1. What is Home Furnace Sizing?

Home furnace sizing involves calculating the appropriate heating capacity (measured in BTU) needed to efficiently heat your living space. Proper sizing ensures optimal comfort, energy efficiency, and system longevity.

2. How Does the Calculator Work?

The calculator uses the standard furnace sizing formula:

Where:

• \( BTU \) — British Thermal Units per hour (heating capacity)
• \( Sq Ft \) — Conditioned square footage of living space
• \( 35 \) — Average BTU per square foot for US homes

Explanation: The formula calculates base heating requirements, with adjustments for insulation quality: +10% for poor insulation, -10% for good insulation.

3. Importance of Proper Furnace Sizing

Details: Correct furnace sizing prevents energy waste, ensures even heating, extends equipment life, and maintains indoor comfort. Oversized furnaces short-cycle, while undersized units struggle to maintain temperature.

4. Using the Calculator

Tips: Enter total conditioned square footage (excluding garages, basements, and attics). Select insulation quality based on your home's characteristics. All values must be valid (square footage > 0).

5. Frequently Asked Questions (FAQ)

Q1: Why is 35 BTU/sq ft used as average?
A: This represents the typical heating load for moderately insulated homes in most US climate zones, accounting for average heat loss.

Q2: What constitutes "conditioned area"?
A: Conditioned area includes all living spaces heated by the furnace, excluding garages, unfinished basements, and unheated attics.

Q3: When should I adjust for insulation quality?
A: Add 10% for older homes with poor insulation or single-pane windows. Subtract 10% for newer, well-insulated homes with energy-efficient windows.

Q4: Are there other factors to consider?
A: Yes - ceiling height, window quality, local climate, number of occupants, and appliance heat output can affect final sizing requirements.

Q5: Should I consult a professional?
A: For precise sizing, always consult with an HVAC professional who can perform a Manual J calculation for your specific home.