Siga Majrex-200 Vapor Control Membrane


Vapor Control Layers are essential for air-tightness, energy efficiency, and prolonging the life of your home.

Majrex-200 is an interior use Vapor Control Layer and is perfect for use to create an air-tight membrane for climate zones requiring one.

It uses Siga's Hygrobrid technology that establishes airtight layers on the warm side of thermal insulation to prevent moisture build up in wall cavities.  The membrane promotes the direction of vapor drive inward to the interior space, which aids in drying the wall assembly.  This means a dryer wall assembly, and thus more likely to resist mold, rot, and damage.  

Majrex-200 is considered a "smart" high performance vapor control layer, which allows vapor to pass more easily in one direction than the other.  When assembled as recommended, it has a higher permeance to the interior space, which promotes vapor drying from the wall cavity/assembly inward, while having a lower permeance outward, limiting how fast vapor transports into the wall.


SIGA Majrex 200 is a PET fiber-reinforced, modified PE/PP sheet membrane

Hygrobrid® vapor variable, permeable vapor control layer

No adhesive backing

Suitable for containment of blown-in insulation products

Specs & Details

Each roll measures:
59in Wide x 164ft Length
Approximate coverage area: 820sqft

Vapor variability (Perms):
<.097 to ≥4.25

Measuring instructions

To calculate order size for number of rolls needed:

Square footage = (estimated total interior square footage) * (10% overage)

Divide your total estimate by 820sqft/roll to find the number of rolls needed. Always round up to next full roll.
Rough interior room dimensions (Room 1): 15'L x 12'W x 10'H
Calculate the four walls and ceiling ~ approx.:
2*(15x10) + 2*(12x10) + (15x12) = 720sqft

Rough interior room dimensions (Room 2): 15'L x 18'W x 10'H
Calculate four walls and ceiling ~ approx.:
2*(15x10) + 2*(18x10) + (15x18) = 930 sqft

For Room 1 and Room 2 = 1650sqft

Calculate overage:
1650 * 1.1 = 1815sqft needed

Divide 1815sqft by 820sqft/roll = 2.21 rolls
Round to 3 full rolls as order size
Pro Tip: estimated square footage should include all exterior wall surfaces, possibly including walls walls, roof/attic facing ceilings, any wall contours, cut-outs, etc.

Shipping & Fulfillment

Estimated delivery is 5-8 business days from date of order.
Delivery dates will be confirmed upon order confirmation and coordination with freight/carrier service.

See Go Green Home Supply Shipping & Returns Policy for more details on rates and process.

per Roll
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Significantly Better

High-Performance Products

SIGA products are engineered by building science professionals - who are passionate about building better homes to help preserve the environment. The use of SIGA control layer products provides greater comfort to the interior spaces of your home, they save you money and help with better energy efficiency. They also contribute to the longevity of your house by adding integrity to the wall and ceiling assemblies by reducing the risk of damage from water, insects, mold and rot.

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Smart Vapor Membrane

Vapor variable depending on the direction of vapor drive/flow - Majrex 200 is the only directional air/vapor barrier control layer on the market

eco friendly insulation in new homes

Air - Tight

SIGA's tape products seal seams, intrusions, and cut-outs around any openings like windows and doors, providing comprehensive solutions to air sealing challenges

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Easy To Use

Printed grid makes layout and cutting easier and saves time, while the material is dimensionally stable making for wrinkle free instal

Additional product information


SIGA Majrex Smart Vapor Membrane Install Video

Majrex installation should be done in conjunction with other SIGA products for best results.

Rissan-60 Seam Sealing Tape is recommended for sealing most seams in the Majrex projects:

The goal with any interior vapor retarder is to create a continuous layer, without openings/gaps. Complete continuity is the goal - and the more thorough the installation, the better results.

For more SIGA specific installation videos, visit their YouTube channel:

SIGA Majrex Cut Sheet and Quick Install Guide

Care & Maintenance

Full SIGA Air/Vapor System Guidelines document provides the most comprehensive details of the SIGA system - Go Green Home Supply's recommended system air/vapor and water resistive layers.

SIGA Air/Vapor Control Full System Guidelines


SIGA products are covered by a Factory 10-Year Limited Warranty

For more warranty information, please contact:

SIGA 10-Year Limited Warranty