Duct Insulation Requirements in Texas
The 2018 IECC, adopted in Texas, mandates minimum insulation levels for ducts based on location and size:
| Duct Location | Duct Size | Minimum Insulation R-Value |
|---|---|---|
| Attics | ≥3 inches | R-8 |
| Attics | <3 inches | R-6 |
| Other Unconditioned Spaces | ≥3 inches | R-6 |
| Other Unconditioned Spaces | <3 inches | R-4.2 |
Note: If ducts are fully inside the conditioned space, no insulation is required.
Duct Sealing Requirements
All ducts, air handlers, and filter boxes must be sealed to prevent air leaks.
✔ Approved Sealing Methods:
– Mastic
– Liquid Sealants
– UL 181-rated Tapes
– Air-impermeable Spray Foam (allowed as both duct insulation and sealant under the 2018 IECC)
✔ Air Handler Leakage Limits:
– Air handlers must be rated for ≤2% leakage of design airflow (per ASHRAE 193).
Duct Leakage Testing Requirements in Texas
If any ducts are outside the building’s thermal envelope, a duct leakage test is required.
✔ Testing Method: Duct Blaster Test
✔ Required for: Any ducts in attics, crawlspaces, garages, or exterior wall cavities.
✔ Not Required If: All ducts are inside conditioned space
Texas Duct Leakage Limits
Leakage limits are based on the conditioned floor area (CFA) of the home and the testing method
| Test Condition | Max Leakage Allowed |
|---|---|
| Total Leakage (pressurized at 25 Pa) | ≤4.0 CFM per 100 sq. ft. of CFA |
| Leakage to Outdoors (if applicable) | ≤4.0 CFM per 100 sq. ft. of CFA |
Exception: If the home follows the Performance Path or ERI Compliance Path, slightly higher duct leakage may be offset by improvements in other areas.
Building Cavities Cannot Be Used as Ducts
🚫 No Panned Returns Allowed!
The 2018 IECC prohibits using building cavities (such as walls, floors, or ceilings) as return ducts.
✅ Alternative Solution: Use properly insulated and sealed ducted returns instead.
📞 888-213-3975 – Local Energy Audits – Schedule your required duct leakage test today!
The 2018 IRC/IECC does not allow building cavities to be used as ducts.
