Power Roof Fan Ventilators
Proper ventilation requires that there be a movement or circulation of the air within the space and that the temperature and humidity be maintained within a range that allows adequate evaporation of perspiration from the skin It was formerly believed that the discomfort headache and lethargy commonly associated with poor ventilation were caused entirely by the increase in the amount of carbon dioxide and the decrease in the oxygen content of the air There is evidence to show however that the deleterious effects result largely from interference with the heat mechanism of the body Lack of air currents and the increase in relative humidity and temperature noticeable in crowded poorly ventilated places prevent normal evaporation of perspiration and loss of heat from the surface of the skin
A simple roof ventilator is essentially an opening in the roof with a cover to keep out rain and to prevent winds from interfering with its functioning Natural convection is an appreciable aid to ventilation in a large building only if it contains sources of large amounts of heat A further useful adjunct is a fan fan device for agitating air or gases or moving them from one location to another Mechanical fans with revolving blades are used for ventilation in manufacturing in winnowing grain to remove dust cuttings or other waste or to provide draft for a fire The addition of distribution ducts to the fan and a system for forcing air into the building provides greater efficiency Outlets are designed to attain maximum mixing of air and to move large amounts of air at low velocity so that temperature layers are eliminated Factories have special suction hoods and enclosures to draw away localized dust fumes and heat Incoming air may be cleaned of dust by filters or electrostatic precipitators
Natural ventilation depends on winds outside and convection currents inside a building Winds raise air pressure slightly on the windward side of a building and lower it slightly on the lee side The pressure difference promotes circulation into the building on the windward side and out of it on the lee side Convection currents are caused by the sinking of colder and therefore heavier air which displaces the warmer air A building may have a roof ventilator to allow the rising warm air to escape If there is an opening to the outside at the bottom of the building fresh cool air will be drawn in
Deep mines underwater tunnels and other subterranean and submarine environments require elaborate mechanically operated systems for maintaining the air supply in a healthful condition The lives of those working in or traveling through such areas depend upon a constant supply of fresh air; not only must the systems used be highly efficient but there should be provision for emergencies in case of failure of the apparatus in operation An outgrowth of studies of problems of ventilation is the development of methods of air conditioning heat pump is a reversible device that does mechanical work to extract heat from a cooler place and deliver heat to a warmer place The heat delivered to the warmer place is approximately the sum of the original heat and the work done
Such systems unlike ordinary methods of ventilation are independent of outdoor atmospheric conditions and can therefore maintain the indoor atmosphere at the most healthful temperature and humidity and can free the air of dust and other undesirable materials They accomplish this however at a considerable cost in energy
Roof ventilators are another option They work in both summer and winter In summer roof ventilators reduce the build up of heat in the ceiling spaces reducing the heat load on your insulation meaning that the insulation works more effectively In turn you will save on your electricity bills as the air systems will not have to work as hard In winter it reduces the amount of condensation that forms when warm moist air from exhaust fans meets cold surfaces Roof ventilators will also reduce the amount of corrosion and timber that occurs because of condensation Roof ventilators should be installed where there is sarking underneath tiled roofs when metal deck roofing is used and when there is evidence of condensation in the roof spaces or ceilings
A reliable ventilation system that can operate during a fire is both vital and essential It prevents smoke logging allows people to escape quickly minimizes damages to property and contents and enables firemen to attack the fire without hindrance Such power roof ventilators have the added advantage of providing normal day to day ventilation and in many cases can also be fitted with duct work for use in multi storey buildings
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