Rigid PUR/PIR board at 0.020 to 0.028 W/(m·K) closed-cell conductivity and spray-applied closed-cell SPF at R-6 to R-8 per inch remain the two highest-performing polyurethane routes specified on 2026 renovation tenders, with open-cell SPF (R-3.5 to R-4.0 per inch) reserved for sound-damped interior cavities where vapour-permeable behaviour is acceptable [S1][S3][S4].
Renovation differs from new-build on three points that change the spec: existing wall assemblies usually have non-standard cavity depths, so board thickness is cut to fit (10 mm interior to 16-20 mm exterior sandwich formats); the substrate is rarely flat, which pushes most installers toward spray-applied closed-cell foam or factory-cut board with taped joints; and any retrofit must hit a target U-value that is typically 0.18 to 0.30 W/(m²·K) for walls and 0.13 to 0.20 W/(m²·K) for roofs under most EU member-state national annexes [S3][S5].
Closed-cell vs open-cell: which to specify on a retrofit
Closed-cell SPF delivers R-6 to R-8 per inch (about 1.05 to 1.40 RSI per 25 mm) and acts as a Class II vapour retarder at 35 to 50 kg/m³ density, making it the default on basement rim-joists, cathedral-ceiling rafters, and steel-frame external sheathing where space is constrained and moisture drive runs inward during winter [S1][S4].
Open-cell SPF at R-3.5 to R-4.0 per inch (about 0.61 to 0.70 RSI per 25 mm) and 6 to 10 kg/m³ density is vapour-permeable, soft, and acoustically damped; it fits interior partition fills, attic floors where the dew point is already managed by a separate vapour control layer, and around services where the foam needs to expand into irregular voids without crushing [S1][S4]. For most renovation jobs the spec falls out as: closed-cell wherever the assembly is moisture-sensitive, open-cell wherever the assembly needs to dry toward the interior.
R-value, conductivity and thickness math for retrofits
Renovation spec sheets need three numbers in a single line: conductivity λ in W/(m·K), board or spray thickness in mm, and the resulting R-value in m²·K/W. At the 0.020-0.028 W/(m·K) band published on Chinese factory datasheets, an 80 mm PUR board hits 2.86 to 4.00 m²·K/W, which covers most wall U-value targets for 2026 EU residential renovation grants [S3].
Spray foam complicates that arithmetic because the R-value is stated per inch rather than per mm; R-6.0 to R-7.0 per inch converts to roughly 0.91 to 1.06 RSI per 25 mm, so a 100 mm cavity fill in a renovation wall reaches 3.6 to 4.2 m²·K/W, which clears the 0.18 to 0.30 W/(m²·K) wall target in most jurisdictions with margin for thermal bridging at studs [S1][S4]. The polyurethane insulation reference page lays the closed-cell ratio and λ-value out as the two datasheet numbers worth pinning on every quote.
Fire grade: PUR vs PIR for occupied buildings
PIR (polyisocyanurate) panels are typically specified where building codes demand Class B or C surface behaviour under EN 13501-1, while commodity PUR is accepted in cold-room and industrial applications where the rating requirement is lower; both chemistries can sit in the 0.020 to 0.024 W/(m·K) λ-window, so the fire certificate, not the conductivity number, is what separates the two quotes [S3].
The fire-grade delta shows up in the limiting oxygen index (LOI) band: PIR boards are commonly supplied at LOI ≥ 28, with fire-rated lines reaching LOI ≥ 30, while commodity PUR foam without flame-retardant additive tests in the 22 to 25 LOI band [S3]. For renovation work in schools, healthcare and multi-occupancy residential, B1/B2 fire-protection ratings on PU insulation panels are the typical contractual line item, and a 0.23-0.27 mm metal skin on the panel face is what holds the rating in a real fire test rather than the foam alone [S5].
Format, density and edge detail on site
Four factory formats dominate 2026 Chinese and EU procurement, and the renovation choice is driven by where the insulation lands in the build: plain rigid board, sandwich panel with metal skin both faces, insulation-and-decoration integrated board with factory-applied render, and door-fill foam for insulated steel doors [S3]. The TH160 insulated steel door example shows why density alone is not enough: what matters at the door leaf is that 100% cavity fill is achieved at the bead-pack or pour-in stage, because any unfilled pocket becomes a thermal bridge [S3].
Density windows are tighter than most renovation buyers realise: building-grade PUR board is commonly produced in the 30-50 kg/m³ range, cold-storage panels in 38-45 kg/m³, and high-pressure pipe-support block-form in 60-120 kg/m³, with the higher end reserved for load-bearing applications such as flat-roof walkways rather than wall retrofits [S3]. On a real retrofit, board-edge detailing (tongue-and-groove, ship-lap, or rebate) matters more than the λ-value, since a 5 mm gap every 600 mm drops effective R-value by 8-12 % on measured assemblies.
Procurement realities: MOQ, supply and lead-time
Buying volume is a real lever on renovation tenders: factory-direct pricing on PUR/PIR sandwich panels typically kicks in at a 500 m² minimum order quantity per SKU, with monthly OEM line capacity in the 100,000 m² band on Chinese supply listings, which is the gate for project-level rather than spot pricing [S3].
For small renovation jobs (under 200 m² of board or under 100 m² of spray area), the supply path is usually a regional distributor carrying 30-45 kg/m³ building-grade PUR board in standard 1200 × 600 mm formats, with lead times of 5-10 working days in EU stock and 21-30 days for factory-direct on Asian SKUs [S3]. A practical polyurethane insulation for industrial facilities spec gate walks through the same density and λ trade-off on warehouse and cold-store retrofits, and the polyurethane insulation for high-rise buildings gate covers the higher fire-class lift on tower-block recladding work where the renovation overlaps with a re-cladding scope.
When polyurethane is the wrong call
Polyurethane is the wrong call on renovation projects where the existing wall already fails moisture drive calculation in winter (condensation risk at the sheathing line), where the cavity contains legacy wiring or pipework that cannot be inspected after pour-in, or where the fire-rating target exceeds Class A1 non-combustible, which rigid PUR/PIR cannot reach regardless of LOI [S3][S5].
It is also the wrong call on tight-budget interior fit-outs where the assembly already has a vapour control layer and only an acoustic upgrade is wanted; mineral wool or open-cell cellulose delivers the same sound-damping at lower material cost and avoids the chemistry-management burden of spray rigs on small sites [S1][S4]. Renovation is about fitting insulation into a constrained assembly, not about picking the highest R-value number on the page.
Specification checklist before signing a PO
Three documents need to travel with the order on a 2026 renovation spec: a factory datasheet listing λ in W/(m·K) at 23 °C mean reference and density in kg/m³ (typically 30-45 kg/m³ for composite panels); a fire certificate referencing B1/B2 fire-protection rating; and a method statement [S3][S5].
For procurement on a renovation programme, two trackable signals over the next 12 months are worth watching: the next revision of EN 13165 (the harmonised standard for factory-made rigid polyurethane foam), which will tighten the declared-aged λ-value tolerance bands, and the EU EPBD recast reporting cycle, which will start demanding lambda values adjusted for ageing rather than the 23 °C mean reference most datasheets still quote. Until those land, the practical ceiling on renovation PUR/PIR procurement is a verified ≤ 0.024 W/(m·K) λ-value at 30-45 kg/m³ density with a documented EN 13501-1 E or F minimum and a project-specific method statement.
Detailed specification references: polyurethane elastomer, and insulation board.