PERM-A-BARRIER® VPL Low Temperature

Fluid applied vapor permeable air barrier membrane for low temperature applications

Product Description

PERM-A-BARRIER® VPL Low Temp (LT) is a two-component, fluid-applied, acrylic membrane that cures to form a resilient, monolithic, fully bonded elastomeric sheet when applied to construction surfaces at temperatures between 20 °F (-7°C) and rising to 60 °F (16°C).

PERM-A-BARRIER® VPL LT membrane provides superior protection against the damaging effects of air and liquid water ingress on building structures. The product creates a solid barrier against air infiltration and exfiltration, which minimizes associated energy loss and condensation problems.

PERM-A-BARRIER® VPL LT membrane is vapor permeable for wall assemblies requiring this “breathable” characteristic. As a vapor permeable membrane, this product permits the transfusion of water vapor that may otherwise condense in the wall structure; but is impermeable to liquid water, which allows the material to act as a water drainage plane.

Drawings are for illustration purposes only. Please refer to for specific application details.

Product Advantages

  • Fire resistant - meets NFPA 285 as part of various wall assemblies with foam plastic insulation
  • Plasticizer, Phthalate and Halogen-free - safe and environmentally-friendly
  • Air tight - protects against air passage and associated energy losses. Meets new ASTM E2357 standard as required by IECC 2012
  • Vapor permeable - prevents moisture from being trapped in the wall cavity by allowing walls the ability to dry
  • Low Temperature - can be applied at temperatures as low as 20°F (-7°C) 
  • Fully bonded - transmits wind loads directly to the substrate
  • Seamless - continuous membrane integrity with no laps
  • Damp surface tolerant - can be applied to damp-to-touch surfaces
  • Strong adhesion to common construction substrates such as wood, block, concrete, OSB, gypsum sheathing and metal
  • Compatible with PERM-A-BARRIER® Flashing Systems

Principal Applications

Vapor permeable air barrier for new and remedial commercial and residential applications where application temperatures are between 20 °F (-7 °C) and 60 °F (16 °C):

  • Concrete block walls with brick veneer or pre-formed cladding panels
  • Steel or wood stud walls with exterior gypsum sheathing, brick veneer or pre-formed panels, plywood and OSB

System Components



PERM-A-BARRIER® VPL LT membrane is a two-component product consisting of PERM-A-BARRIER® VPL LT Part A and PERM-A-BARRIER® VPL LT Part B, which is a flammable, solvent-based material. The Volatile Organic Compound (VOC) content of the mixed product as applied, is equal to 71.1 g/L.

Refer to product label and Safety Data Sheet before use. All users should acquaint themselves with this information prior to working with the material. Carefully read detailed precaution statements on the product labels and SDS before use.

SDSs can be obtained from our web site at or by contacting us toll free at 866-333-3SBM (3726).

Surface Preparation

All surfaces must be sound and free from spalled areas, loose aggregate, loose nails or screws, sharp protrusions or other matter that will hinder the adhesion or regularity of the membrane installation. The surface must also be free from frost, dirt, grease, oil or other contaminants. Clean loose dust and dirt from the surface by brushing or wiping with a clean, dry cloth.

Concrete and Other Monolithic Cementitious Surfaces

Surface irregularities greater than 1/4 in. (6 mm) across and/or 1/8 in. (3 mm) in depth should be pre-treated with BITUTHENE® Liquid Membrane or repaired with a lean mortar mix or nonshrinking grout. Remove concrete form lines and any high spots greater than 1/8 in. (3 mm) in height to ensure uniform surface. On highly dusty or porous substrates it may be necessary to apply a scratch coat of PERM-A-BARRIER® VPL membrane prior to spraying to full thickness.

PERM-A-BARRIER® VPL membrane may be applied to green (minimum 3 day cure time) concrete or over damp to-touch surfaces Remove any visible water prior to application.

Concrete Masonry Units (CMU)

The CMU surface should be smooth and free from projections. Strike all mortar joints full and flush to the face of the concrete block. Fill all voids and holes, particularly at the mortar joints, with a lean mortar mix or nonshrinking grout. Alternatively, a parge coat (typically one part cement to three parts sand) may be used over the entire surface.

Exterior Sheathing Panels

PERM-A-BARRIER® VPL LT membrane may be applied directly to exterior sheathing panels such as exterior drywall, plywood and oriented strand board (OSB) and glass faced wall boards. To avoid deflection at the panel joints, fasten corners and edges with appropriate screws. Fasteners should be driven flush with the panel surface (not counter sunk) and into the framing system in accordance with the manufacturers recommendations. Completely fill the sheathing joint with S100 Sealant. Then install a scratch coat (approx. 15-30 mils) of the sealant with a margin trowel or similar onto the face of the sheathing approximately 1 in. (25 mm) on each side of the sheathing joint, ensuring the edges are tapered to prevent shadowing of the spray application. Once the sealant is tack free, the PERM-A-BARRIER® VPL LT membrane may be applied.


