28th Mar 2024 -

Insulation plays a pivotal role in creating seamless building envelopes. Isover offers a comprehensive range of products designed to meet the demanding requirements of modern construction projects. 

For this feature, we explore Isover insulation, exploring its unique properties, versatile applications and installation techniques. This guide equips you with the knowledge and best practices to harness the full potential of Isover insulation.

What is a building envelope?

A building envelope encompasses the various elements of a structure. It forms a system that regulates the flow of heat, air and moisture. The primary function of the building envelope is to maintain a comfortable indoor environment while minimising energy consumption. 

By properly insulating and sealing the envelope, heat transfer through the building's exterior surfaces is minimised. This contributes to energy savings and reduces the building's carbon footprint and environmental impact.

Also, a building envelope protects the interior spaces from external factors such as noise pollution, moisture intrusion and weather-related hazards. A well-designed building envelope acts as a barrier against these elements, ensuring structural integrity.

Isover insulation types for building envelopes

Isover offers a comprehensive range of products which meet the diverse building envelope requirements. Each product is designed to provide superior thermal, acoustic and fire protection. Below, we explore the different types of Isover insulation and their applications. 

1. Glass mineral wool batts and rolls

  • Batt: Flexible glass mineral wool batt insulation is designed for friction-fitting between studs, joists and rafters. It offers excellent thermal and sound insulation for floor, roof and loft spaces.
  • Roll: Continuous glass mineral wool roll such as Isover acoustic partition roll (APR). It is suited for insulating walls, as well as lofts, roofs and floors. This type provides consistent coverage and easy installation.

2. Stone mineral wool boards

  • Exterior wall boards: Rigid stone mineral wool boards are designed for exterior insulation and finish systems (EIFS). They provide superior fire resistance, moisture protection and thermal insulation.
  • Cavity wall boards: Semi-rigid stone mineral wool boards specifically engineered for use in cavity wall applications. Isover cavity wall insulation boards offer excellent thermal value and moisture management.
  • Flat roof boards: Rigid stone mineral wool boards specifically engineered for flat roof applications. They deliver superior fire resistance, moisture protection and thermal insulation.
  • Pitched roof boards: Semi-rigid stone mineral wool boards designed for insulating pitched roofs, offering excellent thermal performance and moisture management.

3. Blown-in glass mineral wool

  • Loose-fill insulation: This type is designed for pneumatic (compressed air) installation. It is ideal for insulating hard-to-reach areas, lofts, roofs, cavities and irregularly shaped spaces in walls.

How to design Isover insulation building envelopes

To create seamless building envelopes, proper installation techniques are important. Application methods may vary depending on the insulation type and building component. Here, we outline the best practices to follow.

Glass mineral wool batts and rolls

  • Fit friction-fit batts and rolls snugly between studs, joists, and rafters to ensure continuous coverage without gaps or compression. Eliminating gaps and compression maximises thermal resistance and acoustic performance.
  • Use backer rods or sealants at penetrations and joints to prevent air infiltration. Sealing gaps minimises thermal bridging and drafts.
  • For exterior wall applications, install a continuous air and vapour barrier behind the batts or rolls. This prevents moisture migration and boosts envelope performance.
  • In loft spaces using Isover APR 1200 or Isover Spacesaver roll, maintain proper ventilation and avoid compression. Adequate ventilation prevents moisture buildup and compression ensures insulation depth.

Exterior wall boards

  • Secure boards using compatible adhesives or mechanical fasteners. This creates a tight fit and continuous insulation layer. Continuous insulation eliminates thermal bridging.
  • Install boards in a staggered pattern, offsetting vertical joints for increased strength and stability. Staggered joints enhance structural integrity and wind resistance.
  • Provide a drainage plane and air gap between every sheet and exterior cladding for moisture management. Air gaps allow for drainage and drying, preventing moisture accumulation.

Cavity wall boards

  • Install boards with a ventilated air space, allowing for moisture management and preventing condensation. Ventilated cavities boost drying and stop moisture buildup.
  • Make sure boards fit tightly between a floor and ceiling slab or timber frame. Tight fits minimise air gaps for optimal thermal performance. 
  • Use sealants and tapes at board joints and penetrations. Sealing joints prevent air leakage and thermal bridging.

Flat and pitched roof boards

  • Adhere boards to the roof deck using adhesives or mechanical fasteners, ensuring a continuous insulation layer. Continuous insulation maximises thermal resistance.
  • For pitched roofs, install boards with a ventilated air space, promoting proper moisture management and preventing condensation. Ventilation allows for drying and prevents moisture accumulation.
  • Stagger board joints and offset corners for increased stability. Offsetting joints enhances structural integrity.

Floor boards

  • Secure boards using adhesives or fasteners, creating a continuous insulation layer beneath floor assemblies. This eliminates thermal bridging.
  • Ensure boards fit tightly together to minimise air gaps for optimal thermal and acoustic performance. Tight fits prevent convective air looping and sound flanking paths.
  • Use compatible sealants and tapes at board joints and penetrations to maintain continuity. Sealing joints tackle air leakage.

