How to choose the best rock wool: measurements, density, and applications for heating your home

Selecting the best insulation for your home can make a huge difference in your quality of life, energy costs, and even the value of your home. Today, rock wool is one of the favorite materials for technicians and users, thanks to its excellent thermal and acoustic performance and its resistance to fire and moisture. However, the market offers a wide variety of options in terms of sizes, densities, and applications, which can lead to uncertainty when choosing.

In this guide, you'll find all the practical and detailed information you need to choose the right rock wool for your home's air conditioning and thermal insulation. We'll break down the benefits of this material, the available options, how to select the best option based on the room and climate, and the key differences compared to other common insulators. You'll also learn which rock wool is best for each part of the house and the technical criteria that really matter. Shall we begin?

What is rock wool and why is it a benchmark in insulation?

Rock wool is an insulating material made from volcanic rocks, primarily basalt, which are melted at extremely high temperatures and then spun into interwoven fibers. These fibers are compacted into panels, mats, rolls, or are packaged in bulk, creating a lightweight, porous material with exceptional properties.

Its structure traps air in thousands of microcavities, making it difficult for heat and sound to pass between the two sides of the insulation. Thanks to this, rock wool becomes an ideal solution for improving the thermal and acoustic comfort of the home, as well as contributing to long-term energy savings.

Main advantages of rock wool for residential insulation

• Excellent thermal insulation: The thermal conductivity of rock wool typically ranges between 0,033 and 0,040 W/m·K, making it one of the best materials for delaying heat transfer. This means the home will stay cool in the summer and warm in the winter, reducing the need for heating and air conditioning.
• High-efficiency acoustic insulation: Its fibrous structure effectively absorbs and dampens noise, ideal for dividing rooms, reducing sound from outside or adjoining homes, and improving tranquility in the home.
• Non-combustible and safe material: Rock wool withstands temperatures above 1.000ºC, does not spread flames or generate toxic fumes, making it a fundamental barrier against fires.
• Durability and stability: It does not deform or degrade over time, does not lose thickness or effectiveness, and maintains its properties even under extreme conditions.
• Vapor permeability: allows the wall to “breathe”, preventing the accumulation of moisture and problems with condensation, mold and mildew.
• Sustainability: Most brands use abundant natural raw materials, are recyclable, and promote a circular economy. Some even incorporate recycled materials in their manufacturing.
• Adaptability: It comes in multiple formats, thicknesses and densities, making it suitable for installation in both new construction and renovation projects, as well as in hard-to-reach areas.

Types and formats of rock wool available on the market

One of the great advantages of rock wool is its versatility: we can find it in different formats to cover any construction or renovation need. The most common are:

• Rigid or semi-rigid panels: They are used for facades, interior cladding, roofs, and partitions. They are available in various densities and thicknesses, and provide excellent insulation for walls and ceilings.
• Blankets or rolls: Flexible and easy to handle, they are ideal for covering large areas such as attics, false ceilings, and loft areas. If reinforced or lined, they are also used in ventilation ducts or around chimneys.
• Bulk fibers: They are used in special applications, such as filling gaps or blowing air chambers in facades or roofs, as well as in acoustic insulation solutions in floating floors.
• Sandwich panels: where rock wool is covered on both sides with metal sheets, wood or other materials, ideal for ventilated facades and large industrial enclosures.

Depending on the manufacturer and the application, rock wool can also incorporate specific additives and coatings (aluminum, mineral veil, kraft paper, fiberglass, etc.), designed to improve the vapor barrier, mechanical resistance or impermeability.

Recommended measurements and thicknesses of rock wool according to each application

The thickness and type of rock wool should be selected based on the part of the building to be insulated, the thermal and acoustic requirements, and the requirements of the Technical Building Code. Although there are different regulations and recommendations, the approximate thicknesses are:

• Facades and walls: 40 to 100 mm as a minimum, although to achieve high energy standards and in cold areas it is recommended to reach 150 mm or more.
• Roofs and coverings: between 80 and 200 mm. The greater the thickness, the better the protection against heat in summer and cold in winter.
• Floors and slabs: from 30 to 100 mm, depending on whether acoustic or thermal insulation is sought, or a combination of both.
• Partitions and cladding: Panels or blankets 40 to 80 mm thick provide outstanding results in comfort and noise reduction.

It's important to keep in mind that increasing the thickness increases thermal resistance, but it also slightly reduces the useful interior surface area, so the optimal balance must be assessed for each case.

Rock wool density: why it's key to its performance

The density of rock wool is expressed in kilograms per cubic meter (kg/m³) and determines both its mechanical resistance and its insulating capacity against heat, noise and fire.

