Overview
EN ISO 15927-5:2004 - "Hygrothermal performance of buildings - Calculation and presentation of climatic data - Part 5: Data for design heat load for space heating" specifies how to define, calculate and present climatic input data used to determine the design heat load for space heating. It defines winter external design temperatures, coincident wind speed and dominant wind direction for the conditions that control peak heating demand. The standard also sets data-quality expectations (e.g., use of WMO-observed measurements and long-term records) and shows how to present results for individual locations or areas.
Key topics and technical requirements
- Design temperature types
- n‑day mean design temperature (n = 1, 2, 3 or 4 days) calculated with an average return period of 1 year.
- Hourly mean design temperature defined as the hourly temperature exceeded on average in 99% of hours during the coldest month.
- Calculation methods
- Priority of input data: hourly → three‑hourly → specified daily observations → daily max/min (least accurate).
- Procedures for averaging across n consecutive days and for interpolating from coarser time resolution.
- Wind considerations
- Coincident wind speed: average wind speed over the period used to define the design temperature.
- Dominant wind direction: range of directions relevant to the design condition.
- Data quality and period
- Preferably use continuous measurement records of at least 20 years; document the period used.
- Measurements should follow WMO Guide No. 8 methods.
- Presentation and geographical representation
- Prescribed formats for presenting data for a specific site, region or zone and for indicating reference altitude.
- Notes
- Ground heat loss depends on longer-term temperatures; ISO 13370 gives methods for ground heat transfer.
Practical applications and users
Who uses EN ISO 15927-5:
- HVAC and heating system designers for sizing boilers, heat pumps and distribution systems
- Building services engineers and energy modelers providing peak-load inputs
- Architects assessing thermal performance and heating strategy
- National/regional standards bodies and consultants producing climate design datasets
- Researchers and meteorologists preparing design-weather files
Practical uses:
- Determining peak heating capacity (design heat load) for residential, commercial and institutional buildings
- Creating site-specific or regional climate input data for dynamic thermal simulation and compliance reporting
- Combining temperature and wind data to estimate infiltration-related heat loss during design conditions
Related standards
- ISO 6243 - Climatic data symbols and terminology
- ISO 13370 - Heat transfer via the ground (ground heat loss methods)
- WMO Guide No. 8 - Guide to meteorological instruments and observation methods
- Other parts of ISO 15927 (e.g., Part 1: monthly means; other parts under development)
Keywords: EN ISO 15927-5:2004, design heat load, winter external design temperature, coincident wind speed, climatic data, space heating, building heat loss, ISO 13370.
