GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Manual J window U-value

Andy McPartland| Posted inGeneral Questionson

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 Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Replies

  1. Expert Member
    Dana Dorsett||#1

    >"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?

    1. Andy McPartland||#2

      MJ8, Wrightsoft Right-J/Right-Draw

  2. Andy McPartland||#3

    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

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |