The number of fires in roofs crossed by chimneys is high. According to the manufacturers' prescriptions, chimneys can be installed in direct contact with roof combustible materials or be spaced from them. In this paper, the influences of the installation mode and of the roof characteristics on the temperatures reached by the combustible materials are investigated by means of twelve experimental tests. Three roofs and four installation modes are analyzed to investigate whether and how they influence the temperatures of the materials surrounding the chimney and, hence, the consequent fire hazard. One roof is representative of the setup currently used in certification procedure, and the other two are representative of roofs in energy-saving buildings. The space between chimney and roof (clearance) has been left open to reproduce the condition in the certification procedure. Then, for reproducing the installation modes that may occur in real installations, the clearance has been sealed with metal sheets, sealed with insulating panels, and filled with insulating materials. Results show that temperatures are strongly affected by these variables, and in real installations, temperatures can be much higher than those measured in the certification procedure. For this, the existing standard should be reviewed accordingly
The number of roof fires due to the passage of chimneys is high. Since the experimental procedure necessary to identify all the variables affecting the temperature reached by roof in the vicinity of a chimney would be expensive, a 2D numerical model for the estimation of the temperatures in the roof has been designed. The model has been validated by means of experimental tests in which a certified chimney has been installed in three roofs and spaced from flammable materials as prescribed by the manufacturer. In order to reproduce the diverse conditions that may occur in real installations, the clearance between chimney and roof has been sealed in three ways (sealed with insulating panels, sealed with metal sheets, and filled with insulating materials). Good agreement between measured and estimated data is shown, and the estimated temperatures are in favour of safety. The effects of the clearance sealing mode and the chimney installation quality on flammable materials temperature are also shown.
To reduce energy consumption for space heating, a coordinated action on energy supply, building fabric and occupant behavior is required to realize sustainable improvements. A reduction in district heating supply temperature is an interesting option to allow the incorporation of renewable energy sources and reduce distribution losses, but its impact on the final users must be considered. This aspect is especially critical as most European countries feature an old building stock, with poor insulation and heating systems designed for high-temperature operation. In this study, a complete methodology is devised to evaluate the effect of district heating temperature reduction on the end users by modeling all the stages of the system, from the primary heat exchanger to the indoor environment. A dynamic energy performance engine, based on EN ISO 52016-1:2017 standard and completed with a heat exchanger model, is implemented, and its outputs are used to calculate thermal comfort indicators throughout the heating season. As a practical application, the method is used to evaluate different scenarios resulting from the reduction of primary supply temperature of a second-generation district heating network in Northern Italy. Several building typologies dating back to different periods are considered, in the conservative assumption of radiator heating. The results of the simulations show that the most severe discomfort situations are experienced in buildings built before 1990, but in recent buildings the amount of discomfort occurrences can be high because of the poor output of radiators when working at very low temperatures. Among the possible measures that could help the transition, actions on the primary side, on the installed power and on the building fabric are considered. The investigation method requires a limited amount of input data and is applicable to different scales, from the individual building to entire urban areas lined up for renovation.
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