Expanded Cork - The Greenest Insulation Material?

Suberosis appears to be specific to the inhalation of cork dust during material processing (e.g. mulching, cutting, forming, etc.). The research paper mentions that it is much like "farmer's lung", "furrier's lung" or other occupational respiratory tract illnesses that arise from the ongoing inhalation of dusts/particulates.

This article doesn't point to any particular health risks associated with cork insulation as a finished product. My understanding from other reading that I've done is that cork insulation testing indicates low-to-no VOC or particulate emissions (assuming no artificial binders or coatings are added).

It would be socially responsible to source your cork from ethical manufacturers who are protecting their workers (e.g. implementing adequate dust control measures, ensuring that their workers are wearing appropriate dust masks, etc.).

You might be interested in looking up the monolithic load-bearing cork residence designed and built by Matthew Barnett Howland, Dido Milne and Oliver Wilton in Berkshire, England.  It's on the shortlist for the RIBA stirling prize for 2019 and there's a great video about it on Youtube.

All these blogs are interesting. I am trying to decide which isulation would be the safest or which I would react to the least, I have many allergies: latex, soy, fiber glass, wool, VOCs, chemicals, etc.. So, my conclusion was that cork might be the safest except I am not sure anymore after I read this article         https://www.ncbi.nlm.nih.gov/pmc/articles/PMC470051/    on Respiratory disease in cork workers (`suberosis'). This was kind of scary, but I wonder if it would be safe how it comes as insulation panels?

From what I've read, it may not be completely natural because of the binding process through steam, but my main concern - is it safe after reading this article above? 

I just had a lunch-n-learn with a SIP sales rep.  I do like the performance of SIP walls and roofs.  But when I asked about alternative insulations he doesn't really have any.  He said they could do Grey EPS but no other alternatives.  I was asking to see if something other than brominated flame retardant could be ordered.  Since then I started to think about this article and I think SIP walls would be great if they came with expanded cork as the insulation.  - No flame retardant chemical- All of the product is now renewable.- Less smoke hazard during a fire.- Less structural compromise during a fire since EPS shrinks when heated.

Does any one know of any SIP manufacturers that offer walls made from expanded cork?

I have a former walk-in freezer insulated in 12" thick cork panels. It is crumbley. Is it worth salvaging the cork or starting from scratch with spray foam? Termites are a problem too. The floor is 2' thick cork with 6" concrete... the concrete has caved in over time... not sure if the cork has compressed. This place was built well over 75 years ago.

Bill:  a well-followed publication like EBN and this blog are ideal places to discuss the various features of building products.  People will make purchasing or specification decisions based on what is written here so I suggested that some care be taken in describing products, especially if (per the Green Guides) a stated feature or claim could be very difficult to substantiate.

Based on your comments, perhaps we are not talking about the same “study.”  I reference the consumer perception study done by the FTC for their October 2010 proposed mods to the Green Guides at http://www.ftc.gov/bcp/edu/microsites/energy/about_guides.shtml

For example, the FTC states:  “The study further examined whether consumers believe that environmental claims suggest anything about any negative environmental impact that may come from the product.  Twenty-seven percent of respondents interpreted the unqualified claims “green” and “ecofriendly” as suggesting the product has no negative environmental impact.”  

Federal Register notice at page 43 - http://www.ftc.gov/os/fedreg/2010/october/101006greenguidesfrn.pdf

Also, here is a longer quote from the FTC on the subject of general env claims like environmentally- and eco-friendly: 

“The consumer perception evidence and some comments reaffirm the current Guides’ advice that unqualified general environmental benefit claims convey a range of meanings. For example, [made from recycled materials, recyclable; made with renewable materials; biodegradable; made with renewable energy; non-toxic; and compostable].  Averaging across these seven attributes, 52 percent of respondents viewing an unqualified “green” claim stated that the claim definitely or probably suggested that the product had these specific green attributes. The percentages are similar for respondents viewing an “eco-friendly” claim.  Moreover, 27 percent of respondents interpreted the unqualified claims “green” and “eco-friendly” as suggesting the product has no negative environmental impact. . . . Given these findings, and because FTC law requires marketers to substantiate every express and implied environmental benefit that consumers reasonably could take from such a claim, unqualified general environmental marketing claims remain very difficult, if not impossible, to substantiate. Very few products, if any, have all of the attributes consumers appear to perceive from general environmental benefit claims. In addition, given that all products have some environmental impact, it is doubtful that a marketer could substantiate that a

product has no or negligible negative environmental impact. The  Commission, therefore, proposes revising the Guides to more directly caution marketers not to make unqualified general environmental benefit claims.”

