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
znName
Name of zone. Enter after the word ZONE; no “=” is used.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| 63 characters | none | Yes | constant |
znModel=choice
Selects model for zone.
| CNE | Older central difference model based on original CALPAS methods. Not fully supported and not suitable for current compliance applications. |
| CZM | Conditioned zone model. Forward-difference, short time step methods are used. |
| UZM | Unconditioned zone model. Identical to CZM except heating and cooling are not supported. Typically used for attics, garages, and other ancillary spaces. |
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| choices above | CNE | No | constant |
znArea=float
Nominal zone floor area.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft2 | x \(>\) 0 | none | Yes | constant |
znVol=float
Nominal zone volume.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft3 | x \(>\) 0 | none | Yes | constant |
znAzm=float
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.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| degrees | unrestricted | 0 | No | constant |
znFloorZ=float
Nominal zone floor height relative to arbitrary 0 level. Used re determination of vent heights
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft | unrestricted | 0 | No | constant |
znCeilingHt=float
Nominal zone ceiling height relative to zone floor (typically 8 – 10 ft).
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft | x \(>\) 0 | znVol / znArea | No | constant |
znEaveZ=float
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.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ft | x \(>\) 0 | znFloorZ + infStories8* | No | constant |
znCAir=float
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).
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| Btu/oF | x \(\geq\) 0 | 3.5 znArea* | No | constant |
znHcAirX=float
Zone air exchange rate used in determination of interior surface convective coefficients. This item is generally used only for model testing.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| ACH | x \(>\) 0 | as modeled | No | subhourly |
znHcFrcF=float
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.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| Btuh/ft2-oF | .2 | .2 | No | hourly |
znHIRatio=float
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.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| x \(>\) 0 | 1 | No | constant |
znSC=float
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.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| 0 \(\leq\) x \(\leq\) 1 | 1 when cooling was used in previous hour, else 0 | No | hourly |
znTH=float
Heating set point used (and required) when znModel=CZM and zone has no terminals.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| oF | 0 < znTH < znTC | none | Per above | subhourly |
znTD=float
Desired set point (temperature maintained with ventilation if possible) for znModel=CZM. Must be specified when zone ventilation is active.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| oF | x > 0; znTH < znTD < znTC | none | if venting | subhourly |
znTC=float
Cooling set point used (and required) when znModel=CZM and zone has no terminals.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| oF | 0 < znTC > znTH | none | Per above | subhourly |
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.
znRSys=rsysName
Name of RSYS providing heating, cooling, and optional central fan integrated ventilation to this zone.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| RSYS name | (no RSYS) | No | constant |
znQMxH=float
Heating capacity at current conditions
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| Btuh | x \(\geq\) 0 | none | No | hourly |
znQMxHRated=float
Rated heating capacity
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| Btuh | x \(\geq\) 0 | none | No | constant |
znQMxC=float
Cooling capacity at current conditions
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| Btuh | x \(\leq\) 0 | none | No | hourly |
znQMxCRated=float
Rated cooling capacity
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| Btuh | x \(\leq\) 0 | none | No | constant |
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.
infAC=float
Zone infiltration air changes per hour.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| 1/hr | x \(\geq\) 0 | 0.5 | No | hourly |
infELA=float
Zone effective leakage area (ELA).
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| in2 | x \(\geq\) 0 | 0.0 | No | hourly |
infShld=int
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 –
| 1 | no obstructions or local shielding |
| 2 | light local shielding with few obstructions |
| 3 | moderate local shielding, some obstructions within two house heights |
| 4 | heavy shielding, obstructions around most of the perimeter |
| 5 | very heavy shielding, large obstructions surrounding the perimeter within two house heights |
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| 1 \(\leq\) x \(\leq\) 5 | 3 | No | constant |
infStories=int
Number of stories in zone, used in ELA model.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| 1 \(\leq\) x \(\leq\) 3 | 1 | No | constant |
znWindFLkg=float
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.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| x \(\geq\) 0 | derived from znEaveZ and infShld | No | constant |
znAFMtr=afMtrName
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.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| name of an AFMETER | not recorded | No | constant |
znLoadMtr=ldMtrName
Name of a LOADMETER object, if any, to which zone heating and cooling loads are recorded.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| name of a LOADMETER | not recorded | No | constant |
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.
xfanFOn=float
Exhaust fan on fraction. On/off control assumed, so electricity requirement is proportional to run time.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| fraction | 0 \(\leq\) x \(\leq\) 1 | 1 | No | hourly |
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 );xfanVfDs=float
Exhaust fan design flow; 0 or not given indicates no fan.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| cfm | x \(\geq\) 0 | 0, no fan | If fan present | constant |
xfanPress=float
Exhaust fan external static pressure.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| inches | 0.05 \(\leq\) x \(\leq\) 1.0 | 0.3 | No | constant |
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.
xfanElecPwr=float
Fan input power per unit air flow (at design flow and pressure).
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| W/cfm | x \(>\) 0 | derived from xfanEff | If xfanEff and xfanShaftBhp not present | constant |
xfanEff=float
Exhaust fan/motor/drive combined efficiency.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| fraction | 0 \(\leq\) x \(\leq\) 1 | 0.08 | No | constant |
xfanShaftBhp=float
Fan shaft power at design flow and pressure.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| BHP | x \(>\) 0 | derived from xfanElecPwr and xfanVfDs | If xfanElecPwr not present | constant |
xfanMtr=mtrName
Name of METER object, if any, by which fan’s energy use is recorded (under end use category “fan”).
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| name of a METER | not recorded | No | constant |
endZone
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.
| Units | Legal Range | Default | Required | Variability |
|---|---|---|---|---|
| none | No | constant |
Related Probes: