Documento descriptivo climas de referencia – Reference Climate Parameters for Spanish Building Codes
The Documento descriptivo climas de referencia is a technical regulatory document issued by the Ministerio de Fomento through the Secretaría de Estado de Infraestructuras, Transporte y Vivienda in Spain. This February 2017 edition (Version 2.0) functions as a fundamental support document for the Documento Básico Ahorro de Energía (DB HE) within the Spanish Technical Building Code (Código Técnico de la Edificación). It establishes the technical framework for characterizing outdoor climatic stresses through standardized data sets used in building energy performance calculations.
The document defines the parameters that characterize reference climates, the correlations established for seasonal climatic severities, and the specific intervals used to define climatic zones. It details the structure of the digital .MET format, which contains 8,760 hourly data lines representing a typical year. Key regulatory domains covered include dry temperature, relative humidity, and global solar irradiance. Furthermore, the document provides proven correlations for calculating dew point, effective sky temperature, and specific humidity, alongside the mathematical formulas for determining winter and summer climatic severities.
This technical reference provides the necessary values and regression coefficients for professionals to perform climate-related modeling and compliance checks. It categorizes geographical areas into specific winter and summer zones based on calculated severity intervals.
Reference Climates and .MET Digital Format
Reference climates represent outdoor calculation stresses for a typical year through parameters such as temperature, humidity, and solar radiation. These data sets are published in .MET format, structured as text files with space-separated fields.
- File Identification: The first line contains the data file's identification string.
- Geographic Data: The second line includes latitude, longitude, altitude, and reference longitude for official time calculation.
- Hourly Data: 8,760 lines follow, each representing an hour of the year and containing 13 distinct fields.
- Fields included: Month, day, hour, dry temperature (°C), effective sky temperature (°C), direct and diffuse solar irradiance (W/m²), specific humidity (kgH2O/kg dry air), relative humidity (%), wind speed (m/s) and direction, solar azimuth, and solar zenith.
Regulatory and Non-Regulatory Parameters
The document distinguishes between parameters that are mandatory for determining regulatory climate behavior and those that allow for simplified calculations.
- Regulatory Parameters: Dry temperature, relative humidity, and global solar irradiance on a horizontal plane.
- Soil Temperature: Deep soil temperature may be taken as equal to the average annual dry air temperature.
- Atmospheric Pressure: A standard value of 1 atm (101.325 kPa) may be used.
- Wind Speed: An average value of 2.8 m/s may be adopted for simplified modeling.
- Appendix A Correlations: Specific formulas are provided for calculating dew point, effective sky temperature, and specific humidity when these are not directly sourced from the .MET file.
Climatic Severity and Zone Definitions
Climatic zones are determined by seasonal climatic severities calculated through regression formulas. These formulas use degree-days and sun-hour ratios to classify locations.
- Winter Climatic Severity (SCI): Calculated using winter degree-days (base 20) from October to May and the ratio of actual sun hours to maximum sun hours.
- Summer Climatic Severity (SCV): Calculated based on summer degree-days (base 20) from June to September.
- Winter Zones: Classified as α, A, B, C, D, or E based on SCI intervals (e.g., Zone E for SCI > 1.51).
- Summer Zones: Classified as 1, 2, 3, or 4 based on SCV intervals (e.g., Zone 4 for SCV > 1.38).
Frequently Asked Questions
What is the structure of a .MET reference climate file?
A .MET file consists of one identification line, one line of geographic data (latitude, longitude, altitude), and 8,760 lines of hourly climatic data for a complete year.
Which solar radiation data are included in the hourly climate files?
The files include direct solar irradiance on a horizontal surface and diffuse solar irradiance on a horizontal surface, both measured in W/m².
What standard value is used for atmospheric pressure in simplified calculations?
For calculations where atmospheric pressure is not measured, a constant value of 1 atm or 101.325 kPa can be assumed.
How is the Winter Climatic Severity (SCI) calculated?
SCI is calculated using a regression formula that combines the sum of winter degree-days (base 20) and the ratio of sun hours recorded between October and May.
What are the specific climatic zones for winter in Spain?
Winter zones are divided into six categories based on the SCI value: α, A, B, C, D, and E.
Which parameters are considered strictly regulatory for climatic behavior?
The regulatory parameters are dry temperature, relative humidity, and global solar irradiance on a horizontal plane.
What value is assigned to sky coverage (N) in effective sky temperature formulas?
The value of N is set to 3 for the months of April to October and 5 for the remaining months of the year.
