duct leakage calculator

Introduction to Duct Leakage

Duct leakage refers to the loss of conditioned air through gaps, cracks, or disconnections in the ductwork of heating, ventilation, and air conditioning (HVAC) systems. This leakage can significantly reduce the efficiency of HVAC systems, leading to increased energy consumption, higher utility bills, and decreased indoor comfort. There are several types of duct leakage, each affecting system performance differently.

Types of Duct Leakage

1. Supply Duct Leakage: Occurs when conditioned air escapes from the supply ducts before reaching the intended spaces. This results in a loss of heated or cooled air, making the HVAC system work harder to maintain desired temperatures.
2. Return Duct Leakage: Happens when unconditioned air enters the return ducts, mixing with conditioned air and forcing the HVAC system to condition more air than necessary. This increases energy use and can introduce pollutants into the indoor environment.
3. Total Duct Leakage: Combines both supply and return duct leakage, providing an overall measure of the duct system’s airtightness.
4. Leakage to Outside: Measures the air leakage from the duct system to the outside of the building envelope. This type of leakage is particularly critical as it directly impacts the overall energy efficiency of the building.
5. Leakage as a Percentage of Airflow: Measures the air leakage from the duct system in relation to the airflow traveling through it.

Measured Airflow vs. Nominal Airflow

Measured Airflow: This is the actual airflow moving through the duct system as determined by testing with specialized equipment such as a duct blower. It accounts for real-world conditions, including any losses due to leakage or other inefficiencies.

Nominal Airflow: This represents the theoretical or design airflow specified by the HVAC system manufacturer. It assumes ideal conditions without accounting for any potential leaks or inefficiencies in the ductwork.