Assessing Indoor Climate Control Strategies in Preventive Conservation Within Historical Buildings

From eSociety, December 2019

Researchers are proposing a multidisciplinary method to improve conservation strategies and thermal comfort for visitors in historical buildings. The method combines microclimate observations with the dynamic simulation of the building and an empirical evaluation of the degradation of hygroscopic artifacts. 

In a recent article from Science and Technology for the Built Environment, Francesca Frasca, Ph.D., with Sapienza University in Rome, Italy, describes how the method was applied to a historic building in Italy and analyzes the results of the simulation and discusses potential applications.

1. What is the significance of this research?

This research focuses on employing a multidisciplinary method that combines indoor climate monitoring along with a whole-building dynamic simulation in the field of the preventive conservation of cultural heritage and historic buildings. Indeed, to our knowledge, few investigations have been conducted regarding the thermal comfort of visitors and the damage risk assessment of cultural heritage, involving environmental monitoring in combination with a whole-building dynamic simulation. 

One of the issues this research has overcome concerns the capability of the indoor climate modeling within the whole-building dynamic simulation, especially the modeling of the relative humidity—a complex issue because it is directly related to model all mechanisms of moisture exchanges. This specific issue is crucial as the relative humidity plays a key role in all the deterioration phenomena affecting vulnerable hygroscopic materials, such as wood, which is a common material within historic buildings. The research shows once the building model is accurately calibrated using long-term indoor climate monitoring, it can be effectively employed to predict the indoor hygrothermal conditions due to new indoor climate control strategies as well as to use such outcomes to solve dose-response functions representative of a degradation phenomenon. 

Indeed, a further insight of this research is related to the multidisciplinary use of hygrothermal hourly measurements, used not only for the calibration of the building model but also for the evaluation of a dose-response function, which is validated by hourly measuring marker-tracking of damage, specifically of mechanical microdamage in wooden material. In this way, the predicted microclimate conditions can be used to foresee the damage evolution of the artwork and the comfort of the visitors inside the building.

2. Why is it important to explore this topic now?

Nowadays, safeguarding irreplaceable cultural and natural heritage is becoming a very important, timely topic. Therefore, the main objective of researchers is to find solutions capable of reducing the degradation phenomenon as well as further damaging occurrences. This can be successfully achieved only through the knowledge of the chemical, physical and biological properties of material and its environment as well as their mutual interaction. 

The increasing awareness on the interaction between indoor climate and objects is leading to the exploration of more sophisticated methodologies, such as whole-building dynamic simulation tools. Such tools have the main benefit of not requiring any direct interventions on the building by complying with the requirements of non-invasivity and non-destructivity of historic structures and, hence, boosting preventive actions.

3. What lessons, facts and/or guidance can an engineer working in the field take away from this research?

The indoor climate conditions that are suitable for the conservation of cultural heritage can conflict with the thermal comfort of people. This is true for both modern and historic buildings that preserve cultural heritage and becomes more relevant when the purpose is also finding solutions satisfying energy savings. It is well known an adequate compromise among conservation, thermal comfort and energy savings is not easily found, especially when it is not possible to modify or change the existing climate control system. 

This study addresses this complex issue suggesting how the management of climate control in historic buildings can be enhanced integrating the thermal comfort, which is a typical topic in building engineer studies, and the conservation of cultural heritage addressed by conservation scientists. An effective and multidisciplinary workflow is proposed on how to search for a compromise between the thermal comfort and the conservation of cultural heritage.

4. How can this research further the industry's knowledge on this topic?

The proposed approach results are completely non-invasive, non-destructive and with zero impact. The conservative quality of the exhibition spaces after a new climate control or a refurbishment is directly assessed in the simulation environment, remarkably reducing the risk of failure after the retrofitting design phase. Coupling the know-how of engineers (in the field of simulation, thermal comfort and energy-saving needs) and conservation researchers (in the field of measurements and conservation requirements) can support the decision for better control and management of the exhibition environment with noteworthy money savings.

5. Were there any surprises or unforeseen challenges for you when preparing this research?

In the case of historic buildings, the achievement of a robust simulation is difficult due to the complexity of establishing accurate hygrothermal properties of building materials and the difficulty of collecting measurements on historic materials protected by national legislation. The latter, particularly in Italy, obligates us to avoid any invasive and destructive measurements on historic buildings, making it nearly impossible to apply existing procedures as regulated by norms. 

Furthermore, the use of existing databases is not always recommended because historic materials of old masonries differ not only from new materials but also from each other due to manufactory and degradation occurred during their life. This implies that a database with such properties and its use is still not feasible.