DesignBuilder has partnered with CIBSE to provide their official UK hourly weather data from our website.  While these datasets are owned by CIBSE, the licence to use the data can be purchased from us by selecting from the options below.


CIBSE members can obtain a 10% discount by entering their membership number at the bottom of this page before ordering.

What Is Weather Data?

The UK Meteorological Office (MO) collects weather data at stations across the UK. Climate variables measured at hourly intervals include air temperatures, wind speed and direction and air pressure etc. CIBSE licenses the historic weather data from the MO for 13 locations across the UK, and 3 in London. The weather variables are synthesised into 2 types of CIBSE weather files: 

  • Design Summer Year (DSY)
  • Test Reference Year (TRY)

The parameters included in the data sets are: dry bulb temperature (°C); wet bulb temperature (°C); atmospheric pressure (hPa); global solar irradiation (W·h/m2); diffuse solar irradiation (W·h/m2); cloud cover (oktas); wind speed (knots); wind direction (degrees clockwise from North); and Present Weather Code.

Why Do People Use Weather Data?

DSYs and TRYs are both used as weather data inputs in DesignBuilder: 


The TRY is composed of 12 separate months of data each chosen to be the most average month from the collected data. The TRY is used for energy analysis and for compliance with the UK Building Regulations (Part L). 


The DSY is a single continuous year rather than a composite one made up from average months. The DSY is used for summertime overheating analysis. 

Packages for Purchase

  1. Current CIBSE TRY/DSY Hourly Weather Data (14 sites)

  2. Future CIBSE TRY/DSY Hourly Weather Data (14 sites)

    • Future hourly weather files, based on the existing Design Summer Years (DSYs) and Test Reference Years (TRYs) which incorporate the UKCIP09 climate change scenarios, are available for 14 sites, for three time periods (2020s (2011-2040), 2050s (2041-2070) and 2080s (2071-2100)), for the following emissions scenarios:
      • 2020s – High emissions scenario – 10th, 50th, 90th percentile, 
      • 2050s – Medium – 10th, 50th, 90th, 
      • 2050s – High –  10th, 50th, 90th,
      • 2080s –  Low, 10th, 50th, 90th,
      • 2080s – Medium – 10th, 50th, 90th, 
      • 2080s – High – 10th, 50th, 90th. 
  3. Combined current & future CIBSE TRY/DSY Hourly Weather Data (14 sites)

    • Purchase options 1 and 2 together and receive a discount on the individual package price.
You can purchase sites individually or all together.

In London, the GLA requires that modelling is carried out using weather data and guidance from CIBSE 'Design Summer Years for London' (TM49: 2014). The guidance advises using weather files which account for both the UHI effect and for future climate change.

In line with this the ‘GLA Energy Planning – Greater London Authority guidance‘ (April 2015) specifies that three different weather data files should be used in overheating analysis:
  •     1976: a year with a prolonged period of sustained warmth.
  •     1989: a moderately warm summer (current design year for London)
  •     2003: a year with a very intense single warm spell.
The TM49 dataset contains each of these weather years for three London sites (urban, suburban and rural) in order to take account of the varying UHI effect.
For buildings with long service lives or where overheating impacts are more critical, CIBSE recommend that the building is modelled using more extreme (‘future’) weather data in addition to modelling against the three weather files above. The TM49 dataset, product code WDD16LON, includes future weather files for this purpose.

What Is Different About The New 2016 Packages?

The previous files (2006 release) have now been updated in the 2016 packages: 


The TRY files have been updated to use a 30 year baseline, instead of the previous 21 years, the average months are selected from 1984 – 2013. This will ensure that the observed effects of climate change will be included in the selection of the months. 


This update of the DSY is a slightly more complex. The warm year is selected from a 30 year baseline 1984 – 2013 and the procedure for selecting the warm year has changed. The methodology for selecting the warm years is the same as that used in TM49: Probabilistic DSY for London. There are now 3 DSYs available per location, representing summers with different types of hot events: 

  • DSY1: Moderately warm summer
  • DSY2: Short, intense warm spell
  • DSY3: Long, less intense warm spell 

Note: New set WDD16LON supports TM49 Probabilistic DSY for London and is identical to the previous set WCSYL.

All the above TRYs and DSYs are also available for future time periods based on the UKCP09 climate projections.

How to order Weather Data

Select the type of weather data you would like to order.

If you are working with DesignBuilder DSM v6 (NCM 2013) then you should choose from the CIBSE 2006 Weather Data selection.

For all other applications, including DesignBuilder DSM v7 (2021 NCM) and overheating discomfort calculations for CIBSE TM49, TM52 and TM59 and BB101, you should choose from the CIBSE 2016 Weather Data selection.

For further advice on which packages to choose please contact our sales team.

CIBSE members can obtain a 10% discount by entering their membership number at the bottom of this page before ordering.

How to Add Hourly Weather Data to a DesignBuilder Model

Once you have received your CIBSE hourly weather data, the next step is to add it to your model. Please view the How to add CIBSE weather files to my calculation Knowledgebase article which explains this process.

Enter your CIBSE membership number to qualify for a 10% discount.

CIBSE Membership Number

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