日本語
Русский
España
عرب .
PE vs TPU Waterproof Breathable Membranes: Which Underlayment Wins in 2026?
2026-09-30
A contractor replacing the water-resistive barrier on a steel-frame warehouse asked why the two candidate rolls carried different classifications even though both looked like thin grey cloth. The roll marked PE moved vapor through microscopic pores; the roll marked TPU moved vapor through the film material itself. That difference in transport mechanism drives every practical decision that follows, from low-temperature handling to the installed cost per square meter.
Two Membranes, Two Physical Methods
A waterproof breathable membrane must block liquid water and release vapor, and PE and TPU membranes achieve that same end through different physics, so the comparison begins with the film structure rather than the brand or the price.
PE membranes are polyethylene-based microporous films, normally laminated to a spunbond polypropylene or woven carrier. The film contains a network of sub-micron pores: water droplets, which measure around 100 microns, cannot pass through, while individual water-vapor molecules, far smaller, diffuse along the pore network. Because performance depends on that physical pore system, a PE membrane can lose vapor capacity if the pores are blocked, compressed, or creased during installation.
PE: the microporous workhorse
High-density polyethylene films in this class typically deliver a hydrostatic head of 1,000 to 3,000 mm and a water vapor transmission rate of roughly 1,000 to 5,000 g/m2/24h, depending on thickness, pore density, and test method. They are thin, inexpensive, and made in very large volumes, which keeps the square-meter cost low.
TPU: the hydrophilic non-porous film
TPU membranes contain no pores. The polymer absorbs water vapor on the warm face, transports it along a moisture concentration gradient, and releases it on the cold face. Because transport is molecular, creasing, dust, and sealant contact do not locally stop vapor flow. The flip side is that transport requires a humidity difference across the film; when both faces approach saturation, the vapor flow slows considerably.
Measured Performance: PE vs TPU
In head-to-head data review, TPU wins most mechanical properties and PE wins the economics; the right specification depends on which properties the building actually exposes the membrane to.
Four numbers frame the decision before any brand literature is opened.
The table below condenses the comparison to the figures that matter on a typical datasheet review.
| Property | PE membrane | TPU membrane | Edge |
| Hydrostatic head | 1,000-3,000 mm | 8,000-15,000 mm | TPU |
| Vapor transmission (WVTR) | 1,000-5,000 g/m2/24h | 500-4,000 g/m2/24h | Test dependent |
| Elongation at break | 15-50% | 300-600% | TPU |
| Low-temperature flexibility | Brittle near -20 C | Flexible to -30 C or lower | TPU |
| Puncture and tear resistance | Moderate | High | TPU |
| Open exposure on site | 4-12 weeks typical | Longer in many grades | TPU |
| Installed cost per m2 | Low | 2-4x PE | PE |
Figure 1. Relative performance profiles; cost value is inverted, with higher meaning cheaper.
When PE Is the Right Call
For standard wall and roof projects in temperate climates, a PE membrane is the rational default, because it delivers sufficient vapor transmission and water resistance at a substantially lower price.
PE microporous membranes dominate volume use under ventilated rainscreen cladding, behind metal panels, and as roof underlay on low-rise residential buildings. The decisive figure is cost: a PE membrane of comparable gauge typically reduces the underlay material cost by 40 to 70 percent per square meter compared with a TPU alternative.
Choose PE when
- The assembly has a ventilated cavity or drainage plane that handles most incidental water.
- Installation temperatures stay above about -10 C.
- The membrane will be covered by cladding within a few weeks.
- Square-meter budget is the controlling procurement criterion.
Choose TPU when
- Detailing includes sharp corners, complex penetrations, or heavy foot traffic on the exposed membrane.
- Installation happens in winter or at consistently low temperatures.
- Long open exposure is expected before the cladding is fixed.
- The structure will move, and the membrane must stretch without tearing.
When TPU Justifies the Premium
TPU earns its higher price when the membrane must survive rough installation, low temperatures, and structural movement without losing its watertight layer.
