Marine Insulation Materials: Thermal & Acoustic Specifications for Ships & Offshore

Scope of This Guide

Marine and offshore insulation is usually described through its fire-protection role — SOLAS A-class divisions, FTP Code, hydrocarbon curves. That is the largest single chapter, but it is not the only one. This guide covers the equally important non-fire performance of marine insulation: controlling heat loss and surface condensation in engine rooms and accommodation, meeting cabin acoustic targets, sizing HVAC ducts and cold rooms, and specifying materials for LNG low-temperature zones that are below −100 °C and have nothing to do with flammability. Salt-spray corrosion and shipboard vibration durability are included as system-level selection criteria.

If you need the fire-rated side (A-60, H-120, class-approval), see our marine fire insulation materials and standards guide and the A-60 marine insulation thickness guide. The material-selection basics for the most common shipboard product — rock wool — are in rock wool marine and offshore applications.

Engine Room and Accommodation Pipe Insulation Thickness

The two governing variables are operating temperature and ambient conditions. On a ship, the ambient envelope swings from a refrigerated cargo hold to a tropical engine room, often on the same voyage. The table below gives typical first-pass thickness (mm) for clean bare steel pipe at an ambient of about 30 °C, suitable for non-fire zones inside the engine room and accommodation.

Three rules fall out of the table:

• Thickness rises roughly linearly with temperature. Every 100 °C step adds about 10 mm for the same pipe at this ambient.
• Glass wool is consistently 5–10 mm thinner than rock wool at the same temperature because its conductivity at low mean temperature is slightly lower.
• PU foam is the thinnest option for moderate service but should not be used above about 110 °C continuous — it is included here for completeness on chilled-water and HVAC lines, not for engine exhaust.

For accommodation cabins the table is usually dialled back to about 80–90 % of the engine-room thickness, balancing heat-loss control with the cabin's own internal heat gains and limited wall depth. On low-temperature cabins the thickness goes the other way — it must be increased to prevent surface condensation. That is the next section.

For the underlying material data and conductivity curves used to build this table, see our industrial pipe insulation types guide and the pipe insulation materials page.

Condensation Control: Calculation and Worked Example

Surface condensation is the most common non-fire failure mode in marine insulation. A cold pipe in a humid cabin sweats, the water pools, corrodes the steel, and drips onto electrical equipment. The cure is a calculation, not a thicker blanket.

The condensation-control formula:

δ = λ × (Ts − Tf) / (αs × (Ta − Td))

where:

• δ = insulation thickness (mm)
• λ = thermal conductivity of the insulation (W/m·K)
• Ts = required outside-surface temperature (°C); set to Td + 0.3 °C to keep a small safety margin
• Tf = process / pipe-wall temperature (°C)
• αs = surface heat-transfer coefficient; for still indoor marine air, use about 8.14 W/m²·K
• Ta = ambient air temperature (°C)
• Td = dew-point temperature (°C), from a psychrometric table for the local (T, RH)

Worked example — HVAC duct in a tropical engine room.

• Air inside duct: 18 °C
• Ambient: 35 °C at 80 % relative humidity
• Dew point Td: 28.5 °C
• Required surface temperature Ts: 28.5 + 0.3 = 28.8 °C
• Insulation: glass wool, λ = 0.040 W/m·K
• Diameter: 200 mm (the calculation is per unit area, so size drops out)

δ = 0.040 × (28.8 − 18) / (8.14 × (35 − 28.5))
  = 0.040 × 10.8 / 52.9
  ≈ 8.2 mm

For shipboard service add a 15 % safety margin for material aging, salt-spray absorption and seam gaps, giving a design thickness of about 10 mm. Round up to the next available product gauge. This matches the HVAC duct table in the next section.

Three correction factors ship designers apply on top of the formula:

• Humidity correction — for outdoor decks and high-humidity spaces, add 10–15 % to the calculated thickness.
• Wind correction — on open decks the αs value rises sharply with wind speed; use a higher αs and re-derive δ.
• Material aging — over a 15–20 year service life, fibrous insulation can absorb 1–3 % moisture by weight, which raises its effective λ. The safety margin covers this.

Cabin and Accommodation Acoustic Performance

Marine insulation is also the acoustic absorber in most accommodation modules. The metric is the Noise Reduction Coefficient (NRC) — the average absorption at 250, 500, 1000 and 2000 Hz. Typical marine targets:

A representative composite wall build-up for an accommodation cabin:

1. Epoxy primer (≈ 50 µm, anti-corrosion)
2. Glass wool acoustic-thermal layer, 48 kg/m³, 40 mm
3. Polyurethane damping layer, 10 mm (to break the structure-borne path)
4. Aluminium vapour barrier, 0.5 mm
5. Decorative acoustic panel, 5 mm

That stack typically delivers NRC ≈ 0.7 and an airborne sound insulation of ≥ 35 dB between 100 and 4000 Hz — the usual spec for a passenger or high-end accommodation cabin. For the acoustic product side, see our rock wool acoustic panels and the glass wool board product page.

