CSE User's Manual

California Simulation Engine

4.14 ZONE

ZONE constructs an object of class ZONE, which describes an area of the building to be modeled as having a uniform condition. ZONEs are large, complex objects and can have many subobjects that describe associated surfaces, shading devices, HVAC equipment, etc.

4.14.1 ZONE General Members


Name of zone. Enter after the word ZONE; no “=” is used.

UnitsLegal RangeDefaultRequiredVariability
63 charactersnoneYesconstant


Selects model for zone.

CNEOlder central difference model based on original CALPAS methods. Not fully supported and not suitable for current compliance applications.
CZMConditioned zone model. Forward-difference, short time step methods are used.
UZMUnconditioned zone model. Identical to CZM except heating and cooling are not supported. Typically used for attics, garages, and other ancillary spaces.
UnitsLegal RangeDefaultRequiredVariability
choices aboveCNENoconstant


Nominal zone floor area.

UnitsLegal RangeDefaultRequiredVariability
ft2x \(>\) 0noneYesconstant


Nominal zone volume.

UnitsLegal RangeDefaultRequiredVariability
ft3x \(>\) 0noneYesconstant


Zone azimuth with respect to bldgAzm. All surface azimuths are relative to znAzm, so that the zone can be rotated by changing this member only. Values outside the range 0o to 360o are normalized to that range.

UnitsLegal RangeDefaultRequiredVariability


Nominal zone floor height relative to arbitrary 0 level. Used re determination of vent heights

UnitsLegal RangeDefaultRequiredVariability


Nominal zone ceiling height relative to zone floor (typically 8 – 10 ft).

UnitsLegal RangeDefaultRequiredVariability
ftx \(>\) 0znVol / znAreaNoconstant


Nominal eave height above ground level. Used re calculation of local surface wind speed. This in turn influences outside convection coefficients in some surface models and wind-driven air leakage.

UnitsLegal RangeDefaultRequiredVariability
ftx \(>\) 0znFloorZ + infStories8*Noconstant


Zone “air” heat capacity: represents heat capacity of air, furniture, “light” walls, and everything in zone except surfaces having heat capacity (that is, non-QUICK surfaces).

UnitsLegal RangeDefaultRequiredVariability
Btu/oFx \(\geq\) 03.5 znArea*Noconstant


Zone air exchange rate used in determination of interior surface convective coefficients. This item is generally used only for model testing.

UnitsLegal RangeDefaultRequiredVariability
ACHx \(>\) 0as modeledNosubhourly


Zone surface forced convection factor. Interior surface convective transfer is modeled as a combination of forced and natural convection. hcFrc = znHcFrcF * znHcAirX^.8. See CSE Engineering Documentation.

UnitsLegal RangeDefaultRequiredVariability


Zone hygric inertia ratio. In zone moisture balance calculations, the effective dry-air mass = znHIRatio * (zone dry air mass). This enhancement can be used to represente the moisture storage capacity of zone surfaces and contents.

UnitsLegal RangeDefaultRequiredVariability
x \(>\) 01Noconstant


Zone shade closure. Determines insolation through windows (see WINDOW members wnSCSO and wnSCSC) and solar gain distribution: see SGDIST members sgFSO and sgFSC. 0 represents shades open; 1 represents shades closed; intermediate values are allowed. An hourly variable CSE expression may be used to schedule shade closure as a function of weather, time of year, previous interval HVAC use or zone temperature, etc.

UnitsLegal RangeDefaultRequiredVariability
0 \(\leq\) x \(\leq\) 11 when cooling was used in previous hour, else 0Nohourly


Heating set point used (and required) when znModel=CZM and zone has no terminals.

UnitsLegal RangeDefaultRequiredVariability
oF0 < znTH < znTCnonePer abovesubhourly


Desired set point (temperature maintained with ventilation if possible) for znModel=CZM. Must be specified when zone ventilation is active.

UnitsLegal RangeDefaultRequiredVariability
oFx > 0; znTH < znTD < znTCnoneif ventingsubhourly


Cooling set point used (and required) when znModel=CZM and zone has no terminals.

UnitsLegal RangeDefaultRequiredVariability
oF0 < znTC > znTHnonePer abovesubhourly

znModel = CZM zone heating and cooling is provided either via an RSYS HVAC system, by “magic” heat transfers specified by znQxxx items, or via TERMINAL (s). One of these must be defined.


Name of RSYS providing heating, cooling, and optional central fan integrated ventilation to this zone.

