In short
- A barndominium insulation R-value checker compares your planned R-values with the energy code's prescriptive table for climate zone 3, where Smith County is listed.
- The 2021 IECC asks for R-49 in the ceiling, R-20 (or R-13 + R-5 continuous) in a wood wall, R-19 in a raised floor and R-10, 2 ft deep at the slab edge.
- The 2015 edition behind the Texas statewide code asks for R-38 in the ceiling and nothing at the slab edge. The other numbers are the same.
- Steel-framed walls need extra continuous insulation to match a wood wall, because steel carries heat through the studs.
On this page
This barndominium insulation R-value checker is for Tyler and Smith County owners who have a builder's R-values on paper and want to know if they clear the energy code before the bid is signed. Pick the code edition and the part of the building, enter the cavity and continuous R-values, and it says pass or short. For board feet of foam, use the spray foam and insulation area calculator; for condensation and foam choices, read the insulation guide.
En español: verificador de valor R del aislamiento
| Your numbers | Result |
|---|
The checks
| Check | Yours | Need |
|---|
Example shown above: 2021 table, wood-framed ceiling, R-38 in the cavity and no continuous layer: it comes out R-11 short. The same R-38 meets the 2015 table.
How the check is worked out
- Climate zone.
The International Energy Conservation Code (IECC) sorts every county into a zone. Smith County is listed in zone 3, warm and humid. Check the county table with your building official.
- Pick the edition.
The 2015 edition is the one behind the Texas statewide residential energy code. The 2021 edition asks for more in the ceiling and at the slab edge. Cities can adopt either.
- Read the row for your assembly.
The prescriptive table (R402.1.3) gives a minimum R-value per assembly. "13 + 5" is R-13 in the cavity plus R-5 continuous insulation over the framing.
- Add what you plan.
For ceilings and floors the checker adds cavity and continuous R-values. Walls use the cavity-plus-continuous options in the table. Steel walls use the steel-frame table (R402.2.6).
The zone 3 table, two editions
| Assembly | 2015 IECC | 2021 IECC |
|---|---|---|
| Ceiling or roof | R-38 | R-49 |
| Wood-framed wall | R-20, or R-13 + R-5 continuous | R-20, or R-13 + R-5, or R-15 continuous |
| Steel truss ceiling | R-49, or R-38 + R-3 | R-38 + R-5 |
| Raised floor | R-19 | R-19 |
| Slab edge | none | R-10, 2 ft deep |
These are the prescriptive minimums for climate zone 3. A design can also comply by a U-factor or software route, which lets a strong wall make up for a weak one.
Common wall combinations
| Wood-framed wall | 2015 | 2021 |
|---|---|---|
| R-19 batt, no foam board | Short | Short |
| R-21 batt | Pass | Pass |
| R-13 batt only | Short | Short |
| R-13 batt + R-5 continuous | Pass | Pass |
| R-15 continuous only (no cavity) | Short | Pass |
| R-15 batt + R-3 continuous | Short | Short |
R-19 batts are the usual miss: one point under the table. A continuous layer also helps with condensation and with heat leaking through the framing; see the insulation and condensation guide.
Steel-framed walls: continuous insulation needed
| Cavity insulation | 16 in studs | 24 in studs |
|---|---|---|
| R-0 (continuous only) | R-14 | R-14 |
| R-13 | R-8.9 | R-7.5 |
| R-15 | R-8.5 | R-7 |
| R-19 | R-7.8 | R-6 |
| R-21 | R-7 | R-5.9 |
These are the 2021 values for a zone 3 wall (continuous R needed, R402.2.6). The 2015 values follow the R-20 path only and are within about R-0.5 of these. Walls built with a pre-engineered metal building frame, girts and wall panels may be reviewed differently.
How deep is the foam to reach the number?
| Target | Closed-cell | Open-cell |
|---|---|---|
| R-20 | 3.4 in | 5.6 in |
| R-38 | 6.4 in | 10.6 in |
| R-49 | 8.2 in | 13.7 in |
Depth needed at the U.S. Department of Energy's typical figures of about R-6 per inch (closed-cell) and R-3.6 per inch (open-cell); your installer's data sheet governs. Roof framing depth can cap what fits, so check it against the spray foam calculator.
Model code, not your permit. Which edition applies, and whether anyone inspects it, depends on your location. Tyler adopts its own codes; much of unincorporated Smith County does not enforce a residential building code (see the Smith County permits guide). A lender, insurer or buyer's inspector may still ask what R-values you built.
Where a barndominium trips up
- R-19 walls. One point short of R-20. Use R-21 or add a continuous layer.
- Roof foam on a metal deck. Foam depth is capped by the purlins or the roof panel gap. Do the math before the order is final.
- Steel without a thermal break. Cavity insulation alone loses a lot at the steel. Ask for the continuous layer in writing.
- Compressed batts. A batt squeezed into a smaller cavity counts at its installed R-value, not the label.
- Slab edge. Under the 2021 table, slab-edge R-10 to 2 ft has to be planned before the pour. See the foundation guide.
- Ceiling with no attic. Vaulted and open-to-the-roof ceilings are limited by depth; ask which rule the bid relies on.
What to ask your builder
- What R-value goes in the roof, walls and slab edge? Ask for cavity and continuous values written separately.
- Which code edition is the plan checked against? See the permits guide and the build checklist.
- Is insulation in the contract or an allowance? Compare bids with the bid comparison calculator.
- Who installs and checks the depth? Foam is a trade; see how to choose a barndominium builder.
Next step: get a written quote
This tool checks R-values, not the building or the price. We are a referral service, not a contractor; we connect visitors with independent local providers. Use the form below to ask independent barndominium builders near Tyler for a written quote that lists the R-value of the roof, walls and slab edge.
Sources
- 2021 International Energy Conservation Code, Chapter 4 [RE], ICC (via UpCodes): Table R402.1.3, R402.2.2 and Table R402.2.6.
- 2015 International Energy Conservation Code, Chapter 4 [RE], ICC (via UpCodes): Table R402.1.2 and the steel-frame table.
- Single-family energy code, State Energy Conservation Office, Texas Comptroller: the statewide residential standard.
- Spray foam guide, U.S. Department of Energy Building America: typical R-value per inch.
Frequently asked questions
What R-value does a barndominium need in Tyler, Texas?
Smith County is listed in IECC climate zone 3. Under the 2021 IECC prescriptive table (R402.1.3), that means R-49 in the ceiling, R-20 or R-13 plus R-5 continuous in a wood-framed wall, R-19 in a floor over a crawl space, and R-10 slab-edge insulation 2 ft deep. The 2015 edition, the one behind the Texas statewide code, asks for R-38 in the ceiling and no slab-edge insulation. Your building official decides which edition applies.
Is R-19 enough for barndominium walls?
Not by the prescriptive table. Zone 3 asks for R-20 in the cavity, or R-13 cavity plus R-5 continuous insulation. R-19 is one point short, so builders usually use R-21 batts or add a continuous layer.
Do steel-framed barndominium walls need more insulation than wood?
On paper, yes. Steel conducts heat through the studs, so the steel-frame equivalent table asks for more continuous insulation. At a 16 in stud spacing, a wall with R-13 in the cavity needs about R-9 of continuous insulation to match the wood-frame R-20 path. Pre-engineered metal buildings are built differently, so ask which table your building official will use.
Does Smith County enforce an energy code on a barndominium?
It depends on the location. Inside Tyler, the city adopts and enforces its own building codes. Much of unincorporated Smith County does not enforce a residential building code, though a lender, insurer or appraiser may still ask what you built. See our permits guide for the local picture.
Does this checker cover spray foam thickness?
It checks the R-value you enter. To turn foam depth into R-value and board feet, use our spray foam calculator; typical figures are about R-6 per inch for closed-cell and R-3.6 per inch for open-cell foam.