If you’ve ever worked in construction, industrial insulation, or commercial building design, you’ve likely come across PU sealed rockwool sandwich panels as a go-to solution for balancing thermal performance, structural integrity, and fire resistance. As a supplier of these panels, I get a lot of questions from architects, contractors, and facility managers: “What exactly is the heat-transfer coefficient of PU sealed rockwool sandwich panels, and why does it matter for my project?” It’s a fair question—one that doesn’t have a one-size-fits-all answer, but one that’s critical to getting right when you’re calculating energy costs, meeting building code requirements, or ensuring long-term operational efficiency. Let’s break this down, from what the heat-transfer coefficient even means, to the specific values you can expect, and why choosing the right panel matters for your bottom line. PU Sealed Rockwool Sandwich Panel
First, let’s define the terms that are central here. For anyone new to the industry, the heat-transfer coefficient—often referred to as the U-value (or U-factor) in building science—measures the rate at which heat passes through a material or assembly, in watts per square meter per kelvin (W/m²·K). In simple terms, a lower U-value means less heat moves through the panel, which translates to better thermal insulation. That’s the key for applications like cold storage warehouses, factory walls, cleanrooms, or office buildings: the less heat that escapes in winter or seeps in in summer, the less energy you spend on heating and cooling.
Now, PU sealed rockwool sandwich panels are a two-part assembly, so their U-value isn’t just based on the rockwool core—it’s influenced by multiple factors, starting with the PU seal itself. Wait, what is that PU seal, anyway? PU stands for polyurethane, and it’s a dense, closed-cell foam that’s typically applied to the edges and joints of the rockwool core, not just the surface. Its job is two-fold: it seals gaps that would otherwise let air pass through (which causes thermal bridging), and it adds structural rigidity to the panel. Because of its own low thermal conductivity (around 0.022 W/m·K, which is far better than many other insulating materials), the PU seal doesn’t just stop air leaks—it also contributes to the panel’s overall thermal performance.
The rockwool core, meanwhile, is made from spun mineral wool, derived from basalt or recycled slag, with a typical thermal conductivity (called lambda, or λ-value) of 0.032 to 0.040 W/m·K, depending on its density. Most standard panels use rockwool with a density of 80 to 120 kg/m³, which strikes a balance between insulation and fire resistance (rockwool is non-combustible, a huge benefit for industrial facilities where fire risk is high). The panel’s facing materials—usually galvanized steel or aluminum sheets on either side—also play a small role in U-value, though metal has high thermal conductivity, so it’s the core and seal that make up the bulk of the insulation performance.
So what’s the actual U-value for a typical PU sealed rockwool sandwich panel? Let’s be clear: this number varies a lot based on panel thickness, because thicker cores mean more insulating material. For reference, here are the ranges we see for standard panels, tested according to ISO 6946 (the international standard for calculating thermal resistance of building components):
- For a 50 mm thick panel: U-values typically fall between 0.58 and 0.65 W/m²·K. This is the thinnest common option, used for interior partitions or non-critical wall applications where insulation isn’t the top priority.
- 80 mm thick panel: U-values drop to 0.38 to 0.45 W/m²·K. This is a popular mid-range option for warehouse walls or mezzanine floors, where you want better insulation without the cost of a thicker panel.
- 100 mm thick panel: U-values of 0.30 to 0.35 W/m²·K. This is a sweet spot for cold storage units, walk-in freezers, and cleanrooms, where consistent temperatures are non-negotiable.
- 150 mm thick panel: U-values around 0.20 to 0.25 W/m²·K. Used for exterior walls in cold climates, or facilities with extreme temperature control needs, like pharmaceutical storage or agricultural warehouses.
- 200 mm thick panel: U-values as low as 0.15 to 0.18 W/m²·K. For projects in very cold regions (like northern Europe, Canada, or Siberia) where meeting strict energy codes requires maximum insulation.
Now, you might be wondering why there’s a range for each thickness instead of a single number. A few factors affect this. First, the quality of the PU seal: poorly applied PU seal, or a seal with gaps from manufacturing, can create thermal bridging at the panel edges, which raises the U-value by up to 10% compared to a perfectly sealed panel. That’s why as a supplier, we invest in automated edge sealing machinery to ensure every panel has a uniform, airtight PU seal—we’ve seen panels from competitors with U-values 15% higher than ours, just because of inconsistent sealing. Second, the density of the rockwool core: a higher-density rockwool (120 kg/m³ vs. 80 kg/m³) has slightly lower thermal conductivity, so it will deliver a marginally lower U-value for the same thickness. Third, the facing material: aluminum has a slightly lower thermal conductivity than galvanized steel, so panels with aluminum faces will have U-values roughly 5% lower than identical panels with steel faces.
Another common question I get: “How does this compare to other insulation products?” For context, a standard 100 mm fiberglass batts has a U-value of around 0.55 W/m²·K, which is significantly higher than our 100 mm PU sealed rockwool panel’s 0.30 to 0.35 W/m²·K. That means our panel will let nearly half as much heat pass through, so over a year, a 1,000 m² warehouse wall made with our panels will use an estimated 30-40% less energy for heating and cooling than the same wall with fiberglass. That’s a huge difference for operational costs, especially for facilities that run 24/7.
