Aerogel vs Polyurethane Foam Insulation: Industrial Selection Guide for Blankets, Boards and Spray PU

For industrial buyers, the relevant question is not which material has the lowest laboratory lambda, but which insulated system delivers the required thermal resistance, service temperature, fire package, moisture resilience and installed cost within the project's real constraints. The answer changes by form:

• A 10 mm flexible silica aerogel blanket can realistically sit near 0.015-0.020 W/m·K at about 25 °C, so it can provide roughly 1.5-2.1 times the RSI of a 10 mm PUR layer when the comparison uses the same temperature and ageing basis. That makes it compelling for tight pipe racks, valve sets, offshore modules, retrofits and weight-sensitive platforms — see our nano aerogel insulation blanket.
• A rigid glass-fibre-reinforced aerogel board is a different product. One documented 250-300 kg/m³ grade declares 0.021 W/m·K at 25 °C — only modestly below a certified PUR board at 0.022 W/m·K — and its conductivity rises with temperature. Its advantage lies in high-temperature capability and a rigid, dimensionally stable panel, not an automatic 3x thermal win.
• PUR is the stronger commercial default where seamless enclosure, compressive strength, fast area coverage or a certified, cost-efficient board matters. A certified PUR board can carry a declared lambda of 0.022 W/m·K, while an aged spray-PU system can be declared at 0.027-0.028 W/m·K after the EN 14315 ageing basis. High-density spray PU can also act as an air-sealing, adhesive monolithic layer.

The temperature boundary is decisive. PUR's continuous envelope is generally bounded near 100-120 °C for the products reviewed; some PIR formulations tolerate intermittent excursions around 140-150 °C, but PIR is excluded from the present thermal comparison. Above roughly 120 °C continuous, move to a verified high-temperature aerogel composite, mineral-fibre or ceramic system. A 650 °C rating is a product-grade claim, not a property of every silica blanket: the same reinforcement chemistry, binder, organic needling fibres, facings and test report determine both temperature and Euroclass.

Fire is a system property. PUR and PUR-modified foams are organic and combustible. Even a spray system with 90% or more closed cells can be EN 13501-1 Class E; factory PUR boards in the sampled certificates appear at Class F. Acceptable use therefore depends on facing, joint detailing, fire stops, clearance, potential ignition sources and the approved assembly. Silica-aerogel blankets may test A1 or A2 in particular compositions, but one published flexible product reports C-s1,d0. Do not specify "non-combustible" from a marketing sheet alone.

Moisture follows the same system logic. Closed-cell PUR and spray PU are strong against bulk water and can serve as vapour retarders, but they are not licences to omit drainage, joint sealing or climate-appropriate drying paths. Aerogel blankets are frequently hydrophobic, yet most are fibrous and open enough that a damaged jacket can wick or transmit water. Hydrophobicity reduces liquid uptake; it does not make the assembly waterproof or eliminate corrosion-under-insulation (CUI) risk — a theme we also cover in our petrochemical application guide.

On a per-RSI basis, aerogel is most competitive when thickness, weight, access, rework or CUI exposure dominates. On a per-cubic-metre basis, the opposite can be true in wide, uninterrupted, ambient-temperature enclosures: spray PU or PUR board may use more volume but need fewer interfaces and less custom labour. Absolute prices are deliberately omitted here — they are market-, region-, specification- and contract-specific. For a cost framework anchored to thickness and R-value, see our aerogel insulation cost and price analysis.

Quick Comparison: Four Products on the Performance-Constructability Frontier

The full product families sit in our aerogel insulation hub. The table below compares the four forms buyers actually meet in an RFQ:

Note: these are not a universal ranking. Values are drawn from dated product declarations and must be normalised for mean temperature, orientation, thickness, density, ageing and test method before appearing in a design. A 10 mm blanket compared with a 100 mm foam assembly is a comparison of layers, not of "aerogel" and "foam" as abstract categories.

