White vinyl faced insulation is a glass wool or mineral wool blanket laminated to a white polypropylene-scrim-kraft facing, not a PVC vinyl sheet. The name stuck because the surface looks like white vinyl, while the material underneath is PSK (polypropylene, scrim, kraft), also sold as WPSK or white PSK facing. Specify it by permeance, puncture resistance and the fire classification of the whole laminate, not by color, because two white facings can land on opposite sides of ASTM C1136.
Quick answer: what should you know about white vinyl faced insulation
- The white layer is a polypropylene film about 38 micron (1.5 mil) thick. There is no PVC in a standard PSK facing.
- Under that film sits a tri-directional fiberglass scrim, and under the scrim sits natural kraft paper. Three layers, held by a flame-retardant adhesive or a polyethylene bond.
- Permeance on published datasheets runs from 0.02 to 0.09 perm measured to ASTM E96 Procedure A. Both figures meet the 0.10 perm ceiling that NAIMA recommends for metal building insulation, but they are not interchangeable on a chilled line.
- The white surface is not a radiant barrier. Its thermal emissivity is around 0.85, against roughly 0.03 for bare aluminum foil.
- Old specifications that say “vinyl facing” are usually asking for this product, or for a scrimless PVC film that is weaker and far more permeable. Ask which one before quoting.
The boring answer is that most buyers who search for white vinyl faced insulation want PP scrim kraft facing. They just do not know the name their supplier uses.
The name is wrong, and that costs money
Johns Manville describes the history plainly in its facing guide. A vinyl facing was a white PVC film with no reinforcing glass fiber scrim and a much higher permeability than FSK, ASJ or poly-film materials. It was specified mostly for looks, in master specifications that some architectural firms still carry. JM’s conclusion is that PSK is the better and cheaper replacement for those old vinyl requests.
That leaves several different products sharing one label on job sites:
| What the drawing says | What is usually supplied | Construction | Typical permeance |
|---|---|---|---|
| White vinyl facing, WPSK, white PSK | PP scrim kraft facing | White PP film / fiberglass scrim / kraft | 0.02 to 0.09 perm |
| Vinyl facing (legacy) | Scrimless PVC film on kraft | PVC film / kraft, no scrim | Much higher, rarely certified low-perm |
| Poly-top jacketing | White PSK on pipe sections | Same PSK laminate, cut for pipe jackets | 0.02 to 0.09 perm |
| WMP-VR, WMP-10, WMP-30 | Trade names for polypropylene/scrim/kraft vapor retarders | PP or metallized PP / scrim / kraft | 0.02 to 0.09 perm |
| FSK facing | Foil scrim kraft | Aluminum foil / scrim / kraft | Near zero for intact foil |
We see the mistake most often on retrofit tenders. A spec writer copies a 1990s clause naming “white vinyl jacket”, two distributors quote a scrimless film and one quotes a proper PSK laminate, and the lowest number wins. Six months later the jacket tears at a hanger and the vapor line is open. The two quotes were never for the same material.
What the three letters actually mean
PSK stands for polypropylene, scrim, kraft. Read from the outside in: a white polypropylene film, a reinforcing scrim of glass fibers laid in three directions, and a backing of natural kraft paper. WPSK simply adds “white”. Some catalogs use PSM or WMP for a variant where the kraft is replaced by a metallized PET or metallized polypropylene film, so no paper at all. That variant is a different laminate with a different fire report.
The abbreviation matters for a second reason. Search for “PSK” on its own and you get phase shift keying, a digital modulation scheme, plus an office software suite and a few listed companies. Anyone buying advertising on the bare acronym pays for telecom students. The word “facing” or “insulation” has to travel with it.
Where the color comes from
The white is the PP film itself, sometimes a white coating over it. Johns Manville points out two practical consequences: the white polypropylene surface can be wiped clean, and it does not show the leakage or water stains that show on standard ASJ paper jacketing. The first is a maintenance benefit in a plant room. The second cuts both ways. A stain on paper jacketing tells an inspector that a joint is wet. A white PP film can hide the same failure for longer, so inspection intervals matter more, not less.
Black PSK exists for the same reason as white, in the opposite direction. JM’s black facing tape data sheet warns against dragging the black surface over abrasive surfaces and against using a metal squeegee, because scuffs show. On exposed ductwork in a busy mechanical room, white hides handling marks better. Where appearance is not a factor, black is often cheaper.
