Overview
EN ISO 15927-2:2009 - Hygrothermal performance of buildings: Hourly data for design cooling load specifies how to calculate and present monthly external design climate using hourly (or three-hourly) meteorological data for determining the design cooling load of buildings and the sizing of air‑conditioning systems. Prepared by CEN in collaboration with ISO, the standard defines required parameters, data sources and the method for identifying representative design days with specified return periods (typical 5 %, 2 % and 1 % exceedance).
Keywords: EN ISO 15927-2:2009, design cooling load, hourly climatic data, hygrothermal performance, air conditioning design.
Key Topics and Requirements
- Scope: Defines methods to derive hourly external climate data to be used in cooling load calculations and HVAC design.
- Required data: Hourly meteorological time series (at least 10 years) containing, as a minimum, dry‑bulb temperature and global solar irradiation (or sunshine hours). Other parameters (dewpoint temperature, wind speed, daily temperature swing) may be included when relevant.
- Data quality: Meteorological observations shall follow WMO Guide No. 8 (Guide to Meteorological Instruments and Methods of Observation).
- Design day identification:
- Compute daily mean dry‑bulb temperature and daily total global solar irradiation (or sunshine hours) for each day in the data set.
- For each calendar month find values exceeded on 1 %, 2 % and 5 % of days (or complementary exceedance for parameters like temperature swing and wind speed).
- Initial parameter intervals are suggested (e.g., daily mean dry‑bulb ±0.5 °C; daily total irradiation ±0.05 kWh/(m²·d); sunshine ±0.5 h).
- Presentation: The standard specifies how to present the resulting monthly design days and hourly peak values (dry‑bulb and dewpoint) required for HVAC equipment selection.
Applications and Users
Practical uses include:
- Sizing and selection of air‑conditioning equipment and refrigeration systems.
- Defining boundary conditions for building energy simulation and cooling‑load calculations.
- Preparing standardized input weather files / design days for performance modelling.
- Informing climate‑adaptive building design and HVAC commissioning criteria.
Primary users:
- HVAC and building services engineers
- Energy modelers and simulation specialists
- Architects and façade consultants concerned with solar gains
- Meteorologists and national standards organizations
Related Standards
- ISO 15927-1: Monthly means of single meteorological elements
- ISO 15927-3: Driving rain index (hourly)
- ISO 15927-4: Hourly data for annual heating/cooling energy assessment
- ISO 15927-5: Data for design heat load (heating)
- ISO 15927-6: Degree‑days (accumulated temperature differences)
EN ISO 15927-2:2009 provides standardized, validated methods to produce reliable hourly climatic inputs-essential for accurate and economical cooling‑load design and consistent building performance assessments.
