• Energy Research

Recycled waste materials obtained from industrial and agricultural processes are becoming promising thermal and acoustic insulating solutions in building applications; their use can play an important role in the environmental impact reduction. The aim of the present paper is the evaluation of the thermal performance of recycled waste panels consisting of cork scraps, rice husk, coffee chaff, and end-life granulated tires, glued in different weight ratios and pressed. Six panels obtained from the mixing of these waste materials were fabricated and analyzed. In particular, the scope is the selection of the best compromise solutions from the thermal and environmental points of view. To this aim, thermal resistances were measured in laboratory and a Life Cycle Assessment (LCA) analysis was carried out for each panel; a cross-comparative examination was performed in order to optimize their properties and find the best panels solutions to be assembled in the future. Life Cycle Analysis was carried out in terms of primary Embodied Energy and Greenhouse Gas Emissions, considering a ‘‘cradle-to-gate” approach. The obtained thermal conductivities varied in the 0.055 to 0.135 W/mK range, in the same order of magnitude of many traditional systems. The best thermal results were obtained for the panels made of granulated cork, rice husk, and coffee chaff in this order. The rubber granulate showed higher values of the thermal conductivity (about 0.15 W/mK); a very interesting combined solution was the panel composed of cork (60%), rice husk (20%), and coffee chaff (20%), with a thermal conductivity of 0.08 W/mK and a Global Warming Potential of only 2.6 kg CO2eq/m2. Considering the Embodied Energy (CED), the best solution is a panel composed of 56% of cork and 44% of coffee chaff (minimum CED and thermal conductivity).

Abstract In building applications, recycled waste materials are becoming promising acoustic absorbers and thermal insulating solutions in order to reduce the environmental impact. The aim of the research is to evaluate the thermal, acoustic, and environmental performance of recycled waste panels consisting of rice husk (RH) produced by gluing and pressing the raw material. Its acoustic and thermal performance were compared with the ones of six panels composed by other recycled materials (cork scraps, end-life tires, coffee chaff, waste paper, textile fiber mats, wool fiber scraps), assembled with similar techniques. Thermal resistance of RH is equal to 0.59 m2K/W, in the same order of magnitude of many traditional systems. Sound absorption coefficients were measured by means of the impedance tube. All the panels present acoustic absorption comparable with traditional ones (peak values 0.87–0.99). RH peak value is 0.87, while the maximum values are obtained for cork and wool fiber scraps (1 and 0.97 respectively). Life cycle analysis, performed in compliance with ISO 14040 showed the best environmental performance for the production of 1 m2 of RH and coffee chaff panels. Taking in account their acoustic and thermal behaviour, the wool fiber scraps presents a very good performance.

Abstract Insulation is one of the most effective methods intended for reducing energy consumption in both heating and cooling of buildings. Selecting the right materials and determining the optimum insulation thickness in building insulation application is an important issue. Moreover it is important to use green insulating materials in order to limit the environmental impact in the use of these solutions. A growing interest is focused on the incorporation of low cost recycled materials in building products and their potential use as insulating panels for both new buildings and refurbishments. In this paper two panels were investigated, composed by waste paper and textile fibres, joined by glue, with a total thickness of 12 mm and 20 mm respectively. The study is focused on the thermal and acoustic characterisation of the panels, in order to provide accurate data for a reliable building integration. Thermal performance was evaluated by using the hot-box apparatus, according to UNI EN ISO 8990. A good thermal behaviour was found for all the investigated panels: k-values vary in the 0.034–0.039 W/m K range. The investigated panels could be a valid solution in place of classic insulation systems, even though thermal resistance is strongly influenced by the environmental humidity, the rate of the compression, and the presence of air between the layers. Therefore a thermal infrared camera was also used during the measurements, aiming to investigate the weak points of the assembled panels and to select the positions of the sensors. The acoustic absorption coefficient was determined by means of a Kundt’s tube, in compliance with ISO 10534-2. The Noise Reduction Coefficient (NRC – the arithmetic value of the absorption coefficient at the frequencies 250, 500, 1000 and 2000 Hz) of the samples varies in 0.23–0.38 range, depending on the layer thickness. Finally an initial Life Cycle Assessment of the proposed solutions was considered and compared to the performance of other replaceable insulating materials. Results showed that the panel composed by recycled papers and textile fibres causes relative large energy consumptions and a high global warming potential. The importance of this kind of insulation system is due to the use of recycled materials: both the waste paper and the TNT fibres should be disposed by means of a large use of energy. This way they will be re-used and the cost for the production of the panels is very low. A disadvantage of these panels could be their high density (about 433 kg/m3): the future step for this work will be the improvement of this new insulating type in order to obtain a competitive solution on the market. The manufacturing of lighter solutions will allow the panels to be more competitive on the market in terms of embodied energy and GHG emissions.

