Ventia Iron Roof & Wall Underlay is a high-performance, synthetic building membrane imported and supplied throughout New Zealand exclusively by EBuilt Ltd (EProducts NZ Ltd).

Developed and engineered in Bielsko-Biała, Poland, by mdm NT—one of Europe’s leading manufacturers of technical building wraps—Ventia Iron represents state-of-the-art building envelope technology. mdm NT operates under a zero-waste manufacturing philosophy, recycling post-production materials to eliminate factory atmospheric emissions. Built for New Zealand's challenging climate, Ventia Iron exceeds the performance standards of conventional kraft paper building underlays, delivering superior durability, moisture control, and weather protection at a cost-effective price point.

Advanced Technical Quality & Material Construction

Ventia Iron is constructed as a heavy-duty, 3-layer microporous membrane:

• Core Layer: A water-resistant microporous polypropylene film that acts as the functional engine—blocking liquid water from penetrating while allowing water vapour to diffuse outward.

• Outer & Inner Layers: High-strength, spun-bonded polypropylene fabrics laminated on both sides. This structure shields the functional inner core against job-site abrasion, tearing, and mechanical damage.

• Physical Profile: Featuring a nominal mass of 120 g/m² and a thickness of 0.5 mm, Ventia Iron balances light weight for easy handling with high mechanical strength (tensile strength of 250 N/50mm MD / 160 N/50mm CD and nail-shank tear resistance of 120 N MD / 160 N CD). This superior tear resistance keeps the membrane intact on windy job sites.

Core Performance Benefits

Exceptional Vapour Permeability & Condensation Protection

Modern homes generate significant internal humidity from living activities. Ventia Iron achieves a water vapour resistance of \(\le 7\text{ MN s/g}\) (comfortably passing NZBC E2/AS1 Table 23 requirements) and an extremely low \(S_d\) value of 0.020 m. With a Lyssy vapour transmission rate of up to 3200 g/m² x 24h, it allows trapped interior moisture to escape freely into the drainage cavity. This active breathability protects internal wall cavities, reduces condensation risks, and safeguards structural timber framing against rot and mould growth.

Class W1 Liquid Water Resistance & High Absorbency

Ventia Iron provides secondary weather protection against wind-driven rain and tile/metal roof leaks, achieving a Class W1 water penetration resistance (\(\ge 100\text{ mm}\) head of water). In roof applications, it features a water absorbency rating of up to 200 g/m², Holding temporary surface moisture until ambient ventilation safely dries the cavity.

All Wind Zones Structural Capability

• Roof Applications: Appraised as a self-supporting roof underlay for pitches from 3° and above across all NZS 3604 Building Wind Zones up to and including Extra High. It spans unsupported up to 1,200 mm between framing supports.

• Wall Applications: Suitable as a stand-alone flexible wall wrap up to Very High wind zones, and up to Extra High wind zones when installed as an overlay over rigid wall underlays.

Fire Retardant Safety

Ventia Iron undergoes rigorous flammability testing to AS 1530.2, achieving a Flammability Index . This meets the surface finish requirements of NZBC Acceptable Solution C/AS2 for suspended flexible fabrics exposed to view in occupied spaces, making it safe for unrestricted residential and commercial use.