Determine Your R-Value Requirements
R-value is a measure of thermal resistance — higher is more insulating. The minimum R-value required for any given assembly is set by the IECC climate zone for that location, subject to local amendments.
Find Your Climate Zone
The US is divided into 8 IECC climate zones. Zone 1 is hottest (South Florida, Hawaii); Zone 8 is coldest (Alaska interior).
| Zone | Examples | 2×4 Wall | 2×6 Wall | Attic |
|---|---|---|---|---|
| 1 | Miami, Honolulu | R-13 | R-19 | R-30 |
| 2 | Houston, Phoenix | R-13 | R-19 | R-30–38 |
| 3 | Atlanta, Dallas, LA | R-13–15 | R-21 | R-38 |
| 4 | DC, KC, Seattle | R-15 | R-21 | R-38–49 |
| 5 | Chicago, Denver | R-20–21 | R-21 | R-49 |
| 6 | Minneapolis, Boston | R-20–21 | R-21 | R-49–60 |
| 7–8 | Montana, Alaska | R-21+ | R-21+ | R-60+ |
IECC 2021 raised the minimum for 2×4 walls to R-15 in zone 4 and R-20 in zones 5+. Many states have adopted IECC 2021 — always confirm with your AHJ.
Select the Right Product
Insulation is specified by R-value and cavity size. Match the R-value to your code requirement and the batt width to your framing.
Batt Width Selection
- 15" wide batts — for studs or joists on 16" centers (most residential 2×4 and 2×6 walls)
- 23" wide batts — for studs on 24" centers (common in advanced framing, engineered floor systems)
Facing Options
- Kraft-faced — vapor retarder on warm side; most common for exterior walls in zones 3+
- Unfaced — no vapor retarder; used in attics (where you don't want vapor barriers) and for fire-blocking requirements
- FSK (Foil Scrim Kraft) — radiant barrier facing; used in hot climates (zones 1–2) to reduce radiant heat gain
Product Reference
| R-Value | Thickness | Common Application | Climate Zones |
|---|---|---|---|
| R-11 | 3.5" | 2×4 walls, mild climates | 1–2 |
| R-13 | 3.5" | 2×4 exterior walls | 1–3 |
| R-15 HD | 3.5" | 2×4 walls, high-density | 4+ |
| R-19 | 6.25" | 2×6 walls, floors | 2–4 |
| R-21 HD | 5.5" | 2×6 walls, high-density | 4–8 |
| R-30 | 9.5" | Attic, ceilings | 1–3 |
| R-38 | 12" | Attic floors | 3–5 |
| R-49 | 14–16" | Attic floors, cold climates | 5–8 |
Fiberglass or Mineral Wool?
For the majority of assemblies — exterior walls, attic floors, floors over unconditioned spaces — fiberglass is the correct choice. Mineral wool is required when the assembly has fire-resistance or high-STC requirements.
- Standard exterior walls
- Attic floor insulation
- Floors over crawl spaces
- Interior partition walls (no fire/STC spec)
- Energy code compliance is the primary driver
- IBC fire-rated party walls
- Hotel corridor walls
- Apartment unit separations (STC 50+)
- Below-grade / high humidity
- Non-combustibility specified by architect or AHJ
Fiberglass batts do not meet ASTM E136 non-combustibility. Do not specify fiberglass for IBC fire-rated assemblies. Mineral wool AFB and SAFB meet ASTM E136.
Calculate How Many Bags You Need
The formula: Square footage ÷ Coverage per bag × 1.10 (the 1.10 adds 10% for cuts and waste).
Measure Square Footage
- Walls: Linear feet × ceiling height − window and door area
- Attic: Conditioned floor area below
- Floor/crawl: Floor area above the unconditioned space
Coverage Per Bag Reference
| Product | Width / Framing | Coverage / Bag |
|---|---|---|
| R-11 | 15" / 16" OC | ~48 sq ft |
| R-13 | 15" / 16" OC | ~40 sq ft |
| R-13 | 23" / 24" OC | ~60 sq ft |
| R-15 HD | 15" / 16" OC | ~36 sq ft |
| R-19 | 15" / 16" OC | ~32 sq ft |
| R-21 HD | 15" / 16" OC | ~28 sq ft |
| R-30 | 16" OC | ~25 sq ft |
| R-38 | 16" OC | ~19 sq ft |
| R-49 | 16" OC | ~14 sq ft |
| Mineral Wool AFB | 15" | ~30 sq ft |
Use the online calculator at prestigeinsulationco.com/calculator.html — enter square footage and R-value, it returns the bag count.
How to Order
The fastest way to order is to text (929) 466-1426 a list that looks like: "50 bags R-21 15", 30 bags R-49, zip 60601, Thursday delivery". We respond with a firm quote, usually within the hour.
What to Look for in a Supplier
No retail markup. The quoted price is the invoice price.
Can confirm delivery window the same day you quote.
10 bags or 1,000 bags — same direct pricing.
No deposit required. You pay after you inspect and confirm the order.
Can deliver to any state — not just your local market.
One supplier for all assemblies — no secondary sourcing for party walls.
Delivery and Payment Details
- Delivery speed: Next-day on stocked products for orders placed before 3 PM EST
- Coverage: All 50 US states — job sites, warehouses, residential addresses
- Site requirements: Tell us about gate codes, loading dock requirements, or truck size restrictions at quote time
- ETAs: Confirmed on invoice, with day-before and day-of updates
- Payment methods: Check, ACH, wire, cash — contact us for card options
- Terms: Net-30 available for established contractors with ongoing volume
- Inspection: Count bags and check product labels before signing off. Call us immediately if anything doesn't match the invoice.