Abstract
The increase in the energy need for cooling is one of the major challenges in nearly Zero Energy Buildings. Recent constructions are characterized by high thermal insulation levels, which can be effective in preventing summer discomfort in combination with accurate control of solar gains through glazed surfaces and discharge of overall gains via ventilation. In addition, urbanization, densification and the global warming trends registered in the last decades can increase the risk and magnitude of overheating effect if an accurate design and use of correct technologies and good practices are not considered. The paper investigates the effects and the potential of natural night ventilation, as a strategy to reduce the energy need for cooling even taking into account the evolution of surrounding urban area with the exacerbation of urban heat island under future weather projections. Among the different tools available for the assessment of the cooling potential in buildings, the research focuses on two methodologies, which are adaptable to the conceptual design phase, where a first approximation of the natural ventilation potential is required. The study is developed on the weather datasets referred to the area of Milan and shows the future evolution of the night cooling potential, highlighting the importance of orienting building design towards greater integration between different passive cooling strategies for the summer period.
Highlights
Heating, ventilation, and air-conditioning (HVAC) is the largest energy end-use both in the residential and non-residential sector [1][2] and due to the temperature rise at a global scale and the heat island effect, energy needs for cooling during summer are expected to grow significantly
The first tool used for the analysis is based on the calculation of the index CPNV (Climatic Potential for Natural Ventilation) defined as the number of hours in a year when natural ventilation could be performed, divided by the total number of hours in a year [27]: CPNV = ∑ni=1 hNV,i htot where hNV,i is the i-th hour when natural ventilation is possible and htot is the total number of hours in a year
The results show the reduction in the night cooling potential in the summer season under future weather projections by using both the proposed tools; the climatic cooling potential (CCP) methodology seems to underestimate the effectiveness of this strategy respect to the use of CPNV
Summary
Ventilation, and air-conditioning (HVAC) is the largest energy end-use both in the residential and non-residential sector [1][2] and due to the temperature rise at a global scale and the heat island effect, energy needs for cooling during summer are expected to grow significantly. Especially non-residential ones, increasingly include air conditioning systems or hybrid solutions and this has entailed growing costs in energy use and mechanical systems. Directive 2010/31/EU states that “Recent years have seen a rise in the number of air-conditioning systems in European countries. This creates considerable problems at peak load times, increasing the cost of electricity and disrupting the energy balance. There should be a focus on measures which avoid overheating, such as shading and sufficient thermal capacity in the building construction, and further development and application of passive cooling techniques, primarily those that improve indoor climatic conditions and the microclimate around buildings”
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