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Expert Exchange

Materials for High-Performance Building Envelopes

A roundup of newer products being adopted by today’s green building–minded pros

HempWool from Hempitecture is among the more cutting-edge products used in high-performance building envelopes.

EDITOR’S NOTE: This post is part of the Expert Exchange series, an editorially directed and expert-driven platform for information and discussion around leading-edge building science principles and projects. The fourth quarter topic—made possible with support from our sponsor*, Rockwool—is “Choosing Products and Materials for a Green Home.” The series will culminate with a webinar panel discussion among contributing experts on Dec. 7 at 6pm ET. Click to register.

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.

Water-resistive barriers

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.

Georgia-Pacific’s new WRB can be roller- or spray-applied.

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.

Exterior insulation

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 exterior insulation

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. 

Foamular NGX insulation

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.

Theramax exterior insulation board

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.

Rockwool exterior insulation
Rockwool Comfortboard 80 is a rigid stone wool board designed for continuous insulation applications. A non-structural sheathing product, it provides increased thermal performance in 4 in. and 5 in. thicknesses, providing thermal performance up to R-21 for building envelopes.

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.

Structural sheathing

LP WeatherLogic exterior insulation
LP WeatherLogic water-resistive panels are available in 4-ft. nominal widths and 8-, 9-, or 10-ft. lengths.

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.

PINK NextGen insulation

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.

*Sponsors are not offered the opportunity to review articles before publication or to edit our authors’ words.


Fernando Pagés Ruiz is a builder and an ICC-certified residential building inspector active in code development. Photos courtesy of manufacturers.


  1. user-5946022 | | #1

    If one of these manufacturer's would sell a continuous slab to wall insulation SYSTEM that includes an effective termite barrier, they will probably have a product that takes off beyond their expectations.

    While mineral wool offers the benefit of "Termites don't like it", it offers neither a barrier nor a system for below grade to slab to wall continuous insulation.

    It is also refreshing to see some other mfg offering systems alternatives to Zip - nothing wrong with Zip, but competition is great.

  2. david_king | | #2

    It would be helpful to see a list price per square foot for these products.

  3. Expert Member
    KOHTA UENO | | #3

    "As a continuous exterior insulation board, mineral wool averages R-5 per in., comparable to foam."

    Exterior Rockwool is great, but it takes a hit on R-value relative to the foam plastic insulations--closer to R-4 than R-5.

    ROCKWOOL Comfortboard® 80
    Thermal resistance R-value / inch @ 75ºF - 4.2 hr.ft2.F/Btu

    ASTM C518 (C177) R-value / inch @ 75ºF - 4.3 hr.ft2.F/Btu

    1. Expert Member
      Michael Maines | | #8

      Kohta, EPS is also R-4/in, XPS degrades to about R-4.2/in and polysio, depending on the application, is roughly R-5 to R-5.5/in once the blowing agents have been displaced by air. So although the numbers are off, mineral wool still compares reasonably well to common rigid foams.

  4. [email protected] | | #4

    Regarding hemp, the article states:
    "This renewable fiber product offers many advantages, most notably a whopping R-7 with just 2-in. thickness.."

    Is R 3.5 per inch considered a big number?

    1. deucevantage | | #5

      Ya think? Touting these products without any price context is tantamount to advertising or ‘build pornography.’ We are all paid subscribers; please treat us like working professional adult custom builders who have to care about price/ more articles like this unless it includes pricing , please. And don’t trot out that ole reliable, ‘we can’t talk about prices because it varies so much between regions’. But manufacturers wholesale prices don’t, and regardless, just pick up phone and price in your market, use that as a benchmark and report relative price differences as a per cent age. That saves every single reader from assembling these cost comparison themselves. Without such information these articles simply aren’t helpful, just mildly entertaining.

      1. Expert Member
        Michael Maines | | #9

        But prices do vary considerably between regions, as well as between manufacturers and over time. Any prices included would soon be criticized for being outdated. You can't just call up a manufacturer and get their wholesale pricing; believe me, I've written about insulation and that's not how it works. If you need to know pricing for niche products like these, contact your local supplier.

        The purpose of articles like these is to make people aware of products they might not already know about, not to make it easy for you to value-engineer your specific project.

        1. deucevantage | | #14

          Michael - totally get that prices vary, and that manufacturers aren’t falling over themselves to allow builders to make facile price comparisons, but the role of a journal like this should be to cut through that and deliver actionable information for subscribers and precisely that-save us time ! What’s the point of knowing about more unobtainium though? As for criticism Re ‘out of date’ prices, agreed, prices change but they generally change in tandem. RELATIVE prices don’t change that much . Rockwool will never be cheaper than fiberglass, but where will hemp wool fall Re these known products? That’s not a theoretical or minor question Re new products, it’s a central question. If you can’t obtain a product, or it costs too much, you aren’t going to use it, and if you aren’t goign to use it, why learn about it? There are hundreds of ‘cool’ commercial products that . Builders can only dream about using. NB- cost is central to the whole pretty good house movement, so I know you ‘get’ this.

      2. jkumon | | #12

        Agreed. Also, the manufacturers trot this stuff out and aren't really forthright with when they are actually available. It's important to pin these reps down who are providing the information for these articles and get real information about availability. If they don't provide it, they don't get put in the article, that simple. Either they have it, or they don't. Because these articles are behind paywalls, it would be really helpful to have rep information, etc, because I've found that most lumber yards have no idea how to get these newer products and you have to go directly to the manufacturers and then shuttle that back down. Otherwise, these types of articles amount to a long list of "unobtainiums".

      3. user-7513218 | | #17

        Sometimes prices are readily available, and we add these to the articles. Sometimes, it’s tough to obtain pricing because the manufacturers will not provide a price and refer you to their distribution network. The salespeople do not have retail prices at the distribution level either and direct you to supply houses. At the supply house, they ask for your account – if you don’t have one, it’s almost impossible to get a “quote.” While the post features a photo of one product in the line, the manufacturer often has several sizes and types. Even with pricing, each item must include a list costing various sizes and thicknesses. However, you will find a link you can click on to obtain information every time. For example, click on DensDefy, which takes you to the manufacturer’s website. Find the product. Click on the “where to buy” tab on the upper right-hand side and add your zip code. I get Home Depot. When I go to Home Depot, they do not sell DensDefy. So, I called the manufacturer and found it only sold through builder supply houses, back to needing an account. Thus, it happens on many of the more advanced, exceptional products.
        On the other hand, click on the link for HempWool and come to a beautiful website with a “buy” tab right up front – no fishing required. However, you must click through several choices and add all kinds of information before receiving a quote. Pricing can become complex when costing building materials not sold at popular outlets.

    2. deucevantage | | #6

      Hemp is a neat product and I wish them well; but at this point they are not producing at scale so price is not competitive, and most concerning, there is no fire retardant and this stuff is simply kindling.

      1. Expert Member
        Michael Maines | | #10

        Hemp has very high levels of natural silicates that work like the borate additives in cellulose and wood fiber insulation as a fire preventative. The first step to market adoption is making the market aware you exist. If we only shared the products everyone is already using, how beneficial would that be?

        1. deucevantage | | #13

          Michael- I may have saved a sample I bought a few months ago here I believe-I will take it outside this weekend and put a flame to it to test that hypothesis-regardless, the rating agencies believe this is a flammable product right now….I don’t understand why they haven’t gotten borate etc into their product by now. That said, I am impressed mold doesn’t love to grow on hemp despite its being ‘organic’

          Well it appears Belinda Carr already did the wing nut test on this !…..hmmmm……
          Hardly a ringing in endorsement Re flame test…..

          1. Expert Member
            Michael Maines | | #15

            There are different types of hemp insulation. I don't have first-hand experience with any of it but I have researched hempcrete, made with the bast fibers of the plant, and it is fire resistant. For what it's worth, spray foam and rigid foam are also flammable; I have caught XPS on fire several times when soldering pipes next to it.

    3. user-7513218 | | #16

      R3.7 for an inch of Hempitecture is remarkable because it represents the highest R-value for commercially available hemp insulation. Foams offer higher values at the outset but also lose R-value over time. Hemp stays at R-3.5 (or R-3.7) for its entire service

  5. deucevantage | | #7

    Hard to believe you didn’t mention TimberHP wood fiber insulation set to start selling in late 2022.

    1. Expert Member
      Michael Maines | | #11

      We are all looking forward to the time that they actually start producing, which has been pushed back repeatedly from their initial goal of being on market in early 2020. Fernando's article is about products currently available, as noted in his introductory paragraph: "Here’s a roundup of reputable offerings on today’s market." I would have liked to see currently available wood-fiber products mentioned, such as Gutex and Steico, but they are not new to the market so they also don't fit the stated goal of the article.

      1. user-7513218 | | #18

        TimberHP has an exterior sheathing to debut in the market in late 2023. I will write about it then. The R-value is about the same as hemp, made with wood fiber and polymeric diphenylmethane diisocyanate (pMDI), the adhesive used in OSB. I am curious to find out how wood pulp becomes hydrophobic. It's too bad it does not provide a braced wall, too. Besides the wood content, I wonder what you gentlemen find most appealing about this material?

        1. Expert Member
          Michael Maines | | #19

          In talking with folks from Timber HP, Gutex and Steico, I learned that the hydrophobic quality is mostly from paraffin additive. ( Rigid wood fiber is mainly a 1:1 replacement for exterior rigid foam, with the added advantages of being easier and healthier to work with, being vapor-open which usually makes assemblies more resilient, and it's a carbon-storing material instead of a carbon-intensive material.

          MSL amkes Sonoclimate Eco4, a wood fiber structural sheathing, somewhere between OSB and other rigid wood fiber.

          1. user-7513218 | | #21

            Thank you.

        2. Expert Member
          KYLE WINSTON BENTLEY | | #20

          Without having tested it, nor having it in hand, I think the promise of wood fiber insulation lies in the mixture of the following

          0. Vapor profile
          1. Ease of installation
          2. Mass properties
          3. Ease of handling / cutting
          4. Sustainability
          5. Market competition

          I'm not under any illusion that it's going to be cheap, though I'd love to be surprised. I haven't see nthe tech doc, but I'm hoping that it's much more stiff than mineral wool, even if it has a tiny bit of elasticity. It's carbon negative, and there's not as much concern about the right ratios of interior:exterior insulation when the vapor profile is open in both directions.

  6. user-7061227 | | #22

    I was just quoted $32,000 to install (excluding the material) 2 x 2" of rigid foam board continuous insulation on approx 4,000 of wall on my 1970s cape colonial. That is insane. Nobody in CT understands the purpose or methods of the foam and so essentially they make it cost prohibitive.

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