The lighting of buildings / by the Lighting Committee of the Building Research Board of the Department of Scientific & Industrial Research.
- Great Britain. Building Research Board
- Date:
- 1944
Licence: Public Domain Mark
Credit: The lighting of buildings / by the Lighting Committee of the Building Research Board of the Department of Scientific & Industrial Research. Source: Wellcome Collection.
22/176 page 20
![dirt. An example of the proposed type of Table is given in Fig. 17. We recommend that such Tables should be included in British Standards, and it is hoped that Tables of this kind will commend themselves to manufacturers as being suitable for inclusion in catalogues. Overall dimensions :— Height 5’ 14”, Width 6’ 64” Area 33-39 sq. ft. Glass Area 25-16 sq. ft. 2. PER CENT. 1 PER CENT 0-5 PER) GENG DAYLIGHT FACTOR DAYLIGHT FACTOR DAYLIGHT FACTOR Angle of |Depth| Breadth} Area |Depth| Breadth) Area |Depth| Breadth| Area Obstruction | ft. ft. sq.ft. | ft. ft. sq. ft. ft: ic: Sq. it. 0° 8°10 12°80 81°43 | 10°98 | 16°10 | 138°84 | 14°20 |. 20°34 | 226°84 rs° Figs 12°50. |--472°16 |. o-42.|, 15°76 |.116-60 | 11°60) 10°74 agora 30° 5°61 11°96 52°70 6:69 | 14°90 78°29 | 7:52.) 18°66 )aie-er 45° 3°79 | 1¥-10° | 33:04 1. 4-34 |) 13°80 | 47°O4| 4°68 | (16865 Gray 60° 2°23 9°90 | 17°34 | 2°55 | 12°16 | 24°35] 2°74 | 14°66 | 31°55 Fig. 17. TABLE OF CONTOUR DIMENSIONS FOR VARIOUS DAYLIGHT FACTORS The National Physical Laboratory is prepared to produce Tables of this kind at the request of manufacturers. 40. The second type of Table resembles the first, but is primarily for the use ot designers. It would contain the same kind of information as the first type but the series would be in terms of a range of dimensions increasing by regular incre- ments of 3 in. in height and 6 in. in width. The smaller height increment is used because the height of a window is more influential than the width in the lighting of rooms under normal conditions. The range would be big enough to cover all the normal needs of practice. In the publication of these Tables the method of use would have to receive a brief description, and in that connection one point should be noted. The Tables, in the form shown, are in terms of five different degrees of obstruction. In the great majority of cases no difficulty should be found in deciding what the average height of obstruction is, or will be, in a given case; roof lines which do not vary by a total of more than about 20° can certainly be averaged without risk of appreci- able error in practice, and by interpolation, the Tables ought then to give satis- factory results. When the obstruction varies more than about 20°, 2.e. 10° either side of normal, then errors might become appreciable; wide and deep gaps in the obstruction, for instance, obviously would result in better illumination than an averaged figure for the obstruction would indicate, and similarly, a projection well above the surrounding sky-line would give an error in the opposite direction.](https://iiif.wellcomecollection.org/image/b3217164x_0022.jp2/full/800%2C/0/default.jpg)
