Winter design weather data

Location tab on model data at Site level

Heating design and simulation autosizing simulations use simplified winter design weather based on a worst case design day.

The weather data used in Heating design calculations is as follows:

• Minimum outside dry-bulb temperature - the winter design outside air temperature.
• Co-incident Wind speed. This data is used to help calculate external convective heat transfer coefficients.

In addition for zone heating load autosizing this additional data is used:

• Coincident Wind direction is used in Calculated natural ventilation autosizing calculations (along with the wind speed above).

The degree of 'confidence' of the design data can be selected, i.e. the probability that the design data will occur in practice based on conditions encountered over recent years. Select either 99.6 or 99% confidence (i.e. 0.4 or 1% chance of more extreme winter weather occurring).

See also the Site level data and weather files and Heating Design Calculations tutorials

Sizing Period

When running simulations, some design features may benefit by using a longer design weather period for HVAC autosizing or loads calculations. Longer design periods may be set up by allowing the hourly weather file to be used in the sizing calculations.

Autosize method

Choose the design HVAC autosizing method to use for simulations from the following options:

• 1-Design day - the default option where data for a single winter design day is used based on the settings described above.
• 2-Weather file days where you can select the period to be used from the weather file for sizing.
• 3-Weather file condition type where you can select from some standard per-defined types of period such as 3-Winter extreme.

When 2-Weather file days is selected, enter the From start day and month and the To start day and month as shown in the screenshot below.

Period selection

When the 3-Weather file condition type Autosize method is selected you must choose the Weather file condition type from the following list.

• 1-Summer extreme
• 2-Summer typical
• 3-Winter extreme (default setting)
• 4-Winter typical
• 5-Autumn typical
• 6-Spring typical
• 7-Wet season
• 8-Dry season
• 9-No wet season
• 10-No dry season
• 11-Tropical hot
• 12-Tropical cold

Note: Not all weather files have all of the valid choices so this option is not completely generic. For example there may be extreme cold periods in some weather files but extreme wet periods (tropical) in others.