Federal Register notice at page 44-46, emphasis added.  Is there another study we should also be looking at?  Thanks.

Bruce Ray

Johns Manville

Bill:  in its October 2010 proposed changes to the Green Guides, the FTC noted consumer impression research that led them conclude an unqualified claim of “environmentally friendly” would tend to convey the message that the product had no adverse environmental impacts and a very broad array of environmental benefits.  They concluded that such claims may be impossible to substantiate.  So we agree there.

As for the kitchen criterion, I think we would agree that any “natural” product should have been only minimally processed else natural products would include gasoline and U-235 nuclear fuel.  The issue is where to draw the line and some have proposed that minimal processing means no more processing than you could do in a typical kitchen.  See, e.g., the Natural Resource Ingredient Center here - http://www.naturalingredient.org/naturalingredients.htm.  ("In the early '80s the FTC came up with a great definition for Natural - never adopted. They said that an ingredient may be called "natural" only if it contains no artificial or synthetic ingredients and has had no more processing than something which could be made in a household kitchen.")  It sounds like you have also thought about this.  What approach do you recommend? 

You’re correct to question our product data sheet for our AP Foil-faced Iso-foam sheathing product.  Iso-foam does have the highest R-value per inch of the three types of foam currently in use for exterior sheathing:  XPS, EPS, and Iso.  We will change the product data sheet to make that clear.

The language on reducing indoor air quality problems is based on the California Air Resources Board IAQ Guideline entitled “Formaldehyde in the Home,” at http://www.arb.ca.gov/research/indoor/formaldGL08-04.pdf and US EPA’s comments to the USGBC on a LEED proposal recommending reduction of formaldehyde exposure.

Thanks,

Bruce Ray, Johns Manville

Tristan,

Here are some thoughts.

Even if you assume that the cork insulation meets all applicable technical, legal, performance, and other standards for insulation (including, as applicable, the FTC Home Insulation Rule at 16 CFR Part 460, the emissions limits in SM v1.1, f/k/a ES-1350, mold resistance, etc.), it is very difficult to objectively compare the sustainability of different types of insulation.  Until there is an objectively based standard (such as the CRI ANSI standard for carpeting) we are pretty much left to compare various single attribute claims and weigh those against the cost – again, assuming all are equal on performance. 

Some consumers (and specifiers, architects, etc.) are more concerned about air pollution and some about water pollution.  Others are focused solely on carbon.  Still others are most concerned about the conditions of the manufacturing workers and whether they are earning a living wage.  But pretty much everyone is concerned about cost.

To me, cork seems interesting but very pricey.  I wonder how difficult it is to cut and install.  For attic applications, it seems a bit heavy, which can be an issue if a home has thin drywall between the living space and attic.

The point about the use of “natural” is that the word has been shown to be a powerful consumer motivator.  And since many consumers and green building professionals look to EBN and this blog for info, it is important that you use some care in describing the products.  Otherwise, someone may just repeat your description in their own marketing or make a purchase or spec decision based on your description. 

A better and more accurate description of cork insulation would be “biobased.”  The manufacturer could clarify but it sounds like the raw cork is exposed to both high temps and high steam pressure in a sealed industrial autoclave.  If it was just heated, it would be done in an oven, not an autoclave.  Perhaps someone can weigh in here but it still seems like this goes beyond minimal processing and should not be considered natural.

Sustainability and LEED APs can weigh in but when a product is available from only one place on earth thousands of miles from the US market, calling it sustainable could be a stretch.

