Dynamic thermal simulation of advanced natural ventilation in buildings : current and future usage, UK exemplar

This paper evaluates the use of advanced natural ventilation (ANV) strategies in a range of climatic conditions from four cities in the UK. A prototype ANV system was proposed to determine the most effective case in mitigating overheating. The case was then assessed under identical simulation conditions for all four ANV strategies. The overheating criteria used in the research include the single temperature criterion from CIBSE Guide A and the adaptive thermal comfort overheating criteria from BS EN 15251. Both the current and future ‘Design Summer Year (DSY)’ weather data were used to examine the thermal performances of the proposed design. The findings show that shading, night cooling and heavy weight structures (ceiling) were all useful in mitigating overheating, with night cooling being identified as the most effective measure. The work assessed the use of ANV in both current and future scenarios to quantify the limits of outdoor environmental conditions under which natural ventilation is an effective strategy for achieving thermal comfort. The adaptive thermal comfort overheating criteria were proved to be easier to meet compared with the CIBSE single temperature criterion. With the adaptive overheating criteria, the given design is predicted to not overheat until 2050 in London Heathrow; and for other places evaluated in the UK (Edinburgh, Manchester & Birmingham), the design passes these criteria. The Centre-in ANV strategies proved to be more effective than the Edge-in strategies for space cooling due to the extended structure thermal mass

Thermal responses of single zone offices on existing near-extreme summer weather data

There have been a number of attempts in the past to define “near extreme” weather for facilitating overheating analysis in free running buildings. The most recently efforts include CIBSE latest release of Design Summer Year (DSY) weather using multiple complete weather years and a newly proposed composite DSY. This research aims to assess how various single zone offices respond to these new definitions of near extreme weathers. Parametric studies were carried out on single zone offices through which four sampling sets of models were employed to examine the thermal responses of dry bulb temperature, global solar radiation & wind speed collectively. London weather data from 1976 to 1995 were used and the overheating assessments were made based on CIBSE Guide A & BS EN 15251. The research discovers that solar radiation and wind both influence the predicted indoor warmth with solar radiation has obvious stronger impacts than wind. No perfect correlation was found from observation and Spearman’s rank order analysis on the ranks between the weather warmth and the predicted indoor warmth. The ranks made using multiple weather parameters show better correlation than some of the dry bulb temperature only metrics. The research also discovers that the Test Reference Year weather behaves warmer than expected. It is also found that a single complete year can not represent the near-extreme consistently and there is no evidence a composite DSY is better statistically. These findings support the notion of using multiple complete warm weather years for overheating assessments