/ Field knowledge · IMC 604
One R-value is not an insulation spec.
IMC 604: one R-value for the whole job is incomplete. Location, vapor retarder, weather jacket, and the 24-inch coil-discharge zone each generate their own redline.
Educational 2024 IMC 604. Confirm adopted energy code and climate zone. This is not an R-value table for your project. Meet both IMC Table 604.3 and the energy code — put the governing standard on M-001.
- Listed, labeled, installed per manufacturer. ASTM E84 or UL 723: max flame spread 25, max smoke developed 50.
- R-values by climate zone and location (supply vs return, conditioned vs unconditioned, attic, crawl, exterior). A single R-value for the entire project is the comment.
- Insulation continuous at hangers and penetrations. Do not fill the firestop annular space or bridge a damper.
- Permanently identify R-value, material type, and flame-spread/smoke-developed index.
- Cooling ducts in unconditioned space: vapor retarder on the outside, joints sealed. Outdoor duct: weatherproof / UV-rated jacket.
- 604.13: water-permeable internal lining is prohibited in the cooling-coil discharge zone. If the AHU instructions do not specify the zone, DCT applies a minimum of 24 inches downstream of the coil face.
- 604.13 coil discharge: no water-permeable exposed liner to the drain-pan end.
Source: DCT 604 · vapor: 604.11–604.12 · coil: 604.13.
What to send
Climate zone, whether ducts are in a vented attic or outdoors, and the AHU discharge detail if one exists.
If the liner runs through the coil discharge
Send the AHU section. Masterbuild will say whether 604.13 is even on the path — or the schedule is one R-value for the whole set.
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.