But it’s not just about U-value—PU sealed rockwool panels have other properties that make their heat-transfer performance even more consistent over time. Unlike foamed insulation like polyurethane or polystyrene, rockwool doesn’t settle or shrink over time, which means its thermal conductivity stays stable for decades. Many of our customers report that their panels’ U-value is within 5% of the original rated value after 20 years, whereas foam panels can see a 20-30% increase in U-value over the same period as they degrade. The PU seal also doesn’t break down easily in high-humidity environments, so even in coastal areas or facilities with high moisture levels (like food processing plants), the panel’s edge seal stays intact, preventing air leaks and maintaining low thermal transfer.
That stability is a big deal for meeting building codes. In many regions, energy codes require a minimum U-value for exterior walls to reduce carbon emissions. For example, in the EU’s Energy Performance of Buildings Directive (EPBD), new commercial buildings require a U-value of 0.25 W/m²·K or lower for exterior walls, which a 150 mm PU sealed rockwool panel can easily meet. In parts of the US, the International Energy Conservation Code (IECC) requires U-values as low as 0.19 W/m²·K for cold climate zones, which a 200 mm panel will satisfy. As a supplier, we work closely with contractors to help them select the right panel thickness to meet local codes, avoiding the cost of rework or non-compliance fines.
Now, it’s important to clarify a common misconception: some people confuse the heat-transfer coefficient (U-value) with thermal conductivity (lambda, λ-value). The lambda value is a property of the insulation material itself, measured in W/m·K, while the U-value is a property of the entire panel assembly, including the metal faces and seal. That’s why you can’t calculate a panel’s U-value just by multiplying its thickness by its lambda value—you have to account for the thermal resistance of the faces, the PU seal, and any air gaps, which is why standardized testing by accredited labs (like ASTM International or ISO) is required for accurate U-value ratings.
As a supplier, we always provide our customers with test reports from third-party labs for every panel thickness we offer. For example, our 100 mm thick PU sealed rockwool panels tested at 0.32 W/m²·K per ISO 6946, which is lower than the industry average for similar panels. That’s not just a number we pull out of thin air—it’s the result of investing in high-quality rockwool cores and precision edge sealing, which we know translates to real energy savings for our clients.
So when should you choose PU sealed rockwool sandwich panels based on their heat-transfer performance? If your project is a cold storage facility, a pharmaceutical warehouse, a food processing plant, or an office building in a moderate or cold climate, these panels deliver a consistent, low U-value that outperforms many alternatives. For interior applications, where thermal bridging at joints is less of a concern, the PU seal still provides the benefit of airtightness, reducing energy loss that would otherwise happen through gaps in the wall. For exterior applications, the combination of insulation and structural rigidity means you get both a high-performing thermal envelope and a durable wall that can withstand weather, impacts, and fire.
I also want to mention that while the U-value is a critical metric, it’s not the only factor. For example, rockwool is non-combustible (Class A, per ASTM E136), which is a huge advantage for facilities where fire risk is a concern, even if you have a slightly higher U-value than a combustible foam panel. That said, our PU sealed panels still have a U-value that’s far better than traditional building materials like concrete blocks (which have a U-value of around 1.5 W/m²·K for a 200 mm concrete wall) or brick (around 1.2 W/m²·K for a 220 mm wall). So you’re getting better insulation than masonry, plus fire resistance and a lightweight panel that’s easy to install.
At the end of the day, the heat-transfer coefficient of PU sealed rockwool sandwich panels is a flexible, performance-driven metric that depends on how the panel is built. But across all standard thicknesses, it delivers a range of U-values that make it a competitive choice for nearly every commercial and industrial insulation application. If you’re in the market for a reliable insulation solution that balances thermal performance, fire safety, and long-term durability, we’d be happy to walk you through the specific U-values for your project, discuss which thickness is right for your climate and code requirements, and provide custom quotes tailored to your needs.
Don’t hesitate to reach out to our team to talk through your heat-transfer needs, ask any additional questions about panel performance, or get a sample of our PU sealed rockwool sandwich panels to test for your project. We’ve worked with hundreds of contractors, architects, and facility managers to find the right panel for their specific goals, and we’re ready to help you do the same.
Translucent Fiberglass Panel References
- International Organization for Standardization. (2017). ISO 6946: Building components and building elements – Thermal resistance and thermal transmittance – Calculation method.
- American Society for Testing and Materials. (2020). ASTM E136: Standard test method for behavior of materials in vertical tube furnace at 750°C.
- Mineral Wool Industry Association. (2021). Thermal Performance of Mineral Wool Insulation: Long-Term Stability and Application Guide.
- Polyurethane Foam Association. (2019). Closed-Cell Polyurethane Foam Properties for Building Sealing and Insulation.
- International Energy Conservation Code. (2022). IECC Requirements for Commercial Building Envelope Thermal Performance.
Handan Donghong Fiberglass & Color Steel Manufacturing Co., Ltd.
Handan Donghong Fiberglass & Color Steel Manufacturing Co., Ltd. is one of the most professional pu sealed rockwool sandwich panel manufacturers and suppliers in China, featured by quality products and good price. Please rest assured to wholesale durable pu sealed rockwool sandwich panel made in China here and get quotation from our factory. Customized orders are welcome.
Address: South side of the road, 2,000 meters west of the intersection of Nanhuan Road and Airport Road, Hanshan District, Handan City.
E-mail: leo@dhpcfrp.com
WebSite: https://www.dhfrpsheet.com/
