Blog Post

Choosing Insulation: What Are Your Deal-Breakers?

Insulation is a critical component of any building--especially one designed and built to minimize environmental impacts.

Part 2 in our series, "What Type of Insulation Should You Use?"

Even our savvy readers had some trouble with BuildingGreen's insulation quiz. Does it really have to be this hard to choose the best insulation for your project?

While paying yet another $3000 heating oil bill this fall, a friend of mine decided it was time to bite the bullet and insulate her 97-year-old home. She mentioned to me offhand that her husband was interested in spray polyurethane foam (SPF) due to its unique performance characteristics: this material can serve as insulation, a continuous air barrier, and a vapor retarder. No other single material does all three.

However, knowing that my friend has adverse reactions even to the mild cleaning products used in her workplace, I told her that in rare cases SPF has caused serious indoor air quality issues. While these incidents appear to come up only when contractors don't follow proper installation procedures, they do seem to make some people very sick and can require invasive remediation when they happen.

"We better think hard about this," she replied after reading links I'd sent her from EBN and Green Building Advisor.

Which ball to drop?

Before you can decide what you think, you have to know which things to think about.

Making good decisions about insulation--or helping your clients make them--requires a thorough working knowledge of the relevant issues. When considering any insulation material, we have to keep in mind what is for most of us the least flexible issue--cost--while also juggling:

  • embodied energy
  • global warming potential
  • offgassing risks
  • potential for moisture and mold
  • interactions with other materials in the wall, roof, or slab assembly
  • structural properties
  • durability
  • vulnerability to insects
  • fire resistance
  • recycled content
  • recyclability
  • downstream effects of landfilling
  • ability to source locally
  • pollution from resource extraction and manufacturing
  • social justice issues related to manufacturing
  • building codes
  • building certification requirements, including red-listed materials and energy performance standards

Keep in mind that the best jugglers on earth can only handle about seven balls at a time for any extended period. Based on results from our GreenSpec insulation quiz, juggling this number of insulation considerations at the same time is nearly impossible--even for you, our exceptionally well informed readers.


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That said, it's better to choose which balls you want to drop based on your own and your clients' priorities rather than just letting them fall willy-nilly.

Finding your deal-breakers

Let's say that you, like my friends, want to maximize what you get out of your insulation by making sure it controls air leaks as well as conductive heat flow (see Part 1 for a primer on heat flow). Do you know which insulation materials are airtight enough to act as a dedicated air barrier?

More than 80% of our quiz-takers knew several materials that would not work: they chose "none of the above" from a list that included cellulose, fiberglass, and mineral wool. However, almost 13% of people who took the quiz thought cellulose could act as the dedicated air barrier.

This is actually a persistent myth that building scientists have been working to debunk for years. Here at BuildingGreen, we love cellulose for its exemplary environmental performance, but we shouldn't let that get in the way of the facts: cellulose is not an air barrier. It does a much better job at air resistance than either fiberglass or mineral wool, but only a handful of insulation materials act as an air barrier, and they are all petroleum-based.

If installing insulation that doubles as an air seal is a high priority for you, SPF might be the way to go. But if you or your client has known chemical sensitivities, even a tiny risk of reacting to SPF might be a deal-breaker for your project. Maybe cellulose is a reasonable compromise--but cellulose might not even work for the extremely sensitive, due to ink in the recycled newspapers that are used to make it. (Cellulose has other potential issues as well, like dust that can be an irritant and vulnerability to moisture.)

Decision-making tools for insulation

Most people make their insulation decisions based on information from manufacturers or installers, which can be problematic--not because they intentionally mislead people (although that can happen) but rather because it has not been their job to cut through greenwash and explain the complexities of building science, environmental considerations, health risks, long-term performance, and all the other issues associated with the panoply of insulation options available on the market right now--and then finish all that off by helping you weigh these considerations against your needs, your personal values, and the limitations of your pocketbook.

That's actually a pretty good description of what BuildingGreen is all about, though, and it's the reason we've added Alex Wilson's new Guide to Insulation Products and Practices to the independently produced resources we offer.

Alex offers a really handy table of BuildingGreen's bottom-line insulation recommendations to use as rules of thumb for various applications. But as we're hopefully communicating with this blog series, deciding what insulation to use for your project can get really tricky; it's a project-by-project decision that we can't make for you. So the book also gives you the tools you need to make different choices based on your own or your clients' priorities and special circumstances. It can be read from cover to cover or used as a reference tool.

