Cooling Loads

Cooling Loads calculates room cooling loads and free-floating temperatures using the ASHRAE Heat Balance Method.

The calculation is carried out for one design day in each of a user-selected range of months, using weather data provided in APlocate. The calculation takes into account the timing and nature of each gain, applying the appropriate radiant fraction to all sources of heat and cooling. Inter-room dynamic conduction and ventilation heat transfer is accounted for.

 

Glazing solar transmission properties are treated using an analysis based on the Fresnel equations. At the user’s option the effects of ventilation air exchanges and external solar shading, as calculated by SunCast, may be incorporated.

Vista presents the Cooling Loads results in tabular or graphical form in a variety of formats. Gains are broken down by heat transfer mechanism and by type (sensible or latent). Results may be displayed by room, by zone or totalled over the building and peak loads are identified. Various measures of room temperature are displayed, together with room relative humidity. Data may be exported to other applications.

 

For a description of the calculation methods used in Cooling Loads see ApacheLoads Methods.

 

 

Tick this box to include a Cooling Loads calculation when you click on Calculate.

Air exchanges specified in Space Data are divided into three categories: infiltration, mechanical ventilation and natural ventilation. Any infiltration air exchanges are included unconditionally, but mechanical and natural ventilation air exchanges may be switched on or off at calculation time.

Tick this box if you wish to include Space Data mechanical ventilation air exchanges in the Cooling Loads calculation.

Tick this box if you wish to include Space Data natural ventilation air exchanges in the Cooling Loads calculation.

Tick this box to include the effects of external solar shading, as calculated by SunCast or SunCast Lite, in the Cooling Loads calculation. The SunCast shading data can also be applied to the calculation of Heating Loads, where it is used to model the effects of sky shielding.

It is important to ensure that the shading data is kept up to date with any changes to the building geometry. The shading calculations should be repeated after any such changes.

If you select ‘Yes’, the diversity factors assigned to the gains will be appiied for the cooling load analysis.

If you select ‘During occupied hours’, the diversity factors assigned to the gains will be appiied for the cooling load analysis at times defined by the ‘Opening Hours’ specified on the System Schedules and Setpoints dialog for the ApacheHVAC system.

If you select ‘Yes’, gains wlll be saturated, meaning that when their modulating profiles are evaluated, all values greater than zero will be adjusted to 100%.

The Cooling Loads calculation is carried out for one design day per month. Indicate which day of the week is to be used to set the profiles used in Cooling Loads for casual gains, ventilation rates and (if appropriate) temperature boundary conditions.

Select the months for which Cooling Loads calculations are required.

Click on this button to leave the ASHRAE Loads dialog and save the data.

Click on this button to start the Heating and Cooling Loads calculations.

Click on this button to leave the ASHRAE Loads interface.