| Baldwin's Table of Heat-Transmitting Power of Building Substances. | ||
| Window glass | ... | 1,000 |
| Hardwood sheathing on walls | ... | 66 to 100 |
| White pine and pitch pine | ... | 80 to 100 |
| Lath and plaster, good | ... | 75 to 100 |
| " " " common | ... | 100 to 150 |
| Common brick, rough | ... | 150 |
| " " hard finish | ... | 200 |
| " " hollow walls, hard finish | ... | 150 |
| Sheet iron | ... | 1,100 to 1,200 |
Mr. Baldwin further implies that the coefficient representing the amount of heat given off by glass surface per square foot per hour per degree difference in temperature between one side of the glass and the other is about the same as the similar coefficient for radiation, which may be taken at about 1.8 British thermal units.
The German Government made an investigation into this subject, and the results of its work have been translated into English measures by Mr. Alfred E. Wolff (Journal Franklin Institute, Vol. 134); and Prof. R. C. Carpenter has translated the results of Péclet's original investigations. The factors given differ very decidedly, as may be seen by the accompanying table, in which are given the coefficients of heat transmission for different surfaces:
| Table of Coefficients of Heat Transmission. (British thermal units transmitted per hour per square foot of surface per degree difference of temperature.) | ||||
| Baldwin. | Peclet. (Carpenter.) |
German Gov. (Wolff.) | ||
| Single skylight | ... | ... | ... | 1.12 |
| Double skylight | ... | ... | ... | 0.62 |
| Single window | ... | 1.8 | .91 to .98 | 1.03 |
| Double window | ... | ... | .60 to .66 | .52 |
| 4-inch brick wall. | .27 | .43 | .68 | |
| 8-inch brick wall. | to | .27 | .46 | |
| 13-inch brick wall. | .36 | .32 | .32 | |
| 17-inch brick wall | ... | ... | .26 | .24 |
| Wooden beams planked over as flooring | ... | 0.083 | ||
| Wooden beams planked over as ceiling | ... | 0.104 | ||
| Fireproof construction as flooring | ... | 124 | ||
| Fireproof construction as ceiling | ... | 145 | ||
| Wooden door | ... | ... | ... | 414 |
Mr. John J. Hogan gives 1.57 British thermal units as the coefficient for glass. Mr. Charles Hood, the English authority, states that one square foot of glass will cool 1.279 cubic feet of air one degree per minute per degree difference in temperature. This is equivalent to a coefficient of heat transmission of about 1.40 British thermal units per hour. Mr. Hood adds that this was determined in still air and that it is very greatly increased by the
