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Preventive conservation of works of art in historic buildings: assessment and modelling
Abstract
Most of the degradation of works of art in historic buildings is caused by unfavourable indoor climate conditions. The most important works of art receive invasive conservation treatment, called direct action, but this treatment is very expensive. To avoid invasive conservation treatments and ensure that works of art are protected for now and for the future, indirect action to mitigate the deterioration process is strongly advised. This holds that exposure to unfavourable indoor climate conditions should be avoided, as far as is compatible with its social use. To improve the indoor climate of the historic building, adaptations to the building or its systems are often necessary. Building performance simulation may be used in predicting the effect of a retrofitting strategy on the indoor climate, and in designing the adaptations to the building. In a previous project (FWO G.0420.05), a coupled 3D-HAM-CFD-model has been developed which predicts the local temperature and relative humidity variations of the indoor air as well as the hygrothermal interaction with hygroscopic materials like sculpture, panel paintings, books,…. Although these results are useful to evaluate the risk of moisture related damage, evaluating the indoor climate of an entire building with CFD is very time-consuming because of the computational cost, certainly if a long time period has to be analysed. Furthermore, besides evaluating preservation conditions, also other criteria, like annual energy use and comfort criteria are of interest. In this case Building Energy Simulation (BES) methods are more appropriate as they are able to simulate the indoor climate dynamics of the whole building for a long time span relatively fast. This allows to simulate, analyse and compare multiple retrofitting strategies and define the most ‘optimal’ solution. To assess the preservation conditions properly, it is necessary to take typical conditions in monumental historical buildings into account in the simulation study. In this work, the main focus is placed on the presence of moisture in heavy building walls and the occurrence of hygrothermal gradients (stratification) in the often very large interior volumes due to the limited control by (older) climate installation system. This PhD-dissertation, part of FWO-project G.0448.10, aims at developing a simulation strategy to estimate the predicted risk for works of art, taking into account these typical boundary conditions of an historical building. The emphasis lies on developing a fast calculating modelling approach intended for practical use.
... Not all methods are directly used within these preservation metrics. This table was compiled by Lien de Backer as part of her doctoral thesis(De Backer 2018) ...
Preservation metrics are used to estimate the risk of probable damage to an object or collection in relation to an institution's indoor climate, by translating a temperature and relative humidity dataset into an expression of risk/probabilities of material change, be it temporary or permanent. The types of material change considered are mechanical (e.g. cracks, deformation, swelling and shrinking), chemical (e.g. oxidation, colour changes and material decay) and biological (mould growth). The series of consecutive calculations that make up a preservation metric express what the change to a theoretical object or collection might be. This paper focuses on the differences between these calculations and their impact on the interpretation of the results.
Buildings are high-energy consumers. In warm and humid climates, it is mainly due to artificial conditioning. The problem being addressed in the present chapter is how to reduce the energy demand for air conditioning in homes with tourist accommodation, taking as case study traditional one-storey buildings in El Vedado, a “garden city” urbanization in Havana. Design variables and strategies for energy retrofit of these buildings in warm and humid urban contexts are defined and discussed in the theoretical framework. A theoretical model of a house with central corridor is made, as well as the parametric models of four types of the immediate context to be used for the evaluation of the indoor thermal environment and energy consumption by dynamic simulations. The monitoring results of one case were taken as the basis to calibrate the input data for simulation with the software EnergyPlus. Once calibrated and validated, the starting situation, possible actions and design solutions proposed for energy retrofit were evaluated. Proposed actions would permit to reduce energy consumption by air conditioning and to verify several criteria and theoretical inaccuracies with respect to the thermal and energy behaviour of these traditional historical buildings (100 years old).
COMSOL Multiphysics was used to model the moisture uptake and release for library and archival collections in response to variations of temperature and relative humidity (RH) in their environment. These results were coupled to the modelling of indoor climate and energy consumption in collection storage spaces with the use of the WUFI®Plus software. The study revealed the crucial impact of air-tightness of the building on the indoor climate stability and the humidification and dehumidification loads required to provide selected climate control classes. In the adequately airtight storage spaces, sizeable paper collections were found to diminish the energy consumption by at least 22%. For the 'cool storage' conditions, optimal for the preservation of library and archival materials, the impact of the collection on the energy consumption was reduced due to high average RH levels which required considerable dehumidification year round.