What is in the laminate
A PSK facing is a four-part system, and each part has a number a buyer can check. The figures below are the construction values published on public datasheets from Bondtape (WPSK-R455A, WPSK-453A), Lamtec (WMP-30, WMP-VR), 3M (Venture Tape 2537) and Cosmicfoil. They are industry-typical values, not Donfoil grade data. Confirm the actual construction against the datasheet for the grade you order.
| Layer | Typical value (imperial) | Typical value (metric) | What it controls |
|---|---|---|---|
| White PP film | 1.5 mil | 38 micron | Appearance, wipeability, water holdout |
| Fiberglass scrim, MD | 5 per inch | 20 / 100 mm | Tear and puncture in machine direction |
| Fiberglass scrim, XD | 4 per inch | 16 / 100 mm | Tear in cross direction |
| Adhesive | Flame-retardant glue or PE | Flame-retardant glue or PE | Bond strength, fire behavior, heat limit |
| Natural kraft | 30.6 lb / 3000 ft2 | 50 g/m2 | Backing, stiffness, vapor path |
| Total basis weight | 17.4 to 26 lb / 1000 ft2 | 85 to 127 g/m2 | Handling strength and cost |
Kraft weight is the option that moves price most. Public catalogs list 38, 49 and 50 g/m2 as standard, and Donfoil’s own PSK page lists 50, 60 and 80 gsm options. Perforation, fire-retardant film, fireproof kraft, film thickness and roll width all vary the quote. There is no single “PSK” price.
A note on the common WMP-VR equivalent facing question. WMP-VR and WMP-30 are Lamtec trade names with published test data, not generic grade names. A request for an equivalent should be answered with a datasheet comparison, line by line: permeance method, puncture in Beach units, tensile in both directions, fire test on the complete laminate. “Equivalent” without those four numbers is a request to guess.
Typical properties and the standards behind them
The table collects values published across the same public datasheets. Read it as a range of what the market offers, not a specification for any one roll.
| Property | Test method | Typical published range | Why it decides the job |
|---|---|---|---|
| Permeance (WVTR) | ASTM E96 Procedure A | 0.02 to 0.09 perm (1.15 to 5.17 ng/(Pa s m2)) | Whether the facing qualifies as a low-perm vapor retarder |
| Puncture resistance | ASTM C1136 | 105 to 125 Beach units (3.1 to 3.7 J) | Survival around hangers, corners and staples |
| Tensile, MD | ASTM D828 | 135 to 185 N/25 mm (30.6 to 42 lb/in) | Pulling the facing around a duct without tearing |
| Tensile, XD | ASTM D828 | 55 to 135 N/25 mm (12.5 to 30.7 lb/in) | The weaker direction, and the one that splits first |
| Burst strength | ASTM D774 | 35 to 65 N/cm2 (50 to 94 psi) | Resistance to a point load on a wrapped surface |
| Low temperature | ASTM D1790, 4 h at -40 C | Remains flexible, no delamination | Cold-store and winter installation work |
| High temperature | ASTM D1790, 4 h at +116 C | Remains flexible, no delamination | The film or adhesive softens above this |
| Dimensional stability | ASTM D1204 at 65 C | Less than 0.5 % | Shrinkage that opens a seam after handover |
| Light reflectance | ASTM C523 | About 85 % | Visible brightness, not thermal reflectance |
| Emissivity | ASTM E408 | About 0.85 | Why the white film is not a radiant barrier |
| Flame spread / smoke | ASTM E84, UL 723 | 5/5 to 15/20 depending on grade and exposed face | Code acceptance of the complete laminate |
| Mold resistance | ASTM C665 / C1338 | No growth | Damp plant rooms and cold rooms |
Two numbers in that table get confused constantly. Light reflectance near 85 percent describes visible light, which is why the surface reads bright under a factory light. Emissivity near 0.85 describes long-wave thermal radiation, which is why the surface does not behave like foil. Bare aluminum foil sits near 0.03 emissivity and reflects about 97 percent of radiant heat. If the design needs a radiant barrier, a white PSK facing is the wrong product, and no amount of whiteness changes that. For the reflective-layer decision, our comparison of foil versus metallised facing sets out the numbers.
