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ture of the air outside. He should know that the ventilating power of a building is to be measured by the difference in weight between the column of warm air inside and a column of cold air of the same height outside. That the warmer in reason he keeps the building in winter, the more air will get into it, and the more air will be expelled from it. If there is too much outlet area in the roof, cold air will come in, give rise to down draughts, and, at the same time, reduce the ventilating power of the building. By using his thermometer for outside temperatures, and closing the ventilators on the roof, he will soon find out at what temperature of the air outside there is any down draught experienced, and he will not be long in learning with certainty whether the ventilators can be opened at all without causing a down draught if the temperature outside is below 4o0 F. Should the caretaker find that there are down draughts and currents of air moving when all the valves are shut at 4o0 F., he will find also doubtless that there is much difficulty in warming his building at all under the circumstances. It will be best to keep the ventilators closed when the temperature is so low outside even whilst the audience is present, but he should call the attention of the managers to the fact, that something should be done to the roof in order to remedy the down draughts and intermittent air currents. As a general rule, in winter, the caretaker should open the ventilators as wide as possible without giving rise to down draughts, then close them to about three-quarters of the area so opened in order to make sure that the outlet air travels with good velocity. This is the best means of getting air through the building in cold weather, but the arrangement can only be carried out in winter if the area of the cracks and interstices has been properly adjusted. It is a practice generally recognised that the caretaker should open the ventilators as wide as possible, and the more movement there is of air the better the ventilation, providing there is no intolerable down draught. This is all very well for summer ventilation, because every one knows that slight currents of air are most refreshing then; but it is in winter that air currents are deprecated, for perceptible movements of air in a building in the winter always mean intermittent air currents. The caretaker will act wisely, therefore, if he closes the ventilators in winter so as to prevent down draughts, and use up the ventilating power of the building in forcing air through the outlets under considerable velocity.
If provision has been made for warming air, however insufficient in volume, before it enters the building, every effort should be made to admit the maximum possible. Where inlets have been closed because too much air came up in one place, some perforated zinc sheets should be obtained from the managers, and an attempt made to more completely distribute the air. Simple shutters of wood or covers which shall rest against the air gratings and inlets in very cold weather so that the air coming in can be entirely shut off or nicely regulated, should be obtained. It would astonish most persons to see what an immense volume of air will get in through a small inlet when the temperature is below 35o F. and the air is very dry. This is why the thermometer for taking the temperature of the air outside is so strongly recommended, because a man reading it, and marking a low temperature, will soon learn how to adjust the inlets accordingly.
Some general remarks respecting the heating of the building come next in order. The caretaker naturally wishes to heat his building in the quickest time possible so that it will not be necessary for him to light the furnace on the Saturday morning in order to be ready for the Sunday morning service. If he succeeds in avoiding this, and lights the fire early on Sunday morning, it stands to reason that less coal will be consumed, and his duty will appear to be better done. If this is possible, he is lucky, and must have the control of a building whose top outlet space is either not excessive or has been properly adjusted. But if the weather is cold, very few buildings can be sufficiently warmed by lighting the furnace on the Sunday morning. The chief value of having the top outlets capable of being closed almost perfectly, is the great saving of coal which can be effected in warming the building; and no caretaker can give satisfaction, or warm his building with certainty and economy, if the outlet spaces in the roof are excessive. Let it be assumed that the outlet spaces in the roof are excessive—what had the caretaker best do to heat his building? The heater is a hot air furnace. See that the cotton and woollen waste which settles inside the heater is cleaned out frequently, and that the gratings are clean also. This is very important. The caretaker should then go to the outside of the building, and find the grating through which fresh air is to get into the heater. Procure a cover which will close this air-tight. It may be argued that there is a lever connected with the apparatus to cut off the supply of fresh air. When the caretaker has had experience of the immense volumes of air that will pass a valve in cold weather, he will take sound advice, and close the air grating on the outside. When the building is ready for the audience, the cover should be lifted, and some fresh air admitted; but the quantity should never be so large that a lighted match or taper will not show a very appreciable movement in the current of cold air descending the grating. If there are any Tobin shafts, see that these are closed perfectly, and all inlets of whatever kind. As in the case of the air inlet to the heater, the most effective way to stop air entering a building is to close the grating perfectly on the outside. Having closed all the inlets, attention should be given to the outlets. The ventilators should be closed, and all window openings as perfectly as possible. If the building is heated very slowly and insufficiently when the temperature is below 350 F. after these precautions have been taken, then the air leaking through cracks and interstices in the
roof and around the valves in the ventilators must be considerable, and the attention of the superintendent should be called to the matter so that expert advice may be obtained as to the best means of remedying such a state of things. Where the top outlets are excessive in area and not under control, and hot water pipes beneath the aisles are used for heating, having air inlets entering the troughs where the pipes are laid, care should be taken that the inlets, the pipes, and gratings, etc., should be cleaned frequently. All these inlets should be closed air-tight outside before the heating is commenced, and opened judiciously so as to allow the largest volume of warm air to enter, just before the audience assembles. As before, all outlets should be closed perfectly to heat the building.
In cold weather, the furnace is to be lit on Saturday, early, and a good fire maintained all night. Every effort should be made to heat the walls of the building to as near 6o0 F. as possible, but this can rarely be done in churches in very cold weather. The double doors in the lobbies should be kept shut during the heating, and ropes of felt having sand inside are useful to place against doors which have much air space under them. Where it is impossible to warm the air in the building sufficiently in consequence of the cold weather, the seat stewards should keep the double doors closed, and admit the audience, as far as possible,' through one door at a time, but no time should be lost in having the outlet spaces in the roof attended to.
The caretakers of buildings where the outlets in the roof are less excessive, may always succeed in getting the temperature sufficiently high. They should, however, see that every inlet and outlet is carefully closed. If this can be done effectively, it will be best, notwithstanding, to light the furnace on Saturday afternoon, and keep it damped somewhat. If the fire is lit on Saturday night, or early on Sunday morning, the air may become warmed, but the walls will not be properly heated; and whilst those in the centre of the building will find the temperature high enough, probably, those seated near windows and walls will be subjected, to currents of cold air circulating and falling upon them in a very uncomfortable fashion. The heater will have unnecessary work to do during the time the audience is assembled, and the forced circulation of the air over hot plates of iron will lead to the formation of strong-smelling products from the oxidation of the organic matters in the breath, and the atmosphere in the building will be rendered very much more foul in consequence. Gn the other hand, if the furnace was lit some hours before, and the walls were heated to 6o° F., cold currents from the walls would not be experienced2 and the heater would have less work to perform. Where the outlets and inlets are alike under control, the temperature of the walls should be raised to 6o° F., and a steady and prolonged heating is best under any circumstances. If the walls have been properly heated, it is best to lower the temperature of the air inside just before the audience assembles, and;this can be done by opening the doors for a few minutes, and one or two windows on each side.
In spring and autumn when the temperature of the air outside is 500 F. or more, the caretaker is not unfrequently afraid to heat the air coming into the building for fear of getting it too hot. This difficulty can be obviated by making arrangements for the best control of the furnaces, and it is always advisable to heat the air a little, if possible, because the ventilation will be much improved. At these times, the inlets may be opened to their fullest capacity, arid.a gentle heat will remove the rawness from the air. A cold atmosphere inside is not only, uncomfortable, but it becomes very foul also, and this is especially the case if the walls axe cold arid there is much .moisture in the air before it enters. If the caretaker reads his thermometer for outside temperatures regularly, he will know by experience how to act» .