Application of biological growth risk models to the management of built heritage

La qualità degli spazi interni è fortemente legata alle condizioni igrotermiche che influenzano il comfort degli utenti e i rischi di conservazione del patrimonio edilizio. Inoltre, una gestione incurante di spazi espositivi con numerosi accessi può causare carichi eccessivi di umidità, e conseguenti fenomeni di degrado. In questo lavoro, è stata considerata una sala espositiva rappresentativa del patrimonio costruito. Il rischio di proliferazione biologica è indagato nelle condizioni climatiche di Milano e Barcellona, con diversi ratei di ventilazione e numero di visitatori. I risultati delineano la necessità di politiche informate da analisi avanzate per prevenire il rischio igrotermico, in assenza di impianti, che non è sempre possibile integrare nel patrimonio edilizio storico.The quality of the interior spaces is strongly related to the hygro-thermal conditions which affect the users’ comfort, and may yield to preservation risk for the built heritage. Moreover, careless management of exposition spaces with excessive occupancy may result in moisture loads that promote degradation. In this paper, as a case study, an exposition hall representative of the built heritage is considered. The microbiological growth risk is investigated at two different climate conditions, namely Milan and Barcelona, considering varying ventilation rates and number of visitors. The results outline the need of policies informed by advanced analyses to prevent hygro-thermal risk in the absence of dedicated building services, that cannot always be integrated in built heritage

Uncertainty of solar radiation in urban canyons propagates to indoor thermo-visual comfort

The incident solar radiation on building facades is strongly affected by the urban characteristics, however frequently overlooked in the assessment of indoor environments due to limited data availability. Here, we show that a simplified representation of the urban environment can drastically affect the estimation of the incident solar radiation within urban canyons. We associate uncertainties with the canyon's geometry, built surfaces, optical properties, as well as vegetation, and resort to a hybrid probabilistic-possibilistic approach to quantify the effects on thermo-visual comfort. Contrasting complex against simplified urban canyons shows that the pattern of incident solar radiation is uneven along the building façade and strongly correlated to the canyon's characteristics. We also demonstrate that simplified models of urban canyons could underestimate the number of thermally comfortable instances by even 365 h a year (i.e., ~ 4% of the time). Similarly, a simplified canyon underestimates the visually comfortable occurrences, especially during the intermediate seasons. While a simplified canyon estimates a glare probability of 1.0, uncertainties within a complex canyon can lower the glare probability to 0.28 throughout the day. We show that for visual comfort, geometric characteristics alone, such as the canyon's skyline, can outweigh optical properties such as the transmissivity of trees. This uncertainty, especially in the estimate of glare probability, may lead to different decisions about building envelope design, including the need for a more or less adaptable façade

Calibrating Perez Model Coefficients Using Subset Simulation

The Perez sky diffuse model has been validated in many locations, however, studies have shown that the precision of estimation can be improved through localization of the model coefficients. This paper studies the effect of tuning Perez irradiance coefficients based on local information for estimating the incident solar radiation on tilted surfaces. The added value of a calibrated Perez model is highlighted by evaluating the heating and cooling energy needs of an office building. Calibration is performed by using Subset Simulation, i.e. a sampling technique based on Markov Chain Monte Carlo. The versatility of the Subset Simulation technique allows for handling multivariant calibration problems and is therefore suitable for finetuning Perez irradiance coefficients. Measurements of global horizontal, direct normal and diffuse horizontal solar irradiation, as well as the global solar irradiation on 90°, 30° and 15° tilted surfaces form the basis of the calibration. It is found that in the studied location, the default Perez model overestimates the incident solar radiation on vertical surfaces facing south. The calibrated coefficients are then embedded in the source code of EnergyPlus. Simulations with a reference office show that the effect of calibrating Perez coefficients can be significant, because it leads to approximately 12% difference in predicted annual cooling energy use and 9% difference in peak cooling loads, respectively