If you haven't had a chance to take the insulation quiz, do head over now and test your knowledge. You might be surprised!

Finding the right balance

Incidentally, my friends have decided to fill their empty wall cavities primarily with blown cellulose but will also use SPF in various hard-to-reach places in the attic.

What would you have done?

Published October 19, 2011

(2011, October 19). Choosing Insulation: What Are Your Deal-Breakers?. Retrieved from

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May 20, 2013 - 3:54 pm


In regards to open-cell spray foam insulation it is a great choice epsecially in your application.  With the right type of spray foam equipment open-cell foam applied in an attic is a superior choice.  The benefit of the open-cell in an attic space is while it does have lower R-values per inch than closed-cell, it will allow you to achieve the higher R-value requirements needed in most climate zones while keeping the cost down.  When it comes to deciding to insulating the floor or rafters, that is typically based on the answer to the question is the attic space going to be a liveable space or does it contain your heating/cooling equipment.  If the answer to either of the previous questions in yes, then you'd want to insulate the rafters, if the answer is no then insulating the floor joist in the simplest and most recommended way to go.  Hope that helps!

May 8, 2013 - 10:56 pm

I am looking for an expert opinion regarding open-cell water-based foam. It is clearly less expensive, and admittedly a bit less effective, than closed-cell foam.  Is it worth considering, especially for attic insulation?  AND, is it better to insulate the attic floor or the attic rafters. Any advice would be greatly appreciated!

February 6, 2012 - 9:52 am

I have long been a fan of cellulose insulation. But even cellulose has its problems. A concern that has recently been raised is about the boric acid flame retardant used in a lot of cellulose insulation. The European Chemicals Agency has added boric acid to its list of "substances of very high concern." It is from this list that the European Union picks chemicals to regulate through the REACH program, which was adopted in 2007. We will be digging into the concerns with boric acid, but it's quite possible that this will dampen our enthusiasm for cellulose insulation.

As for the isocyanates used in producing spray polyurethane foam, polyisocyanurate, polyurethane cushioning, and a wide range of other polyurethane products, the chemicals are derived from fossil fuels. One of the precursor chemicals used in producing MDI is 4,4’-diaminodiphenylmethane
or MDA, which has also been included in the European list of candidate chemicals for regulation through REACH.

February 3, 2012 - 11:47 pm


Thank you for offering this additional info. I understand that these are hard questions to answer. If we could go a bit further, I'd like to ask:

1)Where does MDI come from, how is it manufactured? Presumably it needs to be shipped to the polyiso factory before it can be transformed into product. So I just feel skeptical about trusting any factory to always contain, or even often enough, these chemicals, not to mention the shipping infrastructure.

Clearly, we must reduce energy use, but given these concerns, and concerns about all kinds of micro-plastics, I am still wondering:

2) If we have an opportunity to use cellulose, and if we can possibly figure out a way to use it in any appropriate application, is it not a MUCH more environmentally sound choice to make?

My suggestion is that the need for SPF and even the use of any foam insulation could be easily avoided and drastically reduced in most situations. Your report was very informative in describing some alternatives to foam, including in sub-slab and below grade applications. But I wonder if cellulose deserves a more direct and prominent endorsement?

January 30, 2012 - 8:48 am

These are very good questions, Ethan. Thanks for bringing them up. I can't claim to "answer" them, but will offer a few thoughts:

1. On whether chemicals used in producing or contained in foam insulation materials may escape into the environment (or our buildings), some of the toxics involved are intermediaries that are fundamentally changed during manufacturing, so that if there isn't a spill or industrial emission somewhere in manufacturing, the risk of pollution from that particular chemical is probably fairly low. That might be the case with the benzene used in polystyrene manufacture (both XPS and EPS). That should also be the case with the methyl diisocyanate (MDI) used in spray polyurethane foam (SPF) and polyiso production. MDI is chemically changed during the "thermoset" process that produces the SPF or polyiso. With polystyrene and polyiso production, these chemical emissions are controlled in a factory; with SPF, the chemical reaction occurs in our buildings. Factories are more controlled environments, so containing releases should be easier. MDI is very hazardous, which is why SPF installers should have full supplied-air respirators.

