R-Value Chart for Fiberglass Insulation
Reference chart for every standard fiberglass insulation R-value — thickness, applications, code requirements, and wholesale pricing in one place.
Complete Fiberglass R-Value Chart
The table below covers every R-value in the standard fiberglass catalog. Use it to match your project requirements to the correct insulation spec.
| R-Value | Thickness | Best Application | Wholesale (VR-R Plus) |
|---|---|---|---|
| R-8 | 2.5" | Condensation control, unconditioned storage | $0.48/sq ft |
| R-10 | 3.0" | Light-duty walls, occasional-heat buildings | $0.52/sq ft |
| R-11 | 3.5" | Interior partitions, budget 2x4 walls | $0.55/sq ft |
| R-13 | 3.625" to 4" | 2x4 walls (code minimum Zone 1-2) | $0.65/sq ft |
| R-19 | 6.25" | 2x6 walls (code minimum Zone 3-4) | $0.90/sq ft |
| R-25 | 8.0" | 2x8 walls, cold climate (Zone 5-7) | $1.13/sq ft |
| R-30 | 9.5" | Ceilings, attics, 2x10 framing | $1.36/sq ft |
WMP-10, WMP-30, and WMP-50 facings run 6-9 cents per square foot above the VR-R Plus baseline. Black-faced variants run 4-8 cents higher. See the insulation cost page for full pricing across every facing combination.
R-Value Chart by Building Surface
Wall R-Value Chart
Ceiling R-Value Chart by Climate Zone
| Climate Zone | Ceiling Minimum |
|---|---|
| Zones 1-3 | R-30 |
| Zones 4-5 | R-38 |
| Zones 6-8 | R-49 |
Detailed zone-by-zone code recommendations on the R-Value Guide by Climate Zone.
Understanding R-Value Ratings
R-value measures resistance to heat flow. A higher R-value means the material slows heat transfer better. The R stands for "resistance," and the number is the thermal resistance rating measured in F°-ft²-h/Btu under ASTM C518 testing.
Two key facts about R-value that matter for buying decisions:
R-Value Is Additive
If you install two layers of R-13 insulation, the total assembly R-value is R-26 (R-13 + R-13). This is why some cold-climate buildings combine batts in framing cavities with rigid foam continuous insulation outside the framing — the two add together to exceed what a single layer could achieve in the available cavity depth.
Compression Reduces R-Value
R-value is rated at the insulation's nominal installed thickness. Compressing the material into a shallower cavity reduces the R-value proportionally. R-19 fiberglass (6.25 inches) compressed into a 2x4 wall cavity (3.5 inches) delivers approximately R-13 — not R-19. Always match the R-value to the cavity depth available.
Fiberglass Delivers ~R-3 Per Inch
Standard fiberglass insulation runs about R-3.0 to R-3.5 per inch of installed thickness. High-density fiberglass (used in R-15 batts that fit 2x4 cavities) runs closer to R-4 per inch but costs significantly more.
R-Value Chart by U.S. Climate Zone
Quick code-minimum reference. The IECC divides the U.S. into 8 climate zones, with different minimum R-values for walls, ceilings, and floors in each zone.
R-Value Chart FAQ
What is an R-value chart?
An R-value chart is a reference table showing the relationship between insulation R-value rating, physical thickness, and typical application. R-value measures resistance to heat flow per ASTM C518 testing standard. Higher numbers indicate better thermal performance.
How is R-value measured?
R-value is measured per ASTM C518 using a heat flow meter apparatus. The test measures how much heat passes through a sample under controlled temperature differential. R-value is additive — two inches of R-3 material delivers R-6 total.
What R-value do I need for walls?
What R-value do I need for ceilings?
IECC ceiling minimums: R-30 in Zones 1-3, R-38 in Zones 4-5, R-49 in Zones 6-8. Ceilings need higher R-values than walls because heat rises and the top of the conditioned envelope has the largest temperature differential.
How thick is each R-value?
Standard fiberglass thicknesses: R-8 = 2.5", R-10 = 3.0", R-11 = 3.5", R-13 = 3.625", R-19 = 6.25", R-25 = 8.0", R-30 = 9.5". Each is engineered to fit specific framing depths without compression.
Does R-value increase linearly with thickness?
Roughly yes. Fiberglass R-value runs about R-3.0 to R-3.5 per inch of material. Doubling thickness doubles R-value. Code minimums and practical framing dimensions create the discrete R-value steps (R-8, R-13, R-19, etc.) rather than a continuous scale.
Apply the Chart to Your Project
Pick your R-value from the chart above, enter your square footage in the calculator, and see wholesale pricing for your specific spec.