Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
You may already be aware, but if you did add an averaged-R value for the whole wall, you wouldn't want to simply area-weight average the R-value. Rather, you'd want to area-weight average the U-value, then calculate the R-value from it, since heat transfer is proportional to U-value and not R-value.
For example, if you have 25% R-5 and 75% R-20, the answer is not: 0.255+0.7520 = R-16.25
Rather, the answer is: 1/(0.25/5+0.75/10) = R-11.43
| | 2 | No.2 Revision |
You may already be aware, but if you did add an averaged-R value for the whole wall, you wouldn't want to simply area-weight average the R-value. Rather, you'd want to area-weight average the U-value, then calculate the R-value from it, since heat transfer is proportional to U-value and not R-value.
For example, if you have 25% R-5 and 75% R-20, the answer is not:
0.255+0.7520 0.25x5+0.75x20 = R-16.25
Rather, the answer is: 1/(0.25/5+0.75/10) = R-11.43
