Calculation methods for single-sided natural ventilation - simplified or detailed?

A great energy saving potential lies within increased use of natural ventilation, not only during summer and midseason periods, where it is mainly used today, but also during winter periods, where the outdoor air holds a great cooling potential for ventilative cooling if draft problems can be handled.

This paper presents a newly developed simplified calculation method for single-sided natural ventilation, which is proposed for the revised standard FprEN 16798-7 (earlier EN 15242:2007) for design of ventilative cooling. The aim for predicting ventilative cooling is to find the most suitable simple method that will in average perform well, while reducing the risk of overestimating airflows in individual cases with different temperature difference, wind direction and wind velocity. Therefore, the results from the new and simplified calculation method will underestimate the measured (real) airflow.

The predicted airflow rate from the new and three existing design expressions are compared to full-scale wind tunnel measurements. The new proposed calculation method for single-sided ventilation shows results, limiting the overestimation of air flow rates at especially low driving pressures, while maintaining an acceptable correlation with measurements on average and the authors consider the simplified calculation method well suited for the use in standards such as FprEN 16798-7 for the ventilative cooling effects from single-sided natural ventilation

The comparison of different design expressions reveals strengths and weaknesses based on the aim of the calculation. A guidance on when to use which level of details in the calculations are given.