If you are installing drywall partitions in a residence, office, or commercial space where noise transmission between rooms compromises operations, installing a false ceiling under a zinc or tile roof to curb tropical rain noise, insulating a sun-exposed facade to reduce air conditioning load, or building fire-rated separators in machine rooms and emergency exits, the MOLTEXO 100 kg/m³ semi-rigid rock wool panel is the calibrated insulator for these scenarios. This guide explains how to choose between the three thicknesses (50, 75, and 100 mm), how to properly install it between steel framing studs or drywall profiles without compressing the material, and how to address the vapor barrier in humid Caribbean climates—a critical detail that distinguishes a durable installation from a wall with hidden mold in a few years.
The rock wool panel simultaneously fulfills three functions—acoustic insulation, thermal insulation, and passive fire protection A1—with a calibrated density of 100 kg/m³ that provides significantly better acoustic absorption than standard fiberglass of the same thickness. For industrial pipes, boilers, and cylindrical surfaces, the rigid format does not apply: in those cases, the correct product is the wired rock wool roll with galvanized mesh, which covers curved surfaces with a structural fastening platform.
Product Specifications
The rock wool panel is offered in a 120 × 60 cm format with a density of 100 kg/m³, natural light brown color, in three thicknesses chosen according to the thermal or acoustic severity of the project. The following table shows the full technical specifications of the three variants:
| Specification | 50 mm | 75 mm | 100 mm |
|---|---|---|---|
| SKU | 543777 | 452321 | 983215 |
| Material | Hydrophobic semi-rigid volcanic rock wool | Hydrophobic semi-rigid volcanic rock wool | Hydrophobic semi-rigid volcanic rock wool |
| Density | 100 kg/m³ (6.24 pcf) | 100 kg/m³ (6.24 pcf) | 100 kg/m³ (6.24 pcf) |
| Panel Dimensions | 120 × 60 cm (47 × 23 in) | 120 × 60 cm (47 × 23 in) | 120 × 60 cm (47 × 23 in) |
| Thickness | 50 mm (2 in) | 75 mm (3 in) | 100 mm (4 in) |
| Package | 6 panels (4.32 m²) | 4 panels (2.88 m²) | 3 panels (2.16 m²) |
| Thermal Conductivity λ | ~0.040 W/m·K | ~0.040 W/m·K | ~0.040 W/m·K |
| Thermal Resistance R | ~1.25 m²·K/W | ~1.88 m²·K/W | ~2.50 m²·K/W |
| Fire Reaction | A1 non-combustible | A1 non-combustible | A1 non-combustible |
| Recommended Application | Interior partition with acoustic priority | Mixed thermal-acoustic partition, false ceiling | Sun-exposed facade lining, roof |
The installation procedure is identical for all three thicknesses. The choice is made based on the dominant function: 50 mm covers interior partitions where the priority is acoustic (offices, bedrooms) and thermal is secondary; 75 mm is the balanced option for partitions with dual acoustic-thermal requirements and for false ceilings under roofs with solar exposure; 100 mm is reserved for sun-exposed facades, roofs with high thermal loads, and projects where maximum possible thermal resistance justifies the extra space occupied by the thicker panel.
The wired roll with galvanized mesh is the choice when the surface to be insulated is cylindrical or curved (industrial pipes, boilers, tanks): the rigid panel does not adapt to these geometries and the wired mat provides a fastening platform with soft wire.
Step-by-step guide to using it
The following procedure covers the complete installation cycle of the rock wool panel in dry construction (drywall, steel framing) and linings. The instructions apply to all three thicknesses with specific notes where the technique differs.
Selection of thickness according to dominant function
Identify the critical function of the insulation in your project: if it is acoustic (separating bedrooms, offices, meeting rooms, reception areas from operational zones), 50 mm covers the standard case and 75 mm the premium case with executive privacy. If it is thermal (sun-exposed facade, zinc or tile roof, air conditioning in a hot area), 75 mm is the practical balance and 100 mm is the maximum recommended product. If the function is mixed (partition between conditioned rooms with adjacent sun-exposed walls), 75 mm is the natural choice for covering both with margin. The 100 kg/m³ density is constant: thickness is the variable that scales performance.
Quantity calculation and package purchase
Measure the net m² to be insulated (wall/ceiling area minus doors, windows, and openings) and add 8-10% for cuts and adjustments. Divide by the m² per package of the chosen thickness: 4.32 m² for 50 mm, 2.88 m² for 75 mm, 2.16 m² for 100 mm. Always round up. For a 30 m² wall with 75 mm panels: 30 × 1.10 = 33 m² ÷ 2.88 = 11.46 → 12 packages. The leftover will be useful in secondary applications (window edges, roof cuts), but it is preferable to the risk of running short and having to order a single extra package for 5 m² with additional freight.
Structure preparation and PPE
The 60 cm panel is calibrated to fit between drywall studs placed 60 cm on center (24 in OC, industry standard). Confirm that the profiles are at that separation; if the existing structure is 40 or 48 cm OC, you will need to cut the panel to size with a long-bladed knife or carpenter's saw. Before starting, equip installers with full PPE: sealed goggles, FFP2 mask, gloves, and long sleeves. Although rock wool panels are less itchy than fiberglass thanks to the treatment, the fibers can still irritate skin, eyes, and respiratory tracts during handling.
In the Caribbean climate, install a vapor barrier (plastic membrane or polyethylene film) on the HOT side of the wall—the side facing outwards, towards the street—not on the cold side of the interior air conditioning. The Caribbean logic is the reverse of cold countries: here, humidity seeks to migrate from outside (hot and humid) to inside (cold and dry due to A/C). If you place the barrier on the cold side, it condenses between the wool and the interior sheetrock, generating hidden mold that spoils sheetrock and insulation in a few years. This inversion compared to North American manuals leads to recurrent failures in Caribbean residential renovations executed with temperate zone plans.
