The Swiss Society of Engineers and Architects (SIA) provides climate data for building physics, energy, and building services calculations, accompanied by the SIA 4028 guidelines. The data basis was developed in 2025 in a collaborative project between the SIA, the Federal Office for the Environment (FOEN), the Swiss Federal Office of Energy (SFOE), and MeteoSwiss, and replaces that of SIA 2028, including corrigenda. The SIA 4028 hourly data sets are available for download here. The corresponding data sets for a future climate from the previous project “Climate-adapted construction – Foundations for the future” have been integrated.
Climate data sets related to SIA 4028 are available for 53 stations of the MeteoSwiss measurement network and seven urban locations. The data for the current climate were compiled based on the period 1994-2023 and are divided into compact data presented in tabular form and hourly data sets over one year (Design Reference Year DRY). The compact data includes evaluations from the entire period in the form of monthly values and design parameters for building technology components. It is summarized in an EXCEL file for all stations and is available on www.energytools.ch. The hourly data sets contain measurements of various meteorological parameters for one year. They form the basis for simulations in the fields of building physics, energy, and building technology. Data sets are provided for an average year and for a year with an exceptionally warm summer. The data can be obtained via an application on this website.
In addition to the data sets for the current climate, the download files also contain scenario-based data sets for simulating future indoor climate. The data was compiled as part of the project “Climate-adapted construction – foundations for the future” and published in 2022. However, some of the results based on the CH2018 climate scenarios have been overtaken by climate change, which is progressing faster than expected (see the CH2025 climate scenarios. For this reason, the results for the period around 2035 and those for the RCP2.6 scenario (concerted climate change mitigation efforts) in the period around 2060 are no longer available in the download files. Only the results for the RCP8.5 scenario (no climate change mitigation) in the period around 2060 are still included. A detailed description of all available data sets and corresponding recommendations for their use can be found in the SIA 4028 guidelines on the climate data (in preparation).
New methodological approaches were applied when developing the climate data sets for SIA 4028:
- The results should describe the current climate as accurately as possible, taking climate change into account. For this purpose, the latest changes in temperature, humidity, and radiation were determined and taken into account based on the climate trend line used by MeteoSwiss.
- To better reflect the climatological conditions in cities, a model was developed to provide data sets for inner-city locations without own measurements. The data takes into account and includes the urban heat island effect.
- A statistical approach was used to provide assistance in assigning station-related data to specific project locations. A corresponding table is included in the file containing the compact data and is available on www.energytools.ch.
A detailed description of the methods used will follow in a technical report by MeteoSwiss (in preparation).