2. What happens to the chemical constituents of polyiso and other foamed-plastic insulation materials at the end of their useful life is also a very good question. The short answer is that we don't know nearly enough about all of the synthetic plastic entering the environment and the biosphere from our degrading materials. Along with foam insulation, we should be worrying more about microfibers from our synthetic clothing that are emitted into the environment when we dry clothes in a dryer. From what I've read, the polyiso constituents should be fairly inert, but I don't know what testing has been done. This is one reason that we at BuildingGreen are excited about research into biobased materials, such as a mycelium- (mushroom) based foam insulation material being developed. Biological materials developed through natural processes will be able to decompose safely into the environment. That goes for wool and hemp insulation as well--and cotton (except for the added polyester).

3. No, we shouldn't avoid all foam-plastic insulation--at least not until we have alternatives that work as well. The benefits of products like polyiso and SPF, in my opinion, often outweigh the negative impacts of the energy consumption (and pollution) that they avoid.

We need to keep asking these types of questions!

January 28, 2012 - 11:58 pm

The insulation report was very informative, but left some questions unanswered for me. Robert and others point to some of these questions in this great discussion above. Can anyone help explore these questions?

1) The report mentions that all or most of the foams contain or are produced with toxic chemicals. Do any of these escape into the environment? Do they impact the workers in the plants? How concerned should we be about the use of these chemicals? More specifically, what are the environmental impacts of polyiso production? Chemicals are mentioned, but where does this leave us?

2) And what happens to the insulation materials when they degrade or are done with their life? The question is raised but not answered in the report. For starters, what happens to Polyiso? Does it wear out and become a dust that goes into the soil? What is the impact of that stuff in the food chain, watersheds and soil? What about all the other insulation materials and their end of life prospects?

3) If we are concerned about the environment, should we avoid foam WHENEVER possible? Will there be foam products in the near future that can feasibly be contained in a cradle to cradle system sustainably?

October 24, 2011 - 7:46 am

Readers who are participating in the conversation here may want to check out the somewhat longer conversation on the GreenSpec webiste, which includes all of your comments as well as additional responses to them: We'll temporarily have these slightly askew conversations going on as we transition GreenSpec Insights over to our new GreenSpec website, and I don't want commenters to miss anything!

November 3, 2011 - 9:24 am

To Mr. Planet and anyone else whose comments are missing: there was a cacheing glitch of some kind that deleted all comments going back five years for a few hours. We're still working on getting them back. They were not deleted intentionally! Hopefully we can get them all back as the day goes on.

November 2, 2011 - 10:27 pm

For removing my posts. People like you are the reason this planet is in trouble. The removal suggests fear or a lack of willingness to discuss real issues.

Have a pleasant day!

October 19, 2011 - 6:24 pm

Robert, I have looked for data or evidence that Air-Krete is an air barrier, and I could not find any. What I did find are consistent reports that it is friable and prone to settling. While Air-Krete is an interesting material with some great characteristics, these characteristics don't seem at all consistent with an air barrier material.

October 19, 2011 - 6:14 pm

You speak of the "persistent myth" that cellulose is an air barrier. But just as how we define a vapor barrier (or, rather, the three classes of vapor retarder) is an arbitrary delineation, precisely what constitutes an air barrier is also an arbitrary determination. And there is still considerable disagreement within the building science community about how tight is tight enough.

Certainly, no fibrous insulation material can meet the extremely stringent standards of the Air Barrier Association of America (? 0.02 l/sec-m² @75 Pa or 0.004 cfm/sf @ 1.57 psf, 25 mph wind equivalent), but the standard for air barrier assemblies is 10 times that rate, and for air barrier enclosures (the entire building shell) is yet another 10 times greater. But the ASTM E-1677-00 Standard Specification for an Air Retarder (AR) Material or System is 50% less restrictive than the AABA assembly standard, and the U.S. DOE Building America Program, the National Building Code of Canada and the Building Services Research and Information Association of Great Britain each have their own standards.

What considerable laboratory and field testing has demonstrated, however, is that cellulose dramatically reduces convective heat loss over an uninsulated house by an order of magnitude (Building Science Corp BSI-043) and over even a tight fiberglass-insulated Energy Star house by 18% to 25% and that the improvement in airtightness of cellulose over fiberglass is more dramatic than the improvement of SPF over cellulose (Energy Design Update, April 2005).

