Multi-functional exterior wall separation materials

Adding more multi-functionality to separation layers would improve building performance at lower cost and complexity.

Desired properties
Layer substitution, tunability, and ease of installation.

Deadline for concept summaries: August 31, 2018

Category 2: Multi-functional exterior wall separation materials
Improve building performance while minimizing cost and complexity

Problem statement

Separation materials are used in wall construction to separate exterior from interior environments. Multiple components are generally needed to perform all the “barrier” jobs necessary (air, water, vapor, fire, sound, and thermal). Construction miscues such as reverse lapping of housewraps or water infiltration at fasteners can compromise in-service performance. To the extent that one component can do multiple jobs, other layers can be eliminated, saving on materials, labor, and miscues.

One separation layer can perform multiple functions. For example, gypsum sheathing can be both a fire barrier and a sound barrier. Air barriers can resist air leakage, water penetration, and vapor diffusion while remaining relatively thin and inexpensive. Adding more multi-functionality to separation layers would improve building performance at lower cost and complexity.

Possible approaches

Any solutions that add multi-functionality to separation materials will be considered. Traditional separation materials include board products such as gypsum board, spray-applied products such as fluid-applied air barriers, sheet goods such as building papers and felts, and polymeric water-resistive barriers. Example solutions include waterborne coatings applied with airless spray equipment or by brush/roller to wood and gypsum based sheathing substrates or coated fabric laminates for factory application onto sheathing.

Known approaches not of interest

Unless significant performance/cost breakthroughs or innovative applications can be achieved, the following materials represent known state-of-the-art and are thus not of interest:

  • Common air barriers such as Polymeric housewraps (e.g. Dupont Tyvek), peel and stick membrane products (e.g. Henry Blueskin), and fluid applied products (e.g. Prosoco R-Guard)
  • Factory-laminated sheathing panels (e.g. USG, Huber Engineered Woods), laminated insulation for cement board (e.g. ThermaDry), and other multi-functional wall separation materials that fail to exceed the performance, cost, or innovativeness of existing state-of-the-art solutions

Key success criteria


  • Performs all existing functions (e.g. air barrier, fire resistance, etc.) without adding layers
  • Adds new functionality (e.g. 3D texture for water drainage, acoustic insulation, etc.)
  • Can be easily installed on-site or pre-applied to existing layers (e.g. sheathing) in-factory


  • Materials that provide superior properties such as structural support and wind load resistance
  • Innovative wall assemblies that take advantage of prefabrication and modular construction
  • Ability to “tune” individual properties (e.g. vapor permeance) in the factory or on-site
  • Fire resistance, which is a highly desired property, is being addressed separately (Category 3)

Technical specifications [Cat. 2]: Multi-functional exterior wall separation materials

Property Standard Requirement
Air leakage resistance ASTM E2178 Less than 0.02 L/s/m² at 50 Pa
Water penetration resistance AATCC 127 modified water column test 55 cm water column – 5 hours without water entry through joint or into sheathing
Water vapor transmission ASTM E96 Greater than 10 perms for permeable membrane

Less than 0.1 perms for impermeable membrane

Restrained environmental conditioning ICC ES AC 212, Section 4.7 No cracking or water penetration after structural transverse loading and structural racking, followed by cycles of wetting, drying, and changes in temperature, and water penetration test
Volatile organic compounds SCAQMD Rule 1113 Less than 50 g/L
Sound control

(desired, not required)

ASTM E90, E413, E1332 Increase STC or OITC wall assembly rating by 5 units

(desired, not required)

ASTM E2273 Greater than 90% drainage efficiency
Surface burning

(desired, not required)

ASTM E84 Flame spread less than 25

Smoke developed less than 75

Fire resistance

(desired, not required)

ASTM E119 1 hour rating as free film or as applied coating or laminate to combustible wood-based sheathing or non-rated gypsum sheathing

(desired, not required)


or NFPA 220