Insulation Guide: R-Values, Types and What Works Here
8 min read · Updated 2026
Insulation is the cheapest comfort you can buy, and it is the item most often trimmed when a budget gets tight. That is backwards: everything else on the house is easier to upgrade later, and the attic is the one place where a few hundred dollars changes the power bill every single month.
This guide covers what R-value actually means, which product belongs where, and the installation mistakes that quietly waste half of what you paid for.
What R-value means
R-value measures resistance to heat flow. Higher is better, and it adds up in a layer — R-19 batts plus R-11 of continuous foam gives you R-30 through that path.
Two things the number does not tell you. First, R-value assumes a perfect installation; a batt compressed around a wire or left with a gap at the top plate performs far below its label. Second, framing members conduct heat around the insulation — thermal bridging — which is why continuous exterior insulation matters, especially on steel-framed walls.
Recommended R-values for West Texas
Seminole and the surrounding Permian Basin sit in a hot-dry climate zone. Attic performance carries most of the load here because roof surfaces bake all summer.
| Location | Target R-value | Typical product |
|---|---|---|
| Attic | R-38 to R-49 | Blown fiberglass, or R-30 batts plus a blown layer |
| 2x4 exterior walls | R-13 to R-15 | Kraft-faced or unfaced batts |
| 2x6 exterior walls | R-19 to R-21 | Batts sized to the cavity |
| Floors over unconditioned space | R-19 to R-25 | Batts held up with supports |
| Interior walls (sound) | R-11 to R-13 | Unfaced batts, friction fit |
If you do one thing to an existing house, top up the attic. It is the highest return per dollar available in the building, and blown insulation goes over what is already there.
Types compared
| Type | Strengths | Watch out for |
|---|---|---|
| Fiberglass batts | Cheap, DIY-friendly, easy to inspect | Performance collapses if compressed or gapped |
| Blown fiberglass / cellulose | Fills irregular attic space completely, fast | Needs a blower; settles over time in some products |
| Rigid foam board | High R per inch, continuous, breaks thermal bridging | Costs more; joints must be taped to work |
| Spray foam | Air seals and insulates in one step | Highest cost; requires a trained applicator |
Faced vs. unfaced
Kraft facing is a vapor retarder, and the facing goes toward the conditioned side of the wall. In our dry climate, wall vapor drive is less of a problem than in humid regions, but the facing also gives you stapling flanges, which is why crews like it.
Unfaced batts belong in interior sound walls, in attic top-up layers over existing insulation, and anywhere a second layer is going in — never install a second faced layer, because you trap moisture between two vapor retarders.
Air sealing comes first
Insulation slows heat conduction; it does not stop air movement. A wall with perfect batts and an unsealed top plate still leaks. Before insulation goes in, seal penetrations: plumbing and wiring holes, top and bottom plates, around window and door frames, and every can light and duct boot in the ceiling.
Caulk and canned foam are the cheapest materials on the job and they change the performance of everything installed after them.
- Cut batts to fit around obstructions rather than compressing them over wiring.
- Split the batt around electrical boxes — half behind, half in front.
- Fill the full cavity depth. A R-19 batt stuffed into a 2x4 wall does not deliver R-19.
- Do not block soffit vents in the attic. Use baffles at the eaves to keep the intake path open.
Frequently asked questions
- What R-value do I need in a West Texas attic?
- R-38 to R-49. In practice most new houses around Seminole get blown fiberglass to that depth, and existing houses benefit enormously from a blown top-up over whatever is already up there.
- Should insulation face in or out?
- The kraft facing goes toward the conditioned space — the inside of the house. Never install a second faced layer over an existing faced batt, since two vapor retarders can trap moisture between them. Use unfaced material for top-ups.
- Is spray foam worth it?
- It air seals and insulates in one operation and gives the highest R per inch, which matters in tight cavities. It also costs the most and needs a trained applicator. For most houses here, well-installed batts plus careful air sealing plus a deep attic gets most of the benefit for far less.
- Do I need insulation in interior walls?
- Not for energy, but unfaced batts in bedroom, bathroom and office walls make a real difference in sound. It is inexpensive to do while the walls are open and impossible to do cheaply afterward.
Need the material, not just the theory?
Bring your numbers to the Seminole counter or send us the plans — we will price the package and set a delivery day. Free Delivery on Qualifying Orders. Call for details.
Products in this guide
Keep reading
Need Materials Priced?
Send us a list or a set of plans and we'll price it, pull it and put it on a truck. Builders, remodelers and DIY homeowners all get the same counter service.
- Mon–Fri
- 7:00 AM – 5:00 PM
- Saturday
- 8:00 AM – 12:00 PM
- Sunday
- Closed
- Mon–Fri
- 8:00 AM – 5:00 PM
- Saturday
- Closed
- Sunday
- Closed
Net terms, job-name billing and repeat-order pricing for builders.
Free Delivery on Qualifying Orders. Call for details.
GAF, Owens Corning, LP SmartSide, Formica and Versetta Stone.
Real inventory on the ground in Seminole and Brookston.