Behavior of leakages exposed to dynamic wind loads. A numerical study using CDF on a single zone model

Wind is a potential dominant factor regarding the air infiltration through building envelopes. Due to its dynamic characteristics, quite complex aerodynamic phenomena arise around a structure or through cracks and openings. Energy perfomance is influenced by the climate conditions and thus it should be much more researched. Despite the fact that steady state measurements of infiltration rates offer a simple and easy way of estimating an enclosure’s airtightness level, a supplement to those methods might be imposed.

The effects of cracks and holes on the exhalation of radon from concrete.

The effects of cracks and holes on the exhalation of radon from concrete have been investigated. It was found that the total radon exhaled from concrete blocks was the same irrespective of the diameters of holes drilled into them, and irrespective of the number of holes drilled. Furthermore, the surface area of the concrete blocks did not have any effect on the total radon exhaled

Sealing cracks in solid floors: a BRE guide to radon remedial measures in existing dwellings.

This report is one of a series giving practical advice on methods of reducing radon levels in existing dwellings. It is intended for the guidance of householders and builders who seek to reduce radon levels in dwellings by sealing cracks and other discontinuities in solid ground floors. The remedial measures described are mainly for concrete floors laid directly on the ground but some of the principles could be used with suspended concrete floors and, to a lesser extent, with floors consisting of large stone slabs.

Experimental study of crack flow with varying pressure differentials.

Existing experimental techniques for calculating air flow through building cracks are usually based upon relationships derived from experimental studies employing relatively simple procedures. Typically, a fixed pressure difference, dP, is established across the crack of interest and then the air flow Q through the crack is determined. Most crack flow equations take the pressure differential dP to be steady-state. In reality, the wind forces which generate much of the driving pressures represent highly fluctuating signals.

Air flow through smooth and rough cracks.

A series of laboratory experiments are described which investigated the effect of surface roughness on the air flow characteristics of simple, straight-through, no-bend cracks with smooth and rough internal surfaces. Thecrack lengths, in the direction of flow, were 50.8mm and 76.2mm. For the rough cracks the roughness was simulated with two different grades of commercially available emery-cloth (grade 60 and 100). The effect of roughness on the reduction of air flowing through a crack is also discussed.

Modelling fluctuating air flows through building cracks.

The paper summarises an approach to determining the equations governing the air flow through simple cracks subject to fluctuating pressures. To this end, an experimental arrangement has been developed that enables the laboratory simulation of fluctuating driving pressure signals. A standard straight crack was subjected to this signal, which fluctuates in both magnitude and frequency. An air control system permits a high level of fluctuating pressure control.

The effect of different air inlet sizes on the air flows through a stairwell.

The effect of airflow through an opening (or a crack) on the natural convection in a stairwell model is presented. The flow is driven by energy input from an electric panel heater located in the lower floor of the stairwell. The work concentrates on the effect of the size of inlet opening by varying it while keeping the area of the outlet constant. New data are presented for the measured temperatures and velocities at various cross-sections of the stairwell.

Balancing ventilation systems using thermography.

It has been shown that thermal imaging can give an indication of air flow rates through small cracks. Using a finite difference analysis package it is possible to determine the surface temperature of an air transfer grille when subjected to airflow rates at higher temperatures than the grille surface. This paper will address this technique by presenting the results of the finite difference analysis package for a specific grille.