Heating Degree Days (HDD) Calculator

HDD Formula:

\[ \text{HDD} = \text{Base} - \text{Avg T} \quad \text{if} \quad \text{Avg T} < \text{Base} \]

Heating Degree Days (HDD):

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1. What is Heating Degree Days (HDD)?

Definition: HDD is a measurement designed to quantify the demand for energy needed to heat a building. It's the number of degrees that a day's average temperature is below a base temperature (typically 65°F).

Purpose: HDD helps estimate heating requirements and energy consumption for buildings, and is used in energy analysis, utility planning, and agriculture.

2. How Does the HDD Calculator Work?

The calculator uses the formula:

\[ \text{HDD} = \text{Base} - \text{Avg T} \quad \text{if} \quad \text{Avg T} < \text{Base} \]

Where:

\( \text{HDD} \) — Heating Degree Days
\( \text{Base} \) — Base temperature (typically 65°F)
\( \text{Avg T} \) — Average daily temperature in °F

Explanation: If the average temperature is below the base temperature, HDD is calculated as the difference. If average temperature equals or exceeds the base, HDD is zero.

3. Importance of HDD Calculation

Details: HDD is crucial for:

Estimating seasonal heating requirements
Comparing energy use between years
Designing HVAC systems
Energy budgeting and forecasting

4. Using the Calculator

Tips:

Enter the base temperature (default 65°F)
Enter the average daily temperature
The calculator will show daily HDD
For monthly/annual HDD, sum daily values

5. Frequently Asked Questions (FAQ)

Q1: Why is 65°F commonly used as the base temperature?
A: 65°F was established as the temperature at which buildings typically need heating. This originated from studies in the 1930s when buildings had less insulation.

Q2: How do I calculate HDD for a month or year?
A: Sum the daily HDD values for the period. Many weather services provide monthly HDD totals.

Q3: What's the difference between HDD and CDD?
A: Cooling Degree Days (CDD) measure cooling demand when temperature exceeds a base, while HDD measures heating demand when temperature is below a base.

Q4: Can I use a different base temperature?
A: Yes, some modern buildings use 55°F or 60°F as they're better insulated. Adjust based on your building's characteristics.

Q5: How is average temperature calculated?
A: Typically (High Temp + Low Temp) / 2. Some methods use more frequent temperature readings for greater accuracy.