sealing ducts with tapes

The problem with many leaky ducts is that they have been sealed with poor quality materials, namely inadequate tapes. Many tapes do not provide a permanent seal: their adhesive dries out after some time…

Mastics are, in most cases, the best duct sealing material. Tapes should only be used in very well defined situations.

General guidelines when using duct tapes

Tapes can be useful, but only in some situations. Pay attention to the following guidelines:

- Prefer tapes that meet Underwriters Laboratories (UL) Standards and take into consideration the sealing locations and type of ducts.

- Do not use cloth-backed rubber-adhesive duct tapes.

- Rigid fiberglass ducts: you may use heat-activated tape UL 181A-H or pressure-sensitive tapes UL 181A-P.

- Flexible ducts and rigid metal ducts and components: use UL 181B-FX tapes.

- Pressure-sensitive metallic tape with non-butyl adhesive: only useful to temporarily seal air handler access panels;

- Pressure-sensitive metallic tape with butyl adhesive: only useful to seal metal-to-metal connections, unless it meets UL Standard 181.

- Rigid fiberglass ducts sealed with pressure-sensitive tape: follow manufacturer’s instructions; rub them firmly.

- When taping traverse joints, wrap the tape at least 3 times.

UL tapes

Do not forget: prefer top tapes, namely those qualified by the Underwriters Laboratories.