Measurements of sub floor ventilation rates - comparison with BREVENT predictions.

The performance of ventilation provision in subfloor cavities is relevant to the fields of energy efficiency, condensation risk, and air quality. Thorough programs of site measurements of ventilation rates by means of tracer gas tests are in general protracted and expensive, and it is quite clear that would be highly desirable to be able to predict ventilation rates given details of building design, ventilation provision, and d.egree of exposure. This paper describes a series of sub-floor cavity tracer gas ventilation measurements performed upon a low energy test house, and compares the results with a set of ventilation rates predicted for the sub-floor cavity by the Building Research Establishment ventilation prediction program BREVENT. Agreement between measured and predicted values is generally good, although significant discrepancies are observed at certain incident wind angles. This is thought to be due to difficulties in obtaining reliable data pertaining to wind pressure effects on ventilation openings at very low levels.