Ducted heating systems use air ducts to distribute heated air throughout a building. The return air plenum via the floor in this video is responsible for circulating the cool or heated air back to the air conditioning system to be re-conditioned. The return air ducts must be airtight to the wall plenum to ensure the system operates efficiently and effectively.

If the return air ducts are not airtight, several negative consequences can occur. Firstly, air leaks can cause the system to lose efficiency, as heated air escapes from the ducts before it can be circulated throughout the building. This can result in increased energy consumption and higher utility bills.

Secondly, air leaks can allow unfiltered air from the roof space to enter the system. This can lead to a buildup of dust and allergens in the ducts, which can be circulated throughout the building and cause health problems for occupants sensitive to these particles, especially asthmatics.

Finally, air leaks can cause negative pressure within the building, leading to back-drafting of flues and chimneys. This can result in carbon monoxide and other dangerous combustion byproducts entering the building, posing serious health hazards.

To avoid these and other problems associated with air leaks in ducted heating systems, the return air plenums in wall cavities and ducts must be properly sealed and airtight. This can be achieved by using Air barrier tapes, XPS Board, caulk products and other sealing materials explicitly designed for use in ductwork mechanical systems.

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00:00 Intro
00:39 Experiencing Poor Performance in HVAC
01:52 Looking at the Leaky Return Cavity
03:21 Smoke testing the return
03:42 Smoking the system while in operation
04:15 Fixing the ducted return
05:41 Leaks around supply boots
06:00 Conclusion and Exhausts potentially causing Mould issues in the roof.