Cooling design Calculation

Cooling design calculations are carried out to determine the capacity of mechanical cooling equipment required to meet the hottest summer design weather conditions likely to be encountered at the site location. In zones which are not mechanically cooled free-floating temperatures are calculated including the effects of natural or mechanical ventilation if these options are selected on the zone HVAC tab. These design calculations are traditionally carried out using periodic steady-state methods such as the admittance and response factor methods provided by CIBSE and ASHRAE. You can use DesignBuilder to carry out effectively the same calculation using the EnergyPlus dynamic thermal simulation engine.

Click on the Cooling design Screen tab to view Cooling Design data. If the necessary data has not yet been generated, a Cooling Design calculation is automatically started to generate the data.

See also the Cooling Design Calculations Tutorial

Cooling design simulations using EnergyPlus have the following characteristics:

• Periodic steady-state external temperatures calculated using maximum and minimum design summer weather conditions.
• No wind.
• Includes solar gains through windows and scheduled natural ventilation.
• includes internal gains from occupants, lighting and other equipment.
• Includes consideration of heat conduction and convection between zones of different temperatures.

For buildings situated in the Northern Hemisphere, Cooling Design calculations are made for the month of July and for buildings in the Southern Hemisphere they are made for the month of January.

Simulation continues until temperatures/heat flows in each zone have converged.  If convergence does not occur then simulation continues for the maximum number of days as specified in the calculation options.

The simulation calculates half-hourly temperatures and heat flows for each zone and determines cooling capacities required to maintain any cooling temperature set points in each zone.

The maximum cooling load in each zone is multiplied by a Safety factor (1.3 by default) to give a Design Cooling Capacity. This design cooling capacity can be written directly into the Cooling capacity model data depending on the setting of the Plant sizing model option on the Data tab under HVAC.

Customise the data displayed and display style using the Display Options panel.

Note: Cooling Design calculations use Scheduled Natural ventilation model data set on the HVAC tab even when the Calculated natural ventilation option is set. This is to help you to document the input data for your Cooling Design calculations. Calculated natural ventilation data input is too complex to be adequately summarised.