Isoflect is not Isoflex
Published on 01.03.2026 · Isoflect Insulation technical team
Two names that sound almost identical, two different things. If you arrived here searching for "Isoflex", you were searching for something else. And if what you actually wanted was Isoflect, a search for "isoflex" does not lead you to us — it leads you to other manufacturers, in other product categories.
The name says everything, if you read it syllable by syllable
ISO · FLECT
FLECT comes from the Latin flectere — "to turn". From the same word comes reflectere: to turn back. Hence, in Romanian: reflectare, reflectivitate, reflectiv (reflection, reflectivity, reflective).
The name describes the mechanism of the product precisely. An Isoflect membrane turns thermal radiation back towards its source. It does not slow it down, as a conventional insulating material does — it turns it back. The name is not a word invented to sound technical; it is a description of the physical phenomenon on which the product is based.
The stress falls on the second syllable: iso-FLECT.
ISO · FLEX
FLEX comes from flexibilis — "flexible". It describes a mechanical property: the material bends without breaking.
This is a real and useful quality for many products. It has, however, no connection whatsoever with thermal radiation. A material may be perfectly flexible and entirely transparent to radiant heat. Flexibility reflects nothing.
Herein lies the entire difference: one name describes what the product does with heat, the other describes how it behaves when bent.
"Isoflex" means, in practice, almost anything
The name does not belong to a single manufacturer and does not designate any particular category. In public listings, it can be found on products that bear no relation to one another:
- ISOFLEX-PU 500 (Isomat, Greece) — a single-component liquid polyurethane waterproofing product for flat roofs and roofs. It is neither a membrane nor a reflective product.
- ISOFLEX NBU 15, ISOFLEX TOPAS, ISOFLEX PDL 300 A (Klüber Lubrication, Germany) — special greases for bearings and machine-tool spindles. Industrial lubricants.
- Isoflex Alu LP Light, Isoflex Alu-PZ — polyethylene vapour barrier films with a metallised surface, sold in Romania through retail and distribution.
A liquid waterproofing product, a bearing grease and a polyethylene film bear the same name. This indicates something important: "isoflex" does not identify a technology. It is a combination of syllables used in industries that have no connection with one another.
"Isoflect" identifies a technology: the reflection of thermal radiation.
Yes, the ranges look similar. No, the products are not equivalent
The confusion does not arise solely from pronunciation. It also arises from the fact that, within the membrane category, the products look similar on the shelf: a roll, a glossy film, a metallic appearance, packaging with specifications. For this reason, the comparison must be made on the basis of data sheets, not appearance.
All the values below are taken from the data sheets published by retailers and manufacturers, without interpretation. The comparison is made within the same family: interior vapour barriers.
Isoflex films in public listings
| Isoflex Alu LP Light | Isoflex Alu-PZ | |
|---|---|---|
| Declared material | air-bubble polyethylene, metallised layer | polyethylene with a metallised surface |
| Mass | 110 g/m² | 55 g/m² (±10%) |
| Thickness | 3 mm | not declared |
| Sd value | 100 m | over 100 m |
| Declared emissivity | — | — |
| Declared reflectivity | — | — |
| Declared function | vapour barrier, interior | vapour barrier, interior |
g/m²: the weight of one square metre of product. What this means →Sd (m): the extent to which the membrane resists the passage of vapour, expressed as an equivalent air layer thickness; high Sd = vapour barrier, low Sd = diffusion membrane, which allows vapour to escape. What this means →Emissivity: an emissivity of 0.05 means that the aluminium face radiates only 5% of the heat that an ordinary surface would radiate, and therefore does not give off heat by radiation. The lower it is, the better. What this means →
Reflectiva membranes from Isoflect
| Reflectiva Multistrat | Reflectiva Gold | |
|---|---|---|
| Declared material | pure aluminium on one face, laminated onto bubble film | pure aluminium on both faces |
| Mass | 175 g/m² | 460 g/m² |
| Thickness | 5 mm | 10 mm |
| Sd value | — | 190 m |
| Declared emissivity | 0,05 | 0,05 |
| Declared reflectivity | 95–97% | 95–97% |
| Declared function | reflective membrane and vapour barrier, interior | reflective membrane and vapour barrier, interior |
Reflectivity: the proportion of the radiant heat reaching the foil that is sent back. What this means →
Placed side by side, the figures show two things.
The first: mass. 55 and 110 g/m² compared with 175 and 460 g/m². From one and a half times up to eight times more material per square metre. The difference is not one of marketing; it is one of quantity of material.
The second, and more important: what is declared. The Isoflex data sheets declare Sd and mass — nothing more. They declare neither emissivity nor reflectivity. The Isoflect data sheets declare both values.
This is not a formal observation. A membrane that does not declare its emissivity cannot be included in a radiant heat transfer calculation. You can install it, but you cannot account for it in a calculation. And if you cannot account for it, you have no means of demonstrating what contribution it makes to the build-up.
Metallised and pure aluminium are not the same thing
Metallisation means depositing a very thin layer of metal on the surface of the polyethylene film. It is an inexpensive, rapid process, appropriate for the declared purpose of these products: a vapour barrier with a glossy surface.
Reflectiva membranes use pure aluminium, laminated onto the polyethylene substrate. For this reason, they can declare an emissivity of 0.05 and a reflectivity of 95–97% as design values, not as commercial statements.
The two products occupy different positions in the market: metallised films are located in the entry-level price segment of the category, where a vapour barrier with a metallic appearance is purchased. Isoflect does not compete there and does not attempt to compete there. Our products are designed to form part of a calculated system, not to be the cheapest roll on the shelf.
What this means for you, in concrete terms
If you require a basic interior vapour barrier, a metallised film performs the task for which it is sold. We have no objection to this.
If, however, you are concerned with the radiant component — in summer, the heat that enters through the roof covering; in winter, the heat that escapes by radiation — then you require a product that declares emissivity and reflectivity and that is designed to work within a build-up, with an air layer and with insulation. This is the purpose of System 10, in which the Reflectiva membranes work together with the Wolle thermal insulation fibre across all three heat transfer mechanisms: radiation, conduction and convection.
These are two different decisions, with different budgets and different outcomes. What matters is that you know which one you are making.
How to verify what you have in hand
- The name printed on the packaging: Isoflect. With a T at the end.
- The manufacturer: S.C. Isoflect Insulation S.R.L., CUI RO30340616.
- The technical data sheet: Isoflect membranes declare emissivity, reflectivity, mass and Sd value. If the data sheet does not contain these values, the product is not Isoflect.
- The source: isoflect.de, isoflect.ro and the retail networks in which we are listed.
If you purchased "Isoflex" believing it to be Isoflect, you have not purchased a poor product. You have purchased a different product, for a different function. It is worth knowing this before installation, not afterwards.
Good-faith notice. This article compares product categories and publicly declared values, not impressions. All data concerning the products bearing the name Isoflex originate from the data sheets and listings published by their manufacturers and retailers, reproduced as such. We make no statement regarding the performance of these products beyond what their own documents declare. Prices are list prices at the date of documentation and are subject to change.
Sources: Isoflex Alu LP Light listing (hornbach.ro); Isoflex Alu-PZ listing (megaizolatii.ro); ISOFLEX-PU 500 data sheet (isomat.ro); ISOFLEX NBU 15 and ISOFLEX PDL 300 A data sheets (klueber.com); Reflectiva Multistrat and Reflectiva Gold data sheets (isoflect.de).
Not sure which Isoflect product suits you? See isoflect.de or open the package configurator to find out exactly what you need and in what quantity.