Everything you need to spec and order right.

Practical guides on R-values, product selection, and how ordering from Prestige works.

R-Value Guide Fiberglass vs Mineral Wool How to Calculate How Ordering Works

Understanding R-Value.

R-value measures thermal resistance — how well insulation slows heat transfer. Higher R-values mean better insulation performance. R-value is additive: stacking two R-19 batts gives you R-38. The IECC (International Energy Conservation Code) sets minimum R-value requirements by climate zone, which most states adopt and some states exceed.

Common R-Values by Application

Application R-Value Range Typical Framing Notes
Exterior Walls (2×4) R-11, R-13, R-15 2×4 studs at 16" o.c. R-15 high-density fills cavity more completely
Exterior Walls (2×6) R-19, R-21 2×6 studs at 16" or 24" o.c. R-21 HD preferred for cold-climate zones
Attic Floor R-30, R-38, R-49 Open floor joist bays R-49 required in Climate Zones 5–8
Cathedral Ceiling R-19, R-30, R-38 Rafter bays Must maintain ventilation channel
Floors over Crawlspace R-19, R-25, R-30 Floor joist bays Unfaced batt friction-fit or with support wire
Interior Sound Walls R-11, R-13 or MW Standard stud bays Mineral wool preferred for STC performance

R-Value by Climate Zone (IECC 2021)

Zone Example States Wall Min. Attic Min.
Zone 1–2FL, HI, AZ (southern)R-13R-30
Zone 3GA, TX, NC (coastal), CA (inland)R-20R-38
Zone 4OH, PA, VA, MOR-20R-49
Zone 5IL, NY, WI, IAR-20+5ci or R-13+10ciR-49
Zone 6–8MN, MT, AK, northern MIR-20+5ciR-49

Always verify with your local AHJ (Authority Having Jurisdiction). Some states and counties exceed IECC minimums. We'll confirm compliant specs on your quote.

Fiberglass vs Mineral Wool.

Both fiberglass batts and mineral wool are ASTM-compliant and widely accepted by inspectors. The choice usually comes down to performance requirements, application, and local building code.

Fiberglass Batts

R-Value Range
R-11 through R-49
Fire Rating
Class A (non-combustible facing)
Sound (NRC)
0.75–0.95
Cost
Lower per square foot
Best For
Walls, attics, floors, residential new construction

The workhorse of residential construction. Available in kraft-faced, unfaced, and FSK-faced. Kraft facing acts as a vapor retarder in cold-climate walls.

Mineral Wool (Rockwool)

R-Value Range
R-15 through R-30 (per layer)
Fire Rating
Non-combustible, 2,150°F melting point
Sound (NRC)
0.85–1.05
Cost
Higher per square foot
Best For
Sound walls, fire assemblies, commercial, multi-family

Preferred in commercial and multi-family construction for its fire resistance and superior sound attenuation. Dimensionally stable — won't sag or settle over time.

When to specify mineral wool

🔥

Fire Assemblies

UL-classified fire-rated wall and floor assemblies often require mineral wool as the cavity insulation. Our SAFB (Safe'n'Sound AFB) is the industry standard.

🔇

Sound-Party Walls

Between units in multi-family, between hotel rooms, or between garage and living space. Mineral wool achieves higher STC ratings than fiberglass at the same thickness.

💧

Moisture-Prone Areas

Mineral wool is hydrophobic — it repels water and doesn't support mold or mildew growth. Preferred in crawlspaces, basements, and coastal applications.

How to calculate insulation quantity.

Insulation is sold by the bag or bundle, with each package covering a specified square footage at a given R-value and width. Here's how to estimate your order.

Step-by-step

01
Calculate total square footage
Measure the length × width of each wall or ceiling surface you're insulating. Add them together. Example: 10 walls × 8 ft high × 12 ft wide = 960 sq ft.
02
Subtract openings
Deduct doors and windows. A standard 3×7 door is 21 sq ft; a 3×4 window is 12 sq ft. For most residential projects, deduct ~10–15% for openings.
03
Divide by coverage per bag
Each bag lists its coverage at a specific R-value and width. Example: an R-15 bag (3.5" × 15") may cover 40 sq ft. Divide your net area by the coverage per bag to get your count.
04
Add 5–10% for waste
Cuts, irregular spaces, and waste factor. For a clean rectangular house with few openings, use 5%. For complex cuts, add up to 10%.

Example calculation

Sample: 2,000 sq ft home, 2×4 exterior walls, R-13

Gross wall area
1,200 sq ft
Less openings (12%)
−144 sq ft
Net wall area
1,056 sq ft
Coverage per bag (R-13, 15")
~40 sq ft
Bags needed
1,056 ÷ 40 = 26.4 → 27 bags
Plus 8% waste
+2 bags
Order quantity
29 bags

Not sure? Send us your square footage and we'll calculate the order for you. No obligation.

Get a Quote

How ordering from Prestige works.

We keep it direct and simple. No account required, no minimums, no retail counter — just a contractor-to-supplier transaction.

Step 01

Submit a quote request

Use our online form or call us directly. Tell us the product, R-value, quantity, and delivery address. We respond the same business day.

Step 02

Confirm pricing and delivery

We'll send you pricing, confirm availability, and lock in a delivery window. Everything is on the invoice before any payment is requested.

Step 03

Pay and schedule

We accept Zelle, Venmo, and check. Payment is made after the quote is confirmed. We schedule delivery once payment clears.

Step 04

Delivery to your site

Next-day delivery on stocked product. We coordinate to your job site, warehouse, or delivery address anywhere in the contiguous US.

No minimums

Order one bag or one truckload. We serve single-job contractors and large GCs alike. Quantity pricing is available for volume orders.

No account required

No sign-up, no membership fee. You submit a request and we quote you directly. Repeat customers get priority response.

Spec-grade product

What's on the quote is what arrives. ASTM-compliant fiberglass and mineral wool — no substitutions, no gray market product.

Have a project? Let's talk specs.

We'll match the right product to your application and confirm pricing same business day.