This dialog box is displayed when you select the Passive Design Analysis... item in main View menu or in the PSYCHROMETRY graph context menu.

Screenshot of the Passive Design Analysis dialog.

Combine Multiple Passive Techniques

Check this box to perform the passive design analysis on a single set of selected passive design techniques instead of each one individually. This will combine their effects to form a single extended comfort zone on the graph and, if you are doing a full analysis, a single comfort percentage graph. The options contained in the box immediately beneath are only active when the Combine Multiple Passive Techniques option is checked. Check them to add each passive technique to the list.

• Passive Solar Heating
  Passive solar heating, in this instance, refers to the use of direct solar radiation to heat a space in winter. This can be done using a direct-gain system, in which sunlight passes through a transparent aperture directly into the habitable space, or indirectly where a separate solar collector is used and the heat transferred to the space via a medium.
  
  NOTE: There are a number of building parameters that control the effect of such a system which can be interactively adjusted in the PSYCHROMETRY control panel.
• Lots of Thermal Mass
  This technique involves the use of high thermal mass materials within the building fabric, both in the external envelope and internally. This has a capacitative effect which tends to even out internal both diurnal and seasonal internal temperature fluctuations.
• Night-Purge Ventilation
  This technique requires high levels of exposed thermal mass within the building. Overnight in summer, when external air temperature are relatively cool, the building is opened up and high-volume air flow is encouraged. This cools the internal mass down to night-time temperatures. The building is then closed up completely during the day. This has the effect of reducing both internal air and mean radiant temperatures, significantly increasing comfort levels within the spaces. For it to work properly, however, the thermal mass must be exposed, not covered over with carpet or ceiling tiles.
• Natural Ventilation
  This technique involves opening up the building whenever overheating occurs to take advantage of cooling breezes, even if the ambient dry-bulb temperature is quite high. This utilises the evaporation of sweat to provide localised body cooling. The effectiveness of natural ventilation also depends significantly on the relative humidity levels.
• Direct Evaporative Cooling
  Basically, air is drawn through a fabric or gauze that is saturated with moisture. As the hot air evaporates some of the moisture, energy is lost in the form of latent heat of vaporisation. A direct evaporative system ducts this cooled air directly into the space. In most instances this is fine, however in areas sensitive to high humidities it can be a problem.
  
  This technique is not purely passive as it usually requires fan-assisted air movement. However the energy required is relatively low compared to the potential cooling effect, so it is considered here.
• Indirect Evaporative Cooling
  In this system evaporative cooling occurs external to the space. The cooled air then interacts with the supply air via a heat exchanger. This way there is no addition of moisture vapour to the air entering the space even if the cooled air approaches saturation. This means increased efficiency even if there are losses in the heat exchange as more vapourisation can be allowed.
  
  Again, this technique is not purely passive however the energy/cooling ratio is still most favourable.

Hours of Operation

Weekdays

Set these values to limit the time range during weekdays of the passive design analysis calculation. If you are designing for an office, it is likely only to be occupied between 8am and 6pm. In this case, simply enter a from value of 8 and a to value of 18. A from value greater than the to value is allowed, in which case the period will wrap around at midnight.

Weekends

Set these values to limit the time range during weekends (Sat & Sun) of the passive design analysis calculation. If you are designing for an office, it is unlikely that it will be occupied at all on the weekends. In this case, simply enter a from value of 0 and a to value of 0. A from value greater than the to value is allowed, in which case the period will wrap around at midnight.