Part I, Sealant Joint Calculation. For the wall panel shown above:

• Draw a sealant joint detail (plan) section cut through a vertical joint (drawn to scale: full size) showing 4"-thick brick veneer, sealant, backup rod, and bond breaker; and indicating the dimensions - depth and width (use 1/8" increments) - of the sealant joint.

• Calculate sealant joint width:
  • length between vertical sealant joints (panel dimension) = 20'
  • air temperature range is from -10 to +85 degrees F.
  • movement capability of 50%
  • cladding material expands over time by 2/100 of 1% (i.e., 0.0002 x original length) due to moisture absorption
  • maximum structural movement (story drift) is 1/8"
  • expect deviations in the panel alignment (construction tolerance) of 1/8"
  • neglect the impact of the glass opening; assume the entire exterior surface is brick for the purpose of this sealant joint calculation
  • For preliminary sizing, use: W = (100/X)[eL(DT) + M] + t; where:
    • W = required width of sealant joint;
    • X = % movement capability of sealant, i.e., 50;
    • e = coefficient of expansion of building "skin" material to be sealed = 0.0000036 (see below for examples);
    • DT = annual range between extreme temperatures (assume 130 degrees F if not known; in this case, use 95 degrees F);
    • L = length of cladding panels between vertical joints (i.e., joint spacing) = 20'
    • M = total anticipated nonthermal movement due to structural deflection, creep, moisture movement, etc.;
    • t = construction tolerance.

    Note: it is important that units are consistent. Convert all dimensions to inch units.

Coefficients of Expansion of Common Building Materials (in/in/degree F)

• Normal weight concrete 0.0000055

• Gypsum board 0.000009
• Gypsum plaster, sand 0.000007
• Glass 0.000005
• Acrylic glazing 0.000041
• Polycarbonate glazing 0.000044
• Polyethylene 0.000085
• PVC (vinyl) 0.000040

Find the total energy loss (BTU/hr) for all possible combinations of wall type and window type listed below (9 different cases), assuming an outdoor temperature of -10 degrees F, and an indoor temperature of 70 degrees F. Note that the average U value for the panel is: U_avg. = (U_wall x A_wall + U_window x A_window) / (A_wall + A_window).

Also note that the heat flow, or total energy loss, expressed in BTU/hr, is given by the expression:

Q = U x A x (temperature differential); where U is as defined above, A is the total area of the panel (including both the wall and window area), and the temperature differential is 80 degrees F.

Show calculations; then place the 9 results in a 3 x 3 grid (with wall types listed vertically and window types horizontally), and comment on the results (i.e., does it seem to be most effective to improve walls or windows, or both?).

Wall types

• 2x4 with R13 insulation
• 2x6 with R19 insulation
• 2x10 with R30 insulation

Window types

• single glazed with R=0.91
• double glazed with R=2.04
• triple glazed plus low-E glass with R=3.13