The failure of SPF in Energy Star homes tested by Bruce Harley, the technical director for residential energy services for the Conservation Services Group (as reported in that article), to make as significant an improvement over cellulose as cellulose did over fiberglass is because, SPF is not, as you claim, "a continuous air barrier" but rather continuous at best only within each framing cavity. Most air leakage occurs at the junctions between various framing assemblies where there is no insulation, and there are more reliable air barrier techniques than the use of expensive, potentially toxic, non-renewable petrochemical foams.

You also state that "only a handful of insulation materials act as an air barrier, and they are all petroleum-based". I believe that AirKrete (cementitious foam insulation) is also an air barrier material, as well as non-toxic, fire-proof, insect, mold and rot proof and containing no non-renewable, global warming petrochemicals.

October 21, 2011 - 5:13 am

Chris and Robert, thanks for keeping us on our toes! We are all certainly in agreement about building science being science. Our motto is "Knowledge That Informs Practice," which acknowledges that science is crucial but applying science in a given situation is complex. Science is descriptive, not prescriptive; it is the basis for recommendations, not a recommendation in itself. Decision-making requires human judgment.

There are dozens of variables and few absolutes when it comes to building science in general and insulation in particular. This is why people need independent and easy-to-digest resources that offer them detailed but holistic recommendations. You won't get a birds'-eye view like this from manufacturers or installers, and too few building professionals understand as much about building science as you and Robert clearly do. You may not realize it, but the depth and breadth of knowledge you're displaying here are quite rare.

Everything we're talking about here is discussed in Alex's report in a way that both building professionals and homeowners can understand.

October 20, 2011 - 12:47 pm

I would have to agree with Robert. The permeability of an air barrier directly influences the condensation inside the building structure, thus it is necessary to design to an empirical standard depending on the prevailing atmosphereic conditions. Sounds like science to me.

October 20, 2011 - 10:46 am

Robert, I'm glad you brought up the fact that "there is still considerable disagreement within the building science community about how tight is tight enough." From my point of view, "tight enough" is a value judgment, not something a scientist can decide.

As you point out, not everyone thinks it's a good idea to seal up a house like an airlock on a spaceship. Some people really do, though. This is only one example of the point we're trying to get at here: that whichever of those camps you fall into, you need to know the best way to achieve your goal without compromising other values or goals in the meantime.

It sounds like using petrochemicals of any type would be a deal-breaker for you. Helping people find high-performance alternatives to destructive, nonrenewable resources is a huge part of our mission, but I think it's fair to say that most people are not ready to categorically forswear high-performance petroleum products--especially if such products prevent them from burning huge quantities heating oil. If you are open to using such products, you need to know what kind of impact that choice could have on your health and the environment.

Moving away from petroleum is goal we support, but it is a massive global transition that will take time. Our hope is to give people the guidance they need to make good choices based on their own values, circumstances, and limitations.

October 20, 2011 - 12:29 pm

"Tight enough" can also be science-based. John Straube, principle founder of Building Science Corporation and professor of engineering has concluded from his years of research and experience in Canadian cold-climate homes that:

> 3 ACH50 tend to have a risk of interstitial condensation
> 5 or 6 ACH50 tend to also be too dry inside
< 2 ACH50 tend to perform quite well
< 1.5 ACH50 have problems with high winter RH

My own research and experience and knowledge of building science and hygro-thermal engineering has resulted in very similar conclusions. Not a value judgement - but empirical.

As far as helping people in the building trades make decisions based on "their own values", I would suggest that we're way past the time as a human culture that we can afford to perpetuate, encourage or support the dysfunctional values that have created the multiple, interconnected global crises that now threaten half the species on earth as well as the continuity of the human race.

Just as the #OWS movement is now stating: enough is enough.

October 28, 2011 - 9:36 am

Andre, thanks for the great feedback! You bring up an important point about the difficulty of weighing the environmental impacts of different insulation types. Have you seen a life-cycle analysis of hemp insulation? I have not, but I gather one of the attractions of hemp is that it grows like...well, a weed. It does, of course, need to be harvested and transported and processed--but the same could be said of cellulose.

You might be interested in Brent's discussion of hemp insulation (including two new ones under consideration for GreenSpec) here:

October 26, 2011 - 2:11 am

Hello Walter.. and humble apologies for the late reply. You have asked for the other two vectors. Here using the meaning for vector, as in a "direction" travelled to arrive at destination.

