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What we think we know about the aerodynamic performance of windows

Sharpe, Patrick; Jones, Benjamin; Wilson, Robin; Iddon, Christopher

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Patrick Sharpe

Christopher Iddon


© 2020 Natural ventilation is a low energy strategy used in many building types. Design approaches are mature but are dependent on variables with high uncertainty, such as the aerodynamic behaviour of purpose provided openings (PPOs), which need improved characterisation. An analytical framework is used to define different types of flow through openings based on the balance of environmental forces that drive flow, and the different flow structures they create. This allows a comprehensive literature review to be made, where different studies and descriptive equations can be compared on a like-for-like basis, and from which clear gaps in knowledge, technical standards, and design data are identified. Phenomena whose understanding could be improved by analysis of existing data are identified and explored. A Statistical Effective Area Model (SEAM) is developed from academic data to estimate the performance of butt hinged openings during the design stage, that accounts for the impact of aspect ratio and opening angle. Its predictions are compared against available empirical data and are found to have a standard error of 1.2%, which is substantially lower than the 15–25% prediction errors of free area models commonly used in practice. An analytical model is made based on entrainment theory to explain the increase in flow rate that occurs through two aligned openings. This model defines characteristic design parameters and predicts a detrimental impact on the ventilation of the wider space. Finally, an analytical model is created to explain the reduction in discharge coefficient that occurs when a large temperature difference exists across an opening. This model defines novel dimensionless parameters that characterise the flow, and predicts empirical data well, suggesting that it should be integrated into design equations.


Sharpe, P., Jones, B., Wilson, R., & Iddon, C. (2021). What we think we know about the aerodynamic performance of windows. Energy and Buildings, 231, Article 110556.

Journal Article Type Article
Acceptance Date Oct 11, 2020
Online Publication Date Oct 16, 2020
Publication Date 2021-01
Deposit Date Nov 19, 2020
Publicly Available Date Nov 19, 2020
Journal Energy and Buildings
Print ISSN 0378-7788
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 231
Article Number 110556
Keywords Electrical and Electronic Engineering; Mechanical Engineering; Building and Construction; Civil and Structural Engineering
Public URL
Publisher URL
Additional Information This article is maintained by: Elsevier; Article Title: What we think we know about the aerodynamic performance of windows; Journal Title: Energy and Buildings; CrossRef DOI link to publisher maintained version:; Content Type: article; Copyright: Crown Copyright © 2020 Published by Elsevier B.V. All rights reserved.


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