What kind of weather data does PreDesign use and where does it come from?
This article provides detail on the underlying data used in the guidance provided by PreDesign. Use this article to:
- How to choose a weather file
- Where the weather data used in PreDesign comes from
- What the weather data is comprised of
- Which sites are covered
- How we decide when to filter-out weather data
Choosing a weather file
PreDesign will list most relevant weather files in the "Weather data source" dropdown based on the "Site location" input. Order in which weather files are listed is based on the proximity of the weather file station to the site location and the status of the "Only show sources with viable rainfall data" checkbox.
Weather filenames typically include the location name, sometimes they include a specific site information (e.g. airport, observatory ...) followed by the country code and the distance from the selected "Site location".
"Only show sources with viable rainfall data" checked filters out and show only the weather files that have passed the rainfall validity test.
Where the weather data in PreDesign comes from
Our source of weather data is Climate.OneBuilding website. Weather files that available at Climate.OneBuilding are typically used for code compliant energy and annual daylight calculations in energy calculation software (including Sefaria.)
What the weather data is comprised of
Weather files have 30 different key meteorological values assigned to each hour of the year (total of 8760).
The most important ones that we use in PreDesign are:
- Dry bulb temperature
- Wet bulb temperature
- Relative humidity
- Global horizontal radiation
- Direct normal radiation
- Wind direction
- Wind speed
- Total sky cover
- Liquid precipitation depth
Most of the weather files use hourly based statistical weather data that is based on Typical Meteorological Year (TMY). TMY weather files are typically created from the 12 years in a row of historical weather data. All hourly values in the TMY file represent the best possible approximation of the long-term averages for a given location.
Which sites are covered
We currently cover around 14,000 locations worldwide. See the interactive map below of our weather files.
Our process for filtering out certain files
Every weather file is checked for the general data validity before it is added to PreDesign. The goal of the process is to search for the potential unexpected or abnormal values. A good example of a rejected weather file from the source would be if the file has an hour timestep where an outside air temperature is 100°C (212°F) or if throughout the whole year there is no wind at all.
Another example is a rainfall validity check where weather files are checked for the expected daily rainfall count distribution but not the amount.
If you feel that the weather file that you are using in your study has wrong values (unexpected for the given climate) please submit a bug and let us know.