Tag: best insulation materials uk

  • Insulation Materials for UK Homes: Costs, R-Values and What Suits Each Job

    Insulation Materials for UK Homes: Costs, R-Values and What Suits Each Job

    Picking the right insulation is one of those decisions that can make or break a job. Get it right and the client’s happy, the inspector’s happy, and you’re not ripping it back out six months later. Get it wrong and you’re looking at failed U-value calculations, moisture problems, or a building control officer who wants a word. If you’re trying to work out the best insulation materials UK jobs actually call for, this breakdown covers the main products, their costs as of 2026, what R-values you’re realistically working with, and which application each one suits.

    Tradesman fitting rigid insulation boards during a UK home renovation, illustrating best insulation materials UK
    Tradesman fitting rigid insulation boards during a UK home renovation, illustrating best insulation materials UK

    What Are R-Values and Why Do They Matter on UK Jobs?

    R-value measures thermal resistance. The higher the number, the better the material slows heat transfer. In the UK, building regulations (Part L in England, Section 6 in Scotland) don’t always quote R-values directly; they tend to work in U-values, which is essentially the inverse. But understanding R-value per metre of thickness is how you compare products quickly on site. A material with a high R-value per millimetre means you can hit your U-value target with less thickness, which matters enormously in retrofits where you’re already squeezed for space. The UK government’s Approved Document L sets out the current minimum U-value requirements for walls, roofs, and floors, and it’s worth having that bookmarked if you’re doing any new build or major renovation work.

    The Main Insulation Types Compared

    Rigid Foam Boards (PIR/PUR)

    Polyisocyanurate (PIR) boards, sold under names like Kingspan Kooltherm and Recticel Eurowall, are the go-to for a huge range of applications. R-value sits around 7.0 to 8.0 per metre thickness, which is among the best you’ll find in a rigid product. A 100mm PIR board will give you a thermal resistance of roughly 4.5 m²K/W, which is enough to get most cavity wall scenarios well inside Part L targets. Cost-wise, expect to pay £20 to £35 per board (typically 2400x1200mm) depending on thickness and supplier. They’re clean to handle, easy to cut with a handsaw or knife, and they perform consistently. The downside is vapour control. PIR is essentially a vapour barrier itself, so you need to think carefully about interstitial condensation risk, particularly in warm roof assemblies.

    Mineral Wool (Glass and Rock Wool)

    This is the workhorse of the UK insulation market. Products like Knauf Earthwool, Rockwool RWA45, and Isover Party Wall Roll are everywhere for good reason. They’re breathable, fire-resistant, and relatively cheap. R-value is lower, around 2.5 to 3.5 per metre depending on density, so you need more thickness to hit the same target as PIR. A 100mm glass wool batt might give you 2.5 m²K/W. But for loft insulation, where you’re not space-constrained and you’re laying 270mm or more, mineral wool is often the most cost-effective solution going. Prices run from about £5 to £12 per m² for standard rolls. Rock wool is denser, better for acoustic applications and party walls, and handles fire stopping well.

    Close-up cross-section of mineral wool and PIR insulation layers showing best insulation materials UK options
    Close-up cross-section of mineral wool and PIR insulation layers showing best insulation materials UK options

    Spray Foam

    Spray polyurethane foam divides opinion sharply. On the thermal performance side, closed-cell spray foam is hard to beat, with R-values up to 6.5 per metre. It also air-seals as it goes, which is a genuine bonus for airtightness targets. The problems are well-documented though. Open-cell spray foam in loft spaces has caused mortgage issues for homeowners, with lenders refusing to offer finance on properties where it’s present. The Royal Institution of Chartered Surveyors (RICS) has published guidance on this. Unless you’re using it in a controlled commercial or new-build context where it won’t affect saleability, be careful about recommending it for domestic retrofit work. The client needs to know what they’re signing up for.