There are mainly three density ranges:

• Low density rock wool (30-50 kg/m³): Lightweight and flexible, it is used in interior partitions, false ceilings, and areas where weight-bearing is not required. It provides good thermal insulation, although it has lower mechanical and compressive strength.
• Medium density rock wool (50-80 kg/m³): The most versatile option. It's the most commonly used option for cladding facades, ceilings, partitions, and floors. It provides a balance of thermal and acoustic insulation, and reasonable resistance to medium loads and impacts.
• High-density rock wool (90 to 200 kg/m³ or more): Very rigid, designed for walkable roofs, ventilated facades, floating floors, and areas exposed to significant mechanical loads. This type of panel is also used as a fire barrier.

For a home, the most common rock wool is usually between 40 and 80 kg/m³, although for roofs, garages and technical areas it is usual to use higher densities.

Thermal conductivity: the data that determines efficiency

Thermal conductivity (λ) shows the material's ability to transmit heat. In rock wool, the lower this value, the better insulation it offers. In practice, products typically range between 0,033 and 0,040 W/m·K, depending on the density, manufacturer, and format chosen.

Manufacturers usually detail this information in the technical specifications, along with the thermal resistance, on which the overall effectiveness of the installed insulation depends. It is advisable to always compare this value with that of other materials and brands to choose the most efficient option.

Main applications of rock wool in the home

Rock wool stands out for its enormous versatility. It's used in both new construction and renovations or energy improvements, and is ideal for virtually any space in the home:

• Facades and enclosures: as exterior insulation (ETICS), in air chambers, cladding, and ventilated façade systems. Rigid or semi-rigid panels and sandwich panels are the preferred options.
• Interior partitions: The panels and blankets provide additional acoustic and thermal insulation between adjoining rooms and homes, reducing the transmission of airborne and impact noise.
• Roofs and coverings: In false ceilings, attics, lofts and flat or pitched roofs, rock wool protects the area most exposed to energy loss.
• Floors and slabs: Insulation between floors and on floors (especially in single-family homes or commercial premises) eliminates thermal bridges and improves acoustic comfort.
• Special facilities: In chimneys, ventilation ducts, wet rooms, garages and machine rooms, rock wool ensures thermal and acoustic insulation and fire resistance.

How is rock wool different from other insulation?

There are different types of thermal insulation on the market, from synthetic (polyurethane, expanded polystyrene EPS, extruded XPS) to ecological (cork, cellulose, sheep wool, wood fiber), as well as other mineral wools such as glass wool. Where does rock wool stand out from them?

• Compared to fiberglass: Rock wool generally exhibits better fire resistance and greater mechanical and moisture resistance. However, fiberglass is somewhat lighter and sometimes more economical.
• Compared to polystyrene: EPS/XPS offer lower water absorption and very good thermal resistance, but they lose acoustic capacity and are less fire resistant. They are also less breathable.
• Compared to ecological insulators: Cork and cellulose have lower thermal conductivity, but their fire resistance and durability may be lower than rock wool. Furthermore, they are usually more expensive.

Rock wool is the mineral insulation that best combines thermal performance, acoustic insulation, fire protection, durability, and sustainability.

How to choose the best rock wool: measurements, density, and applications in home air conditioning

Choosing the right rock wool requires analyzing several specific aspects of your home and the intended use of the insulation. These are the key factors to consider:

• Climate zone: The colder or hotter the climate, the thicker and lower the thermal conductivity of the material. In areas with harsh winters or very hot summers, it's a good idea to prioritize high thicknesses.
• Type of stay: Soundproofing is important for bedrooms, living rooms, and studios. In bathrooms, kitchens, and basements, prioritize water-repellent and mold-resistant materials.
• Requirements of the CTE and local regulations: Each municipality can require a minimum level of insulation for facades, roofs or floors.
• Specific capabilities: For example, if you need high load resistance, opt for high-density panels. If you're looking for simplicity and speed, choose flexible mats or rolls.
• Available space: For interior renovations with limited space, consider thin panels or blankets with high thermal performance.

Comparison of major rock wool brands and manufacturers

Currently, there are several internationally recognized brands for the quality, durability, and innovation of their rock wool products.

Paroc

A Finnish brand with over 80 years of experience, Paroc stands out for its commitment to sustainability and innovation. Its products cover every possible need within a home: from universal panels such as eXtra and eXtra Plus (for walls, ceilings, floors, etc.), to specific ranges for facades (Linio), flat roofs (ROB and ROS), foundations and floors (GRS 20), and variants for interior walls (WAS and WAB). Its thermal conductivity ranges between 0,034 and 0,042 W/m·K and its densities and resistances adapt to different construction requirements.

Rockwool

Rockwool is one of the global leaders in mineral insulation, with a presence in over 28 countries. It offers solutions for residential, industrial, and commercial buildings. Its flagship products include lightweight panels for walls and ceilings (Light Batts), solutions for bathrooms and saunas (Sauna Batts, with an aluminum coating), and acoustic panels to improve interior comfort (Acoustic Batts). For façades, the Venti Batts range stands out for its water repellency and ability to withstand finishing materials. Its products combine low conductivity (0,036 W/m·K), adjusted densities (from 32 to 45 kg/m³) and variable thicknesses, from 50 mm to 200 mm.

