Enter a truss ceiling as a Ceiling row with Ceiling Type Attic, and use the truss bottom chord as the framing. Insulation inside the depth of the bottom chord goes in Cavity R. Insulation piled above the chords goes in Continuous R.
CODE does not model raised-heel (energy-heel) trusses or thinner insulation at the eaves.
What to enter
| Field | What to enter |
|---|---|
| Ceiling Type | Attic when the insulation sits on the attic floor. Use Vaulted Roof / Exposed Exterior only when the insulation follows the roof line and there is no attic space. |
| Stud Type | The size of the bottom chord. 2×4 is most common; 2×6 and 2×8 are also available. |
| Spacing | The truss spacing. Most trusses are 24" o.c.; 16" and 19.2" are also available. |
| Use Custom FF | Leave it off unless the truss design gives you a framing fraction. CODE calculates a default from the chord size and spacing. |
| Cavity R | The R-value of the insulation that sits between the bottom chords, up to the top of the chord. |
| Continuous R | The R-value of the insulation above the top of the bottom chords. |
Example: R-49 blown insulation over 2×4 trusses at 24" o.c.
Say the blown insulation is rated R-2.5 per inch. A 2×4 bottom chord is 3.5" deep.
- Cavity R = 3.5 in × R-2.5 per inch = R-8.8
- Continuous R = R-49 − R-8.8 = R-40.2
- Stud Type = 2×4, Spacing = 24" o.c., Ceiling Type = Attic
Use the R-per-inch from the product label or the installer's certificate.
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