Internal Gains

This tab is only displayed for simulation-based ratings methods. It displays details of room internal gains (sometimes called casual gains).

In VE Compliance the data on this tab is set automatically from the NCM template, and only parts of it are editable.

The dialog displays a list of internal gains present in the room. By clicking on an item from the list of you can view, and if appropriate edit, its specification.

For most gain types, gains are shown in watts as well as W/m². For people (occupancy), gains are specified in watts or W/person, and the occupancy density is 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 by other methods related to illuminance.

The Internal Gains List displayed at the top of the dialog displays the gains present in the room.

Note: Not all items listed below are needed for each type of Internal Gain.

The type of gain (Fluorescent Lighting, Tungsten Lighting, Machinery, Miscellaneous, Cooking, Computers or People)

A verbal description of the gain

The mechanism used to define the internal gain, W, W/m² or (in the case of lighting) lux and inference. For VE Compliance the important options are lux and inference. The lux setting should be used when a full lighting design has been carried out, and the inference setting in other cases.

This parameter is displayed for recent versions of the Regulations, and used to calculate the maximum sensible lighting gain.. By default it will be set to the NCM database illuminance (displayed alongside), but may be edited to specify the installed or estimated design illuminance. In accordance with the rules set out in the Modelling Guide, any value of design illuminance which is less than the database illuminance must be replaced by the latter value, and the interface imposes this condition automatically.

This parameter displays the illuminance value in the NCM activities database, for comparison with the Design illuminance in cases when the latter is displayed. When Design illuminance is not displayed, the NCM Database illuminance is used in its place to calculate the maximum sensible lighting gain.

The lamp type selector is displayed when input mode is set to ‘Inference’.  By selecting an ‘Unknown’ lamp type, you can enter a Lamp Efficacy and a Light Output Ratio, the product of which will be displayed as Luminaire Efficacy. If you choose a lamp type, it will be used to infer a luminaire efficacy value using a table provided in the Modelling Guide. In this case Light Output Ratio remains editable and Lamp Efficacy is a derived parameter.

This is a measure of the efficiency of the luminaires. It is not directly editable, its value being derived from other settings as described above.

This setting applies when the input mode is ‘lux’ or ‘Inference’.  Tick this box to activate NCM simple lighting control, the details of which are documented under the heading ‘NCM lighting data’ in the ratings user guides.

The value used to calculate the Maximum Sensible Gain from lighting if the input mode is ‘lux’ or ‘Inference’.

The maximum sensible heat gain per room from occupants, expressed in watts per person and watts. This is set by the activity, and is non-editable.

The maximum latent heat gain per room from occupants, expressed in watts per person and watts. This is set by the activity, and is non-editable.

The f r action of the gain that is emitted as radiant heat (the remainder being assumed to be convective).  This is set by the activity, and is non-editable.

The peak rate of energy consumption of the device being described. In VE Compliance this parameter always equals the Maximum Sensible Gain (except in the case of occupancy gains).

In VE Compliance this is always set to Electricity.

A modulating profile specifying the variation of the gain throughout the year. This profile modulates the Maximum Sensible or Latent Gain entered above. This is set by the activity, and is non-editable.

A modulating profile specifying the dimming variation of a lighting gain throughout the year, providing a mechanism for simulating lighting control which can be used as an alternative to NCM simple lighting control. The dimming 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 room’s lighting gain which is not subject to daylight control. The illuminance e1 must be computed using the link to Radiance.

This value is valid for all types of gains and will be applied as a multiplicative factor in simulation runs. In VE Compliance the Diversity factor is always 1.

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.