Calculation methods for single-sided natural ventilation: Now and ahead

Abstract

In order to reduce the energy consumption for cooling in our buildings, the use of passive cooling solutions is necessary. One of these solutions is natural ventilative cooling, where airflows generated by single-sided natural ventilation, until today have mainly been calculated from the De Gids & Phaff equation in the European Standard EN 15242:2007. In the revised standard EN 16798-7:2017, a new version of the equation for single-sided natural ventilation is released. The work in this paper will compare the results from the new equation with earlier equations for single-sided ventilation and hold them up against wind-tunnel measurements, full-scale measurements and CONTAM calculations to clarify whether and why the new equation is to be preferred for future design solutions for single-sided natural ventilation and ventilative cooling. Due to the implementation in calculation standards and regulations, the new calculation model should underestimate rather than overestimate the airflow rates, so as to remain on the safe side when estimating ventilative cooling potential. The work in this paper concludes that the new simple direct calculation model in EN 16798-7:2017 predicts the airflows through windows in a more conservative way than earlier equations, by representing an average of the airflow rate in the building that is generally on the safe side. The accuracy of the EN 16798-7:2017 equation was found by comparison to wind tunnel measurements to be 29% but with underestimations in 88% of the cases investigated. For the CONTAM calculations, it was found that the use of the new EN 16798-7:2017 equation (with room based height for the stack effect) slightly underestimates the airflow rate as desired, as soon as the temperature difference across the opening is above 0°C. Based on the comparisons presented in this paper, the authors consider the new calculation model in EN 16798-7:2017 well suited for the use in calculation standards to integrate natural ventilative cooling effects from single-sided ventilation.

Effects of ventilation on the indoor spread of COVID-19

“…Existing models for single-sided ventilation rates driven by wind and buoyancy are based on empirical fits to data from field studies and wind tunnel experiments (Degids & Phaff 1982;Warren & Parkins 1985;Larsen & Heiselberg 2008). These models generally underestimate ventilation rates in full-scale tests (Larsen et al 2018;Gough et al 2020). This is likely to be useful in the context of calculating the time to ventilate a room as this will provide estimates with a safety margin.…”

“…These models generally underestimate ventilation rates in full-scale tests (Larsen et al. 2018; Gough et al. 2020).…”

Analysis of Ventilation Efficiency and Effective Ventilation Flow Rate for Wind-driven Single-sided Ventilation Buildings

“…to equations given in the earlier version of the standard. The calculation model represents an average of the airflow rate in the building which is generally on the safe side (Larsen et al, 2018).…”

Boundary layer wind tunnel modeling experiments on pumping ventilation through a three-story reduce-scaled building with two openings

“…SSV can be divided into SS1 (one opening) and SSn (multiple (n) openings) according to the opening number. According to literature, most wind tunnel experimental studies on SSV focused on SS1 Eftekhari et al, 2003;Yamanaka et al, 2006;Larsen and Heiselberg, 2008;Bu and Kato, 2011;Chu et al, 2011;Larsen et al, 2018).…”