Thermal Conductivity and RSI: Real at the Thin End, but Only on a Declared Basis

The only defensible thermal comparison begins with the tested system, not the material name. Apparent thermal conductivity changes with mean temperature, through-thickness gradient, density, blowing agent, cell or fibre structure, compression, moisture and ageing. ASTM C1728 itself warns that flexible-aerogel transmission properties vary with temperature, gradient, moisture, thickness and shape, and that specification values need not represent installed performance. For context against other materials, see our aerogel vs fiberglass comparison and the broader aerogel vs traditional insulation thickness and cost analysis.

The PUR board and spray PU samples therefore cannot be compared as "both 0.022-0.028" without stating ageing. The spray system's initial EN 12667 figure is attractive; its declared EN 14315 aged value is the more conservative basis for a multi-year envelope design. Conversely, an aerogel blanket's room-temperature highlight is not a licence to ignore conductivity growth at high mean temperature, or the effect of compression in a banded pipe wrap.

Same RSI, Same Flat Basis: Thickness Is Proportional to Lambda

For a flat, homogeneous layer with no significant joints, thermal bridging or curvature effects: RSI = d / λ, so the required thickness d = RSI × λ. Holding RSI constant, the thickness ratio is simply the lambda ratio: d(aerogel) / d(PUR) = λ(aerogel) / λ(PUR).

The commercial implication is narrower than the headline: a thin flexible blanket can replace a noticeably thicker foam layer in a space-critical run. A rigid aerogel panel may be specified for temperature, stiffness, weight or fire reasons even where its 25 °C thermal thickness saving over PUR is small. Spray PU can require more thickness than a high-performance blanket for the same RSI, yet still win on installed cost where it eliminates cutting, fitting and sealing labour.

Pipe Geometry Changes the Answer: Use Mean Radius, Not a Flat Blanket Ratio

For a hollow cylinder with inner radius r_i, outer radius r_o and length L: RSI(pipe) = ln(r_o / r_i) / (2 x pi x L x λ), and r_o = r_i x e^(2 x pi x L x λ x RSI).

Worked example, illustrative only: a 168.3 mm OD pipe is taken as r_i = 84.15 mm and L = 1 m, with a required pipe RSI of 0.50 m²·K/W.

The thickness ranking matches the flat case because the logarithmic term is monotonic. But the absolute thicknesses, surface temperature, jacket area, band loads and volume are not. Doubling the required RSI more than doubles the outer diameter and cladding area; a small lambda advantage therefore becomes increasingly valuable on congested racks. This calculation says nothing by itself about outer surface temperature, touch safety, condensation, wind, solar gain or fire exposure — those require the full steady-state or transient system model.

The procurement meaning: ask for a pipe-segment TDS or test configuration, not only a flat-panel lambda. ASTM C1728 requires pipe-configuration testing for relevant flexible grades and specifically notes that flat and pipe results may differ. For spray PU, density variation, pass thickness, substrate temperature and mixing ratio become part of the thermal deliverable.

Temperature: Above Roughly 120 °C Continuous, PUR Loses

PUR is an ambient-to-moderately-elevated-temperature organic foam; aerogel is a family whose temperature limit is inherited from its reinforcements and binders. The spray-PU data used here gives a service range of -30 to +100 °C for the finished foam, with 90% or more closed cells and 300-310 kPa compressive strength. The certified PUR board carries a declared 0.022 W/m·K but does not become a high-temperature product merely because the certificate exists; the same certificate reports dimensional-stability testing at 70 °C and 90% RH, consistent with a building and envelope basis rather than continuous steam duty.

The practical continuous boundary used in this guide:

The 650 °C figure must be handled carefully. One documented rigid board is made from glass-fibre needle felt impregnated with sol-gel and supercritically dried; its manufacturer states continuous 650 °C, density 250-300 kg/m³, 0.021 W/m·K at 25 °C and 0.041 W/m·K at 600 °C. That is credible evidence for that grade. It is not proof that a 3-10 mm flexible silica blanket with polymer stitching, a foil scrim or an organic binder can survive 650 °C.

