FAQ

Generic FAQs.

Acoustic insulation of a building means limiting the spread of all noises that can disturb the people occupying or living in that space. Unlike thermal insulation, which aims to save energy, acoustic insulation does not provide a direct economic saving on property management costs, but it does contribute to increasing residential and working comfort. The fast-paced nature of modern life means that noise-induced stress in homes is often a source of complaints or disputes between individuals. Therefore, a well-insulated property can have a higher market value compared to one without acoustic insulation.

The sound insulation of a building is evaluated according to the following parameters, in compliance with D.P.C.M. 5/12/1997:

  • Apparent sound reduction index (R’w): assesses the airborne noise insulation of horizontal and vertical partitions separating different residential units.
  • Facade sound insulation (D2m,nT,w): evaluates the insulation against external noise sources (such as road and air traffic, outdoor activities, etc.).
  • Normalized impact sound level (L’n,w): measures the insulation against structurally transmitted noise (such as footsteps, furniture movement, etc.) affecting adjacent spaces both vertically (through intermediate floors) and horizontally (between adjoining rooms).
  • Weighted maximum sound level (LASmax): assesses noise levels produced by intermittently operating systems (such as plumbing systems in bathrooms, etc.).
  • Weighted continuous sound equivalent level (LAeq): evaluates the noise produced by continuously operating systems (such as air conditioning and ventilation systems, etc.).

The decree sets minimum or maximum values for these parameters, while the UNI 11367 technical standard establishes the criteria for classifying residential units based on their acoustic insulation performance.

The sound reduction index (R) is a parameter that defines the airborne sound insulation of a partition, typically a wall or a floor separating living spaces. It is measured in decibels (dB) over a broad noise spectrum (100 Hz – 3150 Hz) according to the following equation:

R = L1 – L2 + 10Log S/A [dB]

(Where L1 is the noise level in the source room, L2 is the noise level measured in the receiving room, S is the surface area of the separating element, and A is the equivalent absorption area of the receiving room).

Since R is derived from the difference in noise levels between two environments, it represents a measure of insulation: the higher the numerical value, the better the soundproofing performance of the wall or floor.

By analyzing the entire frequency spectrum, a single rating index can be derived, denoted by the addition of “w.” When measured in a laboratory, where lateral sound transmission is absent, the index is Rw. However, when assessed on-site in an actual building where lateral transmission is present, it is referred to as the apparent sound reduction index (R’w).
The reference standards for laboratory measurements are defined in the UNI EN ISO 10140 series, while on-site measurements follow UNI EN ISO 16283-1. In both cases, the single-number rating is determined according to UNI EN ISO 717-1.

The normalized impact noise level is a parameter that defines the sound insulation of horizontal partitions separating living spaces (typically floors, but also walkable terraces, etc.). It is measured in decibels (dB) over a broad noise spectrum (100 Hz – 3150 Hz) according to the following equation:

Ln = Li + 10Log A/Ao [dB]

(Where Li is the noise level in the receiving room, A is the equivalent absorption area of the receiving room, and Ao = 10 m² is the reference absorption area.)

The structural noise source is defined as a standardized impact noise generator, consisting of five hammers that strike the floor surface at a constant frequency. Since Ln is derived from a direct noise measurement, its evaluation follows an inverse logic: a higher Ln value indicates poorer insulation (a noisier floor slab); a lower Ln value indicates better insulation (a quieter floor slab).

By analyzing the entire frequency spectrum, a single rating index can be derived, denoted by the addition of “w.” When measured in a laboratory, where lateral sound transmission is absent, the index is Lnw.
When assessed on-site, in an actual building where lateral transmission is present, it is denoted as L’nw.
The reference standards for laboratory measurements are defined in the UNI EN ISO 10140 series, while on-site measurements follow UNI 11569. In both cases, the single-number rating is determined according to UNI EN ISO 717-2.

An acoustic bridge is a preferential path for noise transmission that compromises the performance of a material or an insulating system. For example, in a floating floor system, a rigid connection between the screed and the walls acts as an acoustic bridge, as it prevents the screed from freely vibrating under stress. Instead, vibrations are transmitted to adjacent structures, generating noise in neighboring rooms. Another example of an acoustic bridge is an opening through a wall, which increases the amount of transmitted energy and significantly reduces airborne sound insulation.