Accelerated ageing experiments have been used to identify the critical deterioration factors for silk. These have shown the role of humidity to be more important than previously thought. Monitoring of environmental conditions behind tapestries has identified the formation of high humidity microclimates. High humidity levels may be the reason for the poor condition of sampled unfaded silks. The accelerated ageing results have been used to make preventive conservation recommendations and plot preliminary isoperms for silk deterioration. The use of these tools to improve display environments within mixed collections in historic houses is discussed.
The preservation of early Netherlandish panel paintings gets a lot of attention as they are an important part of the cultural heritage of the lower countries. Indoor humidity fluctuations are the main cause for mechanical damage of these artworks. To estimate the risk of mechanical damage, the intention of the authors is to model the moisture transport in the artwork related to a simulated indoor climate. Because the hygrothermal response of the panel is controlled by the vapour permeability of the wood and the barrier effect of different material layers on top and on the back of the wooden panel, hygric material characteristics of all layers are needed to perform reliable simulations of the local moisture content gradients in the object. In the literature, several values were presented which were used to model the mechanical behaviour of the panel painting. The driving potential in these studies is the moisture content of wood. However, for the coupling of a HAM tool, which predicts the moisture transport in the object, with other simulation tools (BES, CFD, etc.), it is more straightforward using one unique and material-independent driving potential in both tools, such as vapour pressure. The conversion of characteristics presented in the literature using vapour pressure instead of moisture content is not straightforward as information about converting the characteristics is missing. Another difficulty is that the obtained quantitative results in the literature are valid for a specific application method. Consequently, it is disputable whether these characteristics may be applied to early Netherlandish panel paintings. Therefore, the main goal of this study is to measure the moisture properties of early Netherlandish panel paintings. The desired characteristics were determined using inverse modelling of a 1D moisture transport and finding the best fit between the calculated diffusion process and the measurements.
This paper describes a coupled dynamic simulation of indoor environment with HVAC
systems, controls and building envelope heat transfer. The coupled simulation can be
used for the design and control of ventilation systems with stratified air distributions.
Those systems are commonly used to reduce building energy consumption while
improving the indoor environment quality. The indoor environment was simulated using
the fast fluid dynamics (FFD) simulation program. The building fabric heat transfer,
HVAC and control system were modelled using the Modelica Buildings library. After
presenting the concept, the mathematical algorithm and the implementation of the
coupled simulation were introduced. The coupled FFD-Modelica simulation was then
evaluated using three examples of room ventilation with complex flow distributions
with and without feedback control. Further research and development needs were also
discussed.
The early history of preventive conservation is characterized by the progressive integration of science into the museum world and the strengthening of collaboration between curators, conservators and scientists. This article traces the development of this discipline in Great Britain and in the United States, examining the role played by museum controversies, public debates, and pre- and post-war efforts, between 1850 and 1950.
The Conduction Transfer Function (CTF) method is used by many building energy performance simulation programs to calculate 1-D transient heat conduction through multi-layer envelope components. TRNSYS is one of these programs, and several authors have reported problems with the current CTF implementation in its multizone building model, known as Type 56. Reported problems are related to heavy and highly insulated slabs and short time-step simulations (less than 15-minute time-step). This paper documents the current implementation of CTF in Type 56. It then reports on our investigation of some issues with the current implementation and their causes. Workarounds and short-term solutions are assessed and longer-term improvements are discussed.
Knowledge on moisture transport in wood is important for understanding its utilization, durability and product quality. Moisture transport processes in wood can be studied by Nuclear Magnetic Resonance (NMR) imaging. By combining NMR imaging with relaxometry, the state of water within wood can be identified, i.e. water bound to the cell wall, and free water in the cell lumen/vessel. This paper presents how the transport of water can be monitored and quantified in terms of bound and free water during water uptake and drying. Three types of wood from softwood to hardwood were selected covering a range of low to high density wood; pine sapwood and oak and teak. A calibration is performed to determine the different water states in each different wood type and to convert the NMR signal into moisture content. For all wood types, water transport appeared to be internally limited during both uptake and drying. In case of water uptake, free water was observed only after the cell walls were saturated with bound water. In case of drying, the loss of bound water starts only after vanishing of free water, irrespective of the position. Obviously, there is always a local thermodynamic equilibrium of bound and free water for both uptake and drying. Finally, we determined the effective diffusion coefficient (Deff). Experimentally determined diffusion constants were compared with those derived by the diffusion models for conceptual understanding of transport mechanism. We found that diffusion in the cell wall fibers plays a critical role in the transport process.
