Selecting insulation materials for building refurbishment — Which Material, Which Providers?
- Recommended class
- Glaswolle/Steinwolle/EPS
- Typical duration
- Planung
- Cost estimate
- 20-60 €/m²
Overview
Building refurbishment projects require careful selection of insulation materials to meet current thermal performance standards, manage costs effectively, and work within the constraints of existing structures. The choice between glass wool (mineral wool), stone wool (rock wool), and expanded polystyrene (EPS) depends on multiple factors including thermal performance requirements, fire safety classification, moisture conditions, available cavity depth, acoustic demands, and budget constraints. Each material offers distinct advantages: glass wool provides excellent thermal performance at competitive pricing, stone wool delivers superior fire resistance and acoustic insulation, whilst EPS offers lightweight handling and moisture resistance particularly suited to external wall insulation systems.
The planning phase for insulation material selection typically spans several weeks and requires coordination between surveyors, designers, building control officers, and procurement teams. For smaller domestic refurbishment projects involving individual properties or terraced houses, glass wool batts or rolls may suffice with costs at the lower end of the £20-60/m² range. Mid-scale projects such as conversion of Victorian or Edwardian buildings often benefit from stone wool due to fire compartmentation requirements between dwellings, pushing costs toward £35-50/m². Larger commercial refurbishments or external wall insulation schemes frequently specify EPS boards with render systems, reaching £45-60/m² including fixings and finishes. Understanding U-value targets, condensation risk analysis, and compatibility with existing building fabric is essential before committing to material procurement and ensuring compliance with Building Regulations Part L.
Step-by-step
1. Survey existing building fabric and establish performance requirements
Conduct thorough site surveys to measure existing wall, roof, and floor constructions, identifying cavity widths, structural constraints, damp issues, and heritage considerations. Obtain current U-values through calculation or thermal imaging. Determine target U-values from Building Regulations Part L requirements (typically 0.18-0.28 W/m²K for walls, 0.16-0.20 W/m²K for roofs). Assess fire safety requirements particularly for multi-occupancy buildings where stone wool's A1/A2 non-combustible classification may be mandatory. Consider acoustic performance targets for conversions into flats or noise-sensitive spaces where stone wool offers significant advantages over EPS.
2. Calculate required insulation thickness and thermal performance
Use thermal modelling software or U-value calculators to determine insulation thickness needed to achieve target performance. Glass wool (λ 0.032-0.040 W/mK) typically requires 100-150mm for wall applications, stone wool (λ 0.034-0.040 W/mK) similar thicknesses, whilst EPS (λ 0.030-0.038 W/mK) may achieve targets with slightly reduced thickness. Account for thermal bridging at junctions, fixings, and service penetrations. Verify available depth in cavities or internal space constraints. Conduct condensation risk analysis to ensure vapour control layers or breathable membranes are correctly specified alongside insulation to prevent interstitial condensation damage.
3. Evaluate material suitability for specific refurbishment conditions
Assess moisture exposure risk: stone wool and glass wool handle incidental moisture better than EPS but require proper detailing. For external wall insulation, EPS boards with through-wall fixings and render systems are common; for cavity wall insulation, blown glass wool or bead EPS may be appropriate. Consider existing substrate condition: friable masonry may require stone wool batts with mechanical fixings rather than adhesive-fixed EPS. Evaluate compression resistance for floors and roofs with foot traffic. Check compatibility with existing finishes, adhesives, and fixing systems. Heritage buildings may require breathable insulation systems favouring natural fibre or specific mineral wool products over vapour-resistant EPS.
4. Obtain quotations and compare supplier options
Request quotations from multiple insulation manufacturers and specialist distributors, providing detailed specifications including thermal conductivity, thickness, density, fire classification, and quantities. Compare not only material costs (£8-25/m² for product alone) but also delivery terms, minimum order quantities, lead times, and technical support offerings. Major suppliers such as Knauf Insulation, URSA, Rockwool, and Kingspan offer technical advisory services. Consider total installed cost including fixings (£2-5/m²), adhesives or mechanical fasteners, vapour control layers (£1-3/m²), and labour (£8-20/m²). Verify product certification including BBA certificates, CE marking, and fire test reports to EN 13501-1 standards.
