Sound insulation · Stone wool
ROCKWOOL Safe 'n' Silent Pro
- Thickness
- 25–100 mm
- Density
- 40–100 kg/m³
- Sound absorption (NRC)
- 0.90–1.00
What does a ceiling need to block noise from the floor above (or to it)?
In short
A ceiling that really insulates sound needs four things together: a frame decoupled from the floor above (resilient hangers or an independent frame), solid boards with mass and finished joints, insulation in the ceiling cavity, and airtight sealing — especially at recessed downlights, AC diffusers and access hatches. Such a ceiling helps more with speech, TV and music than with footsteps, and the overall result is still limited by sound that travels around it through the walls and structure.
Start by asking what kind of noise it is
- Airborne sound (speech, TV, music from upstairs, or sound from your room that you do not want going up) — a sound-insulating ceiling addresses this directly
- Impact sound (footsteps, dropped objects, dragged chairs) — a ceiling helps partly; treating the floor above works better. See Footsteps from the floor above
- Rain on the roof — the principle is similar but the roof sheet matters too. See Rain noise on a metal roof
A sound-insulating ceiling works in both directions: the same system that reduces sound from above also reduces sound going up from your room.
Why does an ordinary ceiling block so little?
T-bar ceilings and lightweight tiles have little mass and a joint around every tile. ROCKWOOL explains that such tiles are weak sound blockers because they lack mass, and that ceiling systems commonly leak sound around light fixtures and air devices. Acoustic ceiling tiles are therefore suited to reducing echo inside the room rather than separating one floor from another. See Soundproofing vs sound absorption.
Components of a sound-insulating ceiling
| Component | What it does | Watch out for |
|---|---|---|
| --- | --- | --- |
| Frame decoupled from the floor above | Cuts the path by which vibration travels from the floor down to the ceiling boards | Screws long enough to touch the structure, or pipes and trunking rigidly fixed to both the floor and the ceiling, defeat the decoupling |
| Solid boards with mass, e.g. gypsum board with finished joints | More mass blocks more airborne sound. Many systems use two layers with staggered joints | Number of layers and board type follow the chosen ceiling system and the load the frame can carry |
| Insulation in the cavity | Damps sound in the cavity between the floor and the ceiling | Lay it continuously over the whole area with no gaps, and do not pack it so tightly that it pushes on the boards |
| Airtight sealing | Sound gets through small openings even when the boards are thick | Seal the ceiling perimeter to the walls with a sealant that stays flexible, and deal with every penetration |
The physics behind this (mass, air space and decoupling) is explained in Why a double-leaf wall with a cavity beats one thick layer.
Cavity insulation: what to use
Use fibrous acoustic batts or slabs laid above the boards in an airtight cavity.
- ROCKWOOL Safe 'n' Silent Pro — stone-wool slab for sound-control systems, used in wall and ceiling cavities; non-combustible according to the manufacturer
- ISO NOISE Standard — glass-wool batt in a PE bag, 0.60 × 1.20 m, 50 mm thick, for drywall and ceiling cavities
- Drywall partitions carried up to close off the void above the ceiling use wall-cavity insulation such as SCG Cylence ZoundBlock
Insulation is one part of a system. Sound ratings (STC / Rw / IIC) belong to the complete tested floor-ceiling assembly, not to the insulation. See Why cavity insulation improves sound insulation.
Downlights and penetrations: the most common weak point
Every hole through the ceiling boards is a shortcut for sound. BRE (UK) states that installing recessed downlights in a ceiling can reduce its sound insulation and airtightness, and luminaires are tested together with ceilings to ISO 10140 to confirm performance.
- Light fittings — where sound insulation matters, choose surface-mounted or pendant fittings instead of recessed ones, or use recessed fittings and covers that the manufacturer has tested with the ceiling
- Diffusers and ducts — diffuser openings and ducts linking several rooms carry sound. Fixing that is work for the air-conditioning designer
- Access hatches — use a panel with mass close to that of the ceiling boards and with edge seals
- Ceiling-to-wall edge — seal continuously around the room
Heat from light fittings, and electrical work
Do not cover recessed fittings, transformers or electrical equipment with insulation unless the manufacturer states they may be covered — trapped heat is a hazard. Moving wiring and fittings must be done by a qualified electrician, and ceiling work is work at height that should be carried out by installers with proper equipment.
Flanking limits what a ceiling can do
- Walls that stop at ceiling level — if the partition does not reach the floor above, sound from the next room crosses through the void above the ceiling. The wall must be carried up or the void closed off as well
- Walls and columns connected to the floor above — vibration from the floor runs down the walls and radiates into the room. NRC Canada research found that resilient channels in the ceiling markedly reduce flanking through the ceiling, but flanking through the walls still has to be considered separately
- The result therefore depends on the whole room. We do not give ready-made dB figures; to confirm, measure on site before and after. See Flanking transmission
Common mistakes
- Laying insulation on an existing T-bar ceiling and expecting it to block the floor above
- Hanging the new ceiling on a frame rigidly fixed to the soffit at every point
- Cutting many recessed downlights into a ceiling meant to insulate sound
- Not sealing the perimeter, or leaving a shadow gap open to the cavity
- Sticking absorbing panels under the ceiling and expecting them to stop sound coming through
See the solution and related products: Noise from next door / neighbours · Sound insulation · Ceiling applications
Sources
- National Research Council Canada — Canadian Building Digest 239, Factors Affecting Sound Transmission Loss (Warnock, 1985)
- National Research Council Canada — Construction Technology Update No. 1, Control of Sound Transmission through Gypsum Board Walls (Warnock & Quirt, 1997)
- King, F. & Sabourin, I. — The effect of resilient channels on ceiling flanking transmission paths (National Research Council Canada, Canadian Acoustics 37(3), 2009)
- BRE Group — Recessed downlights testing (effect of recessed downlights on ceiling sound insulation and airtightness; ISO 10140-2 / 10140-3)
- ROCKWOOL North America — Using acoustic insulation to soundproof a room
- ROCKWOOL (Thailand) — Safe 'n' Silent Pro data sheet
Related products
Categories and example products for this topic
- ROCKWOOL Safe 'n' Silent Pro — Stone-wool slab for wall and ceiling cavities in sound-control systems; non-combustible
- SCG Cylence ZoundBlock — Moisture-wrapped glass wool for wall cavities - for partitions closing the ceiling void
- ISO NOISE Standard — Glass wool in a PE bag, 0.60 x 1.20 m, 50 mm, for ceiling and drywall cavities
Sound insulation · Glass wool
SCG Cylence ZoundBlock
- Thickness
- 50–100 mm
- Density
- 32 kg/m³
- Thermal conductivity (λ)
- ≤ 0.033 W/m·K
