5.1.1 Net load coefficient worksheet. A simple procedure for
estimating the net load coefficient is presented in this section. The
method was adapted from DOE/CS-0127/2 and DOE/CS-0127/3, DOE Passive Solar
Design Handbook, Volumes Two and Three; and although originally intended for
single-family detached residences and small office buildings, is readily
applicable to more complex structures.
The procedure consists of adding together several estimated
contributions to building heat loss as outlined on Worksheet 2. In order to
determine the heat loss contributions, a number of design parameters must be
specified. Start by recording the total external perimeter (Pt) from
Worksheet 1. Next, specify the area (Ag), and external perimeter (Pg)
of the ground floor alone followed by the horizontally projected roof area
(Ar) and the total south wall area (As) including windows and other
Continuing to specify parameters for Worksheet 2, you will need the
ceiling height (h) and the non-south window fraction (NSF) which is defined
as the fraction of all external walls, except that facing south, that is
occupied by windows. The non-south window fraction will normally be between
0.05, for a situation with minimal window area, and 0.10 for a case with
ample window area. Next, enter the number of glazings in the non-south
windows (NGLn) and the infiltration rate in air changes per hour (ACH).
Finish this part of the worksheet by entering the air density ratio (ADR)
which is a function of elevation as illustrated in figure 24. Since many
Navy bases are located near sea level an ADR of unity is frequently
In the next part of Worksheet 2, two parameters, the non-south window
area (An) and the wall area (Aw) must be calculated using previously
recorded quantities. The wall area is defined as the total area of all
external walls excluding windows and solar apertures.
The various contributions to building heat loss are calculated and
summed in the final part of the worksheet. The necessary equations are
given and all parameters called for are available from the first two parts
of Worksheet 2 or from Worksheet 1. A list of R-values of building
materials from NCEL CR 82.002 is presented in table III and R-values for
air films and air spaces, also from NCEL CR 82.002 are given in table IV.
The original source of the data is the ASHRAE Fundamentals Handbook. The
information in tables III and IV is useful for calculating the total
R-value of layered elements in the building shell; simply add together the
R-values of each layer, air gap and air film to get the total R-value.
Calculate RROOF of a vaulted ceiling with no attic by determining the
total R-value of the roof and scaling that value to the horizontally
projected area as follows:
RROOF = Rtot [multiplied by] (Aa/Ar)