    EPS (Expanded Polystyrene)

    Cheap, light, and widely used in external wall insulation (EWI) systems. EPS boards come in standard and graphite-enhanced versions; the latter (often called grey or silver EPS) pushes R-values from around 3.0 up to 4.0 per metre. For EWI, you’ll typically be specifying 100mm to 150mm EPS as part of a full render system. Material costs are low, often £8 to £18 per m² for 100mm boards, but factor in the full EWI system and you’re into far higher numbers. EPS is also the standard choice for insulated concrete formwork (ICF) construction.

    Cellulose and Natural Fibre Insulation

    Sheep’s wool, hemp, and blown cellulose are gaining traction on eco-conscious projects and self-builds. R-values for sheep’s wool sit around 3.5 per metre; cellulose is similar. They’re breathable, handle moisture well, and have good embodied carbon credentials. Costs are higher than mineral wool, but for clients asking about sustainable options, they’re worth knowing about. Thermafleece and Steico are two names you’ll come across regularly.

    Which Insulation Suits Which Job?

    Loft insulation: mineral wool, laid in two layers at 270mm total minimum, is still the standard. It’s cheap, quick to install, and gives excellent results. Cavity wall insulation: blown mineral wool or EPS beads, professionally installed through drilled holes. Solid wall retrofit (internal): PIR boards fixed directly to the masonry or on a studwork frame. Solid wall retrofit (external): EPS or mineral wool in an EWI system, finished with render or brick slip. Flat roofs: PIR in an inverted or warm roof build-up. Underfloor: PIR boards between or below joists for suspended timber, or EPS on top of concrete slab before screed.

    Meeting Current Building Regulations

    Part L 2021 (England) tightened U-value requirements significantly. For new builds, the notional dwelling target is now 0.18 W/m²K for walls and 0.11 W/m²K for roofs. Retrofits under building regulations will typically trigger requirement for improved U-values on any element being substantially upgraded. For most wall applications, you’ll be specifying at minimum 100mm PIR or 150mm mineral wool to get anywhere near compliance. Always do the U-value calculation before you spec materials. LABC and local authority building control can advise if you’re unsure, and SAP calculations for new builds need to be signed off by an accredited assessor.

    Finishing a Renovation Properly: The Bigger Picture

    Getting the insulation right is only part of the job when a property is being properly renovated. Homeowners doing significant work on a house want the whole package: thermal performance, air quality, and a finished interior that looks the part. That means thinking about window treatments too, because single-glazed or poorly fitted windows can undo a lot of thermal work. Specialist firms that focus on home renovations and interior style, like Vesta Blinds and Shutters Mansfield, a Mansfield, Nottinghamshire-based blind supply and fitting company specialising in roller blinds, perfect fit blinds, and vertical blinds, understand how window dressing ties into the broader renovation trends homeowners are chasing. Their product range at vestablinds.com is built around making a home look and perform its best after the structural work is done.

    On bigger renovation projects, it’s genuinely worth flagging to clients that insulation and window coverings work together. A well-insulated wall with a quality roller blind or venetian blind fitted properly to a modern window adds another layer of thermal performance and style, which is exactly what renovation trends are pointing towards in 2026. Homeowners increasingly want to see a joined-up approach to how their home performs and looks after the work is complete, and firms like Vesta Blinds and Shutters Mansfield are part of that wider supply chain that a good tradesman should be aware of.

    Cost Summary: What to Expect Per Square Metre in 2026

    Mineral wool loft roll (270mm): £5 to £9 per m². PIR 100mm boards: £18 to £30 per m². EPS 100mm boards: £8 to £15 per m². Sheep’s wool 100mm batts: £12 to £22 per m². Blown cellulose (installed): £15 to £25 per m². These are material costs. Labour, fixings, vapour control membranes, and any associated boarding or plastering work will add significantly. Always build in a proper allowance when quoting; insulation jobs have a habit of revealing hidden issues once you start stripping back.