The following must be prefaced with the following stsatement. As long as one treats moisture as an enemy of building instead of an inevitable occurence, one's built environment paradigm is a flawed process that produces complex and expensive fixes.

So Vector 1 is R-Value: The higher the R-Value, the better the insulating properties of the subject materials. R-Values are most often used to express the thermal resistance (ability to stop heat flow) of a building wall, ceiling or floor. Because of this, most R-Values are calculated at normal temperatures of approx. 75 F. R-Values are easy to add together so calculating the total R-Value of a wall is simply done by adding the values for the sheetrock, insulation, sheathing and siding.

There are problems with a sustainable envelope when the goal is "the ability to stop heat flow", as opposed to working with it.

Vector 2 is K-value: K-value is a measure of heat conductivity of a particular material. Specifically, it is the measure of the amount of heat, in BTUs per hour, that will be transmitted through one square foot of material that is one inch thick to cause a temperature change of one degree Fahrenheit from one side of the material to the other. The lower the K-value for a material, the better it insulates. If the K-value of the material is known, the R-value per inch can be determined by dividing 1 by the K-value (R-value per inch = 1/K value). The LOWER a K-Value, the better its performance as an insulator.

Here the question is; why is this important? You should also note theat both vectors 1 and 2 are as important to cooling.

R or K values have nothing to do with whether a material is flame/water proof, flame/water resistant or combustible. Styrofoam, cork, wood and polyester are just some examples of materials which are good insulators but will burn or smoke dangerously when exposed to excess heat; and engineered woods will disintegrate with moisture.

Vector 3 is rh value: Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions. The relative humidity of air thus changes not only with respect to the absolute humidity (moisture content) but also temperature and pressure, upon which the saturated vapor pressure depends. Relative humidity is often used instead of absolute humidity in situations where the rate of water evaporation is important, as it takes into account the variation in saturated vapor pressure.

It is this vector that has produced the most harm in the development of current building standards.

Now to the important points. If your envelope does not embrace all three of these vectors as conditions to be incorporated in said envelope, the result will be inventions like house wrap and fibreglass insulation, drywall and vinyl siding.

Designs that do incorporate these vectors will produce a structure built as close to perfect as you can manage. It will be healthier, more affordable, extremely durable and will last for generations. Their impact on ecosystems will be minimal, (although such designs are more likely to yield eco-restorative results) and they will use little or no proprietary technologies.

Perhaps the editors will request an article in full on the subject. I would welcome the opportunity to elaborate further. Howver, using these vectors will lead you to the answers.

October 24, 2011 - 11:58 pm

Not to hang the product on the basis of one bad install, but I saw AirKrete go horribly awry. Apparently there are seven parts that need to be mixed on site, and the installer got something wrong. When the stucco guys started hammering on the lath, all the AirKrete just cracked out and started falling on the floor. It all had to be ripped out (this is a large high end custom home), and replaced with Spray Foam.

Use with discretion would be my advice.

I'm from, and work in California, so I have no opinion on cold weather air barriers.

October 24, 2011 - 12:48 pm

Robert, thanks for bringing up the issue of anonymous comments. We are working on improving that functionality; very soon (perhaps even today), anonymous comments will no longer be accepted.

October 24, 2011 - 12:39 pm

I don't normally acknowledge anonymous commenters, particularly when they seem to be representing an industry rather than objective science-based building, but the misleading statements must be countered, including Paula's statement that "cellulose is vulnerable to moisture".

In my earlier post, I was merely demonstrating that field testing shows that SPF is not the miracle air barrier that it's claimed to be and that dense-pack cellulose can make a very dramatic reduction in air leakage (even though it's not an air barrier material according to current standards), particularly when it's combined with other, less costly air sealing techniques.

I don't know what Mr. Planet's "other two performance vectors" are, but any comparison of insulation options needs to consider much more than merely R-value and air sealing capability. There's embodied energy and embodied global warming, toxicity and health impacts, life-cycle environmental impacts, recycled content and recyclability, hygric performance, and contribution to flame and smoke.

Contrary to much industry propaganda, cellulosic insulation materials handle transient moisture much better than non-hygroscopic materials like fiberglass or plastic foam. Because they can safely absorb and release large quantities of moisture (up to 30% by weight), they serve as moisture buffers for the interior environment much like thermal mass buffers indoor temperature variations.

