1. Remove & replace unusable material

• Replace or remove deteriorated materials that are rusted, torn, or unrepairable.

• If materials cannot support the weight of connections, they should be replaced with fabricated metal duct.

2. Secure connections

• Attach and secure connections.

• Rectangular duct shall be connected with s-cleats and enclosed with end caps.

• Round duct should overlap approximately 1" and screwed with at least 3 sheet metal screws, evenly spaced.

3. Support ductwork

• Flexible ducts and plenums shall be supported every 4 feet with material that is a minimum of 1 1/2" wide.

• Metal ducts will be supported by 1/2" wide eighteen gauge metal straps or 12-gauge galvanized wire at intervals not exceeding 10'.

4. Secure duct boots

• Duct boots shall be connected to supply lines and secured with a minimum of three sheet metal screws, spaced evenly around duct.

• Duct boot shall meet the surface of the conditioned area without any gaps and secured to surface with nails or screws.

5. (Mobile homes) Install scoops

• When no end cap is installed at the far end of the main trunk install and air seal a "scoop" at the last register take off.

6. (Mobile homes) Secure and seal cross overs and plenums

• On Mobile Homes remove plenum access and secure and seal drop duct and the crossover if applicable.

7. Sealing Gaps

• Follow steps 7a-7d, or. . .

• "Aeroseal" or similar product that  has been approved for use is an option for duct sealing when shown to have a payback by the audit. When using this method, ensure the following:

  • All ductwork is connected, and all holes 1" or bigger are patched as shown in step 7c.

  • This work must be done by a certified professional.

7a. Repair small gaps

• Seal gaps and seams less than 1/4" width with a combination of mesh tape and UL 181 duct mastic.

• Mastic alone is acceptable for seams and holes less than 1/8".

7b. Repair medium gaps

• Seal leaks between 1/4" and 3/4" using a two stage process.

• Install temporary tape as a backing material.

• Seal with fiberglass mesh and mastic that extends at least 1" past the temporary tape on all sides.

7c. Repair large gaps

• Repair leaks larger than 3/4" using a rigid duct patch.

• Mechanically fasten patch before applying mastic.

• Install fiberglass mesh and mastic over the seam, overlapping repair joint by at least 1" on all sides.

7d. Mastic all seams

• Seal all seams with mastic or similar adhesive.

• Mastic covering seams must be a minimum of a "nickel-thick".

8. Duct board

• Existing duct board can be repaired.

• New duct board should not be installed.

9. Worst case draft test

• Conduct a Worst Case Draft Test to verify Category I, II and III appliances are venting safely before leaving home for the day.

• Testing shall be recorded using the Utah WAP Worst Case Draft Test from.