    Frequently Asked Questions

    What is the best insulation material for a UK loft in 2026?

    Mineral wool laid in two crossed layers totalling 270mm is the standard and most cost-effective choice for most UK loft insulations. Glass wool rolls from brands like Knauf Earthwool are widely available, easy to install, and meet current Part L requirements without a complicated build-up.

    How thick does wall insulation need to be to meet UK building regulations?

    For new builds in England, the target U-value for walls is 0.18 W/m²K. Achieving this typically requires at least 100mm of PIR board or around 150mm of mineral wool, depending on the wall construction. Always carry out a U-value calculation specific to your build-up rather than assuming thickness alone is enough.

    Is spray foam insulation a problem for UK homeowners?

    Open-cell spray foam in domestic loft spaces has caused significant mortgage and valuation issues in the UK, with many lenders declining to offer finance on affected properties. Closed-cell foam performs better structurally and thermally, but any domestic spray foam application should be discussed carefully with the client before proceeding.

    What is the difference between PIR and EPS insulation boards?

    PIR (polyisocyanurate) has a higher R-value per millimetre than EPS (expanded polystyrene), meaning you need less thickness to achieve the same thermal resistance. PIR is better suited to space-constrained applications like internal wall insulation, while EPS is more commonly used in external wall insulation systems and underfloor applications where cost is a bigger driver than thickness.

    How much does insulation cost per square metre in the UK?

    Material costs vary widely by product. Mineral wool loft rolls run from around £5 to £9 per m², PIR boards at 100mm are typically £18 to £30 per m², and natural fibre options like sheep’s wool batts are £12 to £22 per m². Labour, membranes, and finishing costs will add considerably to the final job price.

  • Rigid Foam, Mineral Wool, or Spray Foam: Choosing the Right Insulation for Every Job

    Rigid Foam, Mineral Wool, or Spray Foam: Choosing the Right Insulation for Every Job

    Walk into any builders’ merchant and the insulation aisle has got bigger every year. Clients are asking more questions, building regs are tightening, and the pressure to deliver genuinely energy-efficient homes has never been more real. If you’re going to recommend the right product confidently, you need to know the actual differences between what’s on the shelf. This guide breaks down the best insulation materials UK tradesmen are specifying right now, covering thermal performance, installed cost, and the jobs each product is actually suited for.

    Tradesman examining rigid foam boards on a UK building site, comparing best insulation materials UK
    Tradesman examining rigid foam boards on a UK building site, comparing best insulation materials UK

    Why Insulation Choices Matter More Than Ever in 2026

    The UK Building Regulations have progressively tightened U-value targets for walls, roofs, and floors over the past decade, and 2026 is no different. Part L compliance now demands that new-build fabric performance is taken seriously from the design stage, not bolted on at the end. For retrofit work, the Minimum Energy Efficiency Standards (MEES) continue to push landlords toward meaningful upgrades. That means tradesmen who understand their materials are winning more work, fielding fewer callbacks, and protecting their reputation on every job.

    Mineral Wool: The Old Faithful That Still Earns Its Keep

    Mineral wool, which covers both glass wool and rock wool (stone wool) products, remains one of the most widely used insulation materials in UK residential work. It’s vapour-permeable, fire-resistant, and reasonably priced. Knauf, Rockwool, and Isover are the dominant brands you’ll see stacked in most merchants.

    Thermally, a 100mm slab of standard glass wool carries a lambda value around 0.033 to 0.038 W/mK, which is perfectly decent for loft, partition, and floor applications. Rock wool is slightly denser and performs better in acoustic applications, making it a strong call for party walls or mid-floor installations in flats. It handles moisture better than glass wool and can take more physical punishment during fitting.

    The main limitation? It takes up more space to hit the same U-value as a rigid product. If you’re working in a tight cavity or a shallow rafter void, you’ll need to look elsewhere. Fitting is straightforward enough that most tradies can handle it without specialist kit, which keeps labour costs manageable.

