An Experimental Investigation on the Air Permeability of Passive Ventilation Grilles

Abstract The need of increasing both energy saving and acoustic insulation has leaded to the design of lowest air permeability frames resulting in the worsening of indoor air quality. Moreover, sometime in several civil-use existing buildings (i.e. schools or houses, historical buildings) mechanical ventilation systems cannot be installed due to non-removable constraints. In these cases, passive ventilation grilles are a cheap and effective solution for the ventilation. This work deals with an in-depth experimental analysis about the air permeability values measured over a set of passive ventilation grilles available on the market. Obtained results often showed performances very far to those declared. This is not due to multiplicity of involved parameters affecting their behaviour rather to a lack of standardized test methods

The impact of climate change and urban growth on urban climate and heat stress in a subtropical city

Urban residents face increasing risk of heat stress due to the combined impact of climate change and intensification of the urban heat island (UHI) associated with urban growth. Considering the combined effect of urban growth and climate change is vital to understanding how temperatures in urban areas will change in the future. This study investigated the impact of urban growth and climate change on the UHI and heat stress in a subtropical city (Brisbane, Australia) in the present day (1991–2000) and medium term (2041–2050; RCP8.5) during summer. A control and urban growth scenario was used to compare the temperature increase from climate change alone with the temperature increase from climate change and urban growth. Average and minimum temperatures increased more with climate change and urban growth combined than with climate change alone, indicating that if urban growth is ignored, future urban temperatures could be underestimated. Under climate change alone, rural temperatures increased more than urban temperatures, decreasing the effect of the UHI by 0.4 °C at night and increasing the urban cool island by 0.8 °C during the day. With climate change, the number of hot days and nights doubled in urban and rural areas in 2041–2050 as compared to 1991–2000. The number of hot nights was higher in urban areas and with urban growth. Dangerous heat stress, defined as apparent temperature above 40 °C, increased with climate change and occurred on average 1–2 days every summer during 2041–2050, even in shaded conditions. There was higher temperature increases with urban growth and climate change than with climate change alone, indicating that reducing the effect of the UHI is vital to ensuring urban growth does not increase the heat stress risks that urban residents will face in the future

Il progetto e la misura del comfort termico

Il comfort termico, che è uno degli aspetti fondamentali della qualità dell’ambiente interno, influisce non solo sulla sensazione di benessere ma anche, come è ormai ampiamente dimostrato, sulla produttività; d’altra parte, realizzare condizioni di comfort termico significa anche, in genere, consumare energia. Conseguire il comfort termico non è cosa semplice in quanto richiede una progettazione del sistema edificio-impianto avanzata e consapevole, che tenga conto di quali siano i parametri ambientali da cui esso dipende gestendoli con intelligenza. Valutare il comfort termico non è cosa agevole, in quanto richiede attenzione e competenza specifiche. Inoltre, sia la progettazione che la valutazione del comfort termico sono regolati da una serie di norme UNI, alcune delle quali probabilmente non a tutti note. In questo lavoro vengono presentati alcuni criteri per la progettazione e la valuta-zione del comfort termico, allo scopo di guidare sia i progettisti degli impianti HVAC che gli addetti ai lavori nel complesso e articolato mondo delle norme del settore