We're here to help

    Adjusted Calculations for R-value Framing

    Follow

    This article discusses the conductive Heat loss calculations that affect HEAT's walls, attics, windows and doors and basement/floor screens.

    The calculations for the adjusted R-values after selecting a framing option are done in U-Values which are the reciprocals of R-Values, U=1/R.

    For the annual heating season, conductive heat loss through walls, ceilings, windows, doors, and floors uses the following calculation:

    Where n = the discrete temperature bin midpoint (in 5 degree intervals) for all bins under 60oF; h = hours at each temperature annually, U = U-value of the buildings component, and A = the area.

    For annual cooling season conductive heat gain through walls, Attics, windows, doors, and floors:

     

     

    Where n = the discrete temperature bin midpoint (in 5 degree intervals) for all bins over 80oF; h = hours at each temperature annually, U = U-value of the buildings component, and A = the area.

     

    U-values that are used in the bin analysis are generated using assembly U-value methodology by generating a material weighted U-value for each shell component. An example calculation for a wall is as follows:

     

    Example for an R- 13 insulated 2x4 stud wall with wood siding

     

    R-value

     

    Building Component

    stud

    cavity

     

    outside air film

    0.17

    0.17

     

    wood siding

    0.8

    0.8

     

    plywood sheathing 1/2"

    0.63

    0.63

     

    3 1/2" stud

    4.38

    13

     

    1/2" drywall

    0.45

    0.45

     

    inside air film

    0.68

    0.68

     

     

     

     

     

     

    percent of wall area

    0.15

    0.85

     

    total wall component r-value

    7.11

    15.73

     

    wall component u-value

    0.141

    0.0636

     

    total wall assembly u-value

     

     

    0.075

    total wall assembly r-value

     

     

    13.3

     

     

    Was this article helpful?
    0 out of 0 found this helpful

    Comments