Technonikol

The Russian giant Technonikol stands out for its extensive catalogue of both economical (Basalit) and high-performance solutions for roofs (Technorouf and variants), ventilated façades (Technovent) and lightweight frame walls (Technobloc). Offers panels and blankets with densities from 25 to 205 kg/m³ Depending on the application, always with the guarantee of low conductivity and high resistance to compression, water and fire.

Other brands and options

In the Spanish market, brands such as Isover and Idaterm also offer high-performance mineral wools, although specific information on ranges is more fragmented. It is always a good idea to compare the specific technical data sheets for each product, especially those on density, conductivity, thickness, and fire resistance.

Examples of situations and practical recommendations

When choosing rock wool for your project, it's important to consider both technical data and the experience of other users and professional recommendations.

• If you are looking to insulate a façade in a warm and humid area: opt for medium density panels (70-80 kg/m³) and at least 40 mm thick. In areas prone to rain, choose water-repellent or coated products to avoid moisture problems.
• For soundproofing renovations between adjacent homes: a rock wool blanket about 50 mm thick and with a density of 40-60 kg/m³ This is usually enough to notice a dramatic change in noise reduction.
• If you need to improve the air conditioning of an attic or false ceiling: Choose flexible blankets or panels between 80-160 mm thick, prioritizing low thermal conductivity.
• On flat roofs or floors with risk of loads: select high-density panels (more than 120 kg/m³) and check the supported capacity in kg/m² in the technical sheet.
• For areas at risk of fire (garages, boiler rooms, storage rooms): High-density rock wool is irreplaceable due to its fire resistance.

Practical comparison of the most common insulating materials

Material	Thermal isolation	Acoustic isolation	Fire resistance	Main applications
Rock wool	Very high	Excellent	Fireproof	Facades, ceilings, floors, partitions, wet areas
Fiberglass	Alto	Good	Very good	Ceilings, walls, floors
Expanded polystyrene (EPS)	Good	Moderate	Regular	Floors, facades, roofs
Extruded polystyrene (XPS)	Excellent	Moderate	Good	Exterior walls, roofs, floors
Cork, cellulose, sheep wool	Good	Good	Variable	Ecological reforms, rehabilitations

The final choice will depend on priorities: if you're looking for the highest fire safety and the best combination of thermal and acoustic insulation, rock wool is hard to beat.

Criteria to consider for an efficient installation of rock wool

The quality of insulation depends not only on the material; professional installation is essential to ensure maximum effectiveness, safety, and durability.

• It ensures that rock wool adapts perfectly to gaps and leaves no uncovered spaces, especially in corners and perimeters.
• Always check compatibility with vapor barriers, mortars, or decorative coatings in humid areas or areas with a risk of condensation.
• For renovations, choose products and thicknesses that don't compromise the interior space or aesthetics of the property.
• Always seek the help of a specialized installer or technician to assess the current condition of the property and determine the appropriate insulation according to current regulations.

Can rock wool be combined with other insulators?

A growing trend, especially in renovations and nearly zero-energy buildings, is the combination of different types of insulation to enhance performance and maximize energy efficiency.

Rock wool can be easily combined with reflective insulation, mineral wool, polystyrene, XPS, cellulose, etc. In fact, in many cases, multi-layer systems are recommended: for example, rock wool as mass insulation (conductivity), combined with reflective insulation (radiation) and an air chamber, to optimize both thermal resistance and vapor barrier function. This combination is ideal in areas with significant temperature fluctuations or in renovations where improving comfort without losing usable space is a priority.

Frequently asked questions about choosing rock wool

What thickness should I choose for facade insulation?

It depends on the climate and local regulations, but the typical installation is between 60 and 150 mm. If you're looking for a passive or highly efficient house, it's a good idea to go as high as possible within the limits allowed.

Is rock wool resistant to moisture?

Yes, especially if it incorporates water-repellent treatments. It's breathable, prevents condensation, and doesn't degrade, although in particularly humid areas, adding a vapor barrier on the inside may be useful.

Do rock wool and fiberglass provide the same insulation?

They are similar in thermal insulation, but rock wool stands out for its mechanical, acoustic, and moisture resistance, in addition to having better fire resistance.

Can I install rock wool myself?

For ceilings, partitions, cladding, and floors, it may be feasible if you have experience and knowledge, but for roofs, ventilated facades, or ETICS systems, it's best to call on qualified professionals.

What maintenance does rock wool require?

Virtually none. It's a durable material that doesn't rot, doesn't attract insects, and maintains its properties for decades if not exposed to mechanical damage.

Thanks to all these characteristics, rock wool continues to lead the field in residential air conditioning insulation. With the right type, thickness, and density, and professional installation, you can transform your home into a comfortable, safe, and energy-efficient space year-round, ensuring significant savings on your energy bills and enhancing your home's value for the future.