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When building a new house or recladding an old one, the exposed exterior walls provide a unique opportunity to improve the building’s energy efficiency and durability. Adding a well-integrated water-resistive barrier, beefing up the air-sealing, and installing exterior insulation make a building more than a structure; it becomes a high-performance system. Manufacturers of building materials and products used to create this type of enclosure continue to innovate and deliver new products each year. Here’s a roundup of reputable offerings on today’s market.
A water-resistive barrier (WRB) is a thin membrane designed to prevent water from intruding into the wall assembly. When properly integrated with flashing at openings and rooflines, the WRB acts as a drainage plane, channeling water down along its surface, thereby reducing the likelihood of moisture problems like leaks, rot, and degradation. While water-resistant, a WRB must allow water vapor to evaporate, which is where the magic of modern technology is most remarkable.
VaproShield’s WrapShield SA is among the newer offerings in this category. It is a vapor-permeable, self-adhered WRB that does not require a primer. The company says the material goes on easily in cold weather and can remain exposed to the climate and UV rays for six months. In addition to acting as a water barrier, the membrane is approved by the Air Barrier Association of America (AARB). Its installation involves pulling off the clear release film and smoothing the membrane with a roller.
Another new product comes from Georgia-Pacific, maker of DensShield. Their DensDefy Liquid Barrier is a single-component, liquid-applied WRB. Once applied, the fluid film sets to a seamless, durable membrane on exterior gypsum sheathing, wood sheathing, CMU, and concrete walls. It’s spread with a roller or spray in temperatures as low as 25ºF and it cures in temperatures as low as 32ºF. The company sells a suite of compatible liquid flashings and transition membranes to bridge gaps between dissimilar materials.
Builders apply rigid insulation to the exterior surface of a building for added thermal protection, preventing cold bridges from forming at framing members. A continuous, rigid insulation layer keeps walls warm and dry by preventing water vapor from condensing on wood sheathing and studs.
Building codes require continuous exterior insulation in many climate zones; the code specifies the R-value depending on the wall assembly. There several types of exterior insulation options including mineral wool, cellulose, fiberglass, and polymer foams.
FoundationPRO (pictured above) is a product from Progressive Foam Technologies that combines below-grade Neopor foam with a thick, polymeric shell that protects the insulation from UV rays and weed-whacker damage. It is touted as a one-piece solution to cover the exposed area of the foundation while providing needed thermal protection on the exterior face, where it belongs. R-values range from R-5 to R-10. And, according to BASF, their Neopor not only reduces operational carbon, but also demonstrates a substantially lower embodied carbon, meaning less CO2 was released in the creation of Neopor compared to competitive products—based on the Embodied Carbon in Construction Calculator (EC3) tool.
Introduced in 2021, Foamular NGX foam from Owens Corning is an extruded polystyrene (XPS) rigid foam board. The company claims it has a low-global-warming-potential (GWP) blowing agent demonstrating a 90% reduction in embodied carbon. (The manufacturer publishes embodied carbon data in its Product Environmental Footprint Summary.) It was awarded the Manufacturing Leadership Award in 2021 for material science innovation supporting environmental sustainability. The closed-cell foam boards offer a nominal R-5 per in.
DuPont’s new Thermax Non-Halogen Insulation Series has achieved a Living Building Challenge Red List–approved designation. DuPont is the first Class-A polyisocyanurate (polyiso) sheathing manufacturer to phase out the halogenated flame retardants commonly used in building-insulation polyurethane foams. The glass fiber–reinforced rigid boards are suitable for continuous exterior insulation and interior finish systems—in places where they can be left exposed. The manufacturer says the new Thermax qualifies as a low-VOC, HFC-free, and zero-ODP (no chlorine content) material, helping reduce building energy use and the carbon footprint. It’s available in standard 4×8 through 4×12 sheets in thickness of 1/2 to 3 in. with a thermal value of R-7.3 per in.
As a continuous exterior insulation board, mineral wool averages R-5 per in., comparable to foam. Yet mineral fiber adds a fire barrier to the assembly that will not create toxic fumes if the walls should catch fire. The material maintains 90% of its insulating qualities for the product’s life and has a vapor permeance rating of roughly 50 perms. Termites don’t like it. And moisture will not compromise its thermal resistance.
LP WeatherLogic is a new entry to the combined structural sheathing / WRB / air barrier category that is available at builder supply houses carrying Louisiana-Pacific products. WeatherLogic is suitable for walls and roof sheathing. The composite material is ideal for winter construction, when wind, snow, and rain can damage mechanically and fluid-applied membranes. LP makes a compatible seams tape.
DuPont ArmorWall systems incorporate five building enclosure elements into a composite panel. The 5-in-1 product includes the structural sheathing, air barrier, WRB, R-10 to R-21 continuous insulation, and fire retarder. Although primarily designed for commercial use, it offers a high-performance option, especially for homes in the urban-wildland interface zones with high fire hazards. Additionally, ArmorWall sheathing uses insulation components that carry a GWP of 1.
Wall cavity insulation
If you have the opportunity to access your wall cavities, it’s a good time to maximize insulation. Two materials that offer a lot by way of strong R-values per dollar are fiberglass and hemp.
A recent addition to the wall cavity–insulation category is not new but rather improved: Owens Corning’s Pink Next Gen Fiberglas Insulation. The material’s microfiber composition fills cavities without fluffing or compression, cuts cleanly, and eliminates all the negatives associated with traditional fiberglass insulation. My crew is able to remove their hoods, gloves, and even masks to work with Pink without discomfort.
Another old-is-new material is hemp. The U.S. used to grow forests of hemp to make rope, paper, fabrics, parachutes, and even medicines. The Controlled Substances Act of 1970 essentially banned industrial hemp production during the war on drugs. Hempitecture has brought back this old fiber in a big way with its HempWool thermal insulation. This renewable fiber product offers many advantages, most notably a whopping R-7 with just 2-in. thickness; plus no VOCs or other toxins and it’s safe to install without gloves. It is the first and only USDA biobased certified insulation available on the market, and according to the European Industrial Hemp Association, one hectare of industrial hemp can absorb 15 tons of CO2 per hectare.
Invest in the envelope
No matter what you choose to underlie the cladding of your home, think of it as that all-important subcutaneous layer of skin that helps regulate your body temperature by providing insulation, mediating moisture through pores, and acting as a shock absorber to protect muscles from harm. Your home’s skin works precisely the same way. It provides insulation and waterproofing while allowing moisture to evaporate and protecting the structure from wind, rain, and other environmental assaults. The skin is the largest organ of the human body, and your home’s envelope is likewise the most significant structural assembly, which makes choosing products to get it right well worth the effort to ensure the building’s energy efficiency and longevity.
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Fernando Pagés Ruiz is a builder and an ICC-certified residential building inspector active in code development. Photos courtesy of manufacturers.
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