title: Predicted percentage dissatisfied with ankle draft.
abstract: Draft is unwanted local convective cooling. The draft risk model of Fanger et al. (Energy and Buildings 12, 21-39, 1988) estimates the percentage of people dissatisfied with air movement due to overcooling at the neck. There is no model for predicting draft at ankles, which is more relevant to stratified air distribution systems such as underfloor air distribution (UFAD) and displacement ventilation (DV). We developed a model for predicted percentage dissatisfied with ankle draft (PPDAD) based on laboratory experiments with 110 college students. We assessed the effect on ankle draft of various combinations of air speed (nominal range: 0.1-0.6 m/s), temperature (nominal range: 16.5-22.5°C), turbulence intensity (at ankles), sex, and clothing insulation (<0.7 clo; lower legs uncovered and covered). The results show that whole-body thermal sensation and air speed at ankles are the dominant parameters affecting draft. The seated subjects accepted a vertical temperature difference of up to 8°C between ankles (0.1 m) and head (1.1 m) at neutral whole-body thermal sensation, 5°C more than the maximum difference recommended in existing standards. The developed ankle draft model can be implemented in thermal comfort and air diffuser testing standards.
authors.affiliation: Center for the Built Environment, University of California, Berkeley, CA, USA.
authors.forename: S
authors.identifier: 0000-0002-0642-9700
authors.initials: S
authors.lastname: Liu
authors.affiliation: Center for the Built Environment, University of California, Berkeley, CA, USA.
authors.forename: S
authors.identifier: 0000-0003-1285-5682
authors.initials: S
authors.lastname: Schiavon
authors.affiliation: Department of Building, Energy and Environmental Engineering, University of Gävle, Gävle, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Kabanshi
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
authors.forename: W W
authors.identifier: 0000-0001-5645-3357
authors.initials: WW
authors.lastname: Nazaroff
mesh_terms: D000392:Air Movements; D000842:Ankle / Q000502:physiology*; D002140:California; D003020:Clothing; D005260:Female; D006801:Humans; D008297:Male; D010549:Personal Satisfaction; D012044:Regression Analysis; D013334:Students; D013696:Temperature; D013697:Thermosensing / Q000502:physiology*; D014495:Universities; D014691:Ventilation
keywords: displacement ventilation; draft risk model; local thermal discomfort; thermal comfort; thermal stratification; underfloor air distribution