Blown-in glass mineral wool

  • Use pneumatic equipment to install loose-fill insulation. This allows complete cavity fill and uniform density throughout. Complete fill and uniform density maximise thermal and acoustic performance.
  • For wall and floor applications, install a continuous air barrier on one side of the cavity before insulation. Air barriers prevent convective air looping and moisture migration.
  • In loft spaces, maintain proper ventilation and make sure insulation coverage extends to eaves and gable ends. Ventilation prevents moisture buildup and complete coverage stops thermal bridges.

What insulation thickness should you use?

Insulation thickness plays a crucial role in designing building envelopes. When specifying insulation thicknesses, the several factors below must be considered. 


For exterior wall structures, use thicker insulation layers. This boosts thermal resistance and minimises thermal bridging. Recommendations range from Isover insulation 100mm (4 inches) to 200mm (8 inches). This depends on the climate and energy efficiency goals.


With floor assemblies, Isover insulation thicknesses typically range from 50mm (2 inches) to 150mm (6 inches). If you require Isover acoustic insulation 100mm thickness, fix 2 50mm boards on top of one another. Factors such as desired thermal resistance, acoustic performance and available floor depth will need to be considered.

Roofs and lofts

In roof and loft spaces, the following guidelines should be taken into account.

  • Pitched roofs: Typically, 150mm (6 inches) to 300mm (12 inches) of insulation thickness is recommended. This depends on climate and energy efficiency targets.
  • Flat roofs: For flat roof assemblies, insulation thicknesses range from 100mm (4 inches) to 200mm (8 inches). Thicker layers provide better thermal performance and moisture protection.
  • Lofts: In loft and attic spaces, insulation thicknesses of 200mm (8 inches) to 400mm (16 inches) or more may be required. Local building codes and target thermal resistance are the deciding factors. To achieve this, lay multiple Isover spacesaver 100mm slabs. 

Is Isover insulation waterproof?

While Isover insulation products are not completely waterproof, they are designed to manage moisture within building envelopes. They help to tackle potential issues such as condensation, mould growth and degradation. 

Isover's glass mineral wool insulation products are highly water-repellent and resistant to moisture absorption. The unique composition creates an open-fibre matrix that allows water vapour to pass through while minimising liquid water absorption. 

Also, Isover's stone mineral wool insulation boards are designed to be highly moisture-resistant and offer excellent drying potential. The boards are capable of absorbing and releasing moisture vapour, allowing for effective moisture management. Overall, Isover’s moisture-resistant properties can be further enhanced through installation best practices.

Can you maintain building envelope insulation?

Proper maintenance and inspection are essential to ensure the continued performance and integrity of building envelopes. Neglecting maintenance may lead to potential issues that compromise the insulation's effectiveness.

1. Visual inspections

Conduct visual inspections of accessible areas at least annually. Consider quarterly inspections in areas with known moisture or pest issues. Look for signs of moisture damage, mould growth, pest infestations or any physical damage. Use torches and inspection cameras to examine hard-to-reach areas.

Visual inspections allow for the early detection of potential problems. They allow timely intervention and repairs to prevent further deterioration or damage to the insulation and surrounding building components.

2. Moisture monitoring

Install moisture sensors or probes in critical areas prone to condensation or water intrusion, such as roofs, exterior walls and foundations. Monitor moisture levels monthly using data loggers.

Excessive moisture can lead to deterioration of the insulation's thermal and acoustic properties. Also, mould growth and structural damage may occur. Regular moisture monitoring helps identify and address moisture issues promptly.

3. Ventilation maintenance

Clean and inspect ventilation systems, such as loft and crawl space vents, at least once a year. Conduct more frequent maintenance in areas with high humidity or dust accumulation. Make sure vents are free from obstructions and operating as intended. 

Proper ventilation is crucial for preventing moisture accumulation and promoting drying within the building envelope. Blocked or inadequate ventilation can lead to condensation and potential insulation damage.

4. Pest control

Implement an integrated pest management schedule including regular inspections every quarter and preventative measures. This includes sealing entry points and using appropriate pest control methods like traps or baits.

Pest infestations can compromise the integrity of the insulation. They create gaps and potential pathways for air and moisture infiltration, reducing building envelope performance.

5. Repair and replacement

Address any identified issues promptly, within a reasonable timeframe based on the severity and potential impact of the issue. Repair or replace damaged insulation sections, seal air leaks and address the root cause of moisture problems or pest infestations.

Timely repairs and replacement of compromised insulation help maintain the effectiveness of the building envelope. It also prevents further deterioration and ensures optimal thermal, acoustic and fire protection.

Your trusted supplier of Isover insulation 

Building Materials Nationwide is your one-stop shop for high-quality Isover insulation. Our superb range offers diverse requirements which guarantee optimal comfort. Whether you are looking to buy thermal slabs or Isover acoustic insulation, rely on us to deliver dependable solutions. 

Trade professionals seeking a seamless procurement experience will benefit from our trade accounts. By opening a trade account, you access exceptional perks. These include competitive trade pricing, a personal trade account manager and efficient order processing with fast UK delivery options. 

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