Degree days are a measure used to estimate the amount of heating or cooling required for a building over a certain period of time. They are calculated by subtracting the average daily temperature from a base temperature (usually 65 degrees Fahrenheit) for each day of the year. If the temperature is above 65 degrees, no heating is required and degree days are not counted. If the temperature is below 65 degrees, then the number of degree days is equal to the number of degrees below 65. These accumulated degree days can then be used to estimate the amount of energy required to heat or cool a building over a given period of time.
The purpose of using degree days in an energy audit is to evaluate the energy consumption of the building and identify areas for improvement. By tracking the number of degree days over a certain period of time, an energy auditor can determine if a building is using more energy than necessary for heating or cooling.
There are two types of degree days, heating degree days and cooling degree days. Heating degree days are used to estimate the amount of energy required for heating a building, and cooling degree days are used to estimate the amount of energy required for cooling a building.
Heating degree days (HDD) is calculated by subtracting the average daily temperature from the base temperature (65F) for each day where the temperature is below the base temperature. The base temperature is chosen because it’s the temperature at which most buildings are designed to maintain. The HDD are then accumulated over a period of time, usually a year.
Cooling degree days (CDD) is calculated by subtracting the base temperature (65F) from the average daily temperature for each day where the temperature is above the base temperature. The CDD are then accumulated over a period of time, usually a year.
The base temperature for HDD and CDD can be adjusted based on the climate, building characteristics, and the comfort level of the occupants.
In conclusion, degree days are a simple and effective way to evaluate the energy consumption of a building, identify areas for improvement and make informed decisions about energy-saving measures.
65 degrees Fahrenheit is used as the base temperature for calculating degree days because it is a commonly accepted temperature that represents the balance point between heating and cooling for most buildings in the United States. The balance point temperature is the outdoor temperature at which the building does not require heating or cooling to maintain a comfortable indoor temperature.
The balance point temperature varies depending on the climate and the characteristics of the building, such as insulation, airtightness, and window area. In a colder climate, the balance point temperature would be lower, and in a warmer climate, it would be higher.
While the balance point temperature is specific to each building, 65 degrees Fahrenheit is a commonly used base temperature because it represents an approximate balance point for most buildings in the United States. Using this base temperature allows for the comparison of heating and cooling energy consumption between different buildings in different climates.
Additionally, using 65F as a base temperature allows for easy comparison across different regions and building types, as well as being a standard that is used by energy experts and utilities.
In conclusion, 65 degrees Fahrenheit is used as the base temperature for calculating degree days because it is a commonly accepted temperature that represents the approximate balance point between heating and cooling for most buildings in the United States, it is easy to use for comparison and it is a standard used by energy experts and utilities.
There are several benefits to using 65 degrees Fahrenheit as the base temperature for calculating degree days, as opposed to using the balance point temperature specific to each building:
- Consistency: Using 65 degrees Fahrenheit as the base temperature allows for consistency in calculations and comparisons between different buildings in different climates. This allows energy auditors to easily compare energy consumption and identify areas for improvement.
- Simplicity: Using a single base temperature simplifies the calculation process and reduces the need for detailed site-specific data, such as the balance point temperature. This makes it easy to use for energy audits, especially when dealing with multiple buildings.
- Standardization: 65 degrees Fahrenheit is a commonly accepted and widely used standard in the energy industry, and it is used by energy experts and utilities. This makes it easier to compare and interpret results and provides a common basis for evaluating energy consumption.
- Cost-effectiveness: Using a single base temperature reduces the need for detailed site-specific data and simplifies the calculation process, which can reduce the cost of energy audits.
- Comparison: Using a single base temperature allows for easy comparison of energy consumption between different buildings in different climates.
However, it is worth noting that using the balance point temperature specific to each building could provide a more accurate and specific assessment of energy consumption for a building.
Using site-specific balance points (the outdoor temperature at which a building does not require heating or cooling to maintain a comfortable indoor temperature) as the base temperature for calculating degree days can provide several benefits over using a single base temperature such as 65 degrees Fahrenheit:
- Accuracy: Using the balance point temperature specific to each building can provide a more accurate assessment of energy consumption, as it takes into account the unique characteristics of the building and its location.
- Specificity: Using site-specific balance points can provide a more detailed and specific understanding of energy consumption, which can help identify areas for improvement and inform energy-saving measures.
- Customization: Using site-specific balance points allows for the customization of energy audits to fit the specific needs of a building, which can lead to more effective and efficient energy-saving measures.
- Better understanding of the building: Using site-specific balance points can provide a more detailed understanding of the building’s thermal characteristics, which can be used to design more energy-efficient retrofits or new constructions.
- Better Comparison: Using site-specific balance points allows for comparison between buildings in the same location and climate, which can be more informative than comparison between buildings in different locations or climates.
However, it’s worth noting that using site-specific balance points can be more time-consuming and costly to calculate, and may require additional data and analysis to accurately determine the balance point temperature.