Heating design Calculation

Heating design calculations are carried out to determine the size of heating equipment required to meet the coldest winter design weather conditions likely to be encountered at the site location. These design calculations are traditionally carried out using steady-state methods such as those offered by ASHRAE and CIBSE.   You can use DesignBuilder to carry out effectively the same calculation using the EnergyPlus dynamic thermal simulation engine.

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

See also the Heating Design Calculations Tutorial

Heating design simulations using EnergyPlus have the following characteristics:

• Constant (Steady-state) external temperature set to the winter design external temperature.
• Wind speed and direction set to design values.
• No solar gain.
• No internal gains (lighting, equipment, occupancy etc).
• Heated zones are heated constantly to achieve the heating temperature set point using a simple convective heating system.
• Includes consideration of heat conduction and convection between zones of different temperatures.
• Schedules are not used for Heating design calculations which are based on a steady state analysis which does not account for timing.

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 heating capacities required to maintain the temperature set points in each zone and displays the total heat loss broken down as:

• Glazing
• Walls
• Partitions
• Solid floors
• Roofs
• External infiltration
• Internal natural ventilation (i.e. heat lost to other cooler adjacent spaces through windows, vents, doors, holes)

The total heat loss in each zone is multiplied by a Safety factor (1.5 by default) to give a recommended heating Design Capacity. This heating capacity can be written directly into the Heating 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: heating design calculations do not use any Natural ventilation data.

EnergyPlus IDF data

You can view the EnergyPlus IDF data used to carry out the calculation by clicking on the 'View the input data' link in the info panel (Learning mode only) or from the Tools menu.