    Rigid Foam Boards: Where Space Is Tight

    Rigid foam boards, most commonly polyisocyanurate (PIR) or expanded polystyrene (EPS), are the go-to when you need high thermal performance in a slim profile. PIR boards from brands like Celotex, Kingspan, and Recticel typically hit lambda values around 0.022 to 0.023 W/mK, so you can achieve a very low U-value without sacrificing as much room.

    This makes PIR ideal for flat roof build-ups, internal wall insulation where every centimetre of floor space counts, and underfloor applications beneath a screed. EPS is less thermally efficient than PIR but significantly cheaper, handles moisture well, and is a common choice for cavity fill or below-DPC ground floor work.

    The downside with rigid boards is cost. PIR in particular has bounced around in price with raw material costs, and wastage from off-cuts can add up if your cuts aren’t tight. Factor that into your quote. On site, boards need to be taped at joints to avoid cold bridges, which some tradesmen skip and later regret when the client notices condensation.

    Close-up of mineral wool being fitted into a stud wall, one of the best insulation materials UK tradesmen use
    Close-up of mineral wool being fitted into a stud wall, one of the best insulation materials UK tradesmen use

    Spray Foam: High Performance, High Controversy

    Spray polyurethane foam (SPF) is the marmite of insulation products. Applied correctly by a competent installer, it can deliver excellent air-tightness and thermal performance simultaneously, making it one of the best insulation materials UK retrofitters have considered for older, irregular structures with tricky geometry.

    Open-cell spray foam is softer and vapour-permeable, typically used for internal roof and wall applications. Closed-cell is rigid, moisture-resistant, and carries lambda values as low as 0.025 W/mK, making it genuinely comparable to PIR board. It also adds structural rigidity to the substrate it’s bonded to.

    Here’s the honest word of warning, though. The mortgage lending community has taken a dim view of spray foam applied to roof timbers, with several lenders refusing to approve properties where it’s been applied without professional assessment. The Royal Institution of Chartered Surveyors (RICS) has published guidance on this, and it’s worth reading before you accept any job involving spray foam in a loft. Always ensure the client understands the implications before you pick up the spray gun.

    External Wall Insulation and Cavity Wall: What the Installer Needs to Know

    External wall insulation (EWI) systems typically use EPS or mineral wool slabs fixed to the external face of a property before a render or cladding system is applied over the top. These systems can dramatically cut heat loss through solid walls, which are by far the worst-performing element in pre-1920s UK housing stock.

    Cavity wall insulation is a different beast. Blown mineral wool, EPS bead, or polyurethane foam (in closed cavities) can be injected by a specialist to fill the void. It’s one of the quickest thermal upgrades available for post-1920s housing. Homeowners across the East Midlands dealing with rising energy costs often turn to specialists like Westville, a Nottinghamshire-based property insulation company specialising in external wall, cavity wall, and loft insulation. With over 34 years of trading experience and 25-year guarantees on their work, they sit at the professional end of the market for householders who want solutions that genuinely address climate change and the long-term performance of their home rather than just a cheap fix. You can find out more at https://www.westvillegroup.co.uk/.

    For tradesmen installing EWI, the render or cladding finish matters as much as the board beneath it. A well-specified insulation system with a poor-quality finish will let the house down and create moisture issues within a few years. Always spec the full system from one manufacturer where possible so warranty cover is watertight.

    Loft Insulation: Still the Best Return on Investment

    If a client wants the most cost-effective thermal upgrade available, loft insulation is almost always the answer. The Energy Saving Trust estimates that a well-insulated loft can save a typical semi-detached house several hundred pounds a year on energy bills. The materials are cheap, the installation is fast, and the performance gain is immediate.