Cellulose treated with borates not only does not promote fungal growth (or insect or rodent infestation), but its highly hygroscopic quality distributes moisture rather than concentrating it in the wood framing where it may raise the local moisture content sufficiently to cause mold and rot.

Certainly, cellulose fails in a flood or major roof leak, but a wall with any type of insulation will have to be opened and dried in that event, and cellulose is far easier (and less costly) to remove and replace than sprayed foam.

And, certainly, the competence of the installer is important with any insulation material. But cellulose is benign enough to be installed by a home-owner with a little training, while SPF requires a highly-controlled environment, very sophisticated equipment and extreme care to avoid major problems, such as the increasing number of cases of occupants having to permanently vacate their homes due to persistent outgassing, and deadly fires initiated by foam installation.

Disclosure: I am in no way connected to the cellulose industry, but have been designing and building super-insulated healthy homes for 30 years and teach sustainable design & construction as well as hygro-thermal engineering and building science.

October 24, 2011 - 11:45 am

Anonymous, as mentioned in the post, cellulose is indeed vulnerable to moisture. This can be a problem throughout the life of the insulation. People who are retrofitting with *any* insulation should realize that they are probably going to change the moisture dynamics of the structure dramatically.

Your point about finding reputable installers is well taken, although people should also keep in mind that not all "certifications" are created equal, whether we're talking about products or contractors.

October 24, 2011 - 10:56 am

The artitcle sites installation issues as part of why foam can be bad for occupants. What about the installation issues with cellulose? I've had forensic engineers involved in several projects where the dense pack cellulose was applied late in the year and/or water heavy which caused mold to grow on the interior sheathing due to the high relative humidities, sounds real promising for your allergy prone friends. Applicator training and manufacturer support is vital to ANY product's performance. We have to remember that the installer is ultimately providing the finished product for every one of these insulation materials and as such the homeowner needs to be ultimately responsible to ensure their applicator is well trained and certified in the products they are providing. Ask if they are members of trade groups which may have provided training (request certificates) and what training the manufacturers require before certifying their contractors and make them write a letter for the contractor specific to your project making them stand behind the applicator.

October 24, 2011 - 10:54 am

Mr. Riversong,

In your response you state that cellulose outperforms fiberglass and I assume the testing you are referring to is using dense pack cellulose and not a loose fill material given your claims. I find it terribly amusing you compare the performance of cellulose to fiberglass and say it's so much better when we all know fiberglass is terrible and then compare SPF to cellulose and say it compared to cellulose didn't make the same improvement as cellulose compared to fiberglass but it did perform better than the cellulose based on your comment. A true scientific test standardizes the comparisons and uses a base line standard and would compare the foam to fiberglass just as the cellulose was compared to show the performance improvements of each. This sounds like a very misleading interpretation of a test that shows foam performs better than cellulose. As a cellulose supporter admit that dense pack cellulose performs better than loose fill and fiberglass but not as good as SPF. Your benefits are a less expensive product and recycled content but don't waste your time trying to make claims about performance becasue when push comes to shove you don't have what it takes to substantiate an arguement against SPF.

October 23, 2011 - 8:36 am

A reader recently noted that growing and harvesting hemp requires farm equipment which usually runs on diesel, thus that cellulose is much more sustainable. What do you think?
In addition, in a cold climate, don't you think below 1.5 or even below 1 ACH is never too tight if you have a well-installed (balanced) and maintained HRV?
Thanks for the stimulating discussion.
(I publish La Maison du 21e siècle magazine out of Quebec since 1994 and regularly quote EBN)

October 21, 2011 - 10:42 am

A simple solution we in the US miss out on is industrial hemp. This can answer not just insulation dilemmas but also provides minimal impact to the environment. A demonstration of industrial hemp's qualities was shown at a green seminar I attended; a blow torch was fired against the block of fibre and lime composite and merely caused a blackened area and that after being torched for a considerable length of time. The fibre is naturally rounded and hollowed which bolsters the insulation qualities by providing air chambers. A video can be seen here: Information on rolls of hemp matting can be found here:

Let's stop the nonsense, industrial hemp is the answer to many of our woes. It's about time it were available here in the US.

October 21, 2011 - 10:06 am

Mr. Planet,

Could you elaborate on the other two vectors and how to factor them in?

October 20, 2011 - 11:00 pm

Before insulation is considered, one must determine the other two performance vectors of an envelope. Until you do that, you are not even in the sustainability game.