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to furnish openings in the windows which shall throw air upward should be abandoned absolutely, and attention should now be given to make the window openings of the form best suited for summer ventilation. It is most advisable that the windows shall open so as to use the full aspirating power of the wind upon the air in the building. The movable pane falling inwards, shown on Fig. 10, p. 60, does not lend itself well to summer ventilation, for it neither favours the easy
ingress nor the ready egress of air. Wind blowing along the front of a window would not aspirate powerfully on the opening. In order to effect this, hinged windows opening outwards, or window panes having pivots top and bottom, instead of the usual swinging panes pivoted longitudinally, are best. Alternate panes or windows when partly opened could be splayed to face the wind, which would then be caused to blow into the building, whilst the next pane could be splayed in the opposite direction, the result being that the wind blowing against the edge, E., Fig. 25, would aspirate powerfully upon the air in the building. It should not be forgotten that wind blowing against E. will aspirate twice as much as if it blew along the flush front of the window, because the friction encountered will be so much less. Figs. 24 and 25 show these window openings. Windows are best made flush with the outer wall, or nearly so, the rebate being inside. For schools and halls it is also best for the windows to open outwards, as the action of the wind is so much more effective. Want of space prevents further reference, but enough has been said to show how important it is to give more attention to window openings of the form for summer ventilation. These openings can be used in place of the inward V. openings, Fig. 1o, for winter use, and they are quite as effective, although not recommended for the purpose. The upward lift of the incoming air will be found to be much more imaginary than real, because the velocity has to be cut down, or the descending deluge would be intolerable.
The question of inlet air, its warming and introduction to the building, will be considered next. The author maintains that the best way of ventilating a building either with, or without mechanical aid, is by having a heating chamber underneath not less than 8 feet high, and preferably 1o feet if possible. With regard to the fresh cold inlet air, it must be taken from as pure a source as possible, and if it cannot be admitted into the building without being first subject to the effects of wind action, care must be taken to prevent the aspiration of the wind as much as possible at the points where the inlets start through the outer wall. These inlets should enter the heating chamber at the lowest point possible, and pass into the centre. Here a large body of hot water pipes should be laid, and the inlet air carefully distributed and heated by them. A row of small pipes should be carried around the walls in the church or hall just above the floor to heat the air cooled by the walls and windows, and provision should also be made for warming the air in the lobbies, if there are any.
The inlets through the floor of the church or hall above should be covered over in such a way that the warm air can enter at the floor level and yet be prevented from shooting upwards. The opening of each inlet should be about 12 square inches in area, and 12 inches long, and two of these should be fixed in each pew, or six at least in every row of seats or chairs across the building. The inlets are best fixed under the seats or chairs.
With a heating chamber some 1o feet high to the top of the floor of the church or hall, there will be, as stated before, an increased ventilating power in the building. This increase should be used up in forcing the foul air through the outlets, and, whilst ample area should be afforded separately for spring and autumn use, the outlets for winter ventilation should be so under command that the cracks and interstices should not take much more than half the total volume of air coming in even when the temperature of the air outside is at 32o F. This statement is repeated here to show how necessary it is to expel the outlet air at a high velocity, so that the wind effects outside may not give rise to a down draught, or to intermittent air currents. By sending the inlet air through small apertures, and plenty of them, the velocity need not be great —the point is to leave enough ventilating power on the building to expel the outlet air at 1o feet per second if possible, and this can be done in very cold weather.
Where it is not practicable to have a mixing chamber underneath the building, the next best method of heating and ventilating is by hot water pipes under the aisles, in front of the communion rail, and round the walls of the building, so as to heat the cold air falling from windows, etc. The pipes under the aisles should be fed at frequent intervals by fresh air ducts, and to ensure a more even distribution of the air along the pipes, each duct should have three ways ^ at the end joining the pipes. Above the fresh air way and underneath the pipes, sheets of perforated zinc having iron bound edges to keep them flat should be fixed, so as to make sure that no great rush of air can come up in one place. The grating over the pipes should be 2 feet wide, with apertures not less than 1\ inches square. It is most essential to avoid as much friction as possible, and the gratings must not be covered with matting or carpet. In the lobbies the air should be heated so that no draughts are felt in the aisles when the doors are momentarily opened.
The roof should be thoroughly felted, and all outlets placed under proper control. The windows and panes for summer ventilation should all open outwards as shown 'in Figs. 24 and 25.
Whether the pipes are laid under the aisles, or whether a heating and mixing chamber has been built under the church, as suggested, the architect will do well to provide a small window opening, say four square feet in area, as high as possible, and at the end of the church furthest away from the prevailing winds, so that the caretaker can get at it easily and open or shut it without the attention of the audience being directed to what is done. Wherever inlet air is being warmed, either before or as it enters a building, a sudden rush and pressure of the outer air through the doors as they are opened will have the effect of driving back the air from the inlets near the floor level. Any observant person will notice in a church heated with hot water pipes below the aisles and having air inlets entering the trough in which the pipes are fixed, that when the doors of the structure are opened for a few seconds the inlet air is backed, with the result that what remains around the pipes becomes strongly heated and is quickly driven inwards by the sudden rebound of the air through the inlets as soon as the doors are shut again, whilst a moment or two later the incoming air appears to be much colder than it really is. The architect will do well to provide such a window opening as is described above, because this will enable the caretaker at the time the audience is entering the building to throw it more or less open, and relieve the internal pressure caused by the frequent opening of the doors. It may occur to some, perhaps, that if sufficient ventilators were provided, the caretaker could open these, and it would not be necessary for him to have a window for the purpose. It is not at all advisable, however, that the ventilators should be touched when the audience was assembling. These should be most carefully considered and regulated an hour before. If the ventilators were opened wide and forgotten, the church may be subjected to intermittent air currents all through the service. Furthermore, a window opening high up at the east end of the nave of a church would be most valuable for summer ventilation, especially where the prevailing winds blow from the west, south-west or north-west. Double doors are always provided in modern churches and most public buildings, and where air is warmed in quantity and admitted near the floor level, double doors are more necessary than ever.