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

Cool Roof Impact on Building Energy Need: The Role of Thermal Insulation with Varying Climate Conditions

Cool roof effectiveness in improving building thermal-energy performance is affected by different variables. In particular, roof insulation level and climate conditions are key parameters influencing cool roofs benefits and whole building energy performance. This work aims at assessing the role of cool roof in the optimum roof configuration, i.e., combination of solar reflectance capability and thermal insulation level, in terms of building energy performance in different climate conditions worldwide. To this aim, coupled dynamic thermal-energy simulation and optimization analysis is carried out. In detail, multi-dimensional optimization of combined building roof thermal insulation and solar reflectance is developed to minimize building annual energy consumption for heating-cooling. Results highlight how a high reflectance roof minimizes annual energy need for a small standard office building in the majority of considered climates. Moreover, building energy performance is more sensitive to roof solar reflectance than thermal insulation level, except for the coldest conditions. Therefore, for the selected building, the optimum roof typology presents high solar reflectance capability (0.8) and no/low insulation level (0.00-0.03 m), except for extremely hot or cold climate zones. Accordingly, this research shows how the classic approach of super-insulated buildings should be reframed for the office case toward truly environmentally friendly buildings.The work was partially funded by the Spanish government (RTI2018-093849-B-C31). This work was partially supported by ICREA under the ICREA Academia programme. Dr. Alvaro de Gracia has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 712949 (TECNIOspring PLUS) and from the Agency for Business Competitiveness of the Government of Catalonia. This publication has emanated from research supported (in part) by Science Foundation Ireland (SFI) under the SFI Strategic Partnership Programme Grant Number SFI/15/SPP/E3125

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

Thermal stress reduction in cool roof membranes using phase change materials (PCM)

A considerable amount of energy is used in the building sector for air conditioning purposes. Additionally, the building sector contributes to the urban heat island (UHI) phenomenon which causes temperature rise in urban areas. Cool roof is an emerging passive cooling technology that can contribute to reduce the cooling energy use in buildings and to mitigate the UHI effects in the urban area. Cool roofs and reflective coatings, despite of being effective in terms of reducing the cooling thermal loads in buildings and decrease the UHI, can suffer from extreme thermal stress which negatively influences their lifespan and performance. Thermal energy storage (TES) is a promising technology which can be applied together with cool roof technology to decrease the extreme thermal stress due to solar radiation as well as providing thermal inertia to the building. In this study, simulation-based optimization will be used to optimize the PCM melting temperature when integrated into a polyurethane-based cool roof membrane to reduce the thermal stress of the cool roof and also to improve the annual energy performance of the building. The optimization results showed that the application of PCM and cool roof technologies together can reduce the severe thermal stress of the cool roof membrane when the optimization objective is the annual thermal stress of the cool roof. On the other hand, when PCM melting temperature is optimized to reduce the annual energy needs, higher annual energy savings could be achieved with acceptable reductions in the cool roof membrane thermal stress.The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 657466 (INPATH-TES). The work is partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER) and ENE2015-64117-C5-3-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to their research group GREA (2014 SGR 123). GREA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. This project has received funding from the European Commission Seventh Framework Program (FP/2007-2013) under Grant agreement Nº PIRSES-GA-2013-610692 (INNOSTORAGE). Alvaro de Gracia would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-19940. A.L. Pisello’s acknowledgments are due to the UNESCO Chair “Water Resources Management and Culture”, for supporting her research

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

Multifunctional smart concretes with novel phase change materials: Mechanical and thermo-energy investigation

Energy performance in buildings and integrated systems represents a key aspect influencing anthropogenic emissions worldwide. Therefore, novel multifunctional materials for improving envelope thermo-energy efficiency through passive techniques are presently attracting notable researchers' effort. In this view, the integration of phase change materials (PCMs) into structural concrete showed interesting effects in enhancing the material thermal capacity while keeping proper structural strength. This work presents a multiphysics thermomechanical investigation concerning innovative concretes incorporating paraffin-based PCM suitable for structural-thermal multifunctional applications in high-energy efficiency building envelopes. Both classic microPCM-capsules and the novel more pioneering macroPCM-capsules with 18 °C phase transition temperature are used for the new composite preparation. Results confirm the thermal benefits of PCM and demonstrate that the addition of PCM reduces the mass density of concrete by almost twice PCMs weight. Average compressive strength decreases with increasing the amount of PCM, but its coefficient of variation is not as negatively affected, which is promising in terms of structural reliability. Indeed, a 1% weight content of microPCM and macroPCM results in reduced coefficients of variation of the compressive strength, determining an increase in characteristic compressive strength. This benefit might be associated to both a filler effect of the PCM and to a positive thermal interaction between inclusions and cement hydration products. The multifunctional analysis showed promising performance of PCM-based macro-capsules as aggregates, even if their concentration is relatively minor than the classic micro-capsules already acknowledged as effective additives for high energy efficient cement-based materials.Acknowledgments are due to the “CIRIAF program for UNESCO” in the framework of the UNESCO Chair “Water Resources Management and Culture”. The research leading to these results has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No. 657466 (INPATH-TES). The authors also thank the Microtek Laboratories, Inc. for providing the capsulated materials. The work is also partially funded by the Spanish Government (ENE2015-64117-C5-1-R). Prof. Luisa F. Cabeza would like to thank the Catalan Government for the quality accreditation given to her research group (2014 SGR 123)

On an innovative approach for microclimate enhancement and retrofit of historic buildings and artworks preservation by means of innovative thin envelope materials

Energy efficiency and environmental sustainability in building has become a key issue since the built environment is nowadays responsible for more than 30% of the total carbon emissions. While new building design and construction reached massive improvements toward net zero energy and high environmental performance standards, existing and historical buildings are still too much energy needy, with a relatively low indoor comfort conditions for both occupants and artworks preserved inside, especially within heritage buildings. Such high architectural value buildings correspond to almost one third of the Italian building stock and they typically need to be re-functionalized for hosting residential, office, or institutional uses, i.e. museums and exhibition areas. In this view, the present research aims at developing a replicable method for assessing and enhancing indoor comfort in historical buildings frequently characterized by too high relative humidity and thermal losses through the envelope. More in details, an innovative envelope material for indoor application, i.e. hygro-adsorbing plaster, has been tested in an ancient Italian castle and its effect has been assessed by means of coupled monitoring and calibrated dynamic simulation. The experimental campaign shows an increase of the Performance Index (PI) in terms of relative humidity acceptable range from 16.1 to 33.3% by applying the new thin plaster. Moreover, the results show that dedicated HVAC systems may support the action of passive strategies for preserving artworks and indoor comfort levels, but at the same time, such passive low-invasive strategies represent a mandatory first step toward energy efficiency, functional, and comfortable cultural heritage architectures.Prof. Luisa F. Cabeza would like to acknowledge the Spanish Government for the funding PRX17/00221 that allowed her to visit University of Perugia during 6 months. Prof. Cabeza would like to thank the Catalan Government for the quality accreditation given to their research group (2014 SGR 123). GREA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. The corresponding author acknowledgements are due to the ‘CIRIAF program for UNESCO’ in the framework of the UNESCO Chair ‘Water Resources Management and Culture’, for supporting her research. Also, University of Perugia acknowledgements are due to Centro Edile per la Sicurezza e la Formazione–Perugia (in particular to Dr. Cristiana Bartolucci and Dr. Laura Galli), which provided the case study and supported the project COLO ARTE, also financed by Fondazione Cassa di Risparmio di Perugia (“COLO ARTE - COnservazione e vaLOrizzazione degli edifici storici e delle opere d’ARTE” 2016.0276.021)

Experimental testing of cooling internal loads with a radiant wall

Thermally activated building systems (TABS) consist of pipes or ducts embedded in the building structure. This is a well-known technology for its capability to reduce energy use for cooling buildings. Additionally, TABS help integrating renewable energies, such as free-cooling with ground heat exchangers (GHE). However, TABS cooling load is sensitive to the internal load, and the use of GHE for free-cooling is limited to low energy buildings. In a previously published research, a radiant wall cubicle without internal gains demonstrated to achieve significant energy savings. However, the current research showed that under domestic and office scheduled internal gains equivalent to 42 W·m-2 the radiant cubicle increased its energy consumption for cooling more than the reference cubicle with air-to-air heat pumps. As a result, the radiant cubicle used around 20% more energy than the reference at air temperature set-point 24 ºC but saved around 20% compared to the reference at 26 ºC. Despite this, the radiant wall could still reduce the cooling cost through peak load shifting even though it showed to consume more energy than a conventional HP.The work was partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER), ENE2015-64117-C5-3-R (MINECO/FEDER), and ULLE10-4E-1305). GREA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2014 SGR 123) and the city hall of Puigverd de Lleida. This projects has received funding from the European Commission Seventh Framework Programme (FP/2007–2013) under Grant agreement Nº PIRSES-GA-2013-610692 (INNOSTORAGE) and from European Union's Horizon 2020 research and innovation programme under grant agreement Nº 657466 (INPATH-TES). Alvaro de Gracia would like to thank Ministerio de Economia y Competitividad de España for Grant Juan de la Cierva, FJCI-2014-19940

Thermal comfort in the historical urban canyon: the effect of innovative materials

Urban heat island (UHI) can considerably affect the thermal quality of the urban environment, especially within urban canyons, that have typically low sky view factor and limited surface heat re-emission capability. A huge research effort has been registered to develop mitigation solutions for UHI, such as cool materials and greenery. Nevertheless, it is not always possible to apply such strategies in historical urban environments due to constrains for the preservation of their cultural value that do not allow to modify the exterior architectural appearance of heritage buildings. In this scenario, the present paper deals with the analysis of the potential of innovative cool materials characterized by the same appearance of historical ones in mitigating the UHI occurring in the context of a historical urban canyon located in central Italy selected as pilot case study. To this purpose, a preliminary experimental characterization of such innovative highly reflective materials has been performed. Afterwards, an experimental continuous monitoring campaign of the main outdoor microclimate parameters and a numerical modelling of the canyon have been carried out to evaluate the local mitigation capability of such materials when applied over the vertical and horizontal surfaces of the historical canyon. The results show the huge potential of the proposed innovative cool materials in mitigating the local microclimate of the historical urban canyon. In fact, a MOCI reduction up to 0.15 and 0.30 is detected by applying cool red envelope materials and cool red envelope materials plus cool grey paving materials, respectively, on the canyon surfaces