The prediction of on-site sound insulation takes into account lateral transmissions caused by rigid joints and interconnections between structural elements, but does not consider all the specific conditions encountered on-site. Grooves for installations and the placement of electrical and plumbing systems can cause a loss of sound insulation, depending on the base structure, the precision of installation, and the type of system being installed. For example, in a plasterboard partition, the insulation loss due to the insertion of electrical boxes can reach 3-4 dB in the rating index; wall-mounted cisterns in bathrooms locally reduce the thickness of the partition; pipes can transmit noise between different residential units if they are rigidly connected to the partitions in which they are installed.

Acoustic classification is a rating system for the sound insulation performance of buildings. At European level, there is currently no unified document shared among member states, and each country has developed its own criteria to define performance classes. In Italy, the reference technical standard is UNI 11367, which provides the criteria for determining the classification based on all analytical parameters (airborne noise, impact noise, facades, and building systems) and the method for deriving the overall class. Acoustic classification is not mandatory for all buildings in Italy, but it is explicitly referenced in the minimum environmental criteria decree (CAM Decree) for public buildings.

The sound insulation of buildings is assessed through the on-site determination of passive acoustic requirements, so defined because they are independent of the actual noise sources present in the locations where buildings are constructed. In Italy, insulation requirements are established by DPCM 5/12/97, which specifies minimum or maximum values depending on the building type and intended use.
The table within the decree outlines the limits that must be met for new constructions.

A B C D E F G
Houses Offices Hotels, guesthouses Hospitals, clinics, nursing homes School activities Recreational and religious activities Commercial activities
Airborne noise insulation >50 >50 >50 >50 >50 >50 >50
Facade insulation >40 >42 >40 >45 >48 >42 >42
Footfall noise <63 <55 <63 <58 <58 <55 <55
Discontinuous systems noise <35 <35 <35 <35 <35 <35 <35
Continuous systems noise <35 <35 <35 <25 <25 <35 <35

Dynamic stiffness is a parameter that measures the elasticity properties of a material under dynamic conditions. It is measured according to UNI EN 29052-1 by determining the resonance frequency of a mass-spring system, where the “spring” represents the damping material. The value of dynamic stiffness is highly dependent on the load applied to the material (the mass pressing on the product); for this reason, the reference standard specifies a standard load of approximately 200 kg/m². Dynamic stiffness provides an indication of a resilient material’s ability to attenuate vibrations: the lower the value, the lower the frequency that can be effectively insulated, resulting in better insulation performance.

The thickness of an insulating product for under screed impact noise reduction is not simply determined by measuring the panel or mat in its raw form; instead, a more complex procedure must be followed. An impact sound insulation product under load (for example, a sand and cement screed of approximately 5 cm, weighing around 90-100 kg/m²) will have a reduced thickness, depending on the magnitude of the applied load. The UNI EN 29770 standard provides a method for determining the product’s thickness under screed load and simulates long-term behavior by applying a transient, high-intensity load.

The resulting values from the test are:
dL = thickness of the mat measured under a 250 Pa load for 120 seconds.
dF = thickness of the mat measured under a 2000 Pa load for 120 seconds.
dB = thickness of the mat measured under a 2000 Pa load, after the application of an additional 48000 Pa load for 120 seconds.

The compressibility class is determined by evaluating the difference between dL and dB.

Vibrations are mechanical oscillatory movements generated by moving bodies, which can cause unwanted damage to structures and discomfort to individuals. For humans, vibrations can be perceived as oscillatory motion (such as the sensation experienced when a subway passes by). However, vibrations can also convert into noise through the re-radiation of structures (for example, within a building, the noises produced by windows or furniture shifting due to the passage of a nearby train).

The most common vibration-related issues in construction concern disturbances caused by building support machinery (such as air handling units and generators) or by the proximity of transportation infrastructure (such as trains, subways, and urban bus lines).
In the case of machinery, vibrations are generated by moving mechanical components (rotating machines) that, due to inherent imbalances in their parts or specific design requirements, can create cyclic forces and stresses that are transmitted to the machine itself and subsequently to its supporting structures.
In the case of transportation infrastructure, vibrations are caused by the passage of vehicles, where the contact between wheels and rails (or wheels and the road surface) transmits and propagates forces and stresses into the surrounding environment.

The Minimum Environmental Criteria (CAM) are regulatory parameters concerning public buildings, aimed at defining new constructions in terms of health standards and environmental sustainability. The CAM decree for construction establishes that acoustic and thermal insulation products must contain a specified amount of recycled material, supporting circularity and sustainability. Additionally, once installed and in use, they must not emit harmful substances into the environment.

VOCs (Volatile Organic Compounds) are potentially harmful substances emitted by materials exposed in inhabited environments. They include various organic and chemical compounds that sublimate from materials and can come into contact with people, potentially causing long-term reactions and illnesses. A VOC-free product means that it has undergone rigorous emission tests according to reference technical standards and various international testing protocols, consistently meeting the strictest emission classifications. Most Isolgomma products designed for under screed use and on walls have already been tested according to these standards, achieving exemplary results in terms of the absence of harmful substances.

The CE marking of products represents a fundamental step in ensuring free market circulation, compliance with regulations, and certification of the quality of construction materials. A voluntarily CE-marked product, such as Isolgomma’s impact and airborne noise insulation solutions, guarantees reliability for consumers, as well as for professionals and technicians committed to responsible design.

Technical FAQs.

Sound insulation should be planned during the design phase of a building, as achieving compliance with legal limits becomes more challenging once construction is completed. In general, a well-thought-out layout of spaces within a residential complex can help minimize noise disturbance between neighbors. For example, it is always advisable to design adjacent spaces with similar functions (e.g., kitchens next to or above other kitchens, bedrooms next to bedrooms, living rooms adjacent to living rooms, and bathrooms aligned in vertical stacks). On the same floor, entrance doors to residences should not be placed too close to each other to prevent direct noise transmission through door frames. Impact sound insulation should also be considered on ground floors, especially in hybrid-use buildings where commercial spaces are located on the ground level and residential units on upper floors. This prevents flanking transmission of vibrations, such as those caused by carts or pallet-handling machinery in supermarkets.

We offer a wide range of products for impact sound insulation on floor slabs.
Our under screed solutions Roll, Uproll, Grei, and Upgrei are compatible with the most common construction technologies (reinforced concrete slab, brick-concrete slab, precast slab, CLT wooden floor slabs, etc.).
Depending on the base floor slab’s noise level, products with higher DLw values can be selected, and for specific project requirements, customized solutions can be developed.

Excellent sound insulation can be achieved even without demolishing the existing screeds during a renovation. In this case, our Basewood, Sylwood, and Sylcer systems are ideal for acoustic restoration directly under wood or ceramic finishes. Installation must be carried out according to the installation manual guidelines, using the specified adhesives where required.

To effectively reduce impact noise, it is essential to intervene on the upper layers of the floor slab by installing a floating floor system, as this blocks noise and vibration energy directly at the source. However, a well-designed suspended ceiling with the right materials can still achieve excellent levels of airborne and impact noise insulation. When combined with a high-performance floating screed, it allows for compliance with even the most strict acoustic classification standards.

When a room is designed as a music study or listening space, it is essential to insulate the floor, walls, ceiling, and windows. To prevent sound and vibrations from being transmitted to adjacent rooms – such as through a separating wall – it is necessary to intercept not only direct transmission through the wall but also flanking transmissions through connected structures, including the other three walls and both floor and ceiling slabs. For walls, our Mustwall B and Rewall panels provide exceptional sound insulation with minimal thickness. For the floor, a floating floor system with engineered supports like Highmat, combined with a floating finish on Basewood, effectively reduces vibrations generated by even the most demanding musical instruments (double bass, drums, etc.). For the ceiling, a suspended system mounted on Redfix vibration-damping hangers, sealed with Mustwall B and Rewall panels, helps to limit noise transmission through the upper slab. A well-planned combination of these solutions, along with careful space management, allows musicians to fully enjoy their home environment while pursuing their passion without disturbing others.

Having a lot of space to insulate a wall is certainly an advantage, as it allows for the use of more effective technologies that can insulate against lower frequencies. However, even in cases where space is limited, excellent sound insulation improvements can still be achieved with our Mustwall B and Rewall panels. Depending on the product and the base wall structure, performance gains of up to 16 dB can be obtained with only 5 cm of added thickness, as these panels can be applied directly to the existing wall without the need for additional structures.

Our Trywall is a pre-bonded polyester fiber and recycled rubber insulation panel, used as a soundproofing material within the cavities of lightweight structures (walls and linings). Compared to a standard rock wool panel, Trywall offers greater structural stability, easier and healthier installation, and superior sound insulation performance.

To insulate a traditional masonry wall, a lining system with a metal framework containing our Trywall panel and finished with a double layer of drywall provides a significant increase in sound insulation, reaching up to 20 dB. This solution typically requires about 8 cm of space (50 mm steel structure with two 12.5 mm plasterboard sheets, separated by at least 0.5 cm). For projects with limited available thickness, excellent results can still be achieved using directly bonded solutions, such as our Rewall and Mustwall B product lines.

Modern industrial processes rely on highly sophisticated and powerful machinery that, once installed, can transmit forces and stresses into the surrounding environment. These vibrations, generated by moving components or mass impacts (presses, hammers, etc.), can cause structural damage to buildings and nearby machines if no control systems are in place. Additionally, they can create discomfort for people, including exposed workers. We offer a specialized range of products called Megamat, made from selected recycled rubber agglomerated with polyurethane binder, available in panels designed for lining pits and foundation plinths. To achieve a significant reduction in transmitted vibrations, it is crucial to integrate the insulation system during the design phase, before constructing the foundation plinth.

Air Handling Units (AHUs) are relatively lightweight machines that can be installed either on the ground floor or on rooftops of multi-story buildings. Vibration insulation for these units can be achieved using engineered supports such as Megafoot, or by creating a floating base with Megamat and Megapoint anti-vibration products, selected based on the load applied to the mat. In specific cases, the insulating material can be placed directly under the unit, either at the support feet or by constructing a lightweight base with steel beams.

Acoustic insulation in buildings is essential as a hygienic requirement for obtaining the habitability certification of a residential unit. Unlike thermal insulation, it does not generate long-term savings on property management costs, but it significantly enhances quality of life, work environments, and privacy within buildings, helping to reduce disputes and conflicts between neighbors. Moreover, it allows for greater flexibility in space usage, enabling rooms to serve purposes beyond their original design, such as a home cinema room or a basement converted into a music studio.

A well-constructed floating screed must be completely decoupled from walls and surrounding structures. To achieve this, special perimeter strips such as our Profyle are applied along the edges, and the insulating mat is laid to fully cover the floor slab. The joints between rolls should be made without overlapping (to maintain uniform screed thickness) by placing the edges perfectly adjacent and sealing them with the dedicated adhesive strip. The screed can be either a traditional sand-cement mix or a liquid screed (such as anhydrite-based) with a typical density of about 2000 kg/m³. The perimeter strip must remain intact until the tiles or flooring are installed and excess material should only be trimmed before fitting the skirting board, ensuring that it is not rigidly connected to the flooring: a silicone joint can be used to seal the gap between the skirting board and the floor.

Direct wall-cladding products, such as our Rewall and Mustwall B lines, can be installed using fast-setting adhesives or gypsum-based adhesives (refer to the installation manual and product technical data sheets for details) and secured with through-wall anchors. The adhesive is applied in dots, ensuring rapid setting times. For ceiling installation, a support structure is recommended, using properly sized fixing brackets in the appropriate number and type for secure mounting.

Technical specifications and instruction for installation are included in the product technical data sheet, which can be freely downloaded from our website for all products. The instructions are provided in a concise, precise and detailed format to ensure the correct installation procedure and optimal performance of the system.

Our technical support service is available via phone or email at tecservice@isolgomma.com for any inquiries. Additionally, we have a nationwide network of sales representatives and regional agents across Italy, providing continuous technical and commercial support to our customers.
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