UnitsLegal RangeDefaultRequiredVariability
RSYS name(no RSYS)Noconstant


Heating capacity at current conditions

UnitsLegal RangeDefaultRequiredVariability
Btuhx \(\geq\) 0noneNohourly


Rated heating capacity

UnitsLegal RangeDefaultRequiredVariability
Btuhx \(\geq\) 0noneNoconstant


Cooling capacity at current conditions

UnitsLegal RangeDefaultRequiredVariability
Btuhx \(\leq\) 0noneNohourly


Rated cooling capacity

UnitsLegal RangeDefaultRequiredVariability
Btuhx \(\leq\) 0noneNoconstant

4.14.2 ZONE Infiltration

The following control a simplified air change plus leakage area model. The Sherman-Grimsrud model is used to derive air flow rate from leakage area and this rate is added to the air changes specified with infAC. Note that TOP.windF does not modify calculated infiltration rates, since the Sherman-Grimsrud model uses its own modifiers. See also AirNet models available via IZXFER.


Zone infiltration air changes per hour.

UnitsLegal RangeDefaultRequiredVariability
1/hrx \(\geq\) 00.5Nohourly


Zone effective leakage area (ELA).

UnitsLegal RangeDefaultRequiredVariability
in2x \(\geq\) 00.0Nohourly


Zone local shielding class, used in derivation of local wind speed for ELA infiltration model, wind-driven AirNet leakage, and exterior surface coefficients. infShld values are –

1no obstructions or local shielding
2light local shielding with few obstructions
3moderate local shielding, some obstructions within two house heights
4heavy shielding, obstructions around most of the perimeter
5very heavy shielding, large obstructions surrounding the perimeter within two house heights
UnitsLegal RangeDefaultRequiredVariability
1 \(\leq\) x \(\leq\) 53Noconstant


Number of stories in zone, used in ELA model.

UnitsLegal RangeDefaultRequiredVariability
1 \(\leq\) x \(\leq\) 31Noconstant


Wind speed modifier factor. The weather file wind speed is multiplied by this factor to yield a local wind speed for use in infiltration and convection models.

UnitsLegal RangeDefaultRequiredVariability
x \(\geq\) 0derived from znEaveZ and infShldNoconstant


Name of an AFMETER object, if any, to which zone AirNet air flows are recorded. ZnAFMtr defines a pressure boundary for accounting purposes. Multiple zones having the same AFMETER are treated as a single volume – interzone flows within that volume are not recorded. For example, to obtain “building total” flow data, a common AFMETER could be assigned to several conditioned zones but not to adjacent unconditioned zones such as attic spaces.

UnitsLegal RangeDefaultRequiredVariability
name of an AFMETERnot recordedNoconstant


Name of a LOADMETER object, if any, to which zone heating and cooling loads are recorded.

UnitsLegal RangeDefaultRequiredVariability
name of a LOADMETERnot recordedNoconstant

4.14.3 ZONE Exhaust Fan

Presence of an exhaust fan in a zone is indicated by specifying a non-zero design flow value (xfanVfDs).

Zone exhaust fan model implementation is incomplete as of July, 2011. The current code calculates energy use but does not account for the effects of air transfer on room heat balance. IZXFER provides a more complete implementation.


Exhaust fan on fraction. On/off control assumed, so electricity requirement is proportional to run time.

UnitsLegal RangeDefaultRequiredVariability
fraction0 \(\leq\) x \(\leq\) 11Nohourly

Example: The following would run an exhaust fan 70% of the time between 8 AM and 5 PM:

    xfanFOn = select( (\$hour >= 7 && \$hour < 5), .7,
                                          default, 0 );


Exhaust fan design flow; 0 or not given indicates no fan.

UnitsLegal RangeDefaultRequiredVariability
cfmx \(\geq\) 00, no fanIf fan presentconstant


Exhaust fan external static pressure.

UnitsLegal RangeDefaultRequiredVariability
inches0.05 \(\leq\) x \(\leq\) 1.00.3Noconstant

Only one of xfanElecPwr, xfanEff, and xfanShaftBhp may be given: together with xfanVfDs and xfanPress, any one is sufficient for CSE to detemine the others and to compute the fan heat contribution to the air stream.


Fan input power per unit air flow (at design flow and pressure).

UnitsLegal RangeDefaultRequiredVariability
W/cfmx \(>\) 0derived from xfanEffIf xfanEff and xfanShaftBhp not presentconstant


Exhaust fan/motor/drive combined efficiency.

UnitsLegal RangeDefaultRequiredVariability
fraction0 \(\leq\) x \(\leq\) 10.08Noconstant


Fan shaft power at design flow and pressure.

UnitsLegal RangeDefaultRequiredVariability
BHPx \(>\) 0derived from xfanElecPwr and xfanVfDsIf xfanElecPwr not presentconstant


Name of METER object, if any, by which fan’s energy use is recorded (under end use category “fan”).

UnitsLegal RangeDefaultRequiredVariability
name of a METERnot recordedNoconstant


Indicates the end of the zone definition. Alternatively, the end of the zone definition can be indicated by the declaration of another object or by “END”. If END or endZone is used, it should follow the definitions of the ZONE’s subobjects such as GAINs, SURFACEs, TERMINALs, etc.

UnitsLegal RangeDefaultRequiredVariability

Related Probes: