ISO 15927-4:2005

Overview

ISO 15927-4:2005 is an international standard that defines a method for constructing a reference year using hourly meteorological data to assess the annual energy use for heating and cooling in buildings. This part of ISO 15927 focuses on creating a representative climatic dataset, comprising hourly values for key meteorological parameters, intended to simulate the average long-term energy demand for building thermal comfort. It provides a systematic approach to selecting and adjusting data from multi-year records to form a continuous reference year useful for reliable thermal performance simulations. The standard does not cover meteorological instrumentation or extreme weather year construction, focusing strictly on average climatic conditions.

Key Topics

• Reference Year Construction
  The standard outlines a method to piece together the most representative months from at least ten years of meteorological data, creating a continuous year that matches long-term climate averages. Hourly values are adjusted to ensure smooth transitions between months.

• Primary Climate Parameters
  The reference year includes hourly data of:

  • Dry-bulb air temperature
  • Solar irradiance (both direct normal and diffuse on a horizontal surface)
  • Humidity (relative, absolute, or dewpoint temperature)
  • Wind speed at 10 meters above ground

• Selection Criteria Using Statistical Methods
  The Finkelstein-Schafer statistic is applied on daily mean values of the key meteorological parameters to select the “best” months from historic data sets. Additional filtering includes comparing wind speed deviations to finalize the monthly selection.

• Data Quality and Preparation
  The standard emphasizes high data quality, requiring rigorous quality control such as interpolation for missing or erratic values. Data should be measured following the World Meteorological Organization (WMO) guidelines.

• Smooth Transition Adjustments
  To avoid unrealistic jumps in data when months are concatenated, the last and first eight hours of consecutive months are interpolated, ensuring continuity for simulation purposes.

Applications

ISO 15927-4:2005 is primarily used in:

• Building Energy Simulation
  Energy modelers and HVAC engineers use these constructed reference years to estimate long-term average heating and cooling loads with hourly resolution, enabling more accurate energy performance assessments.

• Building Design and Retrofit Assessments
  Architects and designers apply these climatic datasets to optimize building envelopes, HVAC system sizes, and control strategies based on reliable climate input data.

• Energy Policy and Planning
  Policymakers and energy analysts rely on standardized climatic data for regional or national energy demand projections, energy efficiency standards, and the development of energy-saving policies.

• Academic Research
  Researchers studying building thermal performance, renewable energy integration, and climate-responsive design utilize these standard reference years to ensure consistency and comparability in scientific investigations.

Related Standards

• ISO 15927-1: Hygrothermal performance of buildings - Monthly means of single meteorological elements
  Provides monthly average values of basic meteorological parameters for climatic assessment.

• ISO 15927-5: Data for design heat load for space heating
  Focuses on selecting meteorological data relevant to estimating peak heating demands, complementing the annual energy use focus of ISO 15927-4.

• ISO 15927-6: Accumulated temperature differences (degree days)
  Offers methodologies for calculating heating and cooling degree days which support simplified energy demand estimation.

• World Meteorological Organization (WMO) Guide No. 8
  Establishes best practices for meteorological instrumentation and data observation methods referenced for data quality in ISO 15927-4.

By adhering to ISO 15927-4:2005, professionals can ensure consistent, high-quality climatic input data is used in hygrothermal performance calculations and building energy simulations-critical for optimizing energy efficiency and enhancing the sustainability of built environments.