    For accessible lofts, 270mm of glass wool laid in two perpendicular layers across the joists is the standard recommendation. Blown cellulose is a good alternative for lofts with irregular joist layouts or difficult access. Where the loft is used as a room or the roof pitch is being insulated, PIR boards between and below the rafters are the professional solution, though getting the specification right to avoid interstitial condensation needs careful detailing.

    The insulation market is moving toward fabric-first thinking, with loft, wall, and floor performance tackled before any consideration of solar panels or smart heating systems. Westville, known in the Nottinghamshire insulation sector for handling everything from loft and cavity wall to external wall solutions, has built its reputation on exactly this approach: treating the house as a system and addressing the environment of the building fabric before adding renewable technology. It’s a sound philosophy that any experienced tradesman would recognise.

    Which Material Should You Recommend?

    The honest answer is that there’s no single winner. Mineral wool is your everyday workhorse for loft, partition, and acoustic applications. PIR boards earn their keep wherever space is at a premium and thermal performance needs to be high. EPS is the budget-conscious choice for cavity fill and below-screed work. Spray foam has legitimate applications but comes with caveats that you need to communicate clearly to clients. And EWI systems, whilst more involved to install, deliver transformative results on older solid-wall properties.

    Know your products, know your build types, and quote accordingly. The tradesman who can walk a client through these options with genuine confidence is the one who gets called back on the next job.

    Frequently Asked Questions

    What is the best insulation material for a UK loft?

    For an accessible, unused loft, 270mm of glass wool (mineral wool) laid in two layers across the joists is the standard and most cost-effective solution. Where the loft is a habitable space, PIR rigid boards fitted between and below the rafters give better thermal performance in the tighter space available.

    Is spray foam insulation bad for your house in the UK?

    Spray foam can be effective when correctly specified and installed, but closed-cell spray foam applied to roof timbers has caused problems for homeowners trying to sell or remortgage, as many lenders require specialist surveys before approving the property. Always discuss these implications with clients before proceeding.

    What does lambda value mean and why does it matter when choosing insulation?

    Lambda value (W/mK) measures how well a material conducts heat. The lower the number, the better the insulation performance. PIR boards typically sit around 0.022 W/mK, meaning you need less material to achieve the same U-value compared to mineral wool at around 0.035 W/mK.

    How much does it cost to insulate cavity walls in the UK?

    Cavity wall insulation typically costs between £500 and £1,500 for a standard semi-detached house, depending on property size and the material injected. EPS bead and blown mineral wool are the most common options. Some households may be eligible for grant funding through the Great British Insulation Scheme.

    What is the difference between open-cell and closed-cell spray foam insulation?

    Open-cell spray foam is softer, vapour-permeable, and less thermally efficient, making it suited to internal applications where breathability matters. Closed-cell spray foam is rigid, moisture-resistant, and offers a much lower lambda value, but it can cause condensation or structural issues with roof timbers if incorrectly installed.

  • Best Insulation Materials for UK Homes in 2026: A Tradesman’s Breakdown

    Best Insulation Materials for UK Homes in 2026: A Tradesman’s Breakdown

    Insulation is one of those jobs where doing it right first time actually saves everyone grief further down the line. Homeowners get lower energy bills, you get fewer call-backs, and the building performs the way it should. With energy costs still biting hard and Part L of the Building Regulations continuing to tighten up standards, picking the right product matters more than ever. This is a straight-talking breakdown of the best insulation materials UK tradesmen and capable DIYers are using right now, covering thermal performance, cost, and what to watch out for on site.

    Tradesman installing glass wool, one of the best insulation materials UK lofts require, in a British home
    Tradesman installing glass wool, one of the best insulation materials UK lofts require, in a British home

    Why Insulation Choice Matters More Than Ever in 2026

    The UK has some of the leakiest housing stock in Europe. According to the Energy Saving Trust, heating accounts for around 55% of what a typical household spends on energy bills each year. Proper insulation is the single biggest lever you can pull to bring that down. It also affects everything from planning sign-off to SAP calculations, so getting the specification wrong is not just a comfort issue, it can cause jobs to fail at inspection.