Detailing should be completed prior to applying the full coverage of PERM-A-BARRIER® VPL LT membrane. The field application should completely cover the detail areas to provide a continuous membrane.

For a complete description and instructions on individual details, consult the separate detail sheets found on our web site at

Transitions to beams, columns, window and door frames, etc. should be made with a strip of PERM-A-BARRIER® Detail Membrane, PERM-A-BARRIER® Aluminum Flashing or PERM-A-BARRIER® Wall Flashing product. Only PERM-A-BARRIER® Wall Flashing membrane can be used for through wall flashing applications or under masonry units. Optimum adhesion will be achieved when the membrane or flashing is lapped onto the cured PERM-A-BARRIER® VPL LT product. As soon as the product is cured (approximately 24 hrs after application at 50% R.H, 32 °F), it is ready to accept self-adhered membranes or flashings.

A minimum 6 in. (150 mm) wide strip of PERM-A-BARRIER® Detail Membrane, PERM-A-BARRIER® Aluminum Flashing or PERM-A-BARRIER® Wall Flashing product should be installed and centered over all outside corners ensuring that all horizontal laps shed water.

Installation of the self-adhered flashing at corners may be installed prior to the PERM-A-BARRIER® VPL LT application in accordance with the applicable data sheet and installation instructions or after the PERM-A-BARRIER® VPL LT product has cured. Avoid installing S100 Sealant under self-adhered flashing. Best practice would be to install corner flashing prior to detailing exterior sheathing joints with S100 Sealant.

Any gaps around penetrations should be grouted solid or caulked with BITUTHENE® Liquid Membrane or a polyurethane sealant prior to the PERM-A-BARRIER® VPL LT application. Refer to GCP standard penetration detail for PERM-A-BARRIER® VPL.

Membrane Application

PERM-A-BARRIER® VPL LT Part A (4 gallon) and PERM-A-BARRIER® VPL LT Part B (0.5 gallon) products must be mixed together prior to product application. It is recommended that the two components be mixed thoroughly for 5–10 minutes to ensure proper dispersion. It is recommended that mixing equipment be intrinsically safe.

PERM-A-BARRIER® VPL LT product can be installed through a spray application. It is recommended that pumping equipment be intrinsically safe. It may be applied by roller, however spray application is the preferred method. If applying the product by roller, multiple material passes may be necessary to ensure that the required wet thickness is achieved.

Refer to equipment manufacturer’s instructions for handling flammable and combustible materials. Follow OSHA bonding and grounding procedures for flammable and combustible materials.

Contact GCP for further details of local applicators, application techniques and spray equipment.

Application Temperature - PERM-A-BARRIER® VPL LT membrane has the ability to be sprayed or rolled at temperatures as low as 20 °F (-7 °C) provided there is no frost or condensation on the substrate. The temperature must remain above 20°F (-7 °C) until the product completely dries.

Thickness Control

Application thickness is controlled in vertical applications by marking the area and spot-checking the thickness with a wet film thickness gauge. Swipe marks on the surface of the PERM-A-BARRIER® VPL LT membrane are acceptable as long as the minimum thickness is maintained.


PERM-A-BARRIER® VPL LT membrane is dry to touch and can be overcoated within 4 hours under normal conditions (50% R.H, 32 °F). The product dries through in 24 hours at normal conditions (50% R.H, 32 °F). Drying and skinning times may vary depending on temperature, humidity and surface conditions.

Coverage Rates

PERM-A-BARRIER® VPL LT membrane is typically applied at a minimum thickness of 44 mils wet. The theoretical coverage rate (not including waste) at a thickness of 44 mils is approximately 37 ft2/gal to reach a 25 mil dry thickness.

Coverage may vary depending on application technique and may be reduced over rough and uneven substrates. The applicator goal should be a continuous membrane at a thickness of 68 mils wet, adjust coverage rate accordingly.

Application of Insulation and Finishes

PERM-A-BARRIER® VPL LT product is not suitable for permanent exposure. Insulation boards may be installed after it has fully cured. If the insulation or exterior finish cannot be applied within 6 months of the PERM-A-BARRIER® VPL LT application, some form of temporary protection (such as tarpaulins) should be used to protect the product from the effects of sunlight. Installation of insulation boards can be accomplished by using compatible mechanical fasteners or, solvent free insulation adhesive.


Tools and equipment are most effectively cleaned with using a dish soap mix of 1 oz/per gallon water.(i.e. Dawn® Ultra-2x Active Suds). This method works before material is cured. Mineral Spirits can be used on cured material on tools to remove. Flush system before its used to remove the light oil which was left from factory testing. PERM-A-BARRIER® NPL is a water base product, so soapy water mix to prime pump is best (1-2 gallons). For short shutdown periods, material can remain in equipment and delivery lines. Material should not be left in system for any period of time if temperatures are expected to drop below 40 °F (4 °C). Normal flushing of system use soapy mix until clear/clean mix is observed (stored at 40 °F or above).