HVAC Duct and Cold-Room Insulation

Marine HVAC and refrigeration lines are the highest-volume insulation application on most vessels. The two design drivers are heat-loss / heat-gain and anti-condensation, and they usually lead to the same thickness number.

Typical HVAC duct insulation thickness (chilled air at 7–18 °C, ambient 35 °C, glass wool λ ≈ 0.040 W/m·K):

For rock wool add 2–3 mm; for PU foam subtract 2–3 mm at the same diameter.

Cold rooms go further. Two product families dominate:

• PU / PIR foam — λ ≈ 0.022–0.028 W/m·K, closed cell, water uptake < 1 %. The default choice for provision stores at +5 °C down to about −30 °C.
• Silica aerogel blanket — λ ≈ 0.018–0.024 W/m·K. Used where the wall cavity is fixed and every millimetre matters, such as reefer container conversions.

For very low temperature service (−40 °C and below) PU thickness pushes past 100 mm, at which point designers either accept the wall build-up or switch to a vacuum insulation panel (VIP) with λ ≈ 0.007–0.010 W/m·K. VIPs are excellent thermally but expensive and difficult to replace, so they are usually limited to localised hot spots on an otherwise foam-lined room.

For the cryogenic side below −100 °C, the next section applies.

LNG Low-Temperature Zones (Non-Fire)

LNG carriers and LNG-fuelled vessels carry cargo or bunker tanks at about −162 °C. This is outside the range of conventional pipe insulation and well outside the range of fire-rated marine insulation. Three material families do the bulk of the work:

Thickness logic:

• Membrane containment systems (GTT NO96, Mark III) — about 200–250 mm of PU foam as the primary insulation, often with a perlite or foam-glass secondary barrier.
• Independent B-type containment — about 450 mm of PU foam, sized to keep the boil-off rate (BOR) below 0.10 % per day.
• Main cargo piping — 50–80 mm PU foam, sometimes with an outer rubber or GRP jacket.
• Bends, valves and fittings — 30–50 mm LNG elastic felt, which tolerates thermal contraction without cracking.

For vessel-level LNG insulation design, the relevant rule is the IGC Code (IMO) and class society rules (DNV, LR, BV, CCS). This is a different document set from SOLAS Chapter II-2 fire protection. The cryogenic pipe-insulation system for the rest of the plant (not LNG cargo) is covered in our cryogenic pipe insulation guide.

IMO and Class-Society Physical-Property Limits (Non-Fire)

IMO does not write a single “non-fire marine insulation” standard. Instead, the FTP Code, the IGC Code and the individual class-society rules (DNV, LR, CCS, BV) place indirect physical-property limits on every insulation material that goes on a ship. In practice this collapses to four numbers a buyer should check on the datasheet:

Adhesives, facings and jacketing are checked separately. A pull-off test of ≥ 50 kPa on the bond to the substrate is the usual minimum, plus a thermal-cycle test (typically 10 cycles between ambient and the design low temperature) with no delamination. For non-fire zones inside accommodation the adhesive also has to meet the IMO FTP Code low-spread-of-flame criteria, even when the insulation itself is not classed as a fire division.

Salt-Spray and Vibration Durability

A ship is a corrosive, vibrating environment. Two accelerated tests are used to qualify insulation materials for marine service:

Salt-spray test (per DNV-CG-0339 and equivalent class-society guidance)

• Conditions: 5 % NaCl solution, 35 °C, 95 % RH
• Duration: 3000 h standard, up to 5000 h for harsh service
• Pass criteria: strength loss ≤ 15 %, mass loss ≤ 10 %, no visible pitting on the metal jacket

Vibration test (per CCS materials & welding code and equivalent)

• Frequency sweep: 5–30 Hz
• Acceleration: 0.05–0.10 g
• Cycles: ≥ 10 000
• Pass criteria: fibre shed ≤ 5 %, tensile-strength retention ≥ 90 %, thickness change ≤ 3 %

A material that passes both tests is qualified for unrestricted marine service. Fibrous materials (rock wool, glass wool) generally need a vapour barrier and metal jacket to keep salt-laden air out; closed-cell foams and aerogel blankets are hydrophobic enough to pass without an extra barrier, but are still jacketed for mechanical protection on weather-exposed decks.

Quick Selection Matrix

For the product side, our rock wool blanket, rock wool board, glass wool board and nano aerogel insulation blanket cover the four most-used marine materials; the marine & offshore application page maps them to specific shipboard zones. All materials are produced under ISO 9001 quality management and are supported by EN 13501-1 / IMO FTP Code test data on request.