Zone 1 (Warmest – e.g., Florida, Southern California)
Zone 2 (Mild – e.g., Georgia, North Carolina)
Zone 3 (Moderate – e.g., Illinois, New York)
Zone 4 (Cool – e.g., Ohio, Pennsylvania)
Zone 5 (Cold – e.g., Michigan, Minnesota)
Zone 6 (Very Cold – e.g., North Dakota, Maine)
Zone 7 (Extremely Cold – e.g., Alaska)
Poor (No insulation, old windows)
Average (Some insulation, standard windows)
Good (Well-insulated, double-pane windows)
Excellent (Superior insulation, triple-pane windows, air-sealed)
Sheltered (Protected by other buildings or dense trees)
Average (Typical suburban or rural setting)
Exposed (Open area, strong prevailing winds)
Estimated Heating BTU Requirement:
—
BTU per hour
Understanding Your Heating BTU Needs
BTU stands for British Thermal Unit. It's a measure of energy, specifically the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. For home heating, the BTU rating of a furnace or heating system indicates how much heat it can produce per hour. Accurately estimating your heating needs is crucial for selecting an appropriately sized system, ensuring comfort, and maximizing energy efficiency. An oversized system can lead to short cycling, uneven heating, and increased wear, while an undersized system will struggle to keep your home warm during the coldest days.
This calculator provides an *estimate* of your heating requirements based on several key factors. It's important to note that a professional HVAC technician's load calculation (often using ACCA Manual J) is the most accurate method and should be consulted for final system selection.
Factors Affecting Heating Load:
Square Footage: Larger homes require more heating capacity.
Window Ratio: Windows are typically poor insulators. A higher percentage of window area increases heat loss.
Exposure: Homes in exposed locations lose heat more quickly due to wind.
How the Calculation Works (Simplified):
This calculator uses a simplified formula that starts with a base BTU requirement per square foot, adjusted by factors for climate, ceiling height, insulation, windows, and exposure. The general formula is:
Estimated BTU/hr = (Square Footage) * (Average BTU/sq ft based on Climate Zone) * (Ceiling Height Factor) * (Insulation Factor) * (Window Factor) * (Exposure Factor)
Average BTU/sq ft based on Climate Zone (Approximate):
Zone 1: 15-20 BTU/sq ft
Zone 2: 20-25 BTU/sq ft
Zone 3: 25-30 BTU/sq ft
Zone 4: 30-35 BTU/sq ft
Zone 5: 35-40 BTU/sq ft
Zone 6: 40-45 BTU/sq ft
Zone 7: 45-50 BTU/sq ft
*(These are general guidelines and can vary significantly based on specific construction and climate variations within a zone.)*
Ceiling Height Factor: Calculated as (Ceiling Height / 8). This scales the BTU requirement based on the volume of air.
Insulation Factor: A multiplier reflecting how well the building retains heat. Lower values indicate better insulation.
Window Factor: A simplified adjustment based on the percentage of window area. A higher percentage increases the BTU requirement. This is often approximated as 1 + (Window Ratio / 100).
Exposure Factor: Adjusts for the impact of wind and surrounding environment.
Example Calculation:
Let's consider a house with the following characteristics: