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Energy Solutions

Expanded Cork — The Greenest Insulation Material?

All-natural expanded cork boardstock insulation is now available in North America

Expanded cork insulation is available up to 12 inches thick; it can be used much like polyiso.
Image Credit: Amorim Isolamentos
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Expanded cork insulation is available up to 12 inches thick; it can be used much like polyiso. The outer bark of the cork oak tree can be harvested every nine years.
Image Credit: Amorim Isolamentos
A billet of expanded cork coming out of an autoclave.
Image Credit: Amorim Isolamentos
A 40 mm layer of expanded cork insulation resists burn-through for over an hour.
Image Credit: Amorim Isolamentos
An example of cork used as an exterior cladding. This is dramatic, but not an application I particularly recommend--due to cost of replacement.
Image Credit: Amorim

I’m always on the hunt for the latest, most interesting, and most environmentally friendly building materials, and I have particular interest in insulation products — partly because many conventional insulation products have significant environmental downsides. (See “Avoiding the Global Warming Impact of Insulation” and “Polystyrene: Does it Belong in a Green Building?”)

So I was thrilled to learn about expanded cork boardstock insulation made by the Portuguese company Amorim Isolamentos and just now being introduced into the North American market. Francisco Simoes, of Amorim, visited our office in Brattleboro in June and told us all about it.

Familiar to wine drinkers as the traditional bottle-stopper, cork is a natural product made from the outer bark of a species of oak tree that grows in the western Mediterranean region of Europe and North Africa. The bark is harvested after trees reach an age of 18-25 years and it regenerates, allowing harvesting every nine years over the tree’s 200-year life.

In Portugal, the world’s leading producer of cork, these oak trees are federally protected, and many cork forests are certified to Forest Stewardship Council (FSC) standards. Harvesting is done by hand, much as it has for over 2,000 years. While cork oak forests in Portugal are expanding, cork’s market share for bottle stoppers is dropping as plastic stoppers and screw-off caps become more common — motivating the company to look for new markets.

Cork as a building material

I have long been a fan of cork flooring, floor underlayment, and acoustical wall coverings. These materials are made from residual cork that remains after punching cork bottle stoppers from the bark — which consumes only 25% to 30% of the bark.

For cork flooring and these other products, the cork granules are glued together with a binder and then sliced into the finished products.

Expanded cork insulation is quite different. The same cork granules are used, but they are exposed to superheated steam in large metal forms. This heating expands the cork granules and activates a natural binder in the cork — suberin — that binds the particles together. In an in-depth product review about expanded cork insulation in the August issue of Environmental Building News I describe the fascinating history of this process. (It was invented by accident in New York City in the late 1800s).

After producing these large billets of expanded cork, they are sliced into insulation boards in a wide range of thicknesses — in both metric and inch-pound (I-P) sizes. In I-P units, thicknesses from a half-inch to 12 inches are available — with dimensions of 1′ x 3′ or 2′ x 3′.

The material is 100% natural and rapidly renewable as defined by the LEED Rating System. It is durable yet ultimately biodegradable, produced from sustainable forestry operations, and a byproduct from the cork bottle-stopper industry. Though there is significant shipping energy required to bring it here, shipping by ocean-going vessel is relatively energy-efficient. It’s hard to imagine a greener building material.

Cork insulation performance

Expanded cork insulates to R-3.6 per inch. It has a density of 7.0–7.5 pounds per cubic foot and compressive strength of 15 psi (with 10% compression). It is intermediate in its permeability to moisture — with a 40 mm layer having a permeance of 2.2 perms. Although the expanded cork insulation gives off a smoky smell, a test report I examined showed the material to pass France’s stringent requirements for a dozen volatile organic compounds (VOCs) with flying colors. Cork also has superb sound-control properties.

From a fire-resistance standpoint, it meets the European Class E designation (the standard met by other rigid insulation materials) without the need for flame retardants that are used in the most common boardstock insulation products. A 40 mm-thick piece of the boardstock insulation held over a torch will resist burn-through for an 60-90 minutes, compared to less than 10 seconds for expanded or extruded polystyrene, which meets the same Class E designation. (The flawed manner in which we determine fire-resistance properties of materials is the topic for another article.)

Cork insulation has been used as a rigid insulation material for decades in Europe. It is not uncommon to install an 8- to 10-inch layer on exterior walls and a 10- to 12-inch layer on roofs. The first Passive House built in Austria (in 1995) used a 350-mm layer (nearly 14 inches) of the material. It is typically used as an exterior insulation layer, much like polyisocyanurate.

Cost and availability

North American distribution channels are just being set up, so pricing is far from certain. (One U.S. distributor of cork insulation is Small Planet Workshop.) But Simoes told me the price to a distributor will be about $0.70 per board-foot, not including shipping, markups, or the exchange rate. If those mark-ups come to 50%, the cost per board foot would be $1.05 and the cost to achieve R-19 would come to about $5.50 per square foot for cork, vs. $1.10 – $1.60 for polyisocyanurate insulation and $2.00 – $2.25 for extruded polystyrene.

That’s a significant upcharge for cork, but you end up with one of the greenest building materials anywhere. I’m so excited about expanded cork insulation, in fact, that I’m hoping to use it on an upcoming building project later this year.

You can read my full review of Amorim Isolamentos’ expanded cork insulation board at (membership required). You can also visit the company’s website or send an e-mail: [email protected].

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.


  1. albertrooks | | #1

    I'm pretty excited about Cork as insulation also.

    After Francisco left Brattleboro, he came out west to see us at The Small Planet Workshop. We spent a day with him talking about cork, cork buildings and Portugal. Harmony Counsellor had just joined our company that week as Marketing Assistant to help us keep the online store maintained, add new blog items and such. The interesting thing is that she applied for the job while living in Lisbon Portugal. She's seen buildings who's entire facade is only cork, first hand. No siding, just cork. Cool stuff!

    Additionally here is a picture that she took of of a convent door, covered in cork that was built in 1560:

    Quoting Wikipedia on Convent of the Capuchos (where the door is): "The whole building is small.[4] Its windows and doors are coated with cork, the traditional material of Portugal, the last being smaller than a man's height, to induce genuflection." for full text:

    The point being here is that cork is an extremely durable material.

    Harmony started a blog on the subject, and we've started experimenting on how to apply it to exterior sheathing. The exterior plywood sheathing in this application is often the air barrier and puncturing it with a thousand fastener penetrations won't due in my mind... You need to protect the air barrier. In the really poor video that we made (as fun for trading idea's with Mike Eliason of, we began trying double stick tape to apply the 2" and 6" cork to the wall and hold it in place until I applied a 1x4 rainscreen batten. The tape idea worked well and once we get more stock in, we try more experiments and a project. Blog and video here:

    We've agreed to be the cork distributor for the Pacific Northwest, and already are rushing to see if we can fill an order for exterior insulation for an Oregon residential project. I'm hoping that others see the possibility of cork in other regions. Cork is just soooo much better than exterior foam in so many ways. From production, to application, to local Portuguese economy, cork is a winner!

    I'm glad to see that your supporting cork as insulation too. I wish we could grow cork oaks in the US.

  2. Expert Member
    Dana Dorsett | | #2

    Do the math
    In order for something like expanded cork to have any real market penetration or relevance, you first have to figure out how many hectares would need to be under cultivation to garner even 1% of the rigid-insulation market. I suspect the hectares required to cover 10% of the rigid-insulation market is larger than the land area of Spain, (but I could be wrong)- but whatever it is, it's a lot of land, land that may have more important economic & agricultural value.

    This is sort of like the bio-fuel game- stuff often looks good and even economic in the lab doesn't scale to production levels in the real world: An algae farm the size of Texas wouldn't cover more than half the existing US consumption rate of diesel, even at as-yet-unattained (but theoretically possible) solar-conversion efficiencies in algae. Great concept, but nothing approaching a real answer.

    Then there's the not inconsequential price/performance of expanded cork relative to other insulating materials. At 4-5x the cost of iso and more than 10x the cost of cellulose per unit R it will not likely to be cost-rational- people would normally design it out of the larger or higher-R assemblies in favor of cellulose or other renewable fiber insulation. It might be really cool stuff, but for any of it to be effective it first has to be cost effective.

  3. user-1045979 | | #3

    vs. rockwool?
    It looks like an interesting product, but because of cost (5x the cost of rigid? Ridiculous!) I don't see it as a reasonable product.

    I've become pretty interested in rockwool, lately -- specifically comfortboard IS -- which is supposed to be on par with rigid for cost, is vapor permeable, fire-proof (for practical purposes) and is essentially impervious to water, UV, and insects. I don't know about embodied energy or recycling but would love to hear if someone knows.

    Cork seems like a "green" product that would only be used because money was no object and you wanted some novelty product to brag about.
    If cost and availability changed my opinion might as well... it does look like a great product on it's own merits.

  4. albertrooks | | #4

    Daniel, I really like rock wool too...
    Daniel, I really like rock wool too. It has been a favorite because of all of the aspects that you mentioned. The drawbacks are that it has urea formaldehyde in the North American products (it doesn't in Europe) and it takes a lot of energy to make it: MW is exploded basalt, steel slag, and binder all cooked together. It's does take some significant juice to turn that basalt rock to wool fibers, and then into a board...

    The cost of cork appears to be about 30% up from the cost of Comforboard IS (looking at both in small qty's.) We buy and sell both MW and cork, so I'm using our numbers. I like the cork because it will go up much faster than MW and would be a lot more pleasant to work with.

    I'm pegging the price of Comfoboard IS at $0.75BF in no great qty. The cork would run about $0.90/BF in the same qty. I don't buy EPS, XPS etc so I can't comment on what it costs.

  5. albertrooks | | #5

    Single frame vs, double frame

    We've done some math for high R assemblies. It's not 10x time the cost of installed dense packed cellulose. You need to drop the labor and materials of the second frame as you would with any exterior insulation scheme. You can come up with your own numbers. It's an up charge for sure over exterior foam, but foam is really such a poor choice when looked at quality for quality.

    I always puzzel over the fact that we all talk about sustainability and taking steps to protect the environment from continuous stress and degradation, but as soon as a discussion begins on such a benign insulation material as this, it's gets dismissed out of hand as "too expensive", "not scalable" and therefore not of apparent interest.

    I resist the idea that only large scale solutions are worth considering. The optimum situation is a diversity of materials and methods. less foam, more bio based. Note the new ICC's Green Building Codes proposed requirement of 52% bio based building materials. Back to thinking of the "planet as a system" rather than "what's cheapest and easiest on the wall".

    People and their "price choices" are so sad. Sure... $60,000.00 for kitchen cabinets, but not $5000 to $9000 for additional exterior insulation? I suppose if you can't see that far, then you can't convincingly argue in favor of it...

  6. Expert Member
    Dana Dorsett | | #6

    So, what IS the multiplier, then? (reponse to albert)
    You say you've done the math, so let's have it- if not 10x the cost of dense-packed cellulose, what IS the relative cost factor?

    At the costs stated in the article I suspect going beyond ~R20 or so the 100 year or building lifecycle heating/cooling energy savings are more expensive than the current cost of photovoltaics driving air-source heat pumps in most US climate zones (including the intermittent heat pump repair/replacement/repair during the building's lifecycle.)

    While it's a benign product, to have a relevant impact has to be scalable. It's great to put the bottle-stopper scrap to a good use, but the total displacement of less-benign products in the marketplace is going to be well below that of even the scrap-cotton insulation products (currently a sub-1% fraction of the fiber insulation market.) It's great stuff, but ultimately of very modest impact on anything.

    Cellulose is pretty benign and bio-based too , but much more ubiquitous & lower cost, with many more potential feedstocks than are currently being used. Similarly, rice hulls are also a VERY available. low cost, and underutilized bio-based insulating material with far more potential than cork.

    Paying the price for cork would make more sense if it had truly superior qualities relative to other methods. Extravagant spending on kitchen cabinets is no way relevant to spending an extra $10-20K to insulate with cork rather than polyiso or cellulose at equivalent whole-wall R on a high-R house.

    Sure, go ahead and use it if you like, but there's a real long term environmental benefit of going 3-4x the R value for the same cash outlay, even if it meant using non-bio iso (blown with pentane at much lower impact than spray polyurethane or extruded polystyrene). Costs and performance matter, and insulation isn't some luxury item like kitchen cabinets- the cost/performance ratio is relevant.

  7. albertrooks | | #7

    I got 2x?? Response to Dana
    I didn't throw this out there because I wanted to be a little more sure, but... you called me on it :)

    A current project:

    2000 ft2 (2200 ft3) of wall area. We got a dense packed cellulose quote to blow the wall at around $5k+. Add to that the cost of building a "two frame" (for a 10" double stud wall). Fill in your number, the regional framing costs differ.

    Now look at it as a single frame code wall with blown in. I did not get a quote on it but it's not dense packed, but bibbed, has an air barrier at the sheathing layer to Passive House quality and exterior R16 or R20 cork outside. In that qty call the cork cost $0.87/BF. For R16 it's $6900, R 20 it's $8700. If we go with a generous 60% of the blown-in quote, That looks to me like $3000 + $6900 = $9900; or $3000 + $8700 = $11,700. I'm not sure where to value dropping the second frame vs the speed of a standard frame, but there are savings there to take into account. All three scenarios get to R36 or R40. (Cork being about R4/inch.).

    In all, do you agree that it's not 10x cost of cellulose in application? I hesitate to get too strict with the math because costs do vary.

    Perhaps we see value differently. I think the kitchen cabinet argument is valid. We all typically buy based on a value perception. If we didn't, we would not opt for a $60k high end kitchen when functionally, a $6k set of melamine boxes would fill the same need.

    Insulation material is loaded with perceived values as well. It's not just reduced to it's pure function. Some people choose SPF because it air seals in addition to insulating, the admirable folks of New England choose cellulose because it's environmentally benign, some choose mineral wool because it's nearly indestructible. All of those decisions are based on perceived value, not just strictly the intersection of function and lowest cost.

  8. user-1096505 | | #8

    cork and cousins
    This is a pretty exciting product, and as we build small houses the cost comparison becomes much more a mute point. I see it in the league with wood-fiber boards like Gutex, just with lower perm ratings. The cradle to cradle conversation is very good, and that is what I think most of us mean by 'green' materials. Something that can either be recycled, up-cycled to returned to the earth. That in itself is a value we should hold consumer and architects to uphold. Plastic foams are not a winner if we need to bury the crap after it has served its purpose.

    I am still with Danial on selecting a product like Roxul whose drainboard in rated for below grade and performs as well as the wood fiber boards at the price of plastic. Cellulose filled cavities are still the go to system so I see these products on the exterior of the studs, forming the outside of the cavity bay. As the markets mature and availability is better I can see talking client into paying a couple grand more for an insulation product that does not simply turns into pollution at some point. People will pay a premium for perception of 'better', we just need to prove it out.

  9. wjrobinson | | #9

    Nuts nuts nuts.... This
    Nuts nuts nuts....

    This product is perfect for use in "buying" into the "green status" "my home is a platinum LEED home" sillyness.

    Yes, it does get the thought process going emotionally, but put the idea to a PHD educated engineer and watch the laughing begin.

    Utter green cuteness. As the most logically scientifically speaking Dana persists.... how many hectacres of said trees are there? LOL

  10. Expert Member
    Dana Dorsett | | #10

    Values & value-propositions
    OK, let's assume you can get the cork for $0.87/board-foot (which is about 20% less than $1.05/board foot quoted in the article), and cork is about twice as expensive to hit high-R with cellulose in a double-studwall/Larson truss type high-R wall assembly (as opposed to an open-blow attic/roof insulation, where 10x or more is likely.)

    Where's the (perceived or calculated) 2x value-add that makes it worth paying double?

    How is that a better expenditure of funds than doubling the wall-R to ~R75-R80 with deeper cellulose for a PassiveHouse-level R-value? (The incremental framing costs of 2x deeper double-studs or Larsen Trusses is miniscule, but the cost of the insulation doubles.)

    An application where cork insulation may have a performance proposition is in fire-stop blocking in a cellulose-fill wall, provided it's code-acceptable in that app.

    On the kitchen cabinet aspect, the original comparison was:

    "Sure... $60,000.00 for kitchen cabinets, but not $5000 to $9000 for additional exterior insulation?"

    ...which has now somehow evolved to:

    "We all typically buy based on a value perception. If we didn't, we would not opt for a $60k high end kitchen when functionally, a $6k set of melamine boxes would fill the same need."

    So, while I'm still unclear as to how spending on nice cabinets relate to spending on insulation, I accept the notion that people will spend more for nicer cabinets than crummy ones, and better insulation than crummy insulation.

    But the perception that cork insulation has an enhanced environmental or performance value over cellulose or polyiso that is commensurate with the cost isn't something that I really get. And even were it a 1x cost factor compared to iso in similar applications, the fact that it will never scale enough to displace even 0.01% of the rigid-board market would make it just another cool idea with no relevant impact on the big picture. Sure, every little bit counts, but unless it can affect the big picture the excitement just isn't there for me. Clearly YMMV.

  11. albertrooks | | #11

    Exterior vs, interior insulation
    Dana, your comment:

    "But the perception that cork insulation has an enhanced environmental or performance value over cellulose or polyiso that is commensurate with the cost isn't something that I really get"

    To me, it's the exterior insulation vs. cavity insulation characteristics. These are perhaps nuances that aren't important to you: -No cold sheathing, Better thermal lag than foam boards, less mold risk due at minimal climate thickness, lower thermal bridging, better sound isolation. All of those are attributes of both Cork and Mineral Wool as exterior insulation and in contrast to cavity walls. To me, MW has been superior is these regards, and now I'm seeing where cork might be better in performance and in how one applies it to a wall.. I'm not saying that you have to like it better, I'm saying that I like it better.

    "OK, let's assume you can get the cork for $0.87/board-foot (which is about 20% less than $1.05/board foot quoted in the article)," -I can say that since I'm the one offering it for sale at that price. I'm even offering a further 20% discount to the first projects in Seattle, Portland, Eugene... Just to give the first projects a break.

    "Sure, every little bit counts, but unless it can affect the big picture the excitement just isn't there for me. Clearly YMMV." - OK, fair enough... Perhaps I just get excited by little steps... I'm ok with that.

  12. user-659915 | | #12

    Highest and best use
    Cost issues aside - and disregarding for a moment whether it's available in the huge volumes required for mainstream insulation use - you have to ask if there's not far more valuable uses for this extremely resource-limited material in the green building world. Example - cork beats the pants off hydronic or electric resistance radiant for cosy floors with zero energy input.

  13. user-980774 | | #13

    The article does not discuss
    The article does not discuss the acoustic properties of cork or whether it can be installed on the interior of a wall and left exposed.

    Both of which would increase its value,

  14. Alex Wilson | | #14

    Acoustics and exterior use
    I did not address acoustics at any length, because that's the property for which cork is so well known. The acoustic properties are superb; I'll look for some data to back that up.

    As for leaving the cork exposed, there are a number of buildings that have used expanded cork insulation as an exterior insulation and exposed cladding system. I'll upload a few photos of these buildings. These are dramatic and (I think) beautiful, but it's not an application that I would recommend. I'd prefer keeping the exterior cladding a layer that can more easily and inexpensively replaced in 50 or 100 years.

  15. user-1031655 | | #15

    Not sure if it matters, but apparently while dry cork is considered termite resistant, termites like wet cork. Perhaps something to consider.

  16. user-980774 | | #16

    Was asking about exposed on
    Was asking about exposed on interior application.

  17. user-659915 | | #17

    Interior exposure
    Yes, regularly used on floors, and I was in a home just two days ago where the walls of the ancillary apt. were lined with exposed cork for acoustic reasons. A little dark, but the texture is nice and you can use it as a pinboard anywhere.

  18. albertrooks | | #18

    Interior application

    Just to back up James's comment: You can.. and it's done. (as James attested) . Here are a couple of application reports from Amorim attatched.

  19. albertrooks | | #19

    Production capacity & "Highest and best use"
    Retracing back to questions and comments about the capacity, scalability & best use of cork as building insulation.

    - The cork growing region, or where the cork oak grows, is pretty big. It encompasses most all of Southern Spain, Southern Portugal, and the adjoining tip of Africa.

    - The cork forests are mostly small family farms and not large "agri business" as we are used to here in the US.

    - The ability of the region to produce is cork not anywhere near capacity . There is plenty of unsold capacity. Trees will only get harvested when the production can be sold. Hence why one of the regions manufacturers (Amorim) is over here trying to develop a market, new customers, and US insulation applications.

    The threat to the cork growing region is the lack of cork use. As long as the cork oaks represent a viable income for the local economy, the cork oaks, and the region, is safe from desertification. The growing and harvesting of cork in this region has been an continuous industry since the Romans. I'm sure that's hard for us Americans to get our "head around", but that is the case.

    - As most Americans can appreciate, the system works until one of two things happen:
    1, There is no longer a world market for natural cork, and the land is no longer maintained for production and eventually succumbs to desertification.
    2, The land is re-purposed for a use that generates more profit for the owner.

    In my mind, that means to me that:

    The best thing that can happen is for more people to use cork, and use it in area's that will consume lots of cork: Building insulation.

    More cork use, means greater security for the natural environment of the region. I'm not just reading Amorim literature, I walked a portion of Portugal's cork forests last fall. They are truly beautiful. Consider that the tree is harvested only once every nine years. Really... for eight of nine years, you could walk the forest and not even know that your in the middle of agricultural lands in production. It appears to be just unused forests full of wildlife as far as you can see.

    It might not solve all of our insulation needs or capacities. But cork makes damn fine insulation and the use and sale of it means everything to the the challenged local, regional, and national economies of both Portugal & Spain.

    It's not like anyone is suggesting that we use a lesser quality insulation, or that there's not enough to go around...

    Sorry Alex for jumping in on your blog:)

  20. wjrobinson | | #20

    Albert, top notch response. I
    Albert, top notch response. I applaud you for making what is the best case for your new product line. Integrate your thoughts here in your marketing my man. It should become a proper nitch material for the well off to integrate into their less limited budget home. Happy Sunday.

  21. user-659915 | | #21

    Highest and best use
    Thanks for the full response Albert: good information. Puts it in a different light.

  22. user-942951 | | #22

    Biodiversity, Carbon Sequestration, and Ecological Services
    Just to add to Albert (and Alex's) comments;

    Cork forests support high levels of biodiversity
    Cork forests sequester carbon
    Cork forests provide ecological services

  23. albertrooks | | #23

    Still in outer Mongolia?

    Are you still in the "coldest Capitol in the world": Ulaanbaatar, Mongolia?

    Is "Big Foam" still trying to enter the market? Wouldn't it get confusing in the winter: Knowing which is the foam and which is the ice & snow??

    Perhaps what's needed is a little bit of cork... At least for contrast :()

    Thanks for the link!

  24. user-942951 | | #24

    Weather today: a light dusting of polystyrene beads
    Its snowing little beads of polystyrene today (most probably blown with banned blowing agents, and infused with bio-accumulating toxic fire retardants). Last week I was rowing down a river in a remote part of northern Mongolia and yet I still keep finding pieces of EPS construction waste washed up on the river bank. So its good to hear of an alternative and ecologically beneficial rigid board insulation material.

    We can try to justify various foam insulations with complex arguments and calculations based on the GWP 'payback' e.g. On the other hand, cork insulation has zero (or negative?) GWP, and the embodied energy of manufacturing is more than offset by the carbon sequestration of the forest/material:

    Apparently one ton of cork absorbs one ton of C02 (noted this is a manufacturers claim )

    Embodied Energy of cork insulation (manufacturing) is 4 MJ/kg and Embodied Carbon is 0.19 KgC02/kg (according to note this figure excludes carbon sequestration)

    Perhaps only niche market for now, but interesting none the less.

  25. Francisco Simoes | | #25

    Some corrections
    Dear Alex, once again thank you for the clear article.
    Dear Albert and Andy, thank you for your valuable comments.

    Allow just some small corrections.
    - Environmix is not a producer but a client.
    - Regarding PEI we have: 46 kWh/m3 (2011), so 165,6 MJ/120 Kg, so 1,38 MJ/Kg
    - CO2 emissions (Raw material + production) = 21,87 kg CO2 / cubic meter (0,18 Kg CO2 /kg - so above data is correct from you)
    We know that the mass ratio of CO2/C is 3.664. So, for 1 kg of ICB, carbon corresponds to 0.646 kg and this value corresponds to 2.367 kg of CO2
    So, considering 1 m3 = 120 Kg of Insulation Cork Board, it means 1 m3 represents 284,04 Kg of CO2 ;
    The final results of CO2 are of -262,17 Kg /m3 (negative)

    Indeed a niche market and indeed interesting

  26. user-942951 | | #26

    Thanks for the numbers
    Thanks for the numbers Francisco (mine were merely what I could scrape up off the internet in a couple minutes).

  27. jatson | | #27

    Instead of Hay Bales?
    Twelve inch cork does not compress very much. Why would stick framing be necessary? What if instead of building with hay bales, as some people do, or with foam building blocks filled with concrete, builders tried 2x3' bricks of cork? They would be easy to seal together and so would be air tight. If the exterior were left untreated but protected by a wide eave, it would gradually weather to shades between grey or dark brown, or it could be stained. That would be as attractive as logs. The interior could be left raw or could be painted. What happens to affordability when you don't need double stick framing, or siding, or drywall on the walls? Not for everyone, but it might work quite well. But how long does the reported smoky smell last? Could it be sealed out with shellac?

  28. GBA Editor
    Martin Holladay | | #28

    Response to Ed Christian
    The main problem with your suggestion is that such a wall would be extremely expensive. Even a Portuguese cork farmer couldn't afford it.

    (And I think you mean "straw bales," not "hay bales.")

  29. albertrooks | | #29

    Comment from Thor Metteson
    I got this comment by email from Thor with a request to post it.

    "Albert- I saw your comments at GBA--if nobody else has told you already, cork oaks thrive in Northern California. There are many of them growing around the Chico State campus, and I have seen one in Mariposa (near Yosemite). I actually have pieces of a limb that fell off a cork oak near Bidwell Mansion State Historic Park in Chico."

    Well... That's certainly good news!

  30. albertrooks | | #30

    Response to Ed Christian
    Ed, Yes Cork does not compress easily. The density choices available, and therefore the application choices of cork covers a pretty wide range. Amorim even offers a higher density cork for vibration dampening of heavy equipment. It's from another division than I work with so I don't have any pics, but here is a valve gasket...

    Also, In my limited Straw Bale knowledge, the roof structure is typically supported by a Timber Frame in most designs.

  31. user-485777 | | #31

    Cork insulation
    Right Dana Dorsett. we should just give up and use up all the oil in the world instead of perfecting renewable resources.

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