Energy saving potential of night ventilation: Sensitivity to pressure coefficients for different European climates

Abstract

The suitability of night ventilation to reduce the cooling demand in buildings can be evaluated by coupling Airflow Network Models to Building Energy Simulation tools. To estimate wind-induced ventilation, pressure coefficients (Cp) on the building envelope are key inputs, as well as local wind speed and direction. Cp data obtained by primary sources such as measurements or CFD simulations are considered the most reliable but can be difficult to obtain. An easy alternative are Cp secondary sources, such as databases providing literature data correlations. Therefore an issue arises regarding the choice of the source of pressure coefficients. This paper investigates the effects of Cp from primary and secondary sources on the predicted energy saving potential of night ventilation of an isolated office building for several European climates and some relevant design conditions and simulation parameters. Different Cp sources produce a dispersion of Cp data and differences in the calculated night ventilation rates up to 15%. Contrary to what might be expected, these differences influence only marginally the resulting passive cooling effects. Overall a stronger impact is observed for the colder climates, where higher temperature differences occur between desired indoor temperature and night-averaged outdoor temperature. Finally, for the building under study, the choice of the Cp source appears less crucial than the choice of other building simulation parameters, such as the internal Convective Heat Transfer Coefficient. This study can support building designers towards accurate energy simulations of naturally ventilated buildings

A novel approach for selecting typical hot-year (THY) weather data

“…In this study, THY-I can be used for the situation during a given summer period, THY-E for the most severe event, and THY-N for specially required evaluation of sleeping effects. For example, the THYs can be used for passive design to simulate the indoor environment during extreme heat events, which is important for occupants but unfortunately ignored in most existing projects (Ramponi, 2014).…”

Thermal and visual comfort assessment of natural ventilated office buildings in Europe and North America

“…These individual wind analyses were conducted because, as highlighted in [32], a wrong estimation of the wind pressure coefficients can lead to differences up to 15% in the predicted air change rates and thus to a wrong estimation of the cooling energy savings.…”

Bio-inspired Adaptive Building Skins

“…On a wider scale, bioinspired adaptable building skin design can play an important role in creating a better mutual relationship between buildings and their surrounding local microclimate, through careful integration of principles from urban physics (Moonen et al 2012), for enhancing, e.g. natural ventilation potential (Ramponi et al 2014), pollutant transport in street canyons (Xie et al 2007), acoustic properties (Van Renterghem et al 2013) and wind comfort (Montazeri et al 2013). In the longer term, such design considerations will help in the transition from biological principles on the building scale towards the more holistic notion of ''biophilic cities'' (Beatley 2011).…”