Manual J window U-value
user-971368
| Posted in General Questions on
Looking at Manual J window U-value, I am not sure how the program takes a U-0.31 modeled window and calculates that up to U-0.47? I have done some research as to where the bump up comes from – striking out – any help would be great – thanks!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
>"I am not sure how the program takes a U-0.31 modeled window and calculates that up to U-0.47?"
Which Manual-J tool are you using?
MJ8, Wrightsoft Right-J/Right-Draw
MJ8 U-value vs U-Nom
Same question on wall U value, it calculates U-nom of 0.053 and a MJ8 U-value of 0.065? I run a parallel r-value calc on the wall assembly and it appears that MJ8 already has a 25+ framing consideration in their U-nom?
Is there a source for these considerations/de-rations? I scoured the help section and google. They state not to cook the input numbers, but then it appears the numbers are pre-cooked anyways?
Thanks - andy