The temperature figures also need care. ASTM C1136 covers flexible low-permeance vapor retarders for indoor use between -20 F and 150 F (-29 C to 66 C), with outdoor use allowed where weather protection is provided. The -40 C to +116 C figures on a datasheet come from a four-hour flexibility test to ASTM D1790. They are not a continuous service rating. Faced duct wrap from CertainTeed is published for duct temperatures of 35 F to 250 F (1.7 C to 121 C), while the unfaced version runs to 450 F (232 C). When a line runs hot, facing temperature limits are usually what fail first.
How ASTM C1136 types map onto this facing
ASTM C1136 sets minimum permeance, puncture and tensile values for flexible vapor retarders. The four types quoted on nearly every North American facing datasheet are:
| Physical property | Type I | Type II | Type III | Type IV |
|---|---|---|---|---|
| Permeance, max, perm | 0.02 | 0.02 | 0.10 | 0.10 |
| Puncture, min, Beach units | 50 | 25 | 50 | 25 |
| MD tensile, min, lb/in (N/mm) | 45 (7.9) | 30 (5.3) | 45 (7.9) | 30 (5.3) |
| XD tensile, min, lb/in (N/mm) | 30 (5.3) | 20 (3.5) | 30 (5.3) | 20 (3.5) |
Types I and III are the high-strength grades; II and IV are moderate strength. Later revisions of the standard add further types for very low permeance, so the Roman numeral alone is not enough on a purchase order. NAIMA recommends a permeance no greater than 0.10 US perm for metal building insulation, which is why Type III and Type IV PSK products are common there and Type I or II appear on duct and cold-room work.
We wrote a full walkthrough in ASTM C1136 facing types. The short version for a buyer: name the type, the permeance value and the test method in the same line. A spec that says “low permeance facing” gives a supplier room to quote 0.09 perm where the design assumed 0.02.
For European, British and Australian projects, the equivalent conversations run through EN 13501-1 for reaction to fire, BS 476 for fire tests and AS/NZS 4859.1 for insulation materials. Ask for the report for the complete laminate, in the market’s own test framework. An ASTM E84 sheet is not a substitute for an EN 13501-1 classification.
Where white vinyl faced insulation is used
| Application | What the facing does | What to watch |
|---|---|---|
| HVAC duct wrap | Vapor retarder and clean finish on the outside of the blanket | Every seam and the 51 mm (2 in) overlap flap must be taped |
| White faced insulation for metal buildings | Interior roof and wall liner on glass wool blanket | Permeance at or below 0.10 perm, UV kept off the kraft |
| Glass wool blanket and board | Factory-laminated facing for a roll or slab | Bond method and line temperature at lamination |
| Pipe and duct jacketing | “Poly-top jacketing” on pre-formed pipe sections | Longitudinal seam tape matched to the facing |
| Batts for wall and ceiling cavities | White facing toward the occupied space | Do not compress the batt to make it fit |
| Equipment and air handler casings | Wipeable surface in plant rooms | Fire report for the full laminate, not just the film |
| Cold rooms and chilled water lines | Vapor control on the warm side | Sealed seams, no second low-perm layer on the cold side |
Donfoil supplies the facing roll, not the finished blanket. That distinction matters at the quoting stage. If you run a lamination line, the questions are roll width, length, core ID, bond method and how the film behaves at your line temperature. If you buy finished blanket, the questions are R-value, stretch-out and seaming tape. The material is the same, but the two purchase orders are not.
For matching the facing to a substrate, FSK facing covers the same lamination decisions from the foil side, and glass wool blanket covers the substrate itself.
White PSK duct wrap: the biggest single use
Johns Manville, CertainTeed and Knauf all publish white PSK duct wrap lines, which is why “white psk duct wrap” and “microlite white psk duct wrap” show up in search suggestions with brand names attached. The installation detail is consistent across the three datasheets, and it is where most field failures start.
- Seal the sheet metal duct first. It must be clean, dry and tightly sealed at all joints. Insulation wrapped over a leaking duct hides the leak and does not fix it.
- Cut to stretch-out dimensions from the duct perimeter plus the add-on in the manufacturer’s table. Do not cut tight and stretch the blanket.
- Strip about 51 mm (2 in) of insulation from the facing at one end so the film forms an overlapping flap. Wrap with the facing to the outside and butt the insulation snugly.
- Staple the longitudinal seam with outward-clinching staples at roughly 152 mm (6 in) centers.
- Seal with pressure-sensitive tape matched to the facing. JM specifies a 96 mm white PSK seaming tape and says to rub it down with a plastic squeegee. Do not apply tape below 20 F (-7 C) or above 130 F (54 C); adhesion outside that window is unreliable.