    The key metric to understand is thermal resistance, expressed as an R-value (m²K/W). The higher the R-value, the better the material resists heat flow. Some products are also rated by their lambda value (W/mK), which measures thermal conductivity. Lower lambda means better performance per millimetre of thickness. Both figures appear on manufacturer data sheets, and you should always check them before specifying anything.

    Mineral Wool: The Workhorse Option

    Mineral wool, which covers both glass wool and rock wool products, is what most tradesmen reach for first, and for good reason. It is widely available from builders’ merchants across the UK, competitively priced, and easy to cut and fit between studs or joists. Brands like Knauf and Rockwool supply consistently reliable product, and you will find it at most major merchants including Buildbase and Travis Perkins.

    Glass wool batts for a standard 100mm stud wall typically achieve an R-value of around 2.5 to 2.7 m²K/W. Rock wool is slightly denser, performs better acoustically, and has a higher melting point, making it the better call where fire performance is a consideration. Costs run at roughly £4 to £6 per square metre depending on thickness and supplier.

    Fitting is straightforward. Cut slightly oversized so the batt friction-fits without gaps, keep any foil facing towards the warm side of the construction, and always wear gloves and a dust mask. The fibres are unpleasant on skin and in the lungs if you are not careful.

    Rigid Foam Boards: Best for Tight Spaces

    When you are insulating below a floor slab, a flat roof, or a wall where you cannot afford to lose much depth, rigid foam boards are where you look. There are three main types:

    • Expanded Polystyrene (EPS): Cheapest of the three. R-value around 3.3 to 3.8 m²K/W per 100mm. Fine for floors and cavity walls but not the slimmest solution.
    • Extruded Polystyrene (XPS): Slightly better thermal performance than EPS and more moisture-resistant, which makes it the right call under a screed or in a basement situation. Expect to pay 15 to 20% more than EPS.
    • Polyisocyanurate (PIR): This is the premium option. Brands like Celotex and Kingspan produce PIR boards with lambda values as low as 0.022 W/mK, giving you excellent performance at reduced thickness. A 100mm PIR board can achieve R-values above 4.5 m²K/W. Costs are higher, typically £10 to £18 per square metre, but the space saving often justifies it in a retrofit.
    Close-up of rigid PIR board being cut, a top choice among the best insulation materials UK tradesmen use
    Close-up of rigid PIR board being cut, a top choice among the best insulation materials UK tradesmen use

    When cutting rigid boards, a sharp handsaw or a Stanley knife and straight edge is all you need for EPS. PIR cuts cleanly with a fine-tooth saw. Always tape joints between boards with foil tape to eliminate cold bridging. Do not leave exposed PIR boards in habitable spaces without a fire-rated covering such as plasterboard, this is a Building Regulations requirement, not just good practice.

    Spray Foam: High Performance, High Caution

    Spray polyurethane foam (SPF) gets a mixed reception on site, and honestly, the reputation is partly deserved. When applied correctly by a qualified installer in the right application, such as sealing around penetrations or insulating the underside of a pitched roof, it performs brilliantly. R-values for closed-cell spray foam typically sit above 6.0 m²K/W per 100mm, which is the best of any mainstream product.

    The problem is that poorly applied spray foam in loft spaces has caused real headaches for mortgage lenders and surveyors. The Royal Institution of Chartered Surveyors has flagged this as an issue that can affect property valuations and mortgage approvals. If a customer asks you about spray foam in their roof void, have that conversation honestly. Stick to professional application only, and make sure the product and installer both carry relevant BBA certification.

