R Value | k Value | Perimeter of a round duct is |
1 | 0.86 | 85% a rectangular duct |
2 | 0.80 | 80% a rectangular duct |
3 | 0.72 | 72% a rectangular duct |
4 | 0.65 | 65% a rectangular duct |
5 | 0.60 | 60% a rectangular duct |
6 | 0.55 | 55% a rectangular duct |
7 | 0.51 | 51% a rectangular duct |
8 | 0.48 | 48% a rectangular duct |