- On ducts 610 mm (24 in) wide or more, add mechanical fasteners and speed clips at about 457 mm (18 in) centers on the underside to stop sagging. Cut fasteners flush and seal over them with the same tape.
- Butt adjacent sections tightly, with the circumferential 51 mm flap overlapping and taped like the long seam.
Two constraints sit behind those steps. Compressing the blanket raises thermal conductivity and cuts the installed R-value, which is why JM calculates its published R-values at material compressed to a maximum of 25 percent. And an untaped seam breaks the vapor line even when every other square meter of facing is intact. On chilled lines, that is where condensation appears first.
The duct wrap specification itself belongs to ASTM C1290. Our separate article on FSK vs PSK facing goes deeper into choosing between the two for duct work, metal buildings and cold rooms.
What the white facing cannot do
Every one of these is a real limit, not a disclaimer.
A radiant barrier it is not. Emissivity around 0.85 puts the white film at the opposite end of the scale from aluminum foil. If the assembly credits reflective performance, use FSK facing or a metallized product and show the emissivity test.
Outdoor weathering needs a different layer. ASTM C1136 allows outdoor use only with weather protection. UV degrades polypropylene, and kraft paper absorbs water. An exposed roof or an open-sided structure needs a separate metal or coated jacket over the insulation.
Fire rating does not come with the film. Devrel’s facing comparison makes the point directly: some PSK products meet Class A to ASTM E84 and some do not, and the buyer should request the test report. The rating belongs to the complete laminate with the film face and, where relevant, the polyester face exposed. A white PP film bought cheaply can fail a 25/50 flame spread and smoke requirement.
Hot surfaces kill it. The adhesive and the film set the ceiling before the glass wool does. Check the continuous service temperature, not only the four-hour flexibility number.
Less visible damage is a mixed result. A clean white surface hides scuffs, but it also hides the water staining that would otherwise flag a failed joint on ASJ jacketing. Plan inspections accordingly.
Corrosion resistance is a genuine advantage. A plain white PP laminate has no aluminum layer, so chloride-laden coastal air and alkaline contact do not attack the facing the way they can attack foil. That is one honest reason to pick PSK over FSK in a wash-down plant or a coastal mechanical room. The metallized PSM variant does have a metal layer, so check which one is being quoted.
Two vapor retarders are worse than one. Low-perm layers on either side of an assembly trap construction moisture in the insulation. This shows up on cold-room jobs where a polyethylene sheet is added “for safety”. Choose one vapor control layer and place it on the warm side.
Naming and specification mistakes we see on enquiries
- Ordering “vinyl” without naming the construction. Say polypropylene film, tri-directional fiberglass scrim, kraft backing. If the buyer actually wants scrimless PVC, that is a different quote.
- Specifying by color. White and black PSK use the same base laminate. Color decides appearance and scuff visibility, not permeance or fire behavior.
- Quoting permeance without the test method. ASTM E96 Procedure A and Procedure B give different numbers for the same material.
- Assuming all PSK is Class A. Ask for the ASTM E84 or UL 723 report for the specific grade, with both faces tested.
- Using a 0.09 perm facing where the dew point calculation assumed 0.02 perm. On a chilled line the difference is condensation, and it shows up inside the insulation where nobody looks.
- Forgetting the matching seaming tape. A facing with no compatible tape on site gets sealed with whatever is in the van.
- Treating the -40 C to +116 C flexibility test as a service temperature. It is a four-hour test, not a rating.
- Ignoring roll tolerances. Published datasheets allow +/-10 percent on weight and thickness and +/-3 mm on width. A lamination line set to exact nominal width will wander.
How to write the facing into a purchase order
Copy the structure, then fill in the numbers from your own calculation and the supplier’s datasheet.
- Product name and construction: white polypropylene-scrim-kraft facing, 38 micron white PP film, tri-directional fiberglass scrim at 20 by 16 per 100 mm, 50 g/m2 natural kraft, flame-retardant adhesive. State white or black, perforated or solid.
- Governing standard: ASTM C1136 Type I, II, III or IV, or ASTM C1290 for external HVAC duct wrap, plus the market equivalents EN 13501-1, BS 476 or AS/NZS 4859.1 where the project requires them.
- Permeance: maximum value in perm, measured to ASTM E96 Procedure A, with the metric equivalent.
