Ductwork airtightness can be defined as the resistance to inward air leakage through the ductwork envelope (or ductwork shell). This air leakage is driven by differential pressure in the ductwork envelope of the combined effects of stack and fan operation (in case of a mechanical ventilation system). For a given HVAC system, the term ductwork refers to the set of ducts and fittings (tees, reducers, bends, etc.) that are used to supply the air to or from the air. It does not include such components as air handlers, heat recovery units, air terminal devices, coils. Attenuators, dampers, access panels, etc. are a part of the ductwork, but they do not have the same function as ductwork. Ductwork airtightness is the fundamental ductwork that impacts the leakage of air through duct leaks. Typical reasons for poor ductwork airtightness include: In the US, there is a significant amount of work-saving energy saving potentials on the order of 20-30% in homes; and 10-40% in commercial buildings with airtight ducts The ASIEPI project technical report on construction and ductwork airtightness estimated the heating energy impact of duct leakage in a ventilation system on the order of 0-5 kWh per m 2 of floor area per year more additional fan energy for a moderately cold European region (2500 degree-days). Duct leakage affects more severely the energy efficiency of systems that include air heating or cooling. Typical reasons for poor ductwork airtightness include: In the US, there is a significant amount of work-saving energy saving potentials on the order of 20-30% in homes; and 10-40% in commercial buildings with airtight ducts The ASIEPI project technical report on construction and ductwork airtightness estimated the heating energy impact of duct leakage in a ventilation system on the order of 0-5 kWh per m 2 of floor area per year more additional fan energy for a moderately cold European region (2500 degree-days). Duct leakage affects more severely the energy efficiency of systems that include air heating or cooling. Typical reasons for poor ductwork airtightness include: In the US, there is a significant amount of work-saving energy saving potentials on the order of 20-30% in homes; and 10-40% in commercial buildings with airtight ducts The ASIEPI project technical report on construction and ductwork airtightness estimated the heating energy impact of duct leakage in a ventilation system on the order of 0-5 kWh per m 2 of floor area per year more additional fan energy for a moderately cold European region (2500 degree-days). Duct leakage affects more severely the energy efficiency of systems that include air heating or cooling. and 10-40% in commercial buildings with airtight ducts The ASIEPI project technical report on construction and ductwork airtightness estimated the heating energy impact of duct leakage in a ventilation system on the order of 0-5 kWh per m 2 of floor area per year more additional fan energy for a moderately cold European region (2500 degree-days). Duct leakage affects more severely the energy efficiency of systems that include air heating or cooling. and 10-40% in commercial buildings with airtight ducts The ASIEPI project technical report on construction and ductwork airtightness estimated the heating energy impact of duct leakage in a ventilation system on the order of 0-5 kWh per m 2 of floor area per year more additional fan energy for a moderately cold European region (2500 degree-days). Duct leakage affects more severely the energy efficiency of systems that include air heating or cooling.

There are two major systems to classify ductwork airtightness, one based on European standards, the other based on ASHRAE standard 90.1-2010. Both are based on the production of airflow rate and the production of the surface area and the same duct pressure to the power 0.65.

The relationship between pressure and leakage is defined by the rule of law as follows: q L = CL Δpn where: Threshold limits in ductwork airtightness classifications usually assumes an airflow exponent of 0.65.

Ductwork airtightness levels can be measured by means of a duct-to-air-flow device. This type of measurement is generally considered to be of general importance in the production of air pollution. standard test methods such as EN 12237 and EN 1507, ASHRAE standard 90.1-2010.

At construction stage, the airtightness of individual components depends on the design (rectangular or rounded ducts, pressed or segmented bends, etc.) and assembly (seam type and welding quality). Components with factory-fitted sealing devices (eg, gaskets, clips) are widely used in Scandinavian countries. A variety of techniques are widely used on site, including gaskets, taps, sealing compound (mastic), internal duct lining, aerosol duct sealing. So-called “duct tapes” are often not suitable for sealing ducts, which explains why, in the US, the International Energy Conservation Code (IECC) requires any tape used on duct board or flexible ducts to be labeled according to UL 181A or 181B.