Degree days: theory and application (TM41)

Tony Day

• Publisher: The Chartered Institution of Building Services Engineers
• Year: 2006
• eBook ISBN: 9781903287767
• Topic: Technologie et ingénierie
• Subtopic: Ingénierie de la construction et de l'architecture

Degree-days are a tool that can be used in the assessment and analysis of weather related energy consumption in buildings. They have their origins in agricultural research where knowledge of variation in outdoor air temperature is important, and the concept is readily transferable to building energy. Essentially degree-days are a summation of the differences between the outdoor temperature and some reference (or base) temperature over a specified time period. A key issue in the application of degree-days is the definition of the base temperature, which, in buildings, relates to the energy balance of the building and system. This can apply to both heating and cooling systems, which leads to the dual concepts of heating and cooling degree-days.This TM replaces previous guidance given in section 18 of the 1986 edition of CIBSE Guide B [CIBSE 1986] and Fuel Efficiency Booklet 7 [Energy Efficiency Office 1993]. It provides a detailed explanation of the concepts described above, and sets out the fundamental theory upon which building related degree-days are based. It demonstrates the ways in which degree-days can be applied, and provides some of the historical backdrop to these uses. This TM can be read alongside Good Practice Guide 310: Degree days for energy management – a practical introduction [Carbon Trust 2006], which serves as an introduction to their use. The material in this document provides deeper insights into the degree-day concept, but can be used in conjunction with GPG 310 for advanced building energy analysis.

Table of contents

• TM41 Degree-days: theory and application OFC
• Foreword
• Contents
• 1 An introduction to degree-days and their uses
• 2 Calculating degree-days
• 3 Energy estimation techniques
• 4 Worked examples
• 5 Using degree-days in energy management
• Nomenclature
• References
• Appendix A1: Degree-day errors
• Appendix A2: Ratios and corrections
• Appendix A3: Base temperature conversion using Hitchin’s formula
• Appendix A4: Derivation of mean internal temperature for intermittent heating
• Appendix A5: Areas of on-going work