5. Plan logistics, storage, and installation sequencing
Coordinate delivery scheduling with site programme to minimise double handling and weather exposure. Glass wool and stone wool require dry storage protected from moisture; compressed packaging expands after opening requiring adequate storage space. EPS boards are lightweight but bulky and vulnerable to mechanical damage and UV degradation if stored externally. Plan installation sequencing to maintain weathertightness and allow proper curing of adhesives. Schedule building control inspections at appropriate hold points before concealing insulation. Ensure installers have appropriate training and PPE, particularly for mineral wool handling. Arrange waste management for off-cuts and packaging, with mineral wool typically recycled and EPS requiring specific disposal arrangements.
6. Specify quality control and performance verification procedures
Establish inspection protocols to verify correct insulation thickness, continuous coverage without gaps, proper treatment of thermal bridges, and correct installation of vapour control layers and air barriers. Document installation with photographs for building control and future reference. Consider thermographic survey post-completion to verify thermal performance and identify installation defects. Ensure handover documentation includes product datasheets, thermal calculations, guarantees (typically 25-50 years for material performance), and maintenance recommendations. For external insulation systems, specify render curing periods and protection during installation to prevent moisture ingress or mechanical damage before system completion.
Cost breakdown
| Glass wool insulation material (100-150mm batts/rolls) | £8-18/m² | Varies with density (12-45 kg/m³) and thermal conductivity specification |
|---|---|---|
| Stone wool insulation material (100-150mm slabs) | £12-25/m² | Higher cost reflects fire performance; non-combustible A1 classification adds premium |
| EPS insulation boards (100-150mm, various densities) | £10-22/m² | Price varies with density (15-30 kg/m³); graphite-enhanced EPS adds 15-25% cost |
| Fixings, adhesives, and mechanical fasteners | £2-6/m² | Mechanical fixings for EPS external systems; adhesive for internal applications |
| Vapour control layers, breather membranes, tapes | £1-4/m² | Essential for condensation control; specification depends on wall build-up |
| Labour and installation (experienced insulation contractors) | £8-22/m² | Higher rates for complex details, confined spaces, or external scaffold work |
| Delivery, storage, waste disposal, and site protection | £1-5/m² | Depends on site access, project scale, and distance from supplier distribution centre |
Common pitfalls
- Specifying inadequate insulation thickness based on outdated U-value calculations — resulting in Building Regulations non-compliance and costly remedial works adding £15-30/m² to rectify
- Failing to address thermal bridging at junctions and fixings — losing 15-30% of theoretical insulation performance and creating condensation risk points requiring £5,000-15,000 remedial investigation and repairs
- Installing moisture-sensitive insulation without proper vapour control — leading to interstitial condensation, mould growth, and structural timber decay requiring £20,000-80,000 in replacement and drying costs
- Using combustible insulation materials in buildings where fire safety requires non-combustible specification — creating regulatory non-compliance and requiring complete removal and replacement at £40-70/m²
- Inadequate protection of insulation materials during storage on site — moisture damage to mineral wool or UV degradation of EPS rendering materials unusable with £3,000-12,000 material replacement costs
- Compressing insulation beyond manufacturer specifications during installation — reducing thermal performance by 20-40% and negating investment in upgraded insulation specification
FAQ
- Do I need Building Regulations approval for changing insulation during refurbishment?
- Yes, most insulation work during refurbishment constitutes a material alteration or change of energy status requiring Building Regulations approval under Part L (Conservation of Fuel and Power). You must submit plans showing proposed insulation specification, U-value calculations, and condensation risk analysis to Building Control before commencing work. Exemptions exist for like-for-like repairs in limited circumstances. Listed buildings also require Listed Building Consent alongside Building Regulations approval. Retrospective applications are possible but incur additional fees and may require opening up works for inspection. Professional guidance from a building surveyor or energy assessor ensures compliance and optimal specification.
