Glimpses of Good Houses
Note: This article is a historical look at opinions on healthy living over a century ago and should not be considered as medical advise or building instructions.
We have discussed now, in these short articles, the need for fresh air and several well-known artificial means of supplying it. I wish, however, to go rather more fully into this question and explain other methods by which agood supply of pure air may be maintained.
A number of small openings should be preferred to one large one, for by means of them a greater diffusion of the air takes place and unpleasant draughts are avoided. There are various ways in which these openings are supplied; simple gratings of iron or zinc are not infrequently used, but unless there is some means of regulating the supply of air from these, they are apt at times to produce an unpleasant draught. What are called louvred openings are occasionally found, but here again owing to the fact that there is no provision for regulating the flow, the method is not a very satisfactory one.
What are called Tobin’s tubes (wayback) are frequently used and altogether form a very good appliance. They consist of a metal or wooden tube which passes through the wall and rises to a fair height in the interior of the room. The mouth of the tube on the outside is covered by an iron grating, and inside, a piece of gauze is frequently placed to protect the channel from dust. If this cover is regularly cleaned the tube will be successful, but if dirt is allowed to accumulate in it, more harm than good may result. In order to purify the incoming air the mouth of a Tobin tube is sometimes made in the form of a drawer in which a layer of water or loosely packed cotton wool is placed. An overhanging flap prevents the direct rush of air into this filter.
Another form of ventilator is called the Sheringham valve, and consists of a metal flap covering an aperture in the wall, and able to be let down by means of a weighted cord. The flap can only fall out a matter of 30° from the wall and the sides are protected by triangular pieces of metal, so that the air is deflected to the ceiling.
In addition to the methods I have named, there are several special ventilating bricks to be obtained. Ellison’s conical bricks have trumpet-shaped holes pierced through them so causing the air entering at the narrow end to become diffused before reaching the room. Jenning’s air brick has apertures so made as to direct the flow of air upwards.
For large rooms or hotels there is another means adopted. It consists of a cornice made of metal, and hollow. The lower half of the cornice supplies, through numerous perforations, fresh air to the room, while the upper half sucks up the stale and vitiated atmosphere and conducts it to a flue or airshaft.
As I mentioned in some previous articles in The House, the disadvantage of this system is that the two apertures are too near one another, so that there is a danger of the fresh air being drawn out without doing its work at all
So much for inlets for fresh air, but a word should also be said concerning the outlets for impure products. Generally speaking these should be as near the top of the room as possible, because the air which has been in a room some time, tends to become warm as its vital properties become exhausted, and, therefore, rises towards the ceiling.
Most ventilation depends upon the chimney, because of the upward draught to be found there. It is due in the winter to the fire, but in the summer there is still a draught upwards, owing to the action of the wind blowing across the top of the chimney and relieving the pressure upon the air it contains. If we utilise the fire grate as an egress for impure air, we are likely to be troubled with unpleasant draughts across the room.
This may be avoided by retaining the chminey as a ventilating flue, but making an apeture somewhere higher up on the wall, so that the impurities may escape that way. It is obvious that with smoke passing up the flue, any aperture made in the wall must be like a valve, so that while the heat can get through one way, smoke cannot escape the other.
Arnott’s valve is a box with a light iron flap which only yields to the pressure from the inside of the room. Boyle’s mica valve is similar in character, but improved in some respects. All arrangements of this kind, however, are likely after a time to become dirty, and consequently the best device of all is an air shaft built side by side with a chimney shaft, so that while the warmth of the fire is used to induce an upward current, the smoke has no opportunity of returning to the room.