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The limitations of animal shelter ventilation with respect to winter heat balance were outlined by Turnbull (4, 5). Pattie (1, 2) showed that better control of humidity could possibly be achieved by use of a porous ceiling air inlet, but that a ceiling of low porosity is not likely to allow any significant water vapor exfiltration. Turnbull (6) at Ottawa found that a 0.31% porosity perforated ceiling resulted in significantly lower relative humidity in winter than a ventilation system with adjustable perimeter slot inlets. This could not be explained by water vapor exfiltration through the ceiling insulation, nor by the conservation of heat resulting from cold air infiltration through the insulation. It is possible that the barn humidity was reduced in the coldest weather by increased condensation on the ceiling surface chilled by the layer of cold air as it was emerging through the perforations. This condensation is not considered satisfactory, and the experiment was extended by installing a fully-porous ceiling at Normandin, Quebec.
ventilation of dairy barns with porous ceiling inlet systems - part ii
Turnbull, J.E. and J.P.F. Darisse 1975. VENTILATION OF DAIRY BARNS WITH POROUS CEILING INLET SYSTEMS - Part II. Canadian Agricultural Engineering 17(1):59-62.
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