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Duct Sizing Formula:
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Duct sizing is the process of determining the appropriate dimensions for HVAC ductwork to efficiently distribute air throughout a residential space. Proper duct sizing ensures optimal system performance, energy efficiency, and comfort.
The calculator uses the basic duct sizing formula:
Where:
Explanation: The formula calculates the required duct area based on the desired airflow and velocity. Typical residential air velocities range from 600-900 fpm for supply ducts and 500-700 fpm for return ducts.
Details: Correct duct sizing is crucial for maintaining proper airflow, minimizing noise, reducing energy consumption, and ensuring even temperature distribution throughout the home.
Tips: Enter the required CFM for the space and select an appropriate air velocity based on duct type (supply or return). The calculator will determine the minimum duct area needed.
Q1: What CFM values are typical for residential systems?
A: Typical values range from 400-2000 CFM depending on home size, with about 1 CFM per square foot of living space as a rough estimate.
Q2: How do I convert duct area to dimensions?
A: For rectangular ducts, common aspect ratios are 1:1 (square) to 1:4 (flat). For round ducts, area = πr².
Q3: What happens if ducts are undersized?
A: Undersized ducts cause reduced airflow, increased noise, higher energy consumption, and potential system damage from excessive static pressure.
Q4: Should I use the same size for all ducts?
A: No, duct sizes should decrease as branches extend further from the main trunk to maintain proper air velocity.
Q5: Are there more advanced methods than this simple formula?
A: Yes, professional HVAC designers use methods like the Equal Friction Method or Static Regain Method for more precise calculations.