Abstract Sound absorption materials structure is generally based on porous synthetic media (rock wool, glass wool, polyurethane, polyester, ect.): they have expensive production processes, important energy consumptions, and high environmental impact. Recycled materials are becoming an interesting alternative, due to their good acoustic behavior, similar to traditional porous materials; they also allow low impact production costs, thanks to the use of wastes derived from other production cycles. This work focuses on the evaluation of the acoustic absorption properties of new panels made of recycled paper and other scrap materials, as wool and nonwoven polyester fabric: different samples were produced and tested by means of impedance tube, according to ISO 10534-2. In order to present the environmental benefits, Life Cycle Assessment was carried out in terms of primary embodied energy and greenhouse gas emissions, considering a “cradle-to-gate” approach. Furthermore, the behavior of innovative absorption materials was investigated in order to improve the acoustic performance of a lecture room, by means of an acoustic simulation software. A comparison with traditional materials was also carried out for both acoustic and environmental aspects. In the simulation model, calibrated by an in-situ experimental campaign of the main acoustic quality indexes (Reverberation Time, Clarity and Definition Indexes, Speech Transmission Index), different acoustic correction solutions were implemented: both the new recycled and traditional panels were applied as wall and ceiling absorbers. The analysis of the acoustic absorption trends, in 100 - 5000 Hz frequencies range, shows that the new materials are suitable as acoustic correction systems, especially the panel composed by waste paper and wool fibers. The LCA analysis results show that, considering the same acoustic performance, the recycled panels allow to reduce the environmental effects and the global production costs.

Abstract An interesting tool for testing and check phases of HVAC systems was developed, in order to evaluate thermal comfort parameters only measuring temperature and relative humidity in moderate environments, for a wide range of clothing thermal insulation. A simplified approach to thermal comfort was developed in the seventies by Rohles, who found a correlation between PMV, air temperature and relative humidity, for sedentary activity and clothing thermal insulation equal to 0.6 clo. An improvement of Rohles model is proposed, aiming to extend results in a wider range of clothing thermal insulation (0.25–1.65 clo). Data from experimental campaigns in moderate environments were used to implement a function PMV = PMV( T , RH) and diagrams PMV vs. temperature, for different values of relative humidity, were traced (nine equations and diagrams for male, female, and both sexes, and for three ranges of I cl ). Standard deviation between measured and calculated data was evaluated and a mean error on PMV of ±0.22 was found; a T-Student test was also performed and results were significant. Mean Radiant Temperature data were used to calculate Operative Temperature and to correlate to PMV and to Neutral Temperature, corresponding to thermal comfort, by means of linear regression method.

Abstract Data collected in an Italian ancient theatre were elaborated in order to compare subjective sensations evaluated by means of questionnaires to data measured in field. A simplified model, developed in a previous paper, was validated by using measured data and by comparing the results to data from questionnaires (PMV Q ). Questionnaire data vary in a wider range of values than measured ones, confirming a higher variability in the personal sensation due to the possibility of giving only whole numbers. Therefore the questionnaire PMV scale needs to be refined to a 0.5 increment (resulting in 13 values). When comparing data calculated with the simplified model developed by the Authors in a previous work to data from questionnaires, more reliable results in the prediction of PMV were found with respect to measured data. Finally, people who voted 0 were about 54%, while about 88% are in the −1 to +1 range, showing a good behaviour of the theatre, nevertheless a wide range of variability for data from questionnaires corresponds to the same value of indoor air temperature. For this reason the PMV questionnaire scale needs to be refined to a 0.5 increment (resulting in 13 values).

Abstract A new 13-value thermal comfort scale is adopted in the present study, in order to evaluate the thermal comfort sensation within non-residential buildings with the adaptive approach. 18 classrooms located both in Pavia and Perugia, the Fraschini Theatre, and one auditorium located in Pavia were investigated from October 2014 to October 2015 collecting about 1600 questionnaires. All the information reported in the questionnaires was correlated by defining several indexes and a comparative analysis was carried out between the two comfort scales (13-value and 7-value scale). Results showed that using the new 13-value scale the percentage of people who declared a thermal sensation equal to 0 greatly decreased: from 66% to 41% for the classrooms and from 47% to 36% for the theatre-auditorium. The percentage of occupants who considered the environments not thermally comfortable, although they declared a thermal sensation equal to 0, also decreased, from a mean value of 10.4% to 2.7% for the classrooms and from 6.0% to 2.6% for the theatre-auditorium. Considering the 7-value scale, although a thermal sensation equal to 0 was declared, a higher percentage of people who would feel a little bit cooler or a little bit warmer was found. Instead using the 13-value scale, this percentage significantly decreased, because people declared a thermal sensation equal to ±0.5 (more than 50% of cases) instead of 0. In agreement with these results, the new scale seems to be more accurate than the traditional one, allowing a better correlation among all the data reported in the questionnaires.

Abstract Questionnaires are an important tool for analyzing the thermo-hygrometric, acoustic, and lighting conditions of indoor environments. In the present work thermal, acoustical, and visual conditions were investigated through both subjective and objective measurements carried out in 7 classrooms at the University of Pavia, Italy. Measurements of the main descriptors of thermal, acoustical, and visual comfort were carried out and new specific questionnaires were purposely developed, in order to investigate the students' perception on acoustic and lighting comfort and to analyze which are the subjective parameters most correlated with the experimental results. Both 7-value and 13-value scales were provided to the occupants for the thermal comfort evaluation and no significant differences in the results were found. Among all the acoustic comfort questions, the ones related to background noise present the highest correlation. Other questions were selected considering the intelligibility - comprehension and the overall assessment of the auditory environment in the classrooms. Classroom 5 is the worst in terms of acoustic conditions and it is confirmed by the correspondent indexes named IBN and ISQ. The analysis of the lighting questionnaire showed that the average measured illuminance value has a high correlation with the perceived visual comfort. The classrooms annoying glares have a strong relationship to the classroom excessive light contrasts and a good correlation with the measured illuminance values. Among the acoustic and lighting questionnaires, ten questions with the best correlation with the experimental results were chosen and ten indexes were proposed, in order to describe the comfort conditions.