Cool, translucent natural envelope. Thermal-optics characteristics experimental assessment and thermal-energy and day lighting analysis

Innovative construction elements are increasingly studied to improve the energy performance of new and existing buildings, to satisfy global regulations and societal needs. In this view, optimizing buildings energy efficiency and sustainability are crucial aspects, given their high energy saving potential with respect to the other sectors characterizing human activities. Natural materials are often preferred to artificial materials, thanks to their more sustainable production and to the reduced content of harmful substances. In particular, light, thin marbles have been recently analyzed as building envelope elements. Their cooling potential demonstrated how such envelopes have the threefold advantages of reducing solar heat gains into the building, accumulating and releasing less heat, reducing the Urban Heat Island (UHI) effect and consequently mitigating global warming. However, an important feature that has not yet been analyzed in literature and that is considered in this research is light passage throughout the translucent envelope, permitting an additional energy saving due to the contribution to artificial lighting. In this work, this feature of the translucent envelope is considered, by experimentally measuring thin, white marble panels’ optic characteristics and implementing them in a thermal-energy dynamic simulation, to demonstrate the additional advantage of natural daylight to the overall building energy balance

Experimental and Numerical Study on Thermal Performance of New Cool Clay Tiles in Residential Buildings in Europe

Abstract Energy demand imputable to buildings corresponds to around 40% of the total in most of the developed countries, showing the great potential in this field to propose and implement effective strategies for energy saving and environmental sustainability. Additionally, urban areas are the most impacted zones by anthropogenic sources and they are often affected by local climate phenomena such as urban heat islands. In this view, several measures to mitigate this effects and to save energy in constructions are dealt with the implementation of cool materials for roofs and urban paving. Since the majority of cities in Europe is characterized by traditional architectures in residential buildings, the implementation of white cool coatings is not feasible and new solutions are being proposed. In particular, starting from previous works of the authors about the development and continuous monitoring of cool clay tiles, this paper deals with the thermal analysis of low-visual-impact cool tiles in single family residential buildings with varying climate conditions (i.e. latitude) in Europe, from hot subtropical semi-arid climate (Tripoli) to oceanic climate (Munich). A calibrated and validated simulation model by mean of experimental in-lab and in-field measurements, has been used for studying the thermal effect of the proposed clay tiles. The analysis shows how the clay tile has a promising potential to decrease the indoor overheating in all the climate conditions, with relatively low penalties in winter even in the coldest areas

Smart cool mortar for passive cooling of historical and existing buildings: experimental analysis and dynamic simulation

In order to mitigate Urban Heat Island Effect and global warming, both governments and scientific community are working to reduce energy consumptions. In particular, the construction sector has a high potential in reducing energy demand, by means of both active and passive solutions. The European building stock is mainly composed by existing buildings as well as historical ones, which happens to be the less energy efficient ones. Moreover, retrofit operations are more complex on historical buildings, due to strict regulations for the preservation of such historical and cultural heritage. Considering this challenge, in this work we described and in lab analyzed possible passive solutions specifically designed for historical and existing buildings. In particular, we developed innovative cool colored mortars and tested them in lab, as well as investigated cool colored mortars, cool clay tiles and cool natural gravels performance when applied as envelope and roof elements, by means of dynamic simulation

On a Cool Coating for Roof Clay Tiles: Development of the Prototype and Thermal-energy Assessment

AbstractClay tiles are the most common roof covering in Italian buildings, in particular in traditional residential buildings. Given the important role of the roof characteristics for building energy efficiency and indoor thermal comfort conditions, innovative solutions for improving the thermal-energy performance of such diffused roof element has become a key research issue. In this view, cool roof applications represent an effective solution to this aim. The present work deals with the analysis of innovative coatings for traditional clay tiles, aimed at increasing their "cooling" potential. Several pigments with the sodium silicate as binder are tested in terms of reflectance and emittance, which mainly determine the cool roof performance. Additionally, the year-round performance of the proposed tile is evaluated when applied to a single family residential building located in central Italy. The developed cool roof solution is characterized by the same visual appearance of traditional "natural brick" color tiles, while the solar reflectance is higher than natural terracotta tile by 13%. Therefore its thermal performance is optimized in order to reduce the roof overheating and the consequent energy requirement for cooling. Results of dynamic simulation of the case study building show how the proposed tile is able to decrease the number of hours when the indoor operative temperature of the attic is higher than 26°C by 18%, while the same effect in lowering the indoor temperature below 20°C in winter is less than 1%. Therefore, the proposed solution could be considered as an interesting strategy for new buildings or for traditional roof retrofitting, without producing any significant architectural impact, even in traditional or historic buildings, where more invasive solutions are too difficult to be implemented

Cool marble building envelopes. The effect of aging on energy performance and aesthetics