- Mechanical: puncture resistance in Beach units, MD and XD tensile to ASTM D828, burst to ASTM D774, dimensional stability to ASTM D1204.
- Fire: flame spread and smoke developed to ASTM E84 / UL 723 for the complete laminate, with the composite UL FHC rating where the duct spec calls for 25/50.
- Temperature: continuous service range and the ASTM D1790 flexibility result, listed as two separate lines.
- Roll format: width, length, core ID, tolerances, perforation, private-label printing, pallet and container loading, MOQ and lead time.
- Documentation: test report per lot, certificate of compliance, mold resistance to ASTM C1338 and accelerated aging to ASTM C1258 where the environment justifies it.
- Closure: the matched seaming tape, in the same order, with the application temperature range.
Line 3 and line 5 are the ones that most often settle a dispute after delivery. Everything else can be adjusted on site. For the wider supplier qualification questions, reinforced aluminum foil facing sets out the document and certification checklist we use, and the metal building facing specification walks through the dew point calculation that fixes the permeance number.
FAQ
Is white vinyl faced insulation actually vinyl?
No, not in current supply. Standard white vinyl faced insulation uses a white polypropylene film, roughly 38 micron thick, laminated to a fiberglass scrim and kraft paper. True vinyl facing was a scrimless PVC film with much higher permeability, specified mostly for appearance. Johns Manville calls PSK the cost-efficient replacement for those old vinyl clauses. Ask the supplier to name the film.
What does PSK stand for?
Polypropylene, scrim, kraft, named from the outside in. WPSK means white PSK. The same laminate appears as poly-top jacketing on pipe work and under trade names such as WMP-VR and WMP-10. PSM or WMP variants replace the kraft with a metallized film and have their own fire report.
Is white PSK facing a vapor barrier?
It is a low-permeance vapor retarder, not a zero-perm barrier. Published values run from 0.02 to 0.09 perm to ASTM E96 Procedure A, against the 0.10 perm ceiling NAIMA recommends for metal building insulation. Intact aluminum foil in FSK is effectively zero perm. On chilled lines, that gap matters, so calculate the dew point before choosing.
Is a white facing a radiant barrier?
No. White PP film reflects about 85 percent of visible light to ASTM C523, which is why it looks bright, but its thermal emissivity is around 0.85 to ASTM E408. Bare aluminum foil is about 0.03. If the design takes credit for radiant performance, specify FSK facing or a metallized laminate instead.
Does PSK facing meet commercial fire code?
Some grades do and some do not. ASTM E84 or UL 723 results published for polypropylene/scrim/kraft laminates range from 5/5 to 15/20 for flame spread and smoke developed depending on grade and which face is exposed. Ask for the report for the exact laminate, and confirm the local classification, EN 13501-1 or BS 476, for export projects.
When should I choose FSK instead of white PSK?
Choose FSK facing when the assembly needs radiant heat reflection, near-zero permeance, or the spec explicitly names foil. Choose white PSK facing when the surface will be visible and wiped, when chloride or alkaline exposure risks attacking aluminum foil, or when cost is the deciding factor on interior work. Our comparison of FSK vs PSK facing covers the full decision matrix by application.
What tape should be used on white PSK duct wrap?
Pressure-sensitive seaming tape matched to the facing, typically 96 mm wide for duct wrap. Johns Manville specifies its white PSK seaming tape and a plastic squeegee to press it down. Do not apply tape below -7 C (20 F) or above 54 C (130 F). Seal the longitudinal seam, the 51 mm overlap flap, all circumferential butt joints and any penetration.
Can white vinyl faced insulation be used outdoors?
Only with weather protection, as ASTM C1136 states. UV degrades polypropylene and kraft paper takes up water. Exposed roofs, open-sided structures and outdoor pipe racks need a separate metal or coated jacket. The facing controls vapor from inside the assembly; a weathering layer protects it from outside.
What is the difference between WPSK, WMP-VR and poly-top jacketing?
WPSK is the generic white PSK construction. WMP-VR and WMP-30 are Lamtec trade names with their own published test values, so “WMP-VR equivalent facing” should be answered with a line-by-line datasheet comparison. Poly-top jacketing is the pipe insulation trade term for the same white PP laminate applied to pre-formed pipe sections.
Next step
The name on the drawing is the least reliable part of the order. Send us the construction, the permeance with its test method, the fire classification for the laminate and the roll format, and we will confirm which grade fits and send a matching sample and seaming tape.
