/ Field knowledge · IMC 802.7–802.8
The appliance collar does not hold the vent.
The appliance collar does not hold the vent. Every run needs support for the actual material and weight. Where the vent goes through attic insulation, a shield keeps the required clearance — at least No. 26 gage, extending at least 2 inches above the insulation, and secured so it cannot be displaced.
Educational 2024 International Mechanical Code (IMC) 802.7 and 802.8 from Daily Code Talk. Confirm the adopted edition. Distinct from termination heights (802.5–802.6) and factory-built chimneys (805) (805.8 has its own insulation-shield language). This is not a hanger design.
- 802.7: every portion of the vent adequately supported for the design and weight of the materials. Manufacturer spacing, vertical and horizontal runs, fittings, roof and wall penetrations, thermal movement, and wind at the termination. The appliance connection should not carry the system.
- 802.8: an insulation shield where a vent passes through an insulated assembly. Constructed of at least No. 26 gage sheet metal, maintaining the vent manufacturer’s clearance to combustibles, extending at least 2 inches above attic insulation, secured against displacement.
- A listed insulation shield that comes with the vent system is installed per the manufacturer. The job of the shield is to keep loose-fill, batt, or blown insulation from contacting or migrating into the clearance zone.
On the set: support type and spacing for the specified material and diameter; every insulated-assembly crossing with gage, clearance, height above insulation, and securement. Walk the path in section, not only in plan.
The attic crossing with no shield
Architectural drawings show insulation. Mechanical drawings show a pipe through the attic and no shield. Future insulation work will bury the clearance. A long horizontal run with no support spacing leaves slope and joints to field judgment.
Source: Daily Code Talk — IMC 802.7–802.8 · chimney shields: 805.8 · heights: 802.5–802.6 · pass-through: 803.10.4 · factory-built: 805.
What to send
Vent material and diameter, attic / insulated-assembly crossings, and the manufacturer’s support and shield sheets if you have them.
If the vent goes through the attic
Send the section. MasterBuild will say whether 802.8 is a missing shield — or 802.7 is an unsupported run hanging from the appliance collar.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
MasterBuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Confirm the adopted edition. No. 26 gage and the 2-inch shield height are 2024 IMC 802.8 education from Daily Code Talk — not a hanger selection. This page is not legal advice.