What Is Mastic For Register

Musings of an Energy Nerd

Sealing Ducts: What'southward Better, Tape or Mastic?

Make sure you choose products that provide durable sealing

**Duct mastic seals leaky seams.** Mastic can be applied to leaky duct seams with a paint brush or gloved fingers.

Almost residential duct systems have numerous leaks that waste material energy and lead to room-to-room pressure imbalances. Unfortunately, though, few edifice inspectors outside of California bother to enforce existing lawmaking requirements that residential duct seams be sealed with mastic or high-quality duct tape.

About model codes, including the International Residential Code (IRC), include duct tightness provisions:

The 2006 IRC department N1103.2.2 requires that "Ducts, air handlers, filter boxes and building cavities used as ducts shall be sealed," while IRC department M1601.iii.i requires that "Joints of duct systems shall be made substantially airtight by means of tapes, mastics, gasketing or other approved closure systems." Hardware-store duct tape is not an approved tape.
Section 403.2.two of the 2004 International Energy Conservation Code (IECC) requires that "All ducts, air handlers, filter boxes, and building cavities used equally ducts shall exist sealed."

To learn how to exam residential duct systems for leaks, see Duct Leakage Testing.

All about mastic

Most energy-conscious builders seal duct joints with mastic. Mastic is a gooey, not-hardening fabric with a consistency between mayonnaise and shine peanut butter. Duct joints should ever be secured with #8 canvas-metal screws before seams are sealed with mastic.

Sealing duct seams is messy work, and then habiliment old dress. The mastic is spread over duct seams with a disposable paintbrush, putty knife, or your fingers. (If you lot spread mastic with your fingers, clothing safety gloves.)

Gaps in ductwork or plenums that are over 1/xvi or 1/8 inch wide can be sealed with mastic every bit long as the gap is first reinforced with fiberglass mesh tape. If you're using mastic to seal seams in fiberglass lath ductwork, apply fiberglass mesh tape for all joints.

Sources of mastic

Manufacturers of mastic include: Hardcast (Versi-Grip 181 mastic), McGill AirSeal (Uni-Mastic 181), Polymer Adhesives (AirSeal #22), RCD Corporation (#vi Mastic), and ITW/TACC (Glenkote mastic).

Among the distributors of…

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