Panel fitting without compression
Insert the panel by pressing it between the studs with the long side (120 cm) vertically. The semi-rigid stiffness of the panel allows it to support itself between studs at 60 cm without the need for adhesives, staples, or additional wires in standard vertical applications. On ceilings, install the panels BEFORE mounting the ceiling grid or the gypsum boards of the false ceiling, supported on the secondary framework, and in inclined applications (under a zinc roof) consider supplementary fastening with galvanized wires attached to the structure to prevent sliding. Critical: DO NOT compress the panel to force it into narrower gaps—see warning below—.
Wall closing and acoustic bridge sealing
After installing all panels, install the vapor barrier on the warm side (see expert tip) and proceed to close with drywall, sheetrock, or exterior sheathing board. Seal all joints, outlet penetrations, and utility passages with elastic acoustic sealant or aluminum adhesive tape on vapor barriers. A wall with well-installed panels but unsealed joints loses much of the declared acoustic insulation due to sound flanking through the bridges. For partitions with high acoustic requirements, consider double gypsum board (two sheets of sheetrock) on one or both sides of the partition.
Do not compress the panel to force it into openings narrower than its nominal size. The insulating capacity of rock wool depends on the air trapped between the fibers: when the panel is compressed into a smaller space, the air is displaced, the fibers are squeezed together, and thermal conductivity increases significantly, while acoustic absorption decreases due to loss of the porous structure. A 75 mm panel compressed to 50 mm performs substantially less than a 50 mm panel at its nominal thickness. If your structure has openings of different sizes, cut the panels with a knife or saw to the exact size—rock wool cuts cleanly with a sharp, long-bladed knife—do not squeeze them.
50, 75 or 100 mm? Panel or wired mat?
The choice between the three thicknesses and between rigid panel and wired mat depends on the type of surface (flat or curved) and the critical function of the insulation (acoustic, thermal, or fire protection). Overpaying for 100 mm in an interior bedroom is wasteful; saving with 50 mm on a sunny facade leaves the A/C running all day. Ask our assistant about your scenario and we will guide you to the correct choice without over- or under-sizing.
Complementary products
To complement rock wool panels in dry construction, false ceilings, facades, and fire-rated partitions, the following products cover the most common adjacent needs:
The rock wool wired mat roll is the sister product in the family for cylindrical and curved surfaces (pipes, boilers, thermal equipment), where rigid panels do not apply. Aluminum adhesive tape is the natural tool for sealing joints between panels and closing the vapor barrier in thermal applications with auditing. Transparent manual PP adhesive tape is used to seal the plastic membrane of the vapor barrier in residential walls where aesthetics matter. The 3-runner plastic pallet is a base for internal transport when packages arrive at the construction site and need to be distributed across floors without damaging boxes with forklifts and ramps.
Maintenance and care
Rock wool panels installed inside a closed partition or false ceiling do not require maintenance throughout the wall's lifespan: the material's dimensional stability, its hydrophobic treatment, and its incombustible nature ensure that it maintains its declared performance for decades without intervention. Inspection should focus on the entire wall—the vapor barrier, joint seals, outlet penetrations—not the insulation itself.
For storage prior to installation, keep packages horizontally on flat pallets, in a covered area away from water and under a roof. Although the material is hydrophobic, direct absorption of tropical rainwater can saturate the wool and temporarily reduce its performance; allow 48-72 hours to dry before installing if a package got wet. Do not open the packaging until installation to minimize exposure to dust and environmental humidity. For projects with long phases, keep any leftover material re-packaged with opaque plastic until the wall is closed.
Frequently Asked Questions (FAQ)
50, 75 or 100 mm for my project?
The criterion is the dominant function: acoustic, thermal, or mixed. 50 mm covers interior partitions with acoustic priority (offices, bedrooms, standard meeting rooms). 75 mm is the practical balance for partitions with double acoustic-thermal requirements and for false ceilings under a roof with sun exposure. 100 mm is reserved for sunny facades with west or southwest orientation, roofs with high thermal load, and projects where the maximum thermal resistance of the product justifies the extra space taken up by the thick panel. If you are between two thicknesses due to reasonable doubts, increase the thickness: the extra cost is usually less than reopening a wall years later to improve insulation.
Should a vapor barrier be used in Caribbean climates?
Yes, and it is CRITICAL to place it on the correct side. In Caribbean climates (hot and humid all year round, A/C indoors) humidity migrates from outside to inside, unlike in cold climates. The vapor barrier must be installed on the WARM side of the wall—the side facing the exterior, towards the street—not on the cold interior side as recommended by North American manuals for temperate zones. If you reverse the order, condensation will occur between the wool and the interior sheetrock, generating hidden mold that will damage the sheetrock and insulation in a few years. This reversal compared to Northern references is a source of frequent failures in residential renovations in the Caribbean.
Does it itch like fiberglass? What PPE should I use?
It itches significantly less than fiberglass thanks to the hydrophobic treatment and because rock wool fibers are less brittle than glass fibers (they don't break into as many fine fragments when handled). Even so, the fibers can irritate skin, eyes, and respiratory tracts during handling, so full PPE is recommended: sealed goggles, FFP2 mask, gloves, and long sleeves. After prolonged handling, wash with COLD WATER before warming up the shower—hot water opens pores and allows surface fibers to enter. The practical rule for experienced installers: a cold shower first to rinse off fibers, then a normal hot shower to clean.