For simplicity's sake the determination method outlined in previous issues of this article did not include the air infiltration through cracks. The graphical method is again demonstrated when allowing for air infiltration as specified in German standard DIN 4701 and examples are given.
Points out mistakes in text book formulae for determining the flow rate of fresh air. Provides a new approximate formula for this. Establishes a differential equation for air change rates and derives a generalized equation for ventilation incorporating only three parameters. Provides curves for determining the fresh air flow rate and gives calculated examples.
Outlines the development of current ideas of effective ventilation from early 19th century when official (U.S.) requirements were unduly high due to misconceptions in health requirements. Examines current requirement.
Reports theoretical and experimental calculations of heat balance of 5 houses. Discusses the extent of air leakage and various factors contributing to heat losses, particularly effects of wind and winter temperatures. Normal air leakage is 0. 5-0.7 air changes/h, mainly through chimneys, air outlets, window, and door cracks. Air leakage of floor, door, and roofs is 0.1-0.2 air changes/h. in winter, temperature differences have the same influence on ventilation as wind velocity. Measurements in attics show 3 air changes/h. This is largely dependent on wind velocity.
Presents a general picture of the consequence of wind on high buildings. States that the air velocity in the lower 250-600m layer of the atmosphere is strongly affected by the shape of the earth's contours, and discusses the effect and size of eddies. Gives the range of wind pressure variations between windward side, leeward side and at corners and edges and outlines problems that can result in ventilating, from draught and other wind hindrance aspects. Brief tips are given to minimize serious mishaps from the result of wind near high rise buildings.
Gives survey of humidity in Canadian homes indicating that humidity depends primarily on outside conditions but is influenced by the ventilation habits of the occupants and moisture storage by hygroscopic material. The difference between indoor and outdoor humidity ratios gave an estimated ventilation rate of 0.44 charges per hour. Resultant indoor relative humidity level is between 25 and 30% on average and approaches the maximum humidity attainable without condensation on double-glazed windows.
Analyses wind pressure records, taken during 5 different windstorms on 2 levels in a 400ft (122m) high office building in downtown Montreal March 1964 pressure fluctuations on an actual building. Preliminary work done to compare full-scale measurements with wind tunnel measurements indicates that simulation of basic statistical properties of wind pressure fluctuations can be successful when carried out in a boundary layer type of wind tunnel.
Wind pressure measurements made over a 4 years period on a 34-storey building in downtown Montreal were used to obtain data for checking and improving wind tunnel techniques of modelling flow characteristics of wind and aerodynamic behaviour of buildings. Specifies the major problems involved in making field measurements and in comparing them with wind tunnel measurements. Comparisons with model measurements are made. Examples have been found of excellent agreements, but for some wind directions the comparisons gave unsatisfactory correlation.
Gives the results of measurements of wind and driving rain carried out over a 1-year period on an 18-storey block of flats, and compares these results with calculated and model scale data. The in-situ measurements indicate that the pressure differences between various locations on a facade, exposed to rain are much smaller than the calculated values, and also pressure differences due to wind at a window between the inside and outside are much lower than the theoretical values.
Discusses current knowledge concerning wind-induced ventilation in buildings. states major difficulty in estimating ventilation and infiltration rates in a building is ignorance of wind pressure distributions around structures. Examines properties of wind with special reference to mean velocity profiles, characteristics of turbulence and wind energy spectrum. Reviews internal and external pressure distributions on an isolated building. Studies effect of grouping of buildings on pressure distribution around a house by considering results of wind tunnel tests.
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