to Cultural Heritage.
In two previous blogs of ‘When the Historic Buildings Talk’ (2)and(3), we have described how does affect and what is the importance of monitoring temperature and humidity as well as lighting (natural and artificial) in historic buildings. To complete this saga of pernicious aspects, the turn to the pollutants is open just now.
We all know, and suffer, that the composition of the air is altered by compounds that come mainly from the use of fuels (road traffic and heating) and industrial activities. These pollutants can trigger chemical reactions in the materials that make up the cultural assets (movable or immovable), degrading them to a greater or lesser extent. The pollutants with the highest concentration in the exterior are sulphur dioxide (SO2), oxides of nitrogen (NOX), ozone (O3) and suspended particles (PM). In addition to these pollutants that “travel free” throughout the air outside the buildings, there are others to be taken into account inside them, such as vapors of organic compounds (COV), products used in conservation and restoration tasks, and even human presence.
Again, we have to ask ourselves: what are their effects? Here it is a short description of the main ones:
SO2 is related to coal combustion and to industrial activities and transportation. It causes metal corrosion, pigment discoloration, weakening of leather and acidification of paper.
Among the NOx, the nitrogen dioxide (NO2) needs to be highlighted. It comes from combustion in vehicles and in industry, and associated effects are the discoloration of pigments and the contribution to the degradation of paper and leather.
The renowned ozone (O3) is naturally present in the stratosphere. This is a good point, because it protects us from malignant solar radiation, but at ground level is linked to road traffic and intense solar radiation. It causes the degradation of natural gums and the discoloration of pigments.
PM are characterized by their diameter, distinguishing between fine particles (PM 2.5: with diameter equal to or less than 2.5 μm), and coarse particles (PM 10: with a diameter between 2.5 μm and 10 μm –keep in mind that 1 μm is one-millionth of a meter-). The fine ones affect the discoloration and dirt of the surfaces. On the other hand, coarse ones contain highly reactive compounds (e.g. residues from incomplete combustion of road traffic). The dust enters this section: apart from its obvious aesthetic impact (denotes sloppiness and lack of care) can lead to chemical deterioration, and can serve as a habitat for insects (do you get bit?…)
In general, the study of outdoors pollution is more developed and legislated than the indoors one. However, in the field of Cultural Heritage, the study of indoor air quality is very important because of the logical conservation demands. Following once again the criteria of the IPCE, which establishes the Spanish National Preventive Conservation Plan (PNCP), these are the evaluation parameters of the risks derived from the pollution to which the historic buildings are exposed:
Medium where the cultural asset is located (rural, urban, industrial, coastal, etc.).
Polluting sources nearby, whether of anthropogenic origin (industrial and transport processes) or of natural origin (volcanoes, fires, sea water, animal life, vegetation, etc.).
Meteorological factors such as winds and precipitations that influence the dispersion and deposition of pollutants.
Sources of indoor pollution.
Quality of the external air and location of the asset in relation to the exterior.
Waterproofing of the building, its compartments and furniture.
Distribution of pollutants by air circulation.
Already existing air conditioning, heating and ventilation facilities, as well as their use and maintenance.
And, these are the criteria that must be taken into account for the assessment of the deterioration produced by the pollutants:
The pollution damage is cumulative, so very low limits needs to be set depending on the detection ability of available devices.
The damage is determined by the dose, i.e. the concentration of the contaminant (in μg/m3 or parts per billion -pbb-) by the exposure time. This exposure time is conveniently estimated to take into account the overall effect.
Keep in mind the mutual influence between pollution and other already known factors, such as humidity and lighting.
In conclusion, the air quality inside and / or outside the built heritage defines its conservation (see Figure). Let me remind you again that CARTIF is ready to advise you, to help you and to offer solutions tailored to your needs. You can have a look to some projects: RESCATAME, SHCITY and EQUINOX. We have been innovating in Natural and Cultural Heritage for more than 20 years. At your disposal!
In a previous post the social and economic importance of heritage conservation were already described. Also we promised that on successive posts we will go into more detail describing the three main aspects that need to be monitored to ensure such conservation. Refreshing your memory, they were:
Relative humidity and temperature.
Lighting (natural and artificial).
As promised is debt, in this post we will focus on the first point (be patient, we will talk about others further on), which makes us to face the heritage “bad boys”. Relative humidity and temperature are very damaging in the effects they can cause on the materials of which historic buildings are made of. Taking advantage of Physics, relative humidity is a very useful indicator of the water content in the air (vapour), and, on the other hand, temperature indicates the level of kinetic energy (movement) of the molecules of the air.
Both parameters vary according to the local meteorological conditions, the human actions and the conservation state of the historical buildings. This means that the atmosphere surrounding the historical buildings consist of a greater or lesser amount of water vapour at a certain temperature, definitely influencing the physical & chemical stability of the materials of which they are built on, or even of which the objects inside are composed.
