In cases where more extended glass structures are desired, they are better if detached from the dwelling. The structure now given in Figs. 40 and 41 is called a curvilinear span-roofed house, 100 feet in length by 20 in width; fig. 40 shows the end view and plan, and fig. 41 gives sufficient of the elevation to show the end and a part of the side. The ends should face north and south, so that the distribution of the sun's rays will be equal on each side. Of course there is nothing arbitrary in the size, it may be made 50, 75, or 100 feet in length, or 20 to 25 feet in width as desired, and may be used either for the purposes of a vinery for the growing of foreign grapes, or for a conservatory as desired. All the walling from the surface of the ground to the glass of a greenhouse, had better be made of wood, unless the walls are made very thick when built of brick or stone; the continued warfare in winter between a zero temperature outside, and 60° to 70° inside, will in a year or two destroy brick or stone walls. When the walls are formed of wood, the best way is to place locust posts at distances of four feet apart, and nail to these a sheathing of boards; against the boards tack asphaltum or tarred paper, and again against that, place the weather-boarding. This forms a wall which, if kept painted, will last for 50 years, and is equally warm as a 12-inch brick wall, and costs less than half. We have had just such a structure in use for the past five years as a cold vinery, that is having no heating apparatus, the forwarding being done only by the action of the sun on the glass, and it has proved a cheap and satisfactory luxury. A conservatory or grapery of this style costs from $10 to $15 per running foot, without heating apparatus. Heated by hot water, it would cost $20 to $30 per running foot. If heated by a horizontal flue in the manner here described, the cost will be only about $15 per running foot. Any good bricklayer should be able to build a smoke-flue from the following instructions. Let the bars for the grate be, (if for a glass surface of say 500 square feet), 2 feet in length and about 10 inches in width; or in the proportion of about one-half a square inch of grate surface to one square foot of glass.
Fig. 40. - End-View And Plan Of Detached Greenhouse Or Grapery.
Fig. 41. - Elevation (Is Past) Of Detached Greenhouse Or Graphey.
Most masons of any experience know how to build a greenhouse flue, but there are a few important points, the knowledge of which is absolutely necessary to complete success. First, the furnace pit, if not naturally dry, must be made so by draining. After setting the grate-bars in the usual way by resting them on an iron plate, let into the brick work at front and back, the sides of the furnace should be built with fire-brick and fire clay if at all procurable, to the hight of from 10 to 20 inches, according to size wanted. On these walls an arch is turned over to cover the furnace; the "neck" of the furnace rising at a sharp angle for from 2 to 4 feet until it is run into the horizontal smoke-flue. The flue must be raised from the ground an inch or two on bricks or flagging. This costs perhaps a third more in building, but it allows all sides of the flue to give off heat. The cheapest and simplest form of flue is made after the bottom is formed by bricks or flagging; brick is best near the furnace, as flagging would crack. Place two bricks on edge, the top being covered by a brick laid flat; this is the smallest size of flue. Larger grate surface will require correspondingly greater hight and breadth. Flues are now commonly made by using cement or vitrified drain pipe, to connect with the brick flue, at from 25 to 40 feet from the furnace, the pipe not being safe to use near the furnace, as the greater heat would be likely to crack it. A flue, to get the full benefit of the fuel, should be so arranged that it goes all around the greenhouse, the base of the chimney being the top of the furnace. The advantage of this plan, (Fig. 42), which has only recently had general publicity, is that the excessive heat given out from the top of the furnace, drives back the cold air that would otherwise pass down the chimney; not only drives it back, but passing rapidly out, "draws" to it the heated air that has to pass through the length of the horizontal flue, causing it to circulate so rapidly that all parts of the flue become nearly equally heated. In the case represented in fig. 42, the greenhouse so heated is 20 feet wide by 100 feet long, having a glass surface of over 2,500 square feet, a size utterly impossible to heat with a flue unless so constructed that the base of the chimney stands on the top of the furnace. It will be seen by the plan that there are two flues running from one furnace, and entering into one chimney. I only illustrate this to show the power given by this method. It would do quite as well, if the house was half or quarter the size, to have it done by one flue instead of the two. I would here say emphatically that no matter what size a flue may be, and whether single or double, it should in every case be made on the principle of being carried all around the building until it enters the upright chimney built on the top of the furnace.
Fig. 42. - Plan Of Greenhouse Heated By Double Flues.