Good discussion.  Thanks.

Bruce Ray, Johns Manville

I guess you always view the world through your own lens.  So, since I am with insulation manufacturer Johns Manville, I always tend to read more closely any article related to insulation.  I have some comments to pass on for discussion purposes

1.       You use the terms “greenest insulation” and “environmentally friendly building materials.”  We should all keep in mind that the Federal Trade Commission considers unqualified, general environmental claims to be essentially misleading per se.  This is because general claims are very difficult or impossible to substantiate.   Most consumers believe that “environmentally friendly” means that there is not a single adverse environmental impact, which is pretty much impossible to substantiate.

[“The FTC’s consumer perception study confirms what the current Guides already state — unqualified claims that an item is ‘‘environmentally friendly’’ or ‘‘eco-friendly’’ are likely to convey that it has specific and far-reaching environmental benefits. Very few products, if any, have all of the attributes consumers seem to perceive from such claims. Therefore, these claims may be impossible to substantiate.”  75 Fed. Reg. at p. 63552 (Oct. 10, 2010).]

When you say “greenest,” this fairly means that there are objective “green” criteria for all forms of insulation and that you have compared or scored all forms of insulation and cork has come out on top.  For example, some insulation generates water pollution and some air pollution.  A comparative or superlative claim means that there is an objective scoring system to appropriately and quantitatively compare these tradeoffs.  I think such a system does not (yet) exist and therefore such claims are not substantiated.

2.       You call cork insulation “all natural” but based on the description, I think that claim is not substantiated.  There is no single regulatory definition of natural and the FTC in the proposed Green Guides mods declined to provide definitive guidance.  75 Fed. Reg. at p. 63,586.  However, there are two frequently cited criteria for “natural:”  1/ the material or product must “come from nature” and, 2/ the material must be minimally processed, which is pretty much limited to the processing you could accomplish in a typical kitchen. 

Cork undoubtedly meets the first criterion as it comes from a tree.  Yet the description seems to disqualify cork as being minimally processed.  The article references that the cork insulation is manufactured by “putting cork granules in an autoclave and exposing them to superheated steam at 660 – 700 degrees F for 20 minutes.”   This sure seems like a high degree of processing requiring special industrial equipment and resulting in some complex chemistry.

 3.       IAQ.  The most important test for the US market is the Standard Method v1.1 (f/k/a ES-1350) using the residential scenario.

Thanks.

Bruce Ray

Johns Manville 

I would agree that cork is a rapidly-renewable insulation that performs very well.  Since the late 1800s until the late 20th century, cork insulation was used extensively in the US for industrial applications like cold storage.  Its use began to wane as demand exceeded supply and it was eventually replaced with foam plastics like EPS, XPS, PIR and SPF.

Here is a great and free textbook on cork insulation:  http://www.archive.org/stream/array00thom/array00thom_djvu.txt

I do have a few questions about cork insulation:

(1) If cork insulation becomes a product of choice for green building projects, is there enough supply to maintain the already high cost of 2-3x that of foam plastics?  Winemakers are already transitioning from natural cork to synthetic (foam plastic) stoppers due to restricted supply of natural cork.  If there is a limit to wine cork production, wouldn't it also constrain the supply of corkboard insulation, which is made from cork stopper scraps?

(2) How does cork insulation perform in terms of air permeance (air barrier material) and water vapor transmission?  Air barrier and vapor retarder performance is inherent in most foam plastics, but would require additional materials if cork insulation is used.  What is the environmental impact of these additional materials?

(3) While natural building products will undoubtedly lower the environmental impact of the building, can a builder or designer be assured of getting consistent quality from these natural materials?  There used to be a material specification (ASTM C640-83 Specification for Corkboard and Cork Pipe Thermal Insulation) but that was discontinued about 20 years ago. 

(4) Do corkboard products meet the current versions of the U.S. model building codes?  Are thermal performance, durability and fire safety issues properly addressed?  Issues of life-safety and product durability certainly must take precedence over environmental impact in any building design.

Rick Duncan

Technical Director, Spray Polyurethane Foam Alliance