Activity tab in model data
The heating and cooling setpoint temperatures, minimum fresh air per person and illuminance requirements are related to the Activity or Usage of the zone and are accessed by opening the Environmental Comfort group header.
Defines the ideal temperature (i.e. the setting of the heating thermostat) in the space when heating is required. Its meaning depends on the Temperature control calculation option. When using 1-Air temperature control the Heating setpoint temperature corresponds to the air temperature in the space and when it is set to set to 2-Operative temperature it is the operative temperature (MAT+MRT)/2.
Some buildings require a low level of heating during unoccupied periods to avoid condensation/frost damage or to prevent the building becoming too cold and to reduce peak heating requirements at startup. Enter the setpoint temperature to be used at night-time, weekends and other holidays during the heating season. Its meaning depends on the Temperature control calculation option (above).
Note: when using the Typical workday timing option, this setback temperature set point is only applied during unoccupied periods such as night-time and holidays during the heating season. It is not applied during the summer (if heating is switched off during the summer.)
Note: if the setback temperature set does not appear to affect results when using a Compact schedule, this may be because the Zone setpoint heating schedule selected uses only 0 and 1, not the 0.5 required to access setback temperature. See Defining setpoint temperature schedules for more on this.
Defines the ideal temperature (i.e. the setting of the cooling thermostat) in the space when cooling is required. Its meaning depends on the Temperature control calculation option. When using 1-Air temperature control the Cooling setpoint temperature corresponds to the air temperature in the space and when it is set to set to 2-Operative temperature it is the operative temperature (MAT+MRT)/2.
Note: the cooling setpoint temperature must be higher than the heating setpoint temperature.
Some buildings require a low level of cooling during unoccupied periods to prevent the building becoming too hot and to reduce the startup cooling load the next morning. Enter the setpoint temperature to be used at night-time, weekends and other holidays during the cooling season. Its meaning depends on the Temperature control calculation option (above).
Note: when using the Typical workday timing option, this setback temperature set point is only applied during unoccupied periods such as night-time and holidays during the cooling season. It is not applied during the winter (if cooling is switched off during the winter.)
Note: if the setback temperature set does not appear to affect results when using a Compact schedule, this may be because the Zone setpoint cooling schedule selected uses only 0 and 1, not the 0.5 required to access setback temperature. See Defining setpoint temperature schedules for more on this.
When using VAV, CAV and unitary Compact HVAC systems you can control humidity. More specifically, in the case of AHU-type systems the humidity in a control zone is actually controlled. The humidification and dehumidification setpoints can be defined here
The zone humidistat Relative humidity setpoint for humidification (0 to 100%).
The zone humidistat Relative humidity setpoint for dehumidification (0 to 100%).
The natural ventilation cooling setpoint temperature controls the activation of natural ventilation. If the inside air temperature is greater than this setpoint temperature (and the natural ventilation operation schedule is on) then natural ventilation can take place. The way this works depends on the Natural ventilation model option.
Note that when using the Calculated natural ventilation model option windows and vents are only opened when:
Also, the data under the Calculated Natural Ventilation header on the Advanced tab of the Model Options dialog can modify ventilation control behaviour.
When using the Scheduled natural ventilationmodel option the Max natural ventilation in-out delta T (below) can prevent natural ventilation from occurring if the outside air temperature is too high.
The Natural ventilation Max. int-out temp difference is used for Scheduled natural ventilationonly and is the temperature difference between the indoor and outdoor air dry bulb temperatures below which ventilation is shut off. This is to allow ventilation to be stopped if the temperature outside is too warm and could potentially heat the space. It is not related to preventing drafts.
For example, if you specify a maximum delta temperature of 2°C, ventilation is assumed to be available if the outside air temperature is at least 2°C cooler than the zone air temperature. If the outside air dry bulb temperature is less than 2°C cooler or warmer than the indoor dry bulb temperature, then ventilation is automatically turned off. The values for this field can include negative numbers. This allows ventilation to occur even if the outdoor temperature is above the indoor temperature. The Delta Temperature control works in the code in the following way:
if (IndoorTemp - OutdoorTemp) < Max ventilation in-out delta T then ventilation is not allowed.
For example:
|
Value of Natural ventilation Max in-out delta T |
Effect |
|
0 |
Natural ventilation only operates when OutdoorTemp < IndoorTemp |
|
-50 |
Natural ventilation unrestricted by Inside-Outside delta T |
|
2 |
Natural ventilation only operates when OutdoorTemp + 2 < IndoorTemp |
Tip: input a large negative number to allow ventilation even if the outdoor temperature is greater than the indoor temperature. This useful for uncontrolled natural ventilation (open windows) or as a way to estimate the effect of required ventilation air for load calculations.
See also Defining setpoint temperature schedules.
The mechanical ventilation cooling setpoint temperature controls the activation of mechanical ventilation when using Simple HVAC data. If the inside air temperature is greater than this setpoint temperature (and the mechanical ventilation operation schedule is on) then mechanical ventilation can take place. This data is not used when working with Compact HVAC data.
The mechanical ventilation Max int-out temp difference is used for Scheduled mechanical ventilationonly and is the temperature difference between the indoor and outdoor air dry bulb temperatures below which ventilation is shut off. This is to allow ventilation to be stopped if the temperature outside is too warm and could potentially heat the space. It is not related to preventing drafts.
For example, if you specify a maximum delta temperature of 2°C, ventilation is assumed to be available if the outside air temperature is at least 2°C cooler than the zone air temperature. If the outside air dry bulb temperature is less than 2°C cooler or warmer than the indoor dry bulb temperature, then ventilation is automatically turned off. The values for this field can include negative numbers. This allows ventilation to occur even if the outdoor temperature is above the indoor temperature. The Delta Temperature control works in the code in the following way:
if (IndoorTemp - OutdoorTemp) < Max ventilation in-out delta T then ventilation is not allowed.
For example:
|
Value of Mechanical ventilation Max in-out delta T |
Effect |
|
0 |
Mechanical ventilation only operates when OutdoorTemp < IndoorTemp |
|
-50 |
Mechanical ventilation unrestricted by Inside-Outside delta T |
|
2 |
Mechanical ventilation only operates when OutdoorTemp + 2 < IndoorTemp |
Tip: input a large negative number to allow ventilation even if the outdoor temperature is greater than the indoor temperature. This useful for uncontrolled mechanical ventilation or as a way to estimate the effect of required ventilation air for load calculations.
See also Defining setpoint temperature schedules.
Minimum fresh air data is defined on the Activity tab because the fresh air requirement of the people in the zone depends on the activity (use) of the space.
The Minimum fresh air per person defines the fresh air requirements of each person in the zone and is used to generate appropriate mechanical outside air distribution rates when the mechanical air distribution Flow type on the HVAC tab is set to any of:
This data is also used to calculate natural ventilation outside air flow rates into the zone when the natural ventilation Flow type on the HVAC tab is set to 2-Min fresh air per person.
The Mech vent fresh air per area defines the fresh air requirements of the zone per floor area and is used to calculate mechanical outside air distribution rates when the mechanical air distribution Flow type on the HVAC tab is set to any of:
The data is not currently used for natural ventilation.
The desired lighting level (in lux) at the first daylighting sensor. This is also the lighting level that would be produced at this sensor position at night if the overhead electric General lighting were operating at full input power. Recommended values depend on type of activity; they may be found, for example, in the Lighting Handbook of the Illuminating Engineering Society of North America and in CIBSE A Guide. A typical value for general office work (excluding computer terminals) is 500 lux.
The typical density of display lighting for the activity. This value is used as a default on the Lighting tab for the Task and Display lighting density.