Old medieval churches hold objects of great historical and cultural value: organs, altars, paintings. But they have no systems for indoor climate control or the church may be heated only at services. These conditions are inadequate for the preservation of cultural heritage. The objective of this paper is to assess an adaptive ventilation (AV) solution in a church for reduction of the relative humidity (RH) in an unheated church to prevent mould growth and disintegration of wooden parts. The operation principle of the system is to ensure ventilation in the church when water vapour content in the outdoor air is lower than that indoors, to lower the RH in the church. A case study in Hangvar Church in Gotland, Sweden, was conducted to test the performance of AV to reduce the RH in the church. Field measurements showed that AV has a positive impact on the indoor RH of the church. During the measurement period without climate control, the RH in the church was higher than 70% of 98% of the time; with AV, the indoor RH was higher than 70% only 78% of the time. Building simulation was carried out to test the performance and energy consumption of AV under different conditions. The simulations showed that auxiliary heating and airflow rate both have high impact on the system performance. The higher the heating power, the more effective the system is; thus, lower airflow rates are needed. Infiltration has also high impact on the system performance: the lower the infiltration rate, the better the AV performance is.
A calibrated building simulation model was developed to assess the energy performance of a large historic research building. The complexity of space functions and operational conditions with limited availability of energy meters makes it hard to understand the end-used energy consumption in detail and to identify appropriate retrofitting options for reducing energy consumption and greenhouse gas (GHG) emissions. An energy simulation model was developed to study the energy usage patterns not only at a building level, but also of the internal thermal zones, and system operations. The model was validated using site measurements of energy usage and a detailed audit of the internal load conditions, system operation, and space programs to minimize the discrepancy between the documented status and actual operational conditions. Based on the results of the calibrated model and end-used energy consumption, the study proposed potential energy conservation measures (ECMs) for the building envelope, HVAC system operational methods, and system replacement. It also evaluated each ECM from the perspective of both energy and utility cost saving potentials to help retrofitting plan decision making. The study shows that the energy consumption of the building was highly dominated by the thermal requirements of laboratory spaces. Among other ECMs the demand management option of overriding the setpoint temperature is the most cost effective measure.
High levels of humidity in buildings lead to building pathologies. Moisture also has an impact on the indoor air quality and the hygrothermal comfort of the building’s occupants. To better assess these pathologies, it is necessary to take into account the heat and moisture transfer between the building envelope and its indoor ambience. In this work, a new methodology was developed to predict the overall behavior of buildings, which combines two simulation tools: COMSOL Multiphysics© and TRNSYS. The first software is used for the modeling of heat, air and moisture transfer in multilayer porous walls (HAM model: Heat, Air and Moisture transfer), and the second is used to simulate the hygrothermal behavior of the building (BES model: Building Energy Simulation). The combined software applications dynamically solve the mass and energy conservation equations of the two physical models. The HAM-BES coupling efficiency was verified. In this paper, the use of a coupled (HAM-BES) co-simulation for the prediction of the hygrothermal behavior of building envelopes is discussed. Furthermore, the effect of the 2D HAM modeling on relative humidity variations within the building ambience is shown. The results confirm the importance of the HAM modeling in the envelope on the hygrothermal behavior and energy demand of buildings.
Nowadays, one of the largest challenges of museums is to achieve sustainability by reducing costs and energy demands without jeopardizing conservation and thermal comfort. The evolution of science seems to show a new trend with the application of less stringent targets, but after more than one century of research in the museum environment field there is still not a consensus. The test of the published risk-assessment and optimization tools in real cases assumes therefore a fundamental role for the change of the approach.
The current work uses data recorded along one year in a Portuguese national museum to test the application of a sequential process to classify the indoor microclimate in terms of HVAC efficiency, risk of damage and thermal comfort, in an attempt to reach a balance between conservation needs, thermal comfort and energy reduction by the climate optimization. A set of three rooms (2 equipped with HVAC system, and the other without control system) was used.
