Duct-Sealing Strategies for Retrofits
Duct sealing can be difficult, costly and disruptive to deal with in a retrofit situation. The Advanced Residential Integrated Energy Solutions (ARIES) Collaborative conducted a field study to compare two techniques: manually applied sealants and injected Aeroseal aerosol. Their goals were to understand and compare the cost and effectiveness of these two approaches and to identify the logistical and technical issues that might affect large-scale implementation in low-rise multi-unit residential public housing complexes.
This study took place in 40 units in two housing developments in North Carolina. The developments included one- and two-story units that utilized central air conditioning and natural gas heating. The ductwork included both flex ducts and metal ducts, attic and floor ducts, and ducts inside and outside of conditioned space. The air handlers were all located in conditioned space.
Half of the units were treated with hand sealing, while the other half were treated with injected Aeroseal aerosol sealant.
Scope of Hand Sealing:
- Register boots were sealed to the floor or to the ceiling.
- Return plenums were sealed inside with mastic.
- Air handlers were sealed from the outside with mastic.
- Where accessible, the ridges trunk ducts and the trunk to flex duct connections inside attics were sealed with mastic.
Scope of Aeroseal Sealing
Aeroseal sealant could reach ducts that were inaccessible by hand. Return ducts were too small to use the Aeroseal system, so these were hand sealed. Air handlers and junctions between registers and walls, ceilings and floors were also hand sealed. (Note: In many cases the Aeroseal can be used to seal return systems. A wide connector in the duct system can split the air stream towards the return and the supply so both are treated at once.)