In this sense, it is not negligible the effect caused by people, not only by our increasingly demanding comfort requirements, but by the number of visitors. We can influence the relative humidity and the temperature in such a way that inadequate values are reached. The effects of people are added to those of the local climate (more or less wet or warm), to the assets by itself (watertightness and ventilation capacity), to the derivatives of the proximity of heat sources (heating, sunny glass surfaces, old artificial lighting systems), the proximity of cold sources (external walls or air conditioning systems), as well as sources of humidity (leaks and floods).
The main factor to be controlled because the risk of direct deterioration that could originate is just humidity. The amount of water vapour in the air results in dimensional changes such as the well-known expansion and contraction of wood, making fractures and cracks when strong fluctuations happen. In addition, extreme relative humidity values cause softening or drying of organic materials such as adhesives and binders. But it also affects the stability of inorganic materials, such as metals, accelerating the corrosion processes, especially in the presence of salts. In poorly ventilation and dirty conditions, high values of relative humidity will cause the proliferation of living organisms causing biodeterioration (from microorganisms to rodents … Disgusting!). Even health problems as shown in the image.
Conversely, the temperature accelerates the chemical reactions and favours the biological activity. It contributes to the softening of waxes and adhesives and the loss of adhesion between different materials, such as enamels.
Perhaps reading all this causes some discomfort (and even itching …). But, what can we do to prevent these adverse effects? The answer is as simple as reasonable: just avoiding too high or too low levels of temperature and relative humidity, ensuring the highest possible stability
Following the indications of the IPCE (Spanish Cultural Heritage Institute, dependent on the Ministry of Culture), which establishes the National Preventive Conservation Plan (PNCP), the evaluation of risks derived from the microclimatic factors of which we are talking about, three aspects must be monitored:
Extreme levels of relative humidity and air temperature.
The magnitude and speed of fluctuations in relative humidity and air temperature.
The proximity of sources of humidity and heating or cooling emission sources.
A wide range of sensors is available on the market to monitor temperature and humidity, either continuously or timely (see image). Indeed, it is necessary to know how to properly treat, interpret and integrate the data they provide.
What is not so frequent is using alternative methods to evaluate the effects of moisture on the materials of the built heritage. Even before these appear and the remedy is worse than the disease. CARTIF is a pioneer in the use of laser scanners to make this assessment. A recent article published in the prestigious international journal Studies in Conservation, together with the developments carried out for the European research project INCEPTION show that while 3D documenting a historical building, the level of humidity present in a known type of material could be registered in parallel. A trustworthy 2×1 to take into account in the minimum conservation expenditure times we live in. The cloister of the Cathedral of Ciudad Rodrigo (Salamanca, Spain) has been the choice for on-site validations.
An important example that gives account of the scope of applied research in cultural heritage by a technology centre within a sector where it still takes more than expected that not so new technologies to be of daily use.
I agree on speaking about cultural heritage as a touristic resource is disappointing when heritage is properly identified as integrator item and a completely intangible social identifier, but also certainly is an economic resource and just making cash its sustainability is ensured. This is the way to fix and create thousands of jobs, which in turn reinforce the character of social backbone that heritage is by itself, even allowing to improve the citizens’ quality of life.
Making sure the protection and the preservation of our built heritage is, today, more urgent than ever. Not only as “prey” of cultural tourism, and not only as a brand of territory (including citizens), but because of their vulnerability to pollution, climate change and socio-economic pressures. We all get sick from time to time and we know it is always better to prevent than cure. The same happens to the built heritage: it is as much desirable as important to have automated systems that continuously tell us how the built heritage is, preventing “ills” just before they are such as expensive as irreparable. It is somewhat comparable to doctor’s auscultation, but what do we need listening to? In the technical jargon we say “monitoring” and many types of sensors are used to, but three aspects are mainly registered:
The temperature and relative humidity. Both are always linked (in fact they are inverse). Any kind of heritage building has greater or lesser water content in the air at a given temperature, having a decisive influence on the physical-chemical stability of the materials they are made of. Inadequate conditions of temperature and humidity produce deformation and rupture; rust and corrosion; as well as bio-deterioration (emergence of organisms).
Natural and artificial lighting. the Sun, or electric sources are electromagnetic radiation mainly covering the ultraviolet (UV), visible (VIS) and infrared (IR) ranges. Together they cause photo-degradation (discoloration) and temperature increases, especially in the case of organic materials (paintings, textiles, books and documents).
Pollutants. The air composition and quality are altered by compounds that mostly come from the use of fossil fuels (road traffic, heating of buildings and industrial activities). These compounds are able to make chemical reactions that affect the materials causing corrosion; spots and coatings; and also bio-deterioration.
These parameters will be particularly broken in subsequent posts.
In any case, the role of technological centres as CARTIF is decisive to take step forward in the technical developments required so that monitoring can be done affordably and fully compatible with the aesthetics and functionality of the building. Relevant international projects on this regard where CARTIF is playing a major role are:
After Italy and recently China, Spain is the country that holds the largest number of human heritage sites. We are also a first order world tourist destination, with a yearly increasing cultural component. Playing at home, Castilla y León accounts for 60% of the Spanish heritage… Do we take the fingers out?
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