Chats on Home Hygiene, ventilation, warming and heating
Home Hygiene Part VII
The question which comes in natural sequence to that of ventilation is the warming of rooms and houses, and it is one which the approaching autumn makes of immediate and pressing interest.
Ventilation and Warming
Despite the fact that warmth is a matter of prime importance to health and life, the proper means of maintaining a comfortable temperature in the house are almost as little understood as those of achieving satisfactory ventilation. It is true that to warm a place is not in itself a very difficult object to accomplish. The real science lies in combining the warming with satisfactory ventilation. To heat impure air is an extremely unsatisfactory process, as the danger is thereby only increased; but, on the other hand, the letting in of pure air is likely to counteract the attempts of warming. Another question which deserves attention is that of economy in fuel. Much has been done by modern domestic engineering to effect some reasonable saving in the enormous amount of coal burnt by stoves and grates of older patterns, and when considering refurnishing the careful housewife will do well to jot this matter down on paper, and work out exactly the relative cost of the older and newer forms of fireplaces.
Methods of Heating
Heat as I have said in the previous article on this subject, may be communicated from one body to another by three processes; (i) conduction, (ii) convection, and (iii) radiation. Conduction is simply the equalisation of temperature which takes place in two bodies brought into contact. Radiation is the passage of heat from one body to another through an intervening space. Convection is the movement which takes place in a liquid or gas brought into contact with some source of heat. The density of the particles nearer the heat is made less, and consequently currents are set up and continue until the density and heat of the various parts of the liquid or gas is the same.
Now these three forms of communication, conduction plays the least part in warming a room. Heat passes from the grate to the mantelpiece, wall and floor, and so on, but the quantity is not great. The warm current set up also by an open fire gives rise to convection, but by far the greatest amount of heat is communicated by the radiation from the grate.
Hot Water Pipes
In the case of hot air pipes, convection is the method generally employed, but the disadvantages which such forms of warming have, in comparison with the open grate, is that the air admitted is in nearly every case dry and lifeless, whereas for the proper keeping-up of an open fire, a supply of fresh air is of absolute importance. The difficulties of the hot water pipe system however are rather due to faultiness of design or manufacture than to the principle itself.
Not only is it Important in the warming of a room to pay attention to proper inlets for fresh air, and to combine, as far as possible, a successful system of ventilation with one of warmth, but it is also essential to see that the quality of the air admitted is satisfactory. Not only must it be pure, but it should contain a certain amount of moisture, and the higher the temperature of the air, the greater its absorbency. This is the reason of the dry, irritating sensation in the throat and nostrils occasioned by sitting in hot dry air, for all the time it is attempting to abstract moisture from any possible source.
I will deal first of all with the question of open grates, which I think are probably the most healthy form of warming a room and maintain¬ ing a reasonable amount of ventilation. The fire in them has two tasks to perform, the one to warm the room,and the other is to set up a current so that impure air may escape up the chimney. It is clear in the first place that if too much air is introduced into the room, a much larger fire will be required than would be the case where only the necessary quantity of pure air was admitted. A big chimney, too, is apt to draw up a great deal of the hot, imperfectly burnt fuel, which thus does not do its part in warming the room. This is the reason that in many old fashioned houses the rooms are cold, although big fires are burnt.
I am afraid that this complaint applies to many modern firegrates also, and it is not perhaps unreasonable to estimate that not more than twelve per cent, of the heat generated in them is actually employed in the room. Some of my readers may remember a fully illustrated article on this subject which I gave some years ago, and I cannot do better than sum up here in the same form some of the faults I enumerated then;
- 1. The back and sides of the grate are constructed of iron instead of fireclay
- 2. The front bars are wide apart, and the coal is liable to fall out, which causes a rush of fresh air and unnecessary combustion
- 3. The wideness of the bottom bars is responsible for similar waste
- 4. The chimney opening is immediately above the grate, and consequently the coal before it is properly consumed passes up the chimney with the heated air
As a protection the following are the rules which should be observed;
- 1. Fireclay should, as far as possible, take the place of iron in the grate
- 2. The bars in all cases should be narrow and closely set
- 3. The air should not be admitted from below
- 4. The flue should so communicate with the stove as not to give rise to undue draughts at the back of the fire, otherwise the products of combustion are carried off before they are consumed.
Mr. Teale, in a paper he read before the Architectural Society of London, advised;
- 1. That the fireplace back should run forward over the fire at an angle of seventy degrees.
- 2. That the sides should be vertical, and incline to one another towards the back, at an angle of sixty degrees.
- 3. That the bottom should be deep from before backwards, varying from nine to eleven inches.
- 4. That the slits in the grid under the fire should be narrow, from a 1/4in. to 3/8in. apart, according to the quality of the coal burnt.
- 5. That the front bars should be vertical and narrow, about 1/4in. in thickness and 3/4in. apart.
- 6. That the chamber under the fire should be closed by a shield, to prevent an unnecessary
P.S. In reply to a question, what is called the Sherringham valve is a wedge-shaped opening in the upper window, formed of pieces of glass and with a flap, opening at the top.
The Hit and Miss ventilator is a disc of glass fastened through the centre to the window pane, and with small triangular apertures which hit or miss other apertures cut in the window. This device will be familiar to everyone.