The optimization process was carried out to limit the risk of damage by limiting the RH fluctuation with the use of a dynamic method (FCT-UNL) based on the past climate and limiting the T to maximize the thermal comfort of the visitors. New targets were achieved, allowing to replace the original set-point of 20–22 °C and 50–60% by new values evidencing the high potential of energy reduction due to less demanding impositions.
Keywords: Museum; Preventive conservation; Risk-assessment; HVAC effectiveness; Thermal-comfort; Museum climate optimization
Painted wood is a multi-layer structure composed of materials which swell or shrink differently in response to the sorption and desorption of moisture. The allowable levels of strain of the gesso layer were determined experimentally by subjecting specimens imitating historic panel paintings to mechanical stretching, and monitoring the development of cracks. These strain values were translated into the magnitudes of cyclic RH fluctuations allowable for unrestrained panel paintings, which depend on cycle duration, panel thickness and the configuration of moisture exchange by a panel with the environment. Panel paintings do not respond significantly to diurnal or shorter fluctuations irrespective of the panel thickness. The panels respond more and more significantly when the duration of the fluctuations increases until the panel fully responds to each cycle. The approach to calculate the accumulated fatigue damage from real-world climatic variations being combinations of climatic cycles of various duration and amplitudes was demonstrated
Moisture management has an important impact on building performance and durability. Problems caused by moisture and moisture transport in buildings are numerous. Rising damp, interstitial condensation and rain penetration are only a few phenomena that cause damage to occur in and on the building envelope. Possible moisture related damage phenomena are mould growth, material degradation by freeze-thaw cycles, wood rot, corrosion, etc…
For some of these moisture related problems, the interaction between the porous building material and the surrounding air has a significant impact. Therefore the current research focusses on the heat and moisture transport in porous building materials and the interaction with transport in the surrounding air.
To better understand the occurring phenomena when convection in the air is present and to avoid moisture related problems from the design stage there is a strong need for accurate modelling tools.
Currently several simulation tools are available but only a few allow a simultaneous and accurate modelling of convective heat and moisture transport in the air.
Therefore a new model was developed which is able to solve the coupled heat and moisture transport in air and porous materials for 2- and 3-dimensional problems. This model was extensively verified and validated both with data from literature and with new experimental data. It was concluded that the model agrees well with measurements.
A case study on a ventilated cavity wall clearly shows the abilities of the newly developed model. With the new model it is now possible to study temperature and moisture distribution in the cavity wall both in space and in time.
Conduction Transfer Function (CTF) and Finite Difference (FD) based numerical methods, are widely used to calculate transient heat conduction in Building Performance Simulation tools (BPSts). The first method is still preferred, when linear system are modelled, to the second one, thanks to the small computational time required during the simulation. However, current BPSts have not yet implemented effective warning messages to stop their “costumers” when these methods are misused. In this article, those methods are compared in terms of computational time and accuracy, with the aim of identifying selection criteria based on the specific addressed problem.
The OLV Hemelvaart church in Watervliet dates back from the 16th century and contains valuable panel paintings and wooden artefacts. They need to be preserved in a stable conservation climate. However, due to the old air heating system, the indoor climate is not stable at all. The air heating system creates sudden strong rises in temperature and due to the position of the supply and extraction grilles, the warm air is not evenly distributed throughout the church. Furthermore, the church suffers from moisture problems such as rain penetration and rising damp. In view of improvement measures to the heating system, from March 2012 to March 2014, the temperature and relative humidity was measured on different locations in the church. The ASHRAE conservation classes were used to analyze the data. Both a frequency analysis and an analysis of the short term and seasonal fluctuations of temperature and relative humidity were performed.
