Your Best Options for Stud Wall Insulation 

20th Sep 2024 -

Stud wall insulation is a cornerstone of modern construction, playing a crucial role in building performance and energy efficiency. Mastering the intricacies of stud wall insulation is essential to staying competitive in the industry. 

Selecting the right insulation solution can greatly impact a project's success. Proper stud wall insulation contributes to energy conservation, sound insulation and indoor comfort. These factors are increasingly important in both residential and commercial construction. 

This guide explores the best insulation options for stud walls, catering to your professional needs. You'll find analysis of various insulation types, installation best practices and advanced solutions to common challenges. By the end, you'll have expanded your toolkit with the latest insights on stud wall insulation. 

Ready to get started on a stud wall insulation project? Open a trade account with Building Materials Nationwide or contact us for any assistance or questions you may have.

What is Stud Wall Insulation?

Stud wall insulation helps create energy-efficient and comfortable buildings. The insulation material, typically installed between wall studs, forms the core of the thermal barrier. The stud and track framework provides structural support and creates cavities for insulation placement. When used, insulated plasterboard combines thermal insulation with wall finishing, offering an efficient solution for certain applications. 

Things Your Customers Might Consider When Choosing the Best Ways to Insulate Walls

Overall, stud wall insulation makes a significant impact on both commercial and residential projects. Depending on whether you’ve chosen timber framed stud walls or metal stud walls, this can influence the insulation approach.

Timber, especially C24 timber, provides natural insulation, while metal studs offer fire resistance and moisture protection but require extra insulation to prevent thermal bridging. When reviewing insulation methods, you should consider these specific factors:

Energy efficiency

R-value is the main measure of thermal insulation effectiveness. Higher R-values indicate better thermal resistance. For example, fibreglass insulation batts typically offer R-13 to R-15 for 2x4 walls. Spray foam insulation can achieve R-values of R-6 to R-7 per inch. 

Advanced insulation techniques, like combining spray foam with fibreglass, can boost R-values. This hybrid approach can reach R-20 or higher in 2x4 walls. Energy-efficient insulation can reduce energy costs, meaning significant savings on client utility bills.

Soundproofing

Sound transmission class (STC) ratings measure insulation's ability to block sound. Higher STC ratings indicate better soundproofing. Standard fibreglass insulation typically achieves an STC rating of 39. Mineral wool insulation like Rockwool achieves STC ratings of 45-52. 

Generally, this makes it an excellent soundproof insulation choice between rooms or units in commercial and residential spaces. Adding a layer of mass-loaded vinyl between drywall layers can increase STC ratings. For maximum soundproofing, consider double-stud walls with separate insulation layers and using soundproof plasterboards for enhanced results. This method can achieve STC ratings of 60 or more.

Indoor comfort

Proper air sealing with insulation is crucial. Use caulk or spray foam to seal gaps around electrical boxes and penetrations. Radiant barrier insulation can be effective in hot climates. It reflects up to 97% of radiant heat, reducing temperatures by up to -1.1°C. 

Consider the specific heat capacity of insulation materials. Materials like cellulose have a higher heat capacity, helping to buffer temperature swings.

Moisture control

Vapour permeability is key in moisture management. Materials like kraft-faced fibreglass batts have a permeance of 1 perm. This means 1 grain of water vapour to pass through 1 square foot of surface area per hour. In humid climates, consider smart vapour retarders. They adjust their permeance based on humidity levels, ranging from 0.1 to 10 perms. Moisture-resistant plasterboards can also help protect against dampness and maintain the integrity of the wall structure.

Closed-cell spray foam acts as a moisture barrier at 50mm thickness. It achieves a low 0.9 perm rating, effectively blocking moisture migration. For basements, use materials with low water absorption; extruded polystyrene (XPS) absorbs only 0.3% water by volume.

Fire safety

Look for insulation materials with Class A fire ratings. These materials have flame spread indices of 25 or less and smoke developed indices of 450 or less. Mineral wool insulation is non-combustible and withstands temperatures up to 1176°C (2148°F). It can provide up to 3 hours of fire resistance in certain assemblies.

Some spray foam products include fire retardants. These achieve flame spread indices as low as 5, well below the Class A requirement. Consider intumescent coatings for added fire protection. These expand when exposed to heat, providing a barrier against flame spread. Fireproof insulation also offers enhanced protection against fire, improving the safety and durability of your construction.

Environmental impact

Some fibreglass insulation contains up to 80% recycled glass, reducing environmental impact. Consider bio-based materials like cellulose insulation. Made from 85% recycled paper products, it has a low carbon footprint.

Also, check for low volatile organic compound (VOC) emissions. Materials certified by GREENGUARD Gold meet strict chemical emissions limits, ensuring better indoor air quality. Some foam insulations use blowing agents with low global warming potential (GWP). Look for HFO-blown foams with GWP values less than 1.

What is the Cheapest Way to Insulate Walls?

When selecting insulation for stud walls, consider material costs, installation expenses and long-term energy savings for your clients. Current UK Building Regulations require U-values of 0.28 Watts-per-metre-square-kelvin (W/m²K) or lower for new builds.

Thermal performance and soundproofing needs can significantly impact budgets. Internal and partition walls have distinct requirements, influencing material choice and installation methods. Here, we explore the cheapest way to insulate internal walls. 

Internal wall insulation

Internal wall insulation can reduce heat loss by up to 65% when properly installed. For internal walls, aim for a U-value of 0.30 W/m²K or lower. Materials like phenolic foam boards (20-40mm) or mineral wool (100mm) can achieve this. 