A hydrophilic TPU film has no pore system, so creasing, dust, and sealant contact do not interrupt vapor transmission. Elongation at break of 300 to 600 percent means the film stretches around fastener heads and profile edges instead of tearing. In curtain-wall and timber-frame projects where the membrane will be inaccessible after cladding installation, that durability argument often outweighs the material cost.
The trade-off is humidity-dependent. Because TPU transports vapor by molecular diffusion, a prolonged rainy period with saturated conditions on both faces reduces the vapor drive; the designer should evaluate the membrane against the project's real climate instead of assuming TPU always breathes better. European timber-frame construction has been moving toward polyurethane-based underlays, a trend visible in the membrane hall at BAU 2025, where Aotelong presented its latest underlay membranes.
Five Numbers to Check Before You Approve the Datasheet
Specify by documented numbers, not by material family; five datasheet values separate a membrane that performs from one that fails on site.
Compare your review against a manufacturer's published series rather than a single brochure line. The building-envelope program from Jiangsu Aotelong New Materials Co., Ltd. (Aotelong), a Yangzhou-based nonwoven and membrane manufacturer, spans low- and higher-permeance underlay grades; the Aotelong T120 waterproof breathable membrane is a useful mid-range baseline with documented values for hydrostatic head and WVTR in standard wall underlay.
Composite SMS/SMMS Nonwoven Fabrics Manufacturers, FactoryJiangsu Aotelong New Materials Co., Ltd. is China composite nonwoven fabrics manufacturers and laminated non woven fabric factory, offer ...View Product →Locking the Decision Into the Specification
The final choice between PE and TPU belongs in the project specification as a performance requirement, not as a brand preference.
Write the required hydrostatic head, WVTR, elongation, and low-temperature flexibility into the spec, then let suppliers bid materials they can document. For most mid-rise cladding and low-slope roofing, PE will win the tender. For high-access-risk, winter-built, or movement-heavy structures, TPU will justify its premium.
The breathable outer layer works together with the vapor control layer on the warm side of the insulation; choosing a highly vapor-open membrane without checking the interior barrier can create the condensation problem the design was meant to avoid. Our summary of how different types of waterproofing in construction behave in practice explains why the interior vapor barrier matters.
For projects that need more drying potential than an economy underlay, the Aotelong T180 waterproof breathable membrane is a useful higher-permeance reference point before the specification moves to premium TPU films.
Composite SMS/SMMS Nonwoven Fabrics Manufacturers, FactoryJiangsu Aotelong New Materials Co., Ltd. is China composite nonwoven fabrics manufacturers and laminated non woven fabric factory, offer ...View Product →Frequently Asked Questions
The most common specification questions, answered with the same data review process used above.
Is a TPU waterproof breathable membrane always better than a PE one?
No. TPU is mechanically superior and lasts longer under abuse, but PE membranes deliver adequate water resistance and vapor transmission at 40 to 70 percent lower cost. For well-detailed, temperate-climate projects, PE is usually the economically correct choice.
Can I substitute PE for TPU on a project that specified TPU?
Only if the PE product matches every performance requirement in the spec, including elongation and cold flexibility. If the spec was written because of winter installation or high building movement, a standard PE film will likely fail the mechanical checks.
Why do two similar membranes show very different WVTR values?
WVTR depends strongly on the test method. Dry-cup and wet-cup methods measure different humidity conditions, so a membrane can report 1,500 g/m2/24h under one standard and 3,000 g/m2/24h under another. Always compare figures measured by the same standard.
Does a higher WVTR always mean less condensation risk?
Not by itself. The breathable membrane removes vapor only when a vapor pressure difference exists across it. If the warm-side vapor barrier is missing or leaky, no outer membrane can compensate, and interstitial condensation can still develop inside the insulation.
© 2024 Jiangsu Aotelong New Materials Co., Ltd.
-
+86-0514-87539226 (Tel)
+86-514-87539218 (Fax)
Tiancheng Road, Shatou Industrial Park, Guangling District, Yangzhou City, Jiangsu.