Fig. 9.
Fig. 9 shows a method of admitting air above the architrave of the entrance door of the room. The opening is made about 2 ft. in length; this, after a little time, becomes marked by the blacklets coming in from the passage. The sweeping flue when the fire is lighted becomes very hot; the smoke ascends speedily and soon leaves it. The flue requires the stove to be formed expressly for it. Mr. Cubitt made the stoves only for his own houses, and the author had some difficulty at Queen’s Gate, in procuring stoves of the right pattern, for manufacturers prefer their own shop patterns, and some of these would have covered up half the descending flue. Those he used were supplied by Messrs. Feetham of Clifford Street, who are well acquainted with the use of the flue and stove. The flue is considered an excellent one; it is a builder’s flue, constructed solely of brick, and is certainly the best of the brick flues. The same attention was paid to it as was given to every part of Mr. Cubitt’s buildings. It may be asked, “Are there no other kinds of flues constructed of superior materials?” Yes, certainly there are; particular attention has often been paid to the flue. There is Hiort’s circular flue, formed in each course of four wedge-formed bricks. Mr. Hiort held a very important position; he was Treasurer of the office of Works at Whitehall, and his flue was extensively used in some of the Government buildings and the houses in Carlton Gardens. It did not bond well with the brickwork, so we have Mr. Moon’s improvement upon it. This was considered not sufficient, and another patent was taken out in 1844 by Messrs. Clark and Reed for its further improvement. The flue was an excellent one, but on Mr. Hiort’s retirement from the Government Board, it went out of use.
There is Seth Smith’s metallic chimney lining, which makes an excellent flue; the lining is a pipe of from 5 to 10 in. in diameter, built in the brickwork. About 150 of these flues are at the Pantechnicon. Mr. Smith announced his determination of never building any house above the value of 30l. per annum, without using them. They could be introduced, to form perfect linings to chimneys in buildings already erected, and allow the stack to be reduced in height, without having the unsightly appearance of contractions made above them. The drawback to the use of these tubes by builders was the price. Without any royalty, the 9 in. tube cost 3s. 4d. per ft. run, the curved tubes 4s. 3d., the starting tube 3s. 8d. The tubes were of the exact form of drain pipes, and they were cheaper, and as effectual.
If Mr. Smith’s metal tubes had been introduced into a large brick flue, they would have rendered the latter an efficient shaft for ventilating every room in its upward course, openings being made for the purpose at the upper part of the rooms. This mode of ventilation was applied to hospitals on a large scale by the late Mr. Jacob Perkins several years ago, with perfect success.
Denley’s flue, introduced in 1843, is believed to have been the precursor of that used by the late Mr. Thos. Cubitt at Belgravia and Pimlico, and there is a great resemblance between the two; but Mr. Denley’s flue has nothing like the simplicity nor ease of construction of Mr. Cubitt’s. The downward flues were merged into one at the basement, and all the soot and cinders were collected or thrown down into a fire-proof box, which must have stood out in the lower rooms, from which they had to be removed. The flues were swept from the roof, the register doors of the stoves being closed, and there was no provision for sweeping the flues between the basement and the stoves. Joined to his system for sweeping, was one of air flues which brought a current of air direct from the exterior of the house to each fireplace.
We have several flue systems which have ventilating flues in connexion with them. Boyd’s flue forms the wythes, or half-brick spaces between the flues, of iron plates, and the open spaces thus gained make ventilating passages. Mr. Doulton’s combined smoke and air flues are manufactured in terra-cotta, in three sizes; the air flues follow the line of the smoke flue, the passages being quite distinct, as in Mr. Boyd’s. The heat from the smoke flue causes a current in the air-flue which carries off the vitiated air admitted by openings near the ceiling. The common drain pipes and the glazed fire-clay pipes make good flues; the use of these pipe-flues has greatly increased during the last few years; they improve the draught, and clean easily. Flues for ventilation from rooms should, like Arnott’s ventilator, enter into the smoke or a hot ventilating flue. Arnott’s ventilator requires careful adjustment, to be balanced in such a way that it should stand closed on a calm day.
The superior patented flues, as they are of considerable cost, and take extra time in construction, are only used in the better class of buildings, or in those erected under the express direction of the owner. In speculative buildings they are never used. The time required for their construction beyond that of the common brick flue, being regarded by the builder as so much money lost.
The great desideratum in a flue is to make it pass off its smoke quickly, and this the small size flue effects more certainly than the larger one, as it warms sooner and keeps its heat longer.
An enthusiastic admirer of the descending or sweeping flue once told the author that with a good fire in the grate, if a kettle of water could be placed on the top of the chimney-cap the water would soon boil, even if the flue were fifty feet high. The flues constructed of metallic or earthenware casings retain also the heat longer, and keep hotter. It may be imagined that with these flues, and the large quantity of gas lamps in the streets, why the temperature of London should be always some degrees higher than that of the country. In winter snow may be seen in the suburban fields, but none is found in town.
Architects have often been blamed for not inventing a good system of flue-construction, not only for the prevention of smoke in our dwellings, but for the hindrance of its presence in the atmosphere. Several, and most excellent attempts, have been made for the former, but very few for the latter, which is one of far greater difficulty. Yet this is one that admits of a cure, great as the evil is. The chimney flue might be so improved as to effect a more certain and larger ventilation of our houses, without any addition of ventilation flues. The introduction of the French Mansard roof with us, one from a country where coal fires are not in use, renders it almost imperative for the chimneys belonging to such buildings to have a different construction, for chimneys when placed against a building or roof that overtops them, are sure, as they are at present made, to become smoky: the wind returning owing to the high construction, and descending in the flues. The following few designs are offered to cure these various evils.