Consider breathable materials in older buildings to manage moisture. Use a vapour control layer to prevent interstitial condensation, a common issue in poorly insulated UK homes.

When insulating internal walls, factor in space loss. Thinner materials like aerogel (10mm) can save space but cost more. Balance thermal performance with room dimensions.

Partition wall insulation

Partition wall insulation focuses on soundproofing, aiming for a minimum airborne sound insulation of 40 decibels (dB). Materials like acoustic mineral wool (50mm) can achieve a sound reduction of 45-50 dB. Alternatively, you can use mass-loaded vinyl (3mm) with standard insulation for similar performance at a lower cost.

For thermal separation, aim for a U-value of 0.40 W/m²K between heated and unheated spaces. This can be achieved with 70mm of glass wool or 50mm of rock wool. Consider a double-layer plasterboard (25mm total) with staggered joints for enhanced soundproofing. This boosts sound reduction by a further 3-5 dB compared to single-layer installations.

Commercial wall insulation

Commercial buildings must meet Part L2A Building Regulations, requiring U-values of 0.26 W/m²K for walls. This often requires higher-performance materials. Spray foam insulation, while more expensive, can achieve the required U-values with just 70mm thickness. 

For fire safety, use materials with a minimum of Class 0 surface spread of flame rating. Mineral wool with a 60-minute fire resistance is often preferred in commercial settings. 

Also, consider the GWP of insulation materials. Low-GWP options like bio-based insulation boards are favoured for Building Research Establishment Environmental Assessment Methodology (BREEAM) certifications.

Residential wall insulation

With residential spaces, proper insulation can reduce heating costs by up to 30%. Focus on materials that balance cost, performance and ease of installation. Mineral wool (100mm) remains popular, offering good thermal and acoustic performance. 

For superior performance, consider PIR boards (50mm). They offer excellent insulation in thinner profiles. In moisture-prone areas, use closed-cell insulation with a water absorption rate below 1.0 kilogram per square metre (kg/m²). 

Stud Wall Insulation Types 

Various insulation types are available for stud walls, each with unique properties and benefits. Your choice can significantly impact a building's thermal performance, acoustics and energy efficiency. Let's explore the best insulation for stud walls.

Insulation rolls

Generally, insulation rolls are a popular choice for stud wall applications. They typically consist of flexible fibreglass or mineral wool materials. You can easily cut and fit these rolls between studs for efficient installation.

These rolls provide excellent thermal insulation and are cost-effective for large areas. You'll find them particularly useful in new construction projects. They offer consistent coverage and can be combined with vapour barriers for improved performance.

Insulation slabs

Rigid or semi-rigid insulation slabs are panels for stud wall cavities. Common materials include mineral wool, fibreglass, or foam-based products. 

These slabs offer excellent thermal and acoustic properties, making them ideal for residential and commercial projects. You can quickly cut them to size and fit snugly between studs. Their density contributes to improved sound insulation performance.

Insulation boards

Typically made from foam materials like polyisocyanurate (PIR) or XPS, insulation boards are rigid panels. You'll find them useful for creating a continuous insulation layer.

These boards offer high thermal resistance in a relatively thin profile. You can easily cut and fit them to cover large wall areas quickly. They're particularly effective in retrofit projects where space is limited.

Multi foil insulation

Multiple layers of reflective foil with insulating core materials make up multi foil insulation. It works by reflecting radiant heat, enhancing the overall thermal performance of stud walls. It’s often used in combination with other insulation types.

This insulation type is lightweight and flexible, making it easy to install. You'll find it particularly effective in reducing heat loss in both summer and winter. 

Acoustic insulation

Acoustic insulation is specifically designed to reduce sound transmission through stud walls. It's typically made from dense materials like mineral wool or recycled fibres. 

Installing acoustic insulation helps create quieter indoor environments in both residential and commercial spaces. You can easily cut and fit it between studs. It's especially valuable in multi-unit buildings or areas with high noise levels.

Common Mistakes to Avoid When Installing Stud Wall Insulation

Improper measuring

Many installers rely on rough estimates, leading to material waste or insufficient coverage. Use a laser distance meter for highly accurate measurements, especially in large spaces. Create a detailed wall map, noting stud positions, electrical outlets and any irregularities. This precision planning minimises waste and improves overall insulation performance.

Leaving gaps 

It’s common to overlook small spaces, creating thermal bridges that reduce insulation effectiveness. Employ thermal imaging cameras to detect hidden gaps or areas of poor insulation. These tools can identify problem areas not visible to the naked eye. 

Compressing insulation

Overstuffing cavities with thick insulation diminishes their insulating properties. In cavity wall insulation, it's essential not to compress the material, as this reduces its effectiveness and how long it will last. For areas where standard insulation thickness exceeds cavity depth, consider using vacuum-insulated panels (VIPs). These materials provide excellent insulation in thin profiles.

Neglecting vapour barriers

Poor vapour barrier installation can lead to moisture issues and reduced effectiveness. In complex climate zones, consider using smart vapour retarders. They change their permeability based on humidity levels, offering excellent moisture control year-round.

Using the wrong insulation

Choosing inappropriate insulation for the specific climate, building type or wall construction can lead to poor performance. Introduce an insulation selection process that considers R-value and factors like moisture resistance, fire rating and acoustic properties. 

If possible, use building energy modelling software to mimic different insulation scenarios and predict long-term performance in various conditions. 

Need Insulation for Your Next Project?

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