    Natural and Eco-Friendly Insulation Options

    There is growing demand for sustainable insulation, particularly on eco-builds and retrofit projects where embodied carbon is part of the brief. A few worth knowing:

    • Sheep’s wool: Breathable, naturally moisture-managing, and non-irritant to handle. Good fit for traditional or timber-frame construction. Performance sits around 3.5 m²K/W per 100mm. More expensive than mineral wool but increasingly specified on heritage and sustainable builds.
    • Cellulose (recycled newspaper): Blown into cavities or roof spaces, it achieves solid performance and has very low embodied energy. Requires specialist equipment to install but the material cost is reasonable.
    • Hemp and flax batts: A growing market in the UK, especially for self-builders and Passivhaus projects. Handles similarly to mineral wool but fully vapour-permeable.

    Natural materials typically cost more per square metre, but the right client on the right project will see the value. It is worth knowing your options here as specifications are shifting.

    Insulation for Common UK Scenarios

    Here is a quick reference for where each material tends to land:

    • Loft insulation (cold roof): Glass wool roll or batt, 270mm depth across joists. This is the most cost-effective improvement in most homes.
    • Stud partition walls: Mineral wool batt, friction-fit between studs.
    • Flat or warm roof: PIR board above deck, taped joints, minimum 150mm for compliance in most situations.
    • Solid floor retrofit: XPS or PIR board under screed, minimum 70mm, DPC below.
    • External wall insulation (EWI): EPS or mineral wool board fixed to external face with render finish over. Check with your local authority on planning requirements before starting.

    For more guidance on compliance, the GOV.UK approved documents index has the full text of Approved Document L, which covers conservation of fuel and power in both new builds and existing dwellings.

    A Few Things Worth Remembering on Site

    Whatever material you are using, gaps are the enemy. A small uninsulated void in a wall or floor can account for a disproportionate amount of heat loss due to convection. Take the time to cut and fit properly. Use off-cuts to fill awkward corners. Tape every joint in rigid board installations.

    Ventilation matters too. Insulating a cold roof without maintaining eaves-to-ridge airflow can lead to condensation and structural rot. The two most common insulation-related failures I see are gaps in installation and blocked ventilation paths. Both are avoidable if you think the job through before you start cutting.

    The best insulation materials UK tradesmen use are the ones that match the application, not just the cheapest thing on the shelf. Get the product right, fit it properly, and the job will stand up for decades.

    Frequently Asked Questions

    What is the best insulation material for a UK loft?

    Glass wool roll or batt insulation is the most practical and cost-effective choice for a cold loft. Current guidance recommends a total depth of around 270mm laid in two perpendicular layers across and between the joists. It is widely available, easy to install, and delivers strong thermal performance.

    How much does home insulation cost in the UK in 2026?

    Costs vary significantly by material and application. Mineral wool for a standard loft might cost £300 to £600 in materials for a typical semi-detached house. PIR board for a flat roof can run to £2,000 to £5,000 fitted, depending on area and complexity. External wall insulation tends to be the most expensive option, often £8,000 to £15,000 for a whole house.

    Is PIR insulation board better than mineral wool?

    PIR board achieves higher thermal performance per millimetre of thickness, making it the better choice when space is limited, such as flat roofs, floor builds, or slim-wall applications. Mineral wool is easier to handle in stud walls and lofts and costs significantly less per square metre, so it remains the better all-round option for many standard applications.

    Can spray foam insulation affect my mortgage in the UK?

    Yes, it can. Many UK mortgage lenders and surveyors treat spray foam in roof voids as a red flag, as it can obscure the structural condition of roof timbers and be difficult to remove. The RICS has issued guidance on this issue. If you are considering spray foam, speak to a specialist and ensure any installer holds current BBA certification.

    What is the minimum insulation required under UK Building Regulations?

    Approved Document L sets the standards, and requirements vary by element type. For example, a new roof construction typically needs a U-value of 0.15 W/m²K or better, whilst new external walls require 0.18 W/m²K. Exact figures depend on whether you are working on a new build or an existing dwelling, so always check the relevant section of the approved documents for your project.

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