Duct Sealants

Duct sealants stop air leaks in residential and commercial HVAC ductwork, boosting comfort, efficiency, and indoor air quality. Use them to seal seams and joints at takeoffs, boots, elbows, plenums, and transitions on metal, flexible, and fiberglass ducts. Proper air sealing cuts energy waste, evens out room temperatures, reduces noise and dust, and helps prevent condensation that can lead to mold or corrosion.

Common product types include water‑based duct mastic (brush, trowel, or spray applied), solvent or silicone sealants for high moisture exposure, and UL 181‑rated foil tapes for quick closures. Look for UL 181 A‑M or B‑M mastics for rigid or flex ducts, and UL 181 A‑P or B‑FX for pressure‑sensitive tapes. For outdoor equipment and rooftop curbs, choose UV‑resistant, fiber‑reinforced, and weatherproof formulas.

Key specs to compare:
- Service temperature and pressure class (low, medium, or high pressure systems)
- Adhesion to galvanized steel, aluminum, PVC, and duct board
- VOC content and odor during cure (low‑VOC options support occupied buildings)
- Fire/smoke ratings, mold resistance, and paintability
- Cure time, sag resistance, and clean‑up method

Application tips:
- Clean and dry surfaces; remove oil, dust, and loose insulation.
- Apply a continuous 1/16–1/8 in layer; embed fiberglass mesh over gaps larger than 1/4 in.
- Seal before insulating to avoid trapped moisture; allow full cure before pressure testing.
- Use brushes, notched trowels, or cartridges for control; spray mastic speeds large jobs.
- Verify closures with a duct blaster or smoke pencil to meet IECC and IMC code targets.

Choosing the right HVAC duct sealant reduces utility bills, protects equipment, and extends duct life. Whether you are sealing a new install or tightening an older system, quality mastic and approved tapes deliver durable, code‑compliant results that keep conditioned air where it belongs. Save energy and improve comfort.