Marble envelopes represent a relatively common architectural solution used in variety of historic, modern and contemporary building facades. White marble envelopes have been shown to reduce solar heat gains, while improving indoor thermal comfort and energy efficiency in summer time. While marble is useful in this context, the urban atmosphere accelerates the degradation of marble elements. This leads to changes in optical characteristics, hence the aesthetics, and affects the energy efficiency benefits offered by white marble facades. These issues are investigated in order to predict the impact of degradation on energy performance and to the aesthetic value, such as change of color and luminosity. In this study, surface degradation of white marble is analyzed by means of accelerated weathering in the laboratory while examining changes to the optical characteristics of the materials. A dynamic simulation is carried out to assess the energy performance of a building as a case study

New experimental technique to investigate the thermal behavior of PCM/doped concrete for enhancing thermal/energy storage capability of building envelope

Abstract In recent years, the scientific community has profusely investigated the chance of implementing advanced Thermal Energy Storage (TES) systems within building envelope components. In particular, several contributions have focused on the use of Phase Change Materials as passive TES strategies, to increment the thermal buffer potentiality of the building envelope. In this context, this work is focused on the development of a new experimental methodology for testing PCM-doped concrete composites in thermal-energy dynamic conditions. Such method, coupling controlled environmental forcing and transient plane source analysis, can be considered as an effective procedure for testing composite materials with adaptive thermal performance

How subjective and non-physical parameters affect occupants’ environmental comfort perception

Employees’ wellbeing and comfort perception demonstrated to largely influence their productivity and tolerability of slight thermal discomfort conditions in the working spaces. Their whole comfort perception indeed depends on several parameters related to physical boundary conditions but also to the adaptation capability of occupants themselves and other personal, difficult to measure, variables. According to the available standards and regulations, only physical and measurable environmental parameters must be considered to evaluate occupants’ comfort conditions. Therefore, non-measurable factors such as socio-psychological, physiological, medical ones are currently not systematically considered. The present work aims to identify possible benefits in terms of occupants’ comfort perception due to non-physical strategies aimed at improving the work-environment quality and livability. To this aim, the environmental multi-physics and multi-domain performance of a mixed industry-office building is investigated through coupled in-field microclimate monitoring and questionnaires campaigns. The experimental microclimate monitoring and survey campaign were carried out to understand (i) the realistic indoor environmental conditions in terms of physical and measurable parameters and (ii) the personal perceptions and attitudes of the occupants with respect to those same ambient parameters, including also acoustic, lighting and medical investigation. Moreover, the collected experimental data were used to determine occupants’ comfort level through the classic comfort models, to be compared to the identified role of non-physical parameters on occupants’ final perception about the indoor environment. The main results show that non-measurable factors induced by virtuous company policy to improve employees’ working environment are effectively able to positively influence their whole-comfort perception even if the majority of workers do not have the opportunity to control their working environment. In fact, the consolidated comfort theories underestimate people satisfaction, as demonstrated by more than the 80% employees, who declared to be positively influenced by the pleasant aesthetics and livability of the workplace. The year-round experimental campaign demonstrated the need to further investigate the key role of non-physical parameters for possible incorporation into whole-comfort prediction models and standards. The role of such strategies could therefore be realistically considered as energy saving opportunities since they make building occupants much more open to tolerate slight uncomfortable conditions

Outdoor thermal and visual perception of natural cool materials for roof and urban paving

Given the acknowledged thermal performance of natural light color gravels applied as cool roof and cool urban paving, this work is aimed at investigating if such behavior is perceivable by pedestrians, who are questioned in this paper about their visual and thermal comfort perception. In fact, there are still related aspects to analyze, in order to optimize their application and provide a comfortable space for users, both on the thermal and the visual point of view. Therefore, the question that this work wants to answer is: given their intrinsic characteristics, do these materials create a sensitive thermally and visually more comfortable environment for pedestrians? In order to address this uninvestigated issue, users’ judgment about visual and thermal comfort of these surfaces is considered, also by comparing them with grassland and asphalt. Also, the statistical correspondence between physical properties of such materials and possible correspondence with respect to human perception with varying weather conditions is analyzed. Given the relatively high reflectance of these materials, it appears particularly important to evaluate these aspects, to consciously apply them as urban paving or roof covering by optimizing their natural passive cooling potential. In this preliminary study, users’ response to these surfaces is evaluated by mean of field surveys, both on the thermal and the visual evaluation, and contemporary in-field measurements of surface parameters. Also, human perception with respect to these high-reflectance surfaces’ is compared with the one related to grassland and asphalt, with varying weather conditions. Then, a statistical analysis is performed to investigate the differences among different gravels, grassland and asphalt, based on surveys’ results. The results show how pedestrians, questioned during summer days, prefer grassland, while asphalt is the less favorite surface both visually and thermally; there is a small difference between gravels’ types evaluation, while weather variability affect the preferences