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Ductwork airtightness can be defined as the resistance to inward or outward air leakage through the ductwork envelope (or ductwork shell). This air leakage is driven by differential pressures across the ductwork envelope due to 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 extract the air from the conditioned spaces. It does not include components such as air handlers, heat recovery units, air terminal devices, coils. Attenuators, dampers, access panels, etc. are a part of the ductwork but have more functions than conveying the air and are therefore also referred to as technical ductwork products. Ductwork airtightness is the fundamental ductwork property that impacts the uncontrolled leakage of air through duct leaks. Typical reasons for poor ductwork airtightness include:〔Lawrence Berkeley National Laboratory (LBNL). "(An Introduction to Residential Duct Systems )". LBNL, 2003〕〔F. R. Carrié, J. Andersson, P. Wouters. "(Improving ductwork—A time for tighter air distribution systems )". Air Infiltration and Ventilation Centre. Coventry, UK., 1999.〕〔 F. R. Carrié and P. Pasanen. "Chapter 3. Ductwork, hygiene and energy. In M. Santamouris and P. Wouters (eds). Building ventilation — The state of the art". pp. 107-136. Earthscan, UK 2006.〕 * inadequate or missing sealing media; * worn tapes; * poor workmanship around duct take-offs and fittings; * ill-fitted components; * physical damage. An airtight ductwork has several positive impacts:〔〔 J. Andersson. "Swedish experience with airtight ductwork". The REHVA European HVAC Journal: Special issue on airtightness. January 2013〕〔TightVent Europe. “Building and ductwork airtightness: Selected papers from the REHVA special journal issue on airtightness”. 2013〕〔C. Delmotte. "(Airtightness of ventilation ducts )". Air Infiltration and Ventilation Centre (AIVC) Ventilation Information Paper 01, 2003.〕 * secured air transport through the duct system; * lower energy bills due to less heat loss and fan energy wastage to compensate the effect of the leaks; * lower leakage airflow rates to/from unconditioned spaces (which can affect energy use, power demand, indoor air quality and comfort); * easier airflow balancing; * lower duct leakage noise. Sweden is often considered as a reference for airtight ducts: the requirements introduced in AMA (General material and workmanship specifications)〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ductwork airtightness」の詳細全文を読む スポンサード リンク
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