This tab is displayed for all building spaces (rooms, voids and plenums). It specifies internal gains to the space (sometimes called casual gains).
Space data dialog – Internal Gains tab
The dialog displays a list of internal gains present in the space. By clicking on an item from the list of you can view, and if appropriate edit, its specification.
The data displayed depends on the type of gain selected.
Gains can be specified in watts or W/m2. For people (occupancy), gains can be specified in watts or W/person, and the occupancy density can be specified in number of persons or m2/person. For lighting gains the power density can also be specified by the Installed Power density per 100lux (or per fc).
If you click on the Add button, the Internal Gains List will appear, allowing you to select those gains you wish to include in the space in addition to those attached to the Space Thermal Template. Any gain you add to a space must first be created in the Internal Gains List. This is done in the Template Manager. Any gain originating from the Space Thermal Template is marked with a ‘T’. Other gains are unmarked.
The data displayed depends on the type of gain selected.
Type
The type of gain (Fluorescent Lighting, Tungsten Lighting, Machinery, Miscellaneous, Cooking, Computers or People)
Reference
A verbal description of the gain,
Input mode
The mechanism used to define the internal gain, W, W/m2 or (in the case of lighting) lux.
Maximum Illuminance
The value defines the illuminance used to calculate the maximum sensible lighting gain if lighting power density is expressed as W/m2/(100lux) or (fc).
Installed power density
The value used to calculate the maximum sensible lighting gain if lighting power density is expressed as W/m2/(100lux) or (fc).
Maximum Sensible Gain per Person
The value used to calculate the sensible heat gain to the space from occupants. Typical values are listed in CIBSE Guide A Table A7.1.
Maximum Latent Gain per Person
The value used to calculate the latent heat gain to the space from occupants. Typical values are listed in CIBSE Guide A Table A7.1
Floor Area / Person
This value is used to calculate the number of people in the space.
Maximum Sensible Gain
The peak sensible heat gain. Typical values can be found in CIBSE Guide A7.
Maximum Latent Gain
The peak latent heat gain. Typical values can be found in CIBSE Guide A7.
Radiant Fraction
The fraction of the gain that is emitted as radiant heat (the remainder being assumed to be convective). Typical values are listed in CIBSE Guide A7.
Maximum Power Consumption
The peak rate of energy consumption of the device being described. This parameter will normally (but not always) be equal to Maximum Sensible Gain, and on this assumption its value will be set automatically when you click in the box.
Meter
Where the gain has an associated energy consumption this parameter specifies the meter it uses.
Variation Profile
A modulating profile specifying the variation of the gain throughout the year. This profile modulates the Maximum Sensible or Latent Gain entered above.
Dimming Profile
A modulating profile specifying the dimming variation of a lighting gain throughout the year. This profile operates in multiplicative combination with the Variation Profile. It therefore does not usually require scheduling with time. Dimming profiles usually involve formulae.
An example of a suitable formula for modulating a lighting gain in response to available daylight is ramp(e1,0,1,500,.4). This formula modulates the lighting gain as a function of the illuminance on the working plane, e1. The value of the profile falls from 1 at zero illuminance to 0.4 at illuminance 500 lux, thereafter remaining constant at this value. The value 0.4 (which you should set as appropriate) represents the fraction of the space’s lighting gain which is not subject to daylight control. The illuminance e1 must be computed using the link to Radiance.
Diversity factor
This value is valid for all types of gains and will be applied as a multiplicative factor in simulation runs. It doesn’t effect any design simulations like CIBSE loads or Apache Loads.
Ballast/driver fraction
This value is the fraction of the Maximum Power Consumption that that will be attributed to the ballast or LED driver for a lighting gain. The ballast or LED driver power consumption is constant irrespective of the dimming or variation profile of the lighting. The ballast or LED driver is also assumed to have the same radiant fraction as the lighting. A typical value for the ballast/driver fraction is 0.1 for fluorescent or LED lighting and 0.0 for incandescent bulbs or other light sources that do not have ballasts or LED drivers. The ballast/driver fraction parameter is ignored for compliance simulations but will be included in cooling loads runs (ASHRAE or CIBSE).
Note on floor area:
Floor area is calculated as the sum of the areas of all opaque floor elements. It excludes the areas of any holes or glazing elements in the floor.