Building thermal mass is a key parameter defining the ability of a building to mitigate inside temperature variations and to maintain a better thermal comfort. Increasing the thermal mass of a lightweight building can be achieved by using Phase Change Materials (PCMs). These materials offer a high energy storage capacity (using latent energy) and a nearly constant temperature phase change. They can be integrated conveniently in net-zero energy buildings. The current interest for these buildings and for better power demand management strategies requires accurate transient simulation of heavy and highly insulated slabs or walls with short time-steps (lower than or equal to 5 minutes). This represents a challenge for codes that were mainly developed for yearly energy load calculations with a time-step of 1 hour. It is the case of the TRNSYS building model (called Type 56) which presents limitations when modeling heavy and highly insulated slabs with short time-steps. These limitations come from the method used by TRNSYS for modeling conduction heat transfer through walls which is known as the Conduction Transfer Function (CTF) method. In particular, problems have been identified in the generation of CTF coefficients used to model the walls thermal response. This method is also unable to define layers with variable thermophysical properties, as displayed by PCMs. PCM modeling is further hindered by the limited information provided by manufacturers: physical properties are often incomplete or incorrect. Finally, current models are unable to represent the whole complexity of PCM thermal behavior: they rarely include different properties for melting and solidification (hysteresis); they sometimes take into account variable thermal conductivity; but they never model subcooling effects. All these challenges are tackled in this thesis and solutions are proposed. The first part (chapter 4) focuses on improving the CTF method in TRNSYS through state-space modeling, significantly decreasing the achievable time-steps. A complete solution to this issue can be reached by implementing in TRNSYS a wall model using a finite-difference method and coupling it with the CTF method in Type 56 (chapter 5). The second part (chapter 6) proposes an in-depth characterization of thermophysical properties of a PCM used in different test-benches, i.e. the density (Appendix A), the thermal conductivity (Appendix B) and the thermal capacity.
Considerable research has been undertaken to measure and characterize the mass convective surface resistance of wood, with particular emphasis on conditions below the fiber saturation point. While the effects of air velocity and wood moisture content have been demonstrated, the influence of other critical factors such as wood specific gravity, surface condition, and specimen size have not been evaluated. Results obtained by several investigators indicate little agreement between them with a wide range of coefficients whose values are a small fraction of those calculated from the classical equations that have been successfully applied to drying from moist surfaces. The low coefficients in the hygroscopic range indicate that surface resistance can add significantly to the energy consumption during drying. Therefore, a better understanding of the convection losses of dry hygroscopic materials such as wood may offer the opportunity of more effective optimization of drying conditions.
Offering readers essential insights into the relationship between ancient buildings, their original and current indoor microclimates, this book details how the (generally) virtuous relationship between buildings and their typical microclimate changed due to the introduction of new heating, ventilation, and air conditioning (HVAC) systems in historic buildings.
The new approach to the study of their Historic Indoor Microclimate (HIM) put forward in this book is an essential component to monitoring and evaluating building and artefact conservation. Highlighting the advantages of adopting an indoor microclimatic approach to the preservation of existing historic materials by studying the original conditions of the buildings, the book proposes a new methodology linking the preservation/restoration of the historic indoor microclimate with diachronic analysis for the optimal preservation of historic buildings. Further, it discusses a number of frequently overlook
ed topics, such as the simple and well-coordinated opening and closing of windows (an example extracted from a real case study).
In turn, the authors elaborate the concept of an Historic Indoor Microclimate (HIM) based on “Original Indoor Microclimate” (OIM), which proves useful in identifying the optimal conditions for preserving the materials that make up historic buildings.
The book’s main goal is to draw attention to the advantages of an indoor microclimatic approach to the preservation of existing historic materials/manufacture, by studying the original conditions of the buildings. The introduction of new systems in historic buildings not only has a direct traumatic effect on the actual building and its components, but also radically changes one of its vital immaterial elements: the Indoor Microclimate.
Architects, restorers and engineers will find that the book addresses the monitoring of the i
ndoor microclimate in selected historic buildings that have managed to retain their original state due to the absence of new HVAC systems, and reflects on the advantages of a renewed attention to these aspects.
Please find the whole thesis in the link below:
http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-24612
Climate induced damage in decorated oak wooden panels is considered to be a high risk for the preeminent museum collections. To advise museums on the development of future sustainable preservation strategies and to define rational guidelines for indoor climate specifications, climate induced physical and mechanical damage has been analysed in a collection study, experimental testing of mock-ups and by finite element modelling . The collection study consisted of the development of a comprehensive methodology to select objects of interest from the collection and analyse their condition using a combination of visual inspection and archival searches. Mock-up samples of wooden panels with representative structural elements were exposed to varying climate conditions in climate controlled rooms and monitored with state-of-the-art experimental mechanics equipment. Further the collection study and experimental testing were used to inform the development of a finite element model of crack growth under 3-point bending. The work was performed within the Cimate4Wood project, a multidisciplinary collaboration between conservators and scientists work. The paper presents the methodology of the museum study and results from the museum study, experimental testing and modelling.
Due to an uncontrolled indoor climate or a poorly designed climate system, the environmental conditions in historical buildings are often suboptimal for the preservation of works of art. This is also the case for Jan and Hubert Van Eyck's Ghent altarpiece, which is located in one of the chapels of the Saint Bavo Cathedral in Ghent, Belgium. Years of poor conservation conditions have led to an urgent conservation treatment in 2010 and a conservation and restoration campaign that started in 2012 and will continue through 2019. In order to contribute to a better understanding of the state of preservation of the altarpiece and the display conditions and to assess damage risks related to the current location, this paper presents the results of a two-year monitoring campaign of the climate conditions in the glass cage in the Saint Bavo Cathedral in which the altarpiece is displayed. Based on the results of the first year, measures were taken to improve the indoor climate, including the installation of a local heating and humidification system. These new conditions were monitored during the second year of the measurement campaign and are representative for the display conditions today. The results of the second year showed that exposure to high humidity's was effectively reduced but conditions with large short-term humidity variations still occurred. However, given a correct management of the new heating and humidification systems, risks for mechanical damage may be largely eliminated.
Building energy design is currently going through a period of major changes. One key factor of this is the adoption of net-zero energy as a long term goal for new buildings in most developed countries. To achieve this goal a lot of research is needed to accumulate knowledge and to utilize it in practical applications. In this book, accomplished international experts present advanced modeling techniques as well as in-depth case studies in order to aid designers in optimally using simulation tools for net-zero energy building design. The strategies and technologies discussed in this book are, however, also applicable for the design of energy-plus buildings. This book was facilitated by International Energy Agency's Solar Heating and Cooling (SHC) Programs and the Energy in Buildings and Communities (EBC) Programs through the joint SHC Task 40/EBC Annex 52: Towards Net Zero Energy Solar Buildings R&D collaboration. After presenting the fundamental concepts, design strategies, and technologies required to achieve net-zero energy in buildings, the book discusses different design processes and tools to support the design of net-zero energy buildings (NZEBs). A substantial chapter reports on four diverse NZEBs that have been operating for at least two years. These case studies are extremely high quality because they all have high resolution measured data and the authors were intimately involved in all of them from conception to operating. By comparing the projections made using the respective design tools with the actual performance data, successful (and unsuccessful) design techniques and processes, design and simulation tools, and technologies are identified. Written by both academics and practitioners (building designers) and by North Americans as well as Europeans, this book provides a very broad perspective. It includes a detailed description of design processes and a list of appropriate tools for each design phase, plus methods for parametric analysis and mathematical optimization. It is a guideline for building designers that draws from both the profound theoretical background and the vast practical experience of the authors.
The correct simulation of energy needs for heating, ventilation, and air conditioning of the rooms of a museum is strictly correlated to the estimation of internal loads deriving from the presence of visitors, who are responsible for both sensible and latent gains. However, visitors’ profiles on short time scales (e.g., 15 minutes) in museum rooms are often not available data. In this work, we present a correlation between the statistical distribution of visitors’ presence in the main exhibition rooms of a museum and the profile of sold tickets, which is usually readily accessible. We apply the procedure to a real museum, using the results of a monitoring campaign for the best-fitting of the correlation curves and for the validation of the model. The fitting curves are the superposition of three Gaussian distributions, where daily and weekly peaks are taken into account. Each distribution refers to a period of the day (late morning/early afternoon, afternoon, and late afternoon), and has a standard deviation obtained by a best-fit procedure, and an integral corresponding to the sum of the sold tickets in its specific period of the day. The model is validated comparing monitored data of temperature and specific humidity in the rooms with the results of a dynamic simulation, run on TRNSYS 17, using the modeled correlation. By means of this validated model, energy-saving measures on the examined museum can be reliably simulated. At the same time, it is reasonable to assume that the same method could be applicable to other buildings with similar occupancy (e.g., galleries, exhibitions).
It is widely believed that smart metering will lead to high power savings. Those practices rely on Non-intrusive Appliance Load Monitoring (NIALM) methodologies. In this work an extension of NIALM to thermal loads is proposed: Non-intrusive Thermal Load Monitoring (NITLM). NIALM and NITLM share the same key point: a good model to calibrate loads. Thermal loads calibration is, at present, a task far from trivial.
This paper addresses the set of measurements required to calibrate Building Energy Simulation (BES) models. This set is found by sensitivity analysis. Weather variables together with indoors air and surface temperatures form a complete set of non-intrusive measurements for free running BES calibration. Adding non-intrusive measurements such as indoors CO2 concentration and door/window is required to validate BES under regular operation conditions.
The proposed NITLM methodology validity is verified on two real-world buildings in different locations. From a complete year of measurements a BES model is validated and calibrated in both buildings for heating and cooling periods. Validity of the model is cross-checked by identifying thermal properties of the fabric and mechanical air exchange rate.
Some NITLM applications are addressed and future work to extend NITLM applicability in real cases is pointed out. As example, simulation design hypothesis are checked for one building. It is shown that thermal load estimation can deviate up to three times depending on the simulation hypothesis selected.
This article presents experimental research on the moisture diffusivity in wood within the range of hygroscopic moisture. This research was carried out on samples of three types of trees: Scots pine, small-leaved linden and pedunculate oak. It included measurements of kinetics of moisture adsorption within the range of air relative humidity from 25% to 85%. For each type of wood, the experiment was carried out with unidirectional flow of moisture, in each of the material principal orthotropic directions, by examining the diffusion coefficient along the fibres, in the tangential direction and in the radial direction. Values of moisture diffusion coefficients and mass surface emission coefficient were found with the use of method of minimizing the objective function, that is, by fitting the computational adsorption kinetics curves to the experimental ones. At the same time, three cases of variations of the moisture diffusion coefficient together with moisture content of the material have been analysed each time: in the form of a constant, linear function and a quadratic function, assuming a constant value of mass surface emission coefficient on the absorbing surface of samples. The performed calculations allowed determining whether the moisture diffusion coefficients have extreme values within the analysed range of moisture content and what is the impact of various diffusion mechanisms on the whole process of transferring moisture in the considered cases.
The environmental factors affecting the chemical stability of objects in the collections of museums and historic sites include temperature, moisture, reactive chemicals in the air, and biological attack. The concentrations of deleterious airborne chemicals such as nitrogen oxides and sulfur oxides are usually a function of a museum's proximity to cities, industrial sites and airports or to materials used in the building's construction. These chemicals can be filtered and avoided. Pest and biological issues such as insect and rodent infestations and mold growth are also important issues but will not be discussed here. The mechanical instability of museum objects may be seen in cracking, delamination, flaking of paint, powdering, etc., and may be the result of chemical changes in the materials and/or environmental action. However, this paper discusses only the principal effects of moisture and temperature on mechanical and chemical stability of collections.
Vertical temperature differences tend to be great in a large indoor space such as an atrium, and it is important to predict variations of vertical temperature distribution in the early stage of the design. The authors previously developed and reported on a new simplified unsteady-state calculation model for predicting vertical temperature distribution in a large space. Comparisons between calculated values and the results of test chamber experiments verified that the model can be used to make accurate predictions for conditions of no solar radiation. In this paper, this model is applied to predicting the vertical temperature distribution in an existing low-rise atrium that has a skylight and is affected by transmitted solar radiation. Detailed calculation procedures that use the model are presented with all the boundary conditions and analytical simulations are carried out for the cooling condition. Calculated values are compared with measured results. The results of the comparison demonstrate that the calculation model can be applied to the design of a large space. The effects of occupied-zone cooling are also discussed and compared with those of all-zone cooling.
Hygroscopic finishing materials and furniture in buildings are able to absorb and release water vapour if the relative humidity of the room increases or decreases. Numerous building applications require an accurate prediction of the indoor relative humidity already from the design stage. In currently available multizone BES tools the emphasis is mainly on the prediction of thermal comfort and energy use. So far they have not been well suited to describe moisture transfer processes in buildings and as a result the relative humidity is predicted in a simplified way. An important simplification is that the heat and mass balance are decoupled, which limits their applicability since the effect of temperature variations on vapour diffusion is neglected.
HAM models on the other hand simultaneously solve the conservation equations for heat and mass transfer in complex porous building structures and are well suited to describe the hygrothermal interactions between the building air and porous surfaces. In this work a one dimensional transient HAM model is integrated with TRNSYS to account for the response of a multizone building on water vapour exchange with porous surfaces in a more detailed way. In contrast to simplified models the coupled model accounts for moisture-dependent conductivity and takes into account the effect of latent heat on the room heat balance. The coupled model was validated with both analytical and experimental results.
This whole-building hygrothermal simulation approach is applicable to numerous building applications and can be used for the evaluation of humidity controlled HVAC systems for which a detailed prediction of the indoor relative humidity is essential. The coupled model is applied to gypsum cooled ceilings for which non-isothermal vapour transfer cannot be neglected, and for the evaluation of humidity controlled ventilation systems. As a case study the coupled model was used for the assessment and optimization of the indoor climate in a library building.
Canvas paintings may show significant dimensional changes and experience internal stresses with fluctuating relative humidity. The relatively high and rapid absorption and drying of moisture within the different layers makes them more vulnerable than panel or wall paintings in comparable conditions. The dynamics of the moisture response is controlled by the water vapour permeability of the different layers. This paper presents a quantitative investigation of the vapour sorption and permeability of a selection of canvas painting components and of reconstructed paintings made of them. The selection of test samples was based on a survey of the materials used by Cuno Amiet in his early work and encompasses linen canvas, collagen glue sizing, chalk-glue ground and brown umber pigmented oil paint. Dynamic Vapour Sorption (DVS) tests were performed to obtain sorption isotherms. The vapour permeability was analysed in terms of the vapour resistance of layers and measured by means of wet cup and dry cup tests as well as in double chamber tests. The principle of incremental resistances was used to discriminate between the properties of the different layers. Whereas glue and canvas are comparable in being strongly absorbent, it appears that their vapour resistance is very different: a continuous glue film has a much higher vapour resistance than a canvas. In this context, we found that the method of applying glue sizing on a canvas influences the permeability of the resulting sized canvas: a gel size forms a more continuous glue film and hence leads to higher vapour resistance of the system, as opposed to a liquid size. Chalk-glue grounds have low moisture sorption, when compared to the high absorption of the proteinaceous glue, because they consist largely of chalk particles, which are not hygroscopic. The umber oil paint stands out for its low sorption and its high resistance to vapour transfer. These results characterise the highly heterogeneous nature of the multi-layered system of a painting in a quantitative way, enabling to better interpret damage phenomena and to make computational predictions of the influence of changing boundary conditions.
To predict the mould growth risk during the design stage, a mould prediction model can be used. Several models are found in literature (e.g. temperature ratio, isopleth systems, biohygrothermal model, ESP-r mould prediction model, empirical VTT-model). Each of these models includes however different assumptions. Consequently, a different conclusion may be drawn depending on the used prediction model. In the current paper, a comparison between the different mould prediction models is made. To do so, the hygrothermal behaviour of two thermal bridges is simulated and the obtained surface temperature and surface relative humidity are used as an input in the different mould prediction models.
Although preserving museum collections is vital, it is equally important to consider the failure mechanisms of the build- ings that house those collections. A combination of research, survey, and experience with high-profile buildings at the Smithsonian Institution has led to broadening the indoor environmental guidelines. The new environmental guidelines are 45% RH ±8% RH and 70°F (21°C) ±4°F (2°C).
This paper presents the discrepancies in applying the power-law model (PLM) for predicting indoor airflow distribution and the methodologies employed to improve this model. First, investigation was made to find an appropriate K value (flow coefficient) for use within the PLM (using the same K value for each cell). Values other than 0.83 were considered, and the result revealed that values other than K = 0.83 could not affect the prediction of the PLM and that K can be given any value, such as 1.0. The result also showed that the PLM could not be improved by using the same K value for each cell. Therefore, to improve the prediction capability of the PLM, other methodologies were pursued: (1) estimating the K value for each cell and (2) combining the PLM with another zonal model-the surface-drag flow model (SDM). The first approach has made the PLM to have variable K values and is referred to herein as PLMK. In the second approach, two types of combination were explored: direct and indirect. The direct combination of the SDM and the PLM has provided different forms of zonal models such as SD-PLM1, SD-PLM2, and SD-PLM3, and the indirect combination gave the modified powerlaw model (MPLM). Comparison of the predictions of all these models with each other and with experimental data showed that the MPLM provides the best predictions of the recirculation in the standard zone, followed by the PLMK.