crack

Describes tests performed on laboratory manufactured and prefabricated concrete specimens, to determine air leakage rates through cracks. Shows the expected increase of air leakage for increasing crack width and the decrease for increased element thickness. Appropriate theoretical assumptions are described, and the results show relationships for the calculation of the magnitude of air leakage through cracks.

Considers the characteristics of flow through small gaps. Discusses relation between wind tunnel measurements and actual wind pressure on buildings and the effect of building shape on ventilation. Derives equations for flow rate through a gap for different temperature and pressure differences and sizes of gap. The equations consider the pressure as a function of time thus modelling the effects of a turbulent wind incident on a gap.

This work deals with different aspects of air movements in building components. The investigation shows to what degree the concept of fluid mechanics can be applied to problems concerning air flows in building componenets. The applicable parts of fluid mechanics are presented as thoroughly as possible. Based on this concept, routines are outlined to make it possible to handle complex flow and pressure distribution problems. Both manual and computer calculation routines are described and the way they can be used is demonstrated in a number of examples.

Discusses the two methods for calculating air infiltration given in the ASHRAE handbook. These are the air change method, a gross estimate based on the number of windows and doors in each room, and the crack method based on measurements of flow through the cracks around windows and doors. Presents comparisons of tracer gas measurements with calculations by both air change and crack methods for test houses in California and Minnesota. Find agreement is adequate for sizing equipment but that the crack method underestimates infiltration at low wind velocity.

Reports measurements of natural ventilation and leakage rates in two test rooms in a university building. Describes rooms and instrumentation. Gives results of pressurization tests with windows closed but not sealed, sealed, and weatherstripped. Gives results of measurements of ventilation rate using N2O as a tracer gas. Discusses the analysis of results and experimental errors. Compares measured rates with ventilation rates calculated using crackand ASHRAE methods.

Describes in detail a multi-cell model for predicting ventilating airflows. Gives equations for flow through cracks, wind and stack effect. States that comparisons between prediction and measurements indicate that the method is capable of giving relatively high accuracy for a wide range of ventilation conditions. Discusses advantages and disadvantages of multi-cell and single-cell methods. Argues that multi-cell approach is potentially more accurate and more useful.

Describes air infiltration measurements made in three apartment houses in the Chicago area using SF6 as a tracer gas. Two were in tenement districts and one was suburban. Data were collected in selected apartments in each building, and these data were used to estimate the infiltration rate for the entire building.

Gives method for calculating air infiltration through window cracks. Calculates pressure drops across windows in buildings for four types of building and discusses resulting pressure differences. Gives values for crack width and length. Recommends design values for rates of air change due to infiltration in buildings heated by off-peak electricity.

Discusses the mechanisms which govern natural ventilation. These are wind speed, flow, characteristics of openings in buildings and pressures generated at building surfaces by wind and temperature difference. Gives formulae for simple cases. Outlines ways of determining natural ventilation rates. Gives brief account of the effect of turbulence and openings in one wall only.

Describes apparatus and test procedure of tests made to show the effect of caulking the crack between the brick wall and window frame and the effect of applying storm sash to the window on air leakage rates. Concludes that the crack between the brick wall and window frame is a very important factor in calculating the infiltration into a room, but that this source of leakage can be practically eliminated by caulking the crack.