** Long-term storage, after system has been cleaned with soapy water mix several options can be used. Procor Flushing Oil, Graco®- Pump Armor™, Titan™-LS-10 Liquid Shield™ Plus or Mineral Spirits can be pumped through system. Be sure to always pump soapy water mix prior to priming system with PERM-A-BARRIER® VPL LT.

Storage and Handling

PERM-A-BARRIER® VPL LT Part A product should be stored under cover in original sealed containers above 40 °F (4 °C) and below 90 °F (35 °C). The shelf life is 12 months in unopened containers.

PERM-A-BARRIER® VPL LT Part B product should be stored under cover in original sealed containers above 20 °F (-7 °C) and below 70 °F (21 °C). The shelf life is 12 months in unopened containers.

PERM-A-BARRIER® VPL LT (mixed, final product) should be stored under cover in containers above 20 °F (-7 °C) and below 70 °F (21 °C). Once PERM-A-BARRIER® VPL LT Part A and PERM-A-BARRIER® VPL LT Part B have been mixed together, the shelf life is 4 weeks and the unused mixed product must be properly disposed of after this time period.

PERM-A-BARRIER® VPL LT is always sold as a system (Part A + Part B together) as 6 gal kit. Part B alone is not available to sell.

Store opened containers with plastic protective liner covering the material.


PERM-A-BARRIER® VPL LT membrane should not be used in areas where it will be permanently exposed to sunlight, weather or traffic. Maximum UV exposure period is 6 months. For indirect or intermittent UV exposure applications, refer to PERM-A-BARRIER® VPL50RS UV Stable.

Do not apply PERM-A-BARRIER® VPL LT membrane in wet weather. The product should not be applied if rain or snow is expected within 24 hrs.

PERM-A-BARRIER® VPL LT Part A product should be kept from freezing as it is subject to freezing at temperatures below 32 °F (0 °C).

Finished and exposed surfaces should be protected from overspray.

PERM-A-BARRIER® VPL LT product should be installed over S100 Sealant at exterior sheathing panel joints only.

PERM-A-BARRIER® VPL LT membrane should not be used in waterproofing applications in hydrostatic condition.

PERM-A-BARRIER® VPL LT product is not compatible with petroleum solvents, fuels and oils, materials containing creosote, pentachlorophenol or linseed oil. It has a maximum in-service temperature of 160 °F (71.1 °C).The shelf life is 9 months in unopened containers.

Physical Properties

Property Typical Value Test Method
Color Green  
Thickness 44Mils Wet Film
25Mils Dry Film
Solids content by volume 59% (approx.)  
Drying time @ 50% R.H., 68°F1 4 hours - tack free
24 hours - fully dry
Water resistance of in-place membrane Pass ASTM E331
Air permeance <0.0001 cfm/ft2 @ 75 Pa ASTM E2178
Assembly air permeance Pass ASTM E2357
Water vapor transmission 20 perms ASTM E96 - Method B
Pull adhesion to glass-mat faced gypsum sheathing2 30 psi ASTM D4541
Pull adhesion to concrete 100 psi ASTM D4541
Elongation 250% ASTM D412 - Die C
Nail sealability Pass ASTM D1970
Low temperature flexibility Pass at -20°F (-29°C) ASTM D1970
Wall assembly fire test Pass as part of various wall assemblies with foam plastic insulation3 NFPA 285

1. Drying and skinning times may vary depending on temperature, humidity and surface conditions. 
2. Failure occurs when glass facing pulls away from gypsum core Lab value, field results may vary. 
3. Specific wall assemblies are available at | North America customer service: 1-877-4AD-MIX (1-877-423-6491)

We hope the information here will be helpful. It is based on data and knowledge considered to be true and accurate, and is offered for consideration, investigation and verification by the user, but we do not warrant the results to be obtained. Please read all statements, recommendations, and suggestions in conjunction with our conditions of sale, which apply to all goods supplied by us. No statement, recommendation, or suggestion is intended for any use that would infringe any patent, copyright, or other third party right.

Bituthene and PERM-A-BARRIER are trademarks, which may be registered in the United States and/or other countries, of GCP Applied Technologies Inc. This trademark list has been compiled using available published information as of the publication date and may not accurately reflect current trademark ownership or status.

© Copyright 2018 GCP Applied Technologies Inc. All rights reserved.

GCP Applied Technologies Inc., 2325 Lakeview Parkway, Suite 475, Alpharetta, GA 30009, USA
GCP Canada, Inc., 294 Clements Road, West, Ajax, Ontario, Canada L1S 3C6.
This document is only current as of the last updated date stated below and is valid only for use in the Canada. It is important that you always refer to the currently available information at the URL below to provide the most current product information at the time of use. Additional literature such as Contractor Manuals, Technical Bulletins, Detail Drawings and detailing recommendations and other relevant documents are also available on Information found on other websites must not be relied upon, as they may not be up-to-date or applicable to the conditions in your location and we do not accept any responsibility for their content. If there are any conflicts or if you need more information, please contact GCP Customer Service.

Last Updated: 2024-06-21