pressure difference

This paper discusses two particular points of the buildings airtightness measurement method (ISO 9972) in relation with the pressure difference: (1) the nature of the pressure tap and (2) the place of the pressure tap outside. 

The purpose of this study was to find out the local intensity and extent of doorway draughts, the functioning of air curtains, and the variation of the neutral pressure levels in 18 industrial premises. The doorway draught can reach the whole workspace and all the employees. At the doorline, close to the doorway, the thermal conditions can be even harsher than those outside. Air curtains significantly decrease the fluctuation of the temperature at work sites, but the functioning of the same type of air curtain varied substantially between the buildings.

Radon concentration in a crawl space remained at the same level during autumn ( 756 Bq m-3 ) and inwinter ( 767 Bq m-3 ) because both air exchange rate and negative pressure (measured across thefoundation wall) increased after a installation of a new ventilation system in the crawl space. Inaddition, relative humidity and water content remained constant in the crawl space air during the sameperiod of time. Radon entry rate was explained by the pressure difference across the crawl space wallwith percentages of 51 % (winter) and 76 % (autumn).

In the study, the factors affecting concentrations of radon vertically lines were surveyed in twolarge office buildings. Integrated concentrations of radon were determined with alpha track etchfilms (2 months) and continuous monitoring (2-6 days) was carried out with Pylon AB-5equipment. The effective air exchange rates were analysed by the tracer gas method with aninfrared analyser and rates of air flows from vents were measured with a thermoanemometer.Pressure differences were measured with a manometer and temperature differences withthermoelements.

Unexpectedly, the indoor-outdoor pressure difference did not affect significantly the moisture content in different layers of two outer walls but the moisture content depended more strongly on the moisture content in outdoor.

Multizone modeling refers to analysis techniques that use a simplified, zonal representation of a building to study building airflows, pressure differences, and contaminant transport. Each zone is assumed to have uniform temperature, pressure, and contaminant concentrations. Zones typically represent individual rooms but can be entire levels depending on the building layout and the goals of the modeling. Zones are connected through flow paths represented mathematically by pressure-flow relationships. This article describes CONTAMW [Dols et al. 2000], a multizone modeling tool.

At present the design pressure difference for air inlets in The Netherlands is 1 Pascal. This paperinvestigates the question whether or not this value is still appropriate.In recent years the airtightness of dwellings has improved remarkably. Self adjusting air inletshave been introduced on the market. What is the effect of these changing building features onthe pressure difference over the building envelope?