- What are the total installed costs for different insulation materials in typical refurbishment scenarios?
- For internal wall insulation, glass wool batts typically cost £20-35/m² installed, stone wool £25-40/m², and EPS boards £22-38/m² including labour, fixings, and vapour barriers. External wall insulation systems using EPS with through-wall fixings and render finish range £45-75/m² installed depending on access requirements and finish specification. Loft insulation using glass wool rolls costs £12-25/m² for 270mm thickness including labour. Commercial projects benefit from economies of scale reducing costs by 15-25%, whilst heritage buildings with complex detailing may increase costs by 30-50%. Always obtain multiple quotations including breakdown of materials, labour, scaffolding if required, and guarantees.
- How do I choose between glass wool, stone wool, and EPS for my specific refurbishment project?
- Selection depends on prioritising key performance criteria: choose stone wool for superior fire resistance (A1 non-combustible) required in flats, terraced houses, or buildings over 18m height, and where acoustic insulation between dwellings is critical. Glass wool offers excellent cost-performance for domestic pitched roofs and internal walls where fire classification is less stringent. EPS suits external wall insulation systems requiring lightweight material with good compressive strength and moisture resistance, particularly for render or cladding applications. Consider existing structure: stone wool handles irregular masonry better, whilst EPS requires flat substrates. Budget constraints often favour glass wool for simple applications, but whole-life costs including energy savings may justify premium materials in high-performance refurbishments.
- Should I hire professional installers or can competent builders install insulation during refurbishment?
- While basic insulation installation appears straightforward, achieving specified thermal performance requires specialist knowledge of thermal bridging details, vapour control, and air tightness. External wall insulation systems absolutely require accredited installers familiar with substrate preparation, mechanical fixing patterns, render systems, and weathering details; poor installation voids guarantees and creates long-term moisture and structural risks. Cavity wall insulation must be installed by registered installers under schemes like CIGA (Cavity Insulation Guarantee Agency). For internal works, experienced builders can install batts and boards if supervised by knowledgeable designers, but specialist insulation contractors ensure quality, typically add only 10-15% to material costs, and provide installation guarantees essential for warranty compliance and future property sales.
- What fire safety regulations apply to insulation materials in building refurbishment?
- Building Regulations Approved Document B sets fire safety requirements with heightened scrutiny following Grenfell. Buildings over 18m height must use materials of limited combustibility (A2-s1,d0 or better, typically stone wool) for external wall systems. For buildings under 18m, risk assessments determine appropriate materials but non-combustible insulation is increasingly specified. Internal fire compartmentation between dwellings requires fire-resisting construction where stone wool's contribution to fire resistance is advantageous. Combustible insulation like EPS can be used in many applications if properly detailed with fire barriers and cavity closers, but compliance demonstration through fire testing and Building Control approval is essential. Always verify current guidance as regulations evolve; professional fire safety consultancy is prudent for complex refurbishments.
- How long does insulation material selection and procurement typically take in refurbishment planning?
- The planning phase for insulation selection typically requires 3-6 weeks for domestic refurbishments and 8-16 weeks for commercial projects. Initial surveys and U-value assessments take 1-2 weeks, thermal modelling and specification development another 1-2 weeks, obtaining quotations from multiple suppliers 1-2 weeks, and Building Regulations submission and approval 2-8 weeks depending on local authority workload. Material procurement lead times vary: standard glass wool and stone wool products are often available within 1-2 weeks from distributors, but specific densities, thicknesses, or large quantities may require 4-8 weeks from manufacture. EPS boards cut to specific sizes require 3-6 weeks. Complex or bespoke specifications for heritage buildings can extend timelines significantly. Early engagement with suppliers and Building Control accelerates the process.