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PHYSICAL LAWS BEARING UPON CHURCHES AND PUBLIC BUILDINGS.
Temperature.—In the majority of churches and public buildings there is no mechanical aid to ventilation, and during the summer months all that is done is to open the windows, and perhaps the doors during very hot weather. If the caretaker does his best to keep the air pure, and thinks fit to open all the apertures, there will be many in the audience probably who will object to any movement of the air, and these will endeavour to shut any air inlets in their neighbourhood. It is always best, therefore, to have the window openings out of the reach of the audience, and not to leave cords or other regulating appliances at their disposal.
The caretaker should carejully note the temperature of the air outside in the shade before he attempts to open the air inlets, in cold weather, and in spring and autumn this precaution is still more necessary. Where there are Tobin shafts near the ground, these cannot be opened wide if the air is 55° F. or less, and if they are, persons sitting close to them may take severe colds or suffer from neuralgia. Windows should not be opened widely unless the temperature is 65°, but at any temperature above 65° F., all the provisions for summer ventilation may be brought into play, and all Tobin shafts may be opened. When the temperature is 70° outside, or more, the doors afford further means of ventilation, and if any wind is moving, they may often be opened with most pleasant and marked benefit in hot weather. In the next chapter this will be dealt with more fully, and illustrations given Jo show how the wind will act.
Where there is fair provision for sending warm fresh air into a building at the floor level, it will be well to begin to heat the air slightly when the outside temperature is less than 55°, and when it is 5o° the air should be warmed in all buildings. During the autumn and early spring, the air is generally humid and raw, and by tempering it a few degrees it is rendered more fit to take up the moisture from the breath of the audience, and more amenable to upward movement, as the ventilating pressure of the building will be increased.
The caretaker will not be long in noting what temperature the audience likes best. He will soon get complaints of being too hot, if it is a degree or two above the usual, and if he goes at once to the thermometer and reads the inside temperature, and then without delay notes the temperature of the air outside, by the thermometer fixed on the north side of the church, or in the shade, he will obtain valuable information. Too much stress or importance cannot be attached to the necessity of providing a good thermometer for taking temperatures outside the building. It is the exception, rather than the rule, to do this, and hitherto a thermometer inside the building was the only one generally provided. The sudden increase or decrease of pressure, due to the rise or fall in temperature which so often occurs in this country, could then be noted, and precautions taken to prevent the close, unpleasant atmosphere which results from overheating air which is charged with moisture. The caretaker should endeavour to keep the temperature of the building at 58°-62° F., according as is best suited to the comfort of the audience, and this will depend upon the volume of warm air which gets into the building at the floor level. In order to maintain this temperature, much more heat will be required in damp, cold weather, and it is only possible to prevent extremes of heat and cold inside the building by carefully observing and considering the temperature of the air outside. When it is a question of admitting unwarmed air, then the temperature of the outside air is equally important, and should be carefully taken before adjusting the inlets prior to the assembling of the audience. In like manner the temperature of the air outside should be the indicator for opening or closing the valves of any ventilators on the roof, or any other foul air exits that may be provided.
In this country it is usual to heat the churches and halls in cold weather to about 55o F. before the audience assembles. In America 7oo F. is nearer the mark, but there is less moisture in the air than here, and more provision is made for removing the overclothing—men and women sitting in their seats dressed much as they are in their own homes. Under these circumstances, which might be imitated in this country with much comfort^ it is possible to stand a higher temperature, but even then 65° will be the limit which can be borne without a feeling of enervation, in England. If men and women could be educated to dress so that the outer apparel might be removed in a church or public building, a much better chance would be afforded for increasing the ventilating power, especially during the autumn and spring months when it is so difficult to get any appreciable ventilating pressure, and when, at the same time, the opening of inlets for fresh air unwarmed is attended with unpleasant experiences. The higher the temperature the more aqueous vapour air takes up and retains, and the breath of the audience will not condense upon the walls and other surfaces if the temperature is 60° or more. It is assumed in saying all this that there is a reasonable volume of fresh air warmed coming into the building, but when that is not the case, as unfortunately it generally is, it is well to recollect that the germs evolved in breath can work best and decompose the organic matters present at a high temperature. On the other hand, however, the higher the temperature the easier it is to ventilate the building, and to attain this, every effort should be made to provide and introduce more warmed air at the floor level. When this is done a temperature of 65° F. after the audience has been present half an hour will be agreeable. In our dwellings 65° F. is the most pleasant temperature when there is enough fresh air moving, and with proper provision in public buildings this temperature would be equally satisfactory.
The caretaker will always take due notice of the increase of temperature which will result from the bodies and breath of the audience. Not unfrequently 5° is allowed for this addition. In other words it is assumed generally that if 600 is the maximum the congregation will stand with their jackets and wraps on without grumbling, then the thermometer must not register more than 55° F. before the audience begins to arrive. When the caretaker reads the thermometer, which is frequently if not usually fixed against one of the walls, and finds it 55° F., he probably ascertains correctly both the heat of the walls on their surfaces as well as the heat of the air in the building. If he consults it after the audience has come in, the thermometer will show an increase of temperature, but if against a wall, it will not give so high a figure as it ought, because the air in the building has been heated quicker than the wall. For this reason the thermometer ought to be fixed or better hung from some projecting woodwork away from the outer walls. When 5o F. or more is allowed for the heating of the bodies and breath of the audience it shows a sad deficiency of inlet air, but in small buildings like mission halls which are crowded, a rise of nearly 10° may be expected during moderately mild and humid weather.
It is during such weather thi1t the difficulties of the caretaker are greatest so far as trying to prevent overheating, but in many if not the majority of churches and public buildings when the temperature of the air outside is less than 35° it is found to be almost impossible to get the walls of the building warm enough to make it comfortable for the audience. The fire is lit on the Saturday evening—not infrequently early on Saturday morning—but, after firing with the utmost care, the building defies to be warmed sufficiently. The thermometer on the wall registers only 5oo and will not go higher, and in some cases will not rise to this. Instead of this result the walls ought to be heated to 6o° F. and should show this temperature when the doors were opened to admit the audience. The air in the building could be lowered by opening the doors and ventilators for a few minutes, and fresh air, mostly cold, admitted half an hour before the meeting. The reason why it is so difficult to warm the building when the air outside is below 35° may in some cases doubtless be due to want of sufficient heating power. But, generally speaking, it is owing to the cracks and fissures in the roof, and to the ill-fitting valves connected with the ventilators. It is not difficult to ascertain what is the matter and to point out the remedy. The advantage of heating the walls of the building rapidly and sufficiently hot needs little advocating. In churches and other buildings where the seats touch the outer walls and the audience sit close to them, the cooling effect of cold walls is unpleasant and injurious. In a large number of places of worship the seats adjoin the outer walls and are fixed thereto, and when the walls are cold, as they generally are, not only is there a cold douche of air descending continually, but the feet of all those in the side seats are rendered frigid by the cold current of air which moves towards the aisles so as to get to the down grating of the heater, or in the direction of any heating medium which may be near. If the inner walls of the building could be heated to 60° quickly, then there would be comfort for those sitting near them, and no moisture from the breath would be deposited on the walls. The upper part of the buildings