This tab is displayed for all building spaces (rooms, voids and plenums). It specifies air flows into the space.
Space data dialog – Air Exchange tab
All air exchanges represent air flow entering the space. The source of the air may be the external environment (optionally with a temperature offset), an adjacent space or a supply at a temperature specified by an absolute profile.
Air exchanges are of three types: Infiltration, Natural Ventilation and Auxiliary Ventilation. Infiltration air exchanges are included unconditionally in ApacheSim, ASHRAE Loads and CIBSE Loads. Natural and Auxiliary Ventilation air exchanges may be switched on and off at calculation or simulation time.
Auxiliary Ventilation air exchanges are intended to be used in the context of the ApSys methodology to specify minimum levels of either mechanical or natural ventilation for fresh air purposes. This type of ventilation can alternatively be specified using the ‘System outside air supply’ settings on the System tab. If this convention is followed ventilation will be correctly handled in simulations for building regulation compliance.
If you click on the Add button, the Air Exchanges List will appear, allowing you to select those air exchanges you wish to include in the space in addition to those attached to the Space Thermal Template. Any air exchange you add to a space must first be created in the Air Exchanges List. This is done in the Template Manager. Any air exchange originating from the Space Thermal Template is marked with a ‘T’. Other air exchanges are unmarked.
Note: Different combinations of Air Exchange types with adjacent condition codes require different items of data.
Type
The type of air exchange (Infiltration, Natural Ventilation or Auxiliary Ventilation)
Reference
A verbal description of the air exchange
Max Flow
The peak air change rate, expressed in air changes per hour, litres per second, litres per second per m2 of floor area or litres per second per person.
Variation Profile
A modulating profile specifying the variation of the air flow throughout the year. This profile modulates the Maximum AC Rate entered above.
Adjacent Condition
The source of air entering the space. The options are: 1) External Air, 2) External Air + Offset Temperature (external air with a temperature offset applied), 3) Temperature From Profile (air at a temperature specified by an absolute profile) and 4) Ventilation From Adjacent Space.
In the case of External Air + Offset Temperature and Temperature From Profile, the humidity ratio of the supply air is assumed to equal that of the space being supplied.
Temperature Offset
In the case of adjacency condition ‘External Air + Offset Temperature’, the offset to be added to the external air temperature
Temperature Profile
In the case of adjacency condition ‘Temperature From Profile’, an absolute profile specifying the (possibly time-varying) supply temperature
Adjacent Room
In the case of adjacency condition ‘Ventilation From Adjacent Room’, the adjacent room (or other space) from which the air is drawn.
