I've lost count of how many contractors have asked me the same question: "What's the difference between Rockwool R22 and Rockfloor 30mm?" Nine times out of ten, it's because the boxes look similar in the warehouse, the labels got skimmed, and now the crew needs the right material by tomorrow morning.
Here's the short version: both are stone wool. Both are made by Rockwool. Both start as volcanic rock, melted and spun into fibers. But they're engineered for completely different problems—and swapping one for the other is an expensive mistake.
In my role coordinating supply at a specialty insulation distributor, I've handled 200+ rush orders in six years, including same-day turnarounds for hotel and hospital construction clients. Every rush job forces three questions: how much time we actually have, whether the material can physically arrive in that window, and what the worst-case failure costs. This comparison is built from those same questions.
Here's what we're comparing, across four dimensions that matter on a real job site:
- What each product was engineered to do
- Real performance specs—not just what the box claims
- Cost per square meter, including the hidden costs
- How they behave when you need them fast
Dimension 1: What Rockwool R22 and Rockfloor 30mm Were Actually Built For
Rockwool insulation R22 is a thermal batt. The "R22" refers to its thermal resistance rating—R-22 when installed at its designed thickness (5.5 inches / 140 mm, which matches standard 2x6 wall framing). The batt density sits around 35–40 kg/m³. It's fluffy, compressible, and designed to friction-fit between studs while sealing up gaps around wiring and framing. Its entire job is keeping heat where it belongs.
Rockfloor 30mm is an acoustic floor slab. It's engineered to reduce impact noise—footsteps, dropped objects, the sound of a chair scraping on the floor above. It's much denser, roughly 125–150 kg/m³, and stiff enough to support load without crushing under screed or floating floor systems. Its job is stopping vibration from becoming noise, not filling wall cavities.
The easy way to remember: R22 is for vertical thermal. Rockfloor 30mm is for horizontal acoustic.
Now the blunt part. R22 in a floor assembly will compress under load, lose its air gap, and fail both thermally and acoustically. And Rockfloor 30mm stacked in an exterior wall to reach R-22? It's mathematically possible—I've done that calculation—but it takes roughly five layers, adds significant weight to the framing, and costs about four times as much as buying the correct batt. Neither substitution makes sense.
Dimension 2: Performance Specs Side by Side
Here are the numbers that matter, placed side by side:
- Rockwool R22: R-value R-22 at 5.5 inches (per ASTM C518). Thermal conductivity ≈ 0.036 W/m·K. Density ~38 kg/m³. Fire: Euroclass A1 per EN 13501-1; in North America, ASTM E84 Class A (flame spread 0, smoke developed 0). Not rated for impact sound.
- Rockfloor 30mm: Thermal conductivity ≈ 0.035 W/m·K. Density ~125–150 kg/m³. Fire: Euroclass A1 as well. Tested for impact sound improvement per ASTM E492 and ISO 140. Not marketed with an R-value, because it's not a thermal insulation product—it's an acoustic one.
Here's the result that surprises people: R22 is actually a decent airborne sound absorber. If you need to quiet a party wall or reduce sound transfer between rooms, R22 inside a framed cavity will knock down transmission noticeably. It's not a dedicated acoustic slab, but I've seen projects pass noise tests with R22 in the walls when the budget didn't allow more—and it worked.
The reverse is not true. Rockfloor 30mm cannot substitute for R22 thermally at its specified thickness. At 30mm, you're nowhere near R-22. Stack it to match, and the cost explodes. A floor product is not a wall hack.
Dimension 3: Rockfloor 30mm Price per m2 vs R22 Cost—Reality Check
If you found this article by searching "rockwool acoustic rockfloor 30mm price per m2," this section is for you.
Based on distributor invoices we've processed across 30+ orders in late 2024 (pricing as of December 2024):
- Rockwool R22 (5.5" batt): about $0.55–$0.75 per square foot, which works out to $5.90–$8.10 per square meter in pallet quantities.
- Rockwool Rockfloor 30mm: about $2.60–$3.50 per square foot, or $28–$38 per square meter.
So Rockfloor 30mm runs four to five times the cost of R22 per square meter. If you only compare price tags, R22 looks like the obvious pick. I understand the temptation.
But here's what I've watched happen on real projects. In March 2024, a contractor client saved about $1,800 by ordering R22 instead of Rockfloor 30mm for a 60m² fourth-floor apartment renovation. His logic: "it's all stone wool, right?" The underfloor acoustic test failed. The flooring crew had to tear up all 60m² of engineered oak, install the correct product, and re-lay the boards. That $1,800 "saving" turned into roughly $6,200 in corrective work, plus a two-week delay. The alternative was failing the building inspection—which carried a $12,000 penalty clause on the handover date.
The most expensive insulation isn't the one with the higher unit price. It's the one installed incorrectly.
One caveat: regional pricing varies more than people expect. Freight and local demand can swing these numbers by 10–20%. The "price per m2" search gets you a starting point; the actual quote from a local supplier gets you a number you can budget against.
Dimension 4: What Happens When You Need Them Fast
When you need material fast, these two products live in different worlds.
R22 is a commodity. Distributors stock it deeply, and next-day availability is standard in most metro areas. In six years, I've rarely had a panic call about R22. The same cannot be said for Rockfloor 30mm. Last quarter alone, we processed 47 rush orders with a 95% on-time delivery rate. The 5% that failed? Almost all traced back to an unclear spec or a product substitution.
Rockfloor 30mm is stocked regionally, not locally, in many markets. I've had three separate clients need it in under 48 hours. In one case, a search result promised "fast delivery" at 20% below everyone else. The price was great; the response times were a warning sign I chose to ignore. That vendor ghosted us after payment. What saved that project—a hotel job where the contractor carried a $50,000 delay penalty—was a distributor with actual shelf stock who put the order on an overnight freight truck. The rush freight cost $380 extra. Trivial next to the alternative.
That experience is exactly why our company now has a spec checklist for every urgent order: product code, application, and a direct phone confirmation before anything ships. We caught the wrong product three times in the first six months. I should have built the checklist after the first close call, not the third.
Rockwool R22 or Rockfloor 30mm: Which One Should You Choose?
Straight answer rather than a wishy-washy "it depends": for roughly 80% of projects, the right choice is obvious once you understand what each product is for. The remaining 20% is where the scenarios below matter.
Choose Rockwool R22 if:
- You're insulating exterior or interior framed walls
- Thermal performance per dollar is your priority
- You need friction-fit batts for 2x4 or 2x6 cavities
- You need the material quickly and want the widest supplier availability
Choose Rockwool Rockfloor 30mm if:
- You need to reduce impact sound between floors—apartments, hotels, multi-story homes
- You're installing under screed, under concrete, or beneath floating floors
- You need a stiff, load-bearing slab, not a soft batt
- Acoustic testing or compliance is on your project's critical path
Budget only allows one? Here's my honest recommendation:
Put the Rockfloor on the floor, and use a cheaper thermal batt in the walls. That recommendation costs me nothing because it is true: correcting a failed impact sound test after floor installation is dramatically more expensive than upgrading wall insulation later. Floors buried under screed and finished materials are hard to fix. Walls are accessible. Choose accordingly.
And if you're ordering under deadline pressure, call the supplier before clicking buy. Confirm the product code, thickness, and stock availability in one two-minute conversation. Every wrong-product mistake I've seen in a rush order would have been caught by that single call.