Other public blanket ranges show the same split. A supplier overview lists flexible blankets at 0.022-0.057 W/m·K from 25-600 °C with maximum use at 650 °C, while a separate low-temperature cryogenic felt specifies -196 °C to room temperature at 0.015 W/m·K or less. The selection rule is simple: the temperature claim travels with the SKU, reinforcement and test report — not with the word "aerogel".

If the asset operates above 120 °C continuously, the thermal-thinness advantage of a low-lambda PUR sample is irrelevant. Require a time-temperature approval and a thermal-conductivity curve to at least the design temperature. If the asset cycles, also require thermal-shock, linear-change, compressive-creep and fastener/jacket testing.

Fire: PU Stays Combustible; Aerogel Stays Grade-Specific

Neither a closed cell nor a hydrophobic claim is a fire rating. EN 13501-1 classifies reaction to fire using test methods plus smoke and droplet indices. Published fire research describes A1 as essentially non-combustible with no contribution to fire growth, A2 as not easily ignited and not making a significant fuel contribution, and classes through E as carrying increasing combustibility risk; F indicates failure of the small-flame criterion in the cited system.

A PUR system can still be used responsibly. The engineering response is to specify the complete fire package: compatible facing or intumescent coating where required; tested joints and terminations; fire stops at compartment boundaries; protection from radiant and external flame exposure; distance from flaring, hot work and ignition sources; and an assembly listing that the authority having jurisdiction accepts. A spray foam that bonds seamlessly is not automatically a fire-rated monolith — the sampled system's Class E declaration makes that distinction explicit.

For aerogel, "inorganic" is a good starting point, not the end of the conversation. Organic needling fibres, stitching, binders, facings and jacketing can affect ignitability, flame spread, smoke and dripping. Request:

1. the full EN 13501-1 report number, specimen build-up and s/d suffix;
2. EN ISO 1182 non-combustibility or the applicable national equivalent;
3. total heat release and smoke data if the asset is offshore, transit, tunnel, nuclear, battery or occupied space;
4. aged and wet-condition fire behaviour where the specification demands it.

Standards also limit what a buyer can infer. EN 13165 covers factory-made building PU boards and states that it does not determine fitness for a particular end use or cover industrial equipment; EN 14315-1 covers in-situ building spray PUR/PIR and excludes industrial installations. ASTM C591 covers unfaced preformed rigid cellular polyisocyanurate, explicitly warns that PUR-modified materials can perform differently, and requires manufacturer-purchaser agreement on specific temperature limits. These are material and product specifications — not a waiver of project fire and process safety engineering.

Moisture and CUI: Closed-Cell PU Controls Diffusion; Aerogel Still Needs a Jacket

PUR wins on air leakage and bulk-water resistance; aerogel wins only conditionally on keeping the insulation layer drier. The sampled high-density spray PUR has 90% or more closed cells, a water-vapour resistance factor of 80 or more, EN 1609 short-term absorption of 0.20 kg/m² or less, and bonds to many clean, dry substrates. The other spray datasheet declares under 0.20 kg/m² by EN 1609 and a density above 35 kg/m³. These are useful indicators of a closed-cell foam system, not proof that water cannot enter through cracks, penetrations, improper passes or failed terminations.

That continuity is a double-edged sword. A thick, continuous closed-cell layer can function as both air barrier and Class II vapour retarder in building assemblies, but it also reduces drying capacity. Technical guidance cautions that closed-cell spray foam around 50 mm can sit at or below 1 perm and recommends project hygrothermal analysis rather than assuming more vapour resistance is always better. For industrial equipment the concern is different: a jacket breach can pool water against metal, and the foam/jacket interface still needs inspection.

Aerogel blankets are often marketed as hydrophobic and CUI-friendly because silica and glass-fibre composites do not wick like some fibrous insulations. The cited cryogenic blanket claims 98% or more hydrophobicity and is intended for LNG and liquid-nitrogen service, while industry CUI guidance stresses that moisture still enters through leaks, condensation, damaged jackets, thermal cycling and poor sealing. Aerogel can slow moisture retention, but it does not replace a vapour retarder, metal jacket, sealant strategy or coating system on the underlying steel.

Selection implication: choose closed-cell PU when the dominant requirement is an air-tight, vapour-retarding monolithic envelope with a validated drying strategy. Choose a hydrophobic aerogel blanket when the dominant requirement is conformance to complex assets, thin build-up and a drier insulation layer — but only inside a clad, sealed and inspectable system.

Mechanics, Installation and Durability: Spray PU Removes Seams; Aerogel Removes Bulk

The best material on paper can lose after seams, density variation and rework are counted. PUR boards are fast on large flat planes: cut, fit, mechanically fix or adhere, tape and seal, then clad. Their rigidity supplies compression resistance and dimensional control, but kerfs, joints and penetrations create thermal bridges and labour. The sampled PUR certificate reports a compressive strength of 150 kPa and dimensional stability at 70 °C and 90% RH — useful indicators for a board system, not guarantees for every installed roof.

Spray PU is the opposite trade. It can self-adhere to concrete, steel, wood and other prepared surfaces, bridge irregularities and remove many seams. Manufacturers still require clean, dry, rust-free metal and warn that adhesion cannot be guaranteed across all substrates and primers. Improper mix ratio, excessive single-pass thickness, substrate temperature or equipment heat can cause exotherm, poor cell structure, odour, dimensional problems and fire risk during application. That is why "spray foam" must appear in an aerogel comparison as a process system, not merely a foam with a lambda.

Flexible aerogel blankets are easy to cut and wrap on valves, flanges, elbows and congested racks, and their thinness reduces leverage on bands and supports. But they rely on good wrapping tension, overlap, banding, termination and jacket integrity. A rigid aerogel composite trades conformability for stiffness and a flat surface; the documented 10 mm rigid grade is explicitly not a curved-pipe product despite being marketed for some pipeline thermal protection, and its value is in planes, liners and equipment where a rigid thin panel is constructable.

Durability evidence must remain experiment-specific. A 2017 accelerated study exposed three commercial aerogel composite blankets, XPS and a blown PUR foam to 65.6 °C at 90%, 60% and 30% RH and to 32.2 °C at 90% RH, measuring conductivity weekly for five weeks. PUR and two of the three aerogel blankets showed meaningful humidity sensitivity, and behaviour varied by aerogel manufacture. This refutes both "PUR is unaffected by moisture" and "aerogel never ages".

Selection implication: spray PU's installed advantage is largest where continuity and coverage dominate; aerogel's installed advantage is largest where the geometry is convoluted or the allowable envelope is thin. Board products win where prefabrication, compression and a predictable flat build-up matter.

Cost: Compare per RSI and per Cubic Metre, Then Add the System Around Them

Material price per cubic metre is not the decision metric, and neither is the thinnest layer by itself. Let C_m be delivered material cost per m³, C_i installed cost per m² of finished system, and λ_d the design conductivity. For a flat layer of thickness d: cost per RSI per m² = (C_m x d + C_i) / (d / λ_d) = λ_d x (C_m + C_i / d).

This equation explains the apparent contradiction in procurement. Aerogel may carry a higher C_m but a much smaller d, so the C_m x d term can fall. PUR may have lower C_m but a larger d; however, if its installed cost C_i is much lower because boards are fast to fit, or spray PU eliminates joints, the total cost per RSI can reverse.

Numerical illustration, ratios only — no currency or absolute prices. Assume the design uses the flat-layer sample lambdas and a common 1.00 m² footprint, with thicknesses scaled to a target RSI of 1.00 m²·K/W:

Note: relative to the PUR board volume in this illustrative, equal-RSI, flat-layer case. If a project pays only for foam volume, the flexible aerogel layer uses 32% less volume than the PUR board and 46% less than the aged spray PU layer. But the commercial question is the bracket around installation:

The correct RFQ question is: what is the total installed cost per declared RSI, including substrate prep, fixings, vapour control, jacket, penetrations, access, waste, QA, removal and recertification? Not: what is the cubic-metre price? Absolute prices are deliberately excluded here because they would obscure the actual procurement variables.

