“Light (God’s eldest daughter) is a principal beauty in a building; yet it shines not alike from all parts of heaven. An east window welcomes the beams of the sun before they are of strength to do any harm, and is offensive to none but a sluggard. A south window in summer is a chimney with a fire in it, and needs the screen of a curtain. In a west window in summer towards night the sun grows low and even familiar, with more light than delight. A north window is best for butteries and cellars, where the beer will not be sour from the sun shining on it.”
A workroom or study requiring steady light, should point north or some point between north-east and north-west. A breakfast room should face north-east to south; while one aspect of a drawing-room should be south-east to north-east. Store-rooms, dairies, larders, should have a northerly aspect. It is preferable, as a rule, for the house not to face in the direction of the four points of the compass, but diagonally to these.
Surrounding Objects of an objectionable character, as factories, noisy or offensive trades are to be avoided. The possibility of neighbouring cesspools contaminating the water supply must be considered. Trees close to a house are objectionable, rendering it damp, and preventing the free access of sun and air. More remote from the house they form a useful shelter, especially when to the north or east.
The banks of water courses are to be avoided for similar reasons. If there is a choice, the slope of a hill should be selected; and it is essential that no part of the dwelling should rest against sloping ground at a higher level. Rank vegetation indicates a damp clayey soil.
The main point is to secure that the house shall receive ample light and ventilation. In calculating the amount and intensity of sunshine which a house built on a given site will secure the variations according to season must be remembered. The direction (orientation) of the sun is the same all the year through; but the altitude of the sun varies with the latitude. Thus in a house facing directly south in the latitude of the south of England the sun’s altitude at noon on the 21st of December is 15° 4´, on the 21st of June 62° 4´. A ray of light entering the highest point of a window facing south at each of these seasons will illuminate a much larger part of the room in summer than in winter. Not only so, but inasmuch as it enters the room more nearly vertically it is more powerful than when entering at an angle more nearly approximating a horizontal direction, in accordance with the general law that the intensity of illumination falling on a horizontal surface (as the floor of a room) is inversely as the square of the width of the area embraced within the same angle of incidence of light.
In houses in a street the angular aperture through which light enters is greatest in the upper stories. It may be increased (a) by increasing the height of rooms; (b) by carrying the window heads nearly to the level of the ceiling; and (c) by avoiding the proximity of other buildings which would impede the access of light. Fig. 36 shows the importance of the last consideration. This represents a three-storied house in a street, of which the opposite house L is of the same height. It will be observed that each room is divided into two regions of different degrees of illumination by a plane Lm, formed by a line connecting the ridge of the roofs of the houses on the opposite side of the street with the interior surface of the rooms and touching the uppermost point of the window in transit. Below this line there is “sky-light” sufficient in quantity; above this line light is insufficient in amount and is diffused and reflected. The area receiving sufficient light increases from the ground floor upwards. We have already seen that its intensity similarly increases in the higher stories, the rays of light being more nearly vertical in these.
Fig. 36.
Showing Variations of Illumination in Different Stories.
The amount of sky-light visible can be expressed in terms of the angle of aperture, i.e. the arc of sky visible at any given point a in the room. Thus in Fig. 36 the triangle of aperture bac is greater than b´a´c´, and this greater than b´´a´´c´´. The sides of the angle of aperture, it will be seen, are formed by drawing one line from the point a to c, which, if prolonged, would touch L, and another line to b, which passes through the highest point of the window.
The amount of light received in a dwelling-house is largely determined by the width of the street and the distance between the backs of the houses in adjacent streets. The model Bye-laws of the Local Government Board insist that no new street shall be less than 36 feet wide if it exceeds 100 yards in length or is intended to be a carriage road, not less than 24 feet in any case. Furthermore, a new house must have in the rear an open space exclusively belonging to the house, at least 150 square feet in area, and free from any erection above the ground level. This must extend along the entire width of the house, and must never measure less than 10 feet from every part of the back wall of the house; the distance must be at least 15 feet, if the house is 15 feet high; 20 feet if 25 feet high, and 25 feet if 35 feet high or more.