A mass loaded vinyl and fiberglass decoupler composite — like the Soundsulate LAG product — outperforms bare mass loaded vinyl because it adds absorption and vibration isolation alongside mass-based blocking, addressing noise that MLV alone cannot stop.

Mass loaded vinyl blocks airborne sound by adding mass to a barrier, but it has no mechanism for absorbing sound energy or isolating structure-borne vibration. The Soundsulate LAG composite laminates 1/8" foil-faced MLV to a quilted fiberglass absorber, so the fiberglass layer handles mid-to-high frequency absorption and decouples the barrier from vibrating surfaces. That combination lifts measured performance from STC 27 for bare 1 lb MLV to STC up to 29 for the LAG wrap — and more importantly, it treats two different noise problems in a single assembly.

  • Bare 1 lb Soundsulate MLV achieves STC 27 as a standalone material.
  • The Soundsulate LAG composite achieves STC up to 29 as a pipe and duct wrap assembly.
  • The LAG fiberglass decoupler layer is 2" thick and quilted between protective facings.
  • The LAG outer facing is Foil Scrim Kraft (FSK), providing a vapor barrier alongside acoustic performance.
  • The Soundsulate LAG product carries a Class A (Class 1) fire rating per ASTM E84.

Important Exceptions

  • Impact noise from footfalls above: neither bare Soundsulate MLV nor the LAG composite stops impact noise — you need a decoupling underlayment at the source floor instead.
  • In-room echo and reverb: when the problem is slap-back reflection inside the room, absorption-only materials like drop ceiling tiles address it; the LAG composite and MLV target transmission, not in-room acoustics.
  • Flat wall assembly with resilient channel: in a multi-layer stud wall with resilient channel already installed, bare 1 lb Soundsulate MLV may outperform the LAG wrap because the channel provides the decoupling the fiberglass layer would otherwise supply.
  • Low-frequency bass transmission: STC ratings weight mid-frequency performance; for deep bass below 125 Hz, additional mass from 2 lb Soundsulate MLV or structural isolation measures are needed beyond what the LAG composite's STC 29 rating captures.
  • Marine or high-chloride environments: the Foil Scrim Kraft facing on the Soundsulate LAG product is not rated for sustained saltwater or extreme chloride exposure — a different vapor barrier strategy is required in those conditions.

How to Choose

  • Pick bare 1 lb Soundsulate MLV if: your problem is airborne noise through a wall or floor and you can seal every seam and penetration completely.
  • Pick the Soundsulate LAG composite if: you're wrapping pipes or ducts where structure-borne vibration is present alongside airborne noise.
  • Pick the Soundsulate LAG composite if: moisture exposure is a factor — the FSK facing provides a vapor barrier that bare MLV does not.
  • Pick the Soundsulate LAG composite if: the installation is in a commercial space requiring a Class A fire rating per ASTM E84 for code compliance.
  • Pick 2 lb Soundsulate MLV over the LAG composite if: low-frequency airborne noise is the primary problem and decoupling from vibrating structure is not a factor.