Application Fit: Specify the System That Removes the Dominant Project Risk

Two notes prevent overreach. "LNG" is not automatically an aerogel win: PU cold-insulation systems are established, and a project may optimise for vapour continuity, cost and repair infrastructure. Likewise, "aerospace" is not one temperature grade — a 650 °C continuous industrial panel cannot be substituted into an aerospace vehicle without programme-specific fire, outgassing, vibration and mass qualifications. For the cold chain in particular, see our cryogenic insulation application guide.

Decision Tree: Choose the Regime First, Then the Form

1. Is the continuous service temperature above about 120 °C? If yes, eliminate general-purpose PUR. Require a high-temperature aerogel composite or another rated refractory system, and verify the exact SKU to at least the design temperature. If no, continue.
2. Is the geometry convoluted — elbows, valves, vessels, tight racks, frequent inspection? If yes, a flexible aerogel blanket is the leading candidate; compare with prefab PUR shapes only if space and weight have low value. If no, continue.
3. Is the dominant requirement an airtight, monolithic, quickly sprayed plane with good compressive and adhesive behaviour? If yes, spray PU is a leading candidate, subject to substrate prep, fire class, vapour-drying analysis and applicator QA. If no, continue.
4. Is the project a large, regular, cold or ambient envelope where board logistics, compressive strength and facing integration dominate? If yes, PUR board is generally the efficient baseline; use aerogel only if profile or weight justifies the premium. If no, continue.
5. Is the asset cryogenic, with complex valves or a severe weight and space penalty? If yes, a qualified cryogenic aerogel blanket with full cold-face vapour and jacket design. Otherwise a PU board or specialty cold-foam system may be the lower-total-cost route.
6. Is fire the governing constraint? For PU, stop at the assembly fire package and authority approval; do not infer safety from closed cells. For aerogel, demand the EN 13501-1 or non-combustibility report for the exact faced product, not the silica chemistry alone.

Procurement Checklist: Turn Marketing Claims into Contractually Usable Data

Design-condition questions for the owner and engineer:

• What are the fluid, inner-surface and expected mean insulation temperatures, including start-up, shutdown and excursions?
• Is the governing constraint RSI, surface temperature, touch safety, condensation control, weight, clearance or access?
• Which code and authority having jurisdiction apply to fire, offshore, cryogenic, food, pharma, LNG or aerospace use?
• Is the assembly required to be an air barrier, vapour retarder, drainage plane, acoustic element or fire barrier — and are those functions tested together?
• What are the maintenance consequences of cutting out spray foam versus rewrapping a blanket?
• Will the aerogel or PU system sit inside a metal jacket, membrane, fire coating or intumescent layer, and who certifies the combined build-up?
• What does "installed cost per RSI" include in the bid: cladding, fasteners, waste, access, QA, removal and recertification?

Final Buying Verdict

Buy flexible aerogel blanket when thickness, complex geometry, weight, high temperature or CUI exposure is the primary cost driver. Its strongest case is not a universal lambda claim but the system consequence of needing far less radial build-up on pipes and valves, fewer heavy box-outs, and a conformable layer that can be inspected and rewrapped. Even then, specify the exact reinforced grade, keep the 25 °C figure separate from high-temperature conductivity, and protect the system with a proper jacket.

Buy PUR board or spray PU when the project rewards continuity, compressive strength, fast area coverage and a mature supply chain more than a minimal profile. PUR board is the rational baseline for many planar ambient and cold envelopes; spray PU can be the most constructable option on irregular decks and tanks because it removes seams and air-leakage paths. Its organic combustibility, process sensitivity and vapour-retarding behaviour must be designed — not marketed — away.

Treat rigid aerogel composite as a high-performance panel, not a thinner PUR clone. At 25 °C, the documented grade's lambda is close to a certified PUR board. Its business case is built on continuous high-temperature capability, stiffness, low profile and weight in a defined grade — not on assuming every rigid aerogel board is 0.015 W/m·K or automatically non-combustible.

The procurement winner is the system that hits the required RSI at the verified service temperature, passes the applicable fire and moisture regime, can be installed and inspected safely, and does so at the lowest total installed cost per RSI for that asset. In that framework, aerogel and PUR are complements with a narrow overlap — not a single-metric race.