Metal Building Insulation Calculator and Envelope Selector
Pick the building use, the climate and the indoor and outdoor conditions. The metal building insulation calculator compares four envelope options: 0.5 mm single-skin profiled sheet, fiberglass wool with aluminum foil facing, 50 mm EPS sandwich panel, and 75 mm rock wool or PU sandwich panel. It checks whether the inner face of the roof and walls reaches the dew point, and says where the vapor control goes.
Know your envelope already? Send the building size, site country and roof and wall insulation requirement for a free layout, specification and itemized quote.
Envelope and Insulation Selector: Roof, Walls and Dew Point in One Check
Set the use, fire requirement, climate and temperatures on the left. The result gives the roof and wall build-up to ask for, a condensation check with the temperature through the build-up, vapor control notes and a comparison of roof sheet fixing.
Estimate for planning only, from a steady-state check with generic material values. We manufacture the profiled sheet and supply the insulation core. Panel type, core thickness, fire data and vapor control are confirmed in the written quote.
The Four Envelope Options and Where Each One Fits
The calculator chooses between four build-ups, from a single sheet to a 75 mm sandwich panel. It starts from your use and climate and steps up only when the condensation check calls for it.
| Option | Build-up | Where the selector picks it | What to watch |
|---|---|---|---|
| 0.5 mm single-skin profiled sheet | One layer of profiled steel sheet on the purlins and girts | Walls of unheated storage, and roofs where the inner face stays above the dew point | The underside of the sheet becomes the condensation surface when it cools below the dew point of the inside air |
| Fiberglass wool with aluminum foil facing | Wool blanket under the sheet, with the foil facing on the warm side | Roofs of unheated storage, and buildings with a heat source in warm climates | The foil works as a vapor retarder only when every seam and penetration is taped |
| 50 mm EPS sandwich panel | EPS core between two steel skins | Heated or air-conditioned space in mild and warm climates | Joints and laps are sealed on the warm side |
| 75 mm rock wool or PU sandwich panel | Rock wool or PU core between two steel skins | Rock wool where a fire requirement applies; PU for cold rooms and cold climates | Panel thickness for chilled or frozen rooms is designed for the room temperature |
The envelope is one of the components of a metal building kit, alongside the frame, purlins, trim and accessories. We manufacture the 0.5 mm profiled sheet, and the insulation core is a part we supply. Thickness, thermal conductivity and fire data for the panels in your project are confirmed with the quote, and where a fire requirement applies, the rating is confirmed against your local code.
The core options and how they are quoted are set out on our page about insulation for metal building kits. For the wall face, our page on pre engineered metal building siding covers sheet and sandwich options; for the roof, see metal roofing systems, with panels, purlins, gutters and downspouts.
Dew Point, Surface Temperature and When Condensation Forms
The condensation check compares two temperatures: the dew point of the air and the temperature of the surface that air touches. Here is how the calculator gets both.
- Dew point of the inside air, from its temperature and humidity: 20 °C at 50% RH gives 9.3 °C.
- U-value of the build-up: one divided by the sum of the layer resistances and the surface resistances (0.10 inside a roof, 0.13 inside a wall, 0.04 outside, in m²K/W).
- Inner face temperature on the coldest day = indoor temperature − U × inside surface resistance × (indoor − outdoor temperature).
- If the inner face is below the dew point, condensation forms on it. Within 2 K of it, the result is marginal.
| Wall build-up, 20 °C and 50% RH inside, −5 °C outside | U-value | Inner face | Result |
|---|---|---|---|
| 0.5 mm single-skin sheet | 5.88 W/m²K | 0.9 °C | Below the 9.3 °C dew point: condensation forms |
| 50 mm EPS sandwich panel (λ 0.038 W/mK) | 0.67 W/m²K | 17.8 °C | 8.6 K above the dew point: clear |
This metal building condensation calculator is a steady-state, one-dimensional check, the same way a designer makes a first pass. It does not see thermal bridges at purlins, fasteners and panel joints, and it does not see the night-sky cooling that can drop an unheated roof below the air temperature. Treat a marginal result as a warning and raise it in your inquiry.
The thermal values in the tool are generic for each core material, not product data. Open the reference values inside the tool to replace them with the figures from a data sheet; the result updates at once.
When a Vapor Barrier Is Needed and Which Side It Goes On
Vapor control always goes on the warm side of the insulation. In most buildings that is the inside face; in a cold store it is the outside.
| Situation | Where vapor control goes | Note |
|---|---|---|
| Heated, cooled or humid inside, cold outside | On the warm (inside) face | If the dew point of the inside air is above the outdoor minimum, moisture can condense inside the build-up |
| Fiberglass wool with foil facing | Foil facing toward the warm side, every seam and penetration taped | An untaped foil lets moist air reach the cold sheet |
| Sandwich panels | The steel skins block vapor; seal side laps, end laps and openings on the warm side | Joints are where moisture gets in |
| Cold storage | On the outside, which is the warm side | Keep the outer skin and every joint vapor-tight so moisture is not driven toward the cold room |
| Processes that release steam or moisture | Vapor control plus ventilation or extraction | Ventilation is sized for the process |
Supply and detailing of vapor retarder facings are confirmed in the quote. Name the indoor conditions and any process moisture in your inquiry, so the envelope is specified for them rather than for a dry warehouse.
Insulation Calculator Questions: Options, Condensation and Panels
What does the metal building insulation calculator check?
It picks a roof and wall build-up from four options for your use and climate, then checks whether the inner face of the build-up stays above the dew point of the inside air on the coldest day. For a cold store it checks the outer face against the dew point of the outside air.
Which insulation options can be quoted?
The calculator works with four: 0.5 mm single-skin profiled sheet, fiberglass wool with aluminum foil facing, 50 mm EPS sandwich panel, and 75 mm rock wool or PU sandwich panel. We manufacture the profiled sheet and supply the insulation core, and the written quote names the core and thickness.
Is a single-skin roof enough for a warehouse?
It can be, when the inner face stays above the dew point. Humid goods, a cold climate or night-sky cooling can push the underside of the sheet below it, and then condensation drips. Run the check with your conditions, and raise a marginal result in the inquiry.
Do sandwich panels need a separate vapor barrier?
The steel skins of a sandwich panel already block vapor. What matters is sealing the side laps, end laps and openings on the warm side, because joints are where moist air gets in.
How thick should cold room panels be?
Panel thickness for chilled or frozen rooms is designed for the room temperature, so 75 mm is a starting point in the calculator, not a final figure. Send the room temperature with your inquiry.
Can the calculator confirm a fire rating?
No. Where a fire requirement applies, rock wool is the usual sandwich core, and the rating you need is confirmed against your local code.
Are the thermal values in the tool your product data?
No. They are generic values for each core material, and you can replace them with data-sheet figures inside the tool. Thickness, thermal and fire data for your panels are confirmed with the quote.
Send Your Envelope Choice for a Layout and Itemized Quote
Copy the result from the insulation calculator into your email or WhatsApp, or send the building size, site country, building use and the roof and wall insulation requirement. We return a free layout, specification and itemized quote, with panel type and core thickness confirmed for your project.
Three sandwich-panel cut-away samples side by side
