MIL-HDBK-1003/19

5.1.4 System parameter worksheet. Worksheet 3 is provided to help keep

track of the various system parameters that must be calculated or obtained

from Appendix A. Note that the worksheet allows for the presence of two

passive solar heating systems on a building and provides formulas for

calculating the properties of the resulting mixed system.

The first step in filling out the worksheet is to calculate the thermal

storage characteristics of the building. For direct gain or radiant panel

systems, the EHC must be determined. If the thermal storage mass properties

and configuration correspond closely to one of the reference designs in

Appendix A, simply enter the specified EHC/Ac in the indicated blank on

the worksheet; the diurnal heat capacity per ft2 of aperture, DHC/Ac, is

then found from the same reference design. Otherwise, it will be necessary

to calculate the EHC and the DHC as described in 5.1.2 and to evaluate

DHC/Ac as outlined below.

Among the remaining reference designs, only TAPS and concrete block

Trombe walls have specified levels of interior mass. For the concrete block

Trombe walls, the interior mass provides secondary thermal storage to the

wall itself and only one representative level is treated (high density

concrete with a thickness of 4 inches and a surface area three times greater

than the block wall area). The TAP reference designs have the same interior

mass options available for direct gain systems. The DHCs for concrete block

walls and TAPs are specified in Appendix A for the reference designs.

After entering values of the EHC/Ac and DHC/Ac on Worksheet 3,

proceed to the first (or only) set of system parameters. Enter the system

type and number (from Appendix A). If interpolation on the EHC has been

employed, enter the numbers of both systems involved. Then enter the first

set of system parameters on the worksheet. Finally, enter the size of the

first solar collection aperture (using projected area for sunspaces).

If two types of passive solar systems are present on the building,

proceed to the next part of the worksheet and enter a second set of

parameters. Next, calculate the area fractions of the two systems and use

the formulas provided on the worksheet to calculate the parameters for the

mixture.

5.1.5 Effective thermostat setpoint. Auxiliary heat consumption can

often be reduced significantly by setting back the thermostat at night. In

order to include this strategy in our design analysis calculations, it is

necessary to determine the effective thermostat setpoint, Te, for use in

the base temperature calculation.

The first step is to calculate the average thermostat setting from the

following equation:

Tave = T1(hr1/P) + T2(hr2/P)

(Equation 5.13)

where T1 and hr1 are the temperature and duration (in hours) of the

first setting, T2 and hr2 are the temperature and duration of the second

setting, and P is the period of the diurnal cycle (24 hours).

69

Integrated Publishing, Inc. |