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Green Building Curmudgeon

Is It Time to Stop Insulating?

Health concerns continue to dog insulation materials

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Will something like autoclaved aerated concrete (AAC) emerge as one of the safest forms of insulation?
Will something like autoclaved aerated concrete (AAC) emerge as one of the safest forms of insulation? In addition to experiencing performance problems, fiberglass insulation is now the subject of a report that classifies inhalable glass fibers as carcinogens. Spray foam insulation is the subject of EPA scrutiny for toxicity of the chemicals used in production.

Author’s Note: Many readers have mistakenly read this post as a serious suggestion that we stop insulating our buildings, and friends and foes alike have given me large rations of grief over this, all of which can be read below. I am a longtime advocate of high-performance homes and in no way would I ever recommend that we reduce or eliminate insulation. I do believe, however, that we need to consider the potential health effects of various products that we use and how they will affect our decisions on construction methods. Now on to the original post:

Most readers of this blog know about my problems with batt insulation from my post earlier this year, and I was pleased to read a recent post by Tristan Roberts about problems with denim batt insulation in which he referenced my insulation post. Now spray foam products, the darlings of the green building industry, are under review by the EPA for health problems related to their blowing agents.

And just last month the U.S. Department of Health and Human Services issued its 12th report on carcinogens, classifying inhalable glass fibers (along with formaldehyde and styrene) as carcinogens. Finally, there are concerns with the dust and additives used in cellulose insulation, raising some suspicions about that product’s green credentials.

What’s left?

Most of the familiar insulation products are under mild to moderate clouds. Batt insulation, in general, is a challenge to install correctly; fiberglass is carcinogenic; spray foam may be a health hazard; many rigid foam boards have high global warming potential; and cellulose may have unwanted fire retardants in it.

Among the few remaining products are Air Krete, a limited availability, proprietary cement-based foaming insulation; and, if the fibers are large enough so as not to be carcinogenic, mineral wool — although it is primarily available in batts and subject to the same installation issues as all batt products.

Let’s not forget about wool insulation, available in both batt and blown forms; however, it is costly and in limited supply.

Is insulation the problem?

Before the advent of insulation, buildings tended to be more durable, if not uncomfortable for the occupants. Uninsulated framed wall cavities generally didn’t have durability or mold problems; it is the insulation added those cavities that held moisture in long enough to cause problems.

Do we stop insulating buildings to avoid being poisoned by them? I don’t think average homeowners would want to forgo insulation. Even if it isn’t installed well, it does make a difference.

Is integration the answer?

If we’re not willing to go back to the dark ages of uninsulated homes, our last hope for healthy and comfortable homes may be structural material with integrated insulation, such as aerated autoclaved concrete (AAC). AAC is a lightweight cement available in blocks and panels that are inherently well insulating. There is no wood to deteriorate, and as far as I can tell, the product looks pretty benign, although it does produce a lot of dust when cut, which raises health issues for the workers using it.

Insulating concrete forms made of products like Durisol use mineral wool for interior insulation; however, we don’t have a definitive answer on the safety of that, either. While these materials are good options, they tend to be labor-intensive, costly products to install and are not likely to gain widespread adoption any time soon. In fact, an AAC plant in Georgia was for sale recently due to low sales volume.

What’s a poor boy to do?

Personally, I’m getting pretty baffled by the whole thing. I am finding it more and more challenging to make recommendations to clients about which insulation product to use — let alone make a decision about what to use in my own house, should I ever get around to building it.

Do we want to give clients asthma or cancer, or empty their bank accounts with something like AAC? Maybe it’s just time to give up and move to Hawaii where the weather is perfect.


  1. GBA Editor
    Martin Holladay | | #1

    OK, Carl -- you need to document your claims
    I know that you relish your role as a curmudgeon (thank goodness), I know that you love to be provocative, and I also know that your tongue is sometimes lodged in your cheek. However, readers of your blogs may not always understand your mischievous nature.

    I'm not going to let you get away with this sentence -- "There are concerns with the dust and additives used in cellulose insulation, raising some suspicions about that product’s green credentials" -- unless you can provide a link or a reference to a source that backs up your implication with facts. Please, tell us more about why you are concerned about health effects related to the installation of cellulose insulation in homes.

    More clarity on the cellulose issue is especially important in light of your inflammatory question, "Do we stop insulating buildings to avoid being poisoned by them?"

    Seriously, Carl -- "being poisoned" is a strong phrase. It's time to show your evidence.

  2. Mike Eliason | | #2

    hmmm... i actually don't feel
    hmmm... i actually don't feel this is curmudgeon-y at all! i oscillate between the no insulation and passivhaus extremes at times (and would love to do both).

    just to throw a little fire on carl's premise - i worked for an architecture firm that believed insulation - especially petroleum-based insulation, was unnecessary for low energy buildings. they drew from regional historic precedents, resulting in some magnificent & durable projects incorporating a combination of direct gain spaces (winter gardens, or as they were called - energy gardens), air collectors, thermal storage walls, effective zoning and utilization of process energy. there are downsides to their approach - the embodied energy of their projects tends to be higher than normal.

    the project i spent the most time on, a brettstapel & polycarbonate 'monopoly' house, utilized AAC on the opposing gabled ends. the only insulation was a few inches under the slab, with air sealing around windows and doors.

    also, i don't feel that mineral wool is benign, as 1-6% of roxul is a phenolic formaldehyde binder...

  3. Gregory La Vardera | | #3

    All Batts are not the same.
    I have to disagree with the lumping of Mineral Wool in with other batt products.

    Mineral Wool's dense composition makes it easy to install without gaps and fully filling the wall cavity. Its rigidity means it does not sag and leave gaps, and that same dimensionality and ease of cutting makes it easy to cut and trim around obstructions maintaining a full installation. Of course an insulation cavity full of wires and obstructions is not an insulation problem - its a wall problem. Mineral wool's ability to work around them is an asset, but even so a wall with a separate wiring chase will be superior.

    Last but not least, mineral wool batts made in europe currently have a bio-soluble formula - meaning particles that are ingested or inhaled break down/dissolve in the body. You can research this, question or accept the science, but this is very highly regarded there. These formulas are on their way to north america as well. Whether or not integrated solutions are "better" these alternate construction systems will always have trouble penetrating the market. Mineral wool is a direct and easy substitute for the fiberglass batts used in 99% of housing. Unless fiberglass makers can clean up their product, and begin offering the higher R-values that mineral wool is available in today, then the writing is on the wall. Mineral wool will become the default insulation in American housing. We could do much worse.

  4. wjrobinson | | #4

    Way too many of us humans on
    Way too many of us humans on the planet. I have worked around every product homes are built from for decades with no ill effects other than over working some joints that healed up over winter slow times. I do not know one person who has been directly killed by a building product, not even by having it crush him or having fallen off of it.

    The sky is falling!!!!

    Just sayin

    Let us know if you are about to die from being in a home insulated with any of the noted insulations...

    Whatever gets us back to 2-3 billion on this planet... I may just not be upset about. I know a few decades from now those living will be glad some or lots of us are, gone (me for sure for some of you)!

  5. greenophilic | | #5

    Natural building anyone?
    I am consistently baffled by the refusal of the green building community to engage natural construction techniques, such as straw bale, staw clay, rammed earth, wattle-daube, etc. Some (not all) of these construction techniques provide exceptional levels of insulation, as well as thermal mass, and they can be made from site-obtained or locally-obtained natural materials. Now I'm sure that problems will arise with them as well (pesticide residue and whatnot), but the shear willfulness of green builders to ignore this whole field is a mystery to me. This is especially perplexing because natural building techniques can fall at the intersect between local sourcing, energy efficiency and health, providing something for everyone's agenda. What gives?

  6. GBA Editor
    Martin Holladay | | #6

    Response to Brennan Less
    You mentioned four building techniques: straw bale, staw clay, rammed earth, and wattle & daub. Of these four methods, only one -- straw bale -- results in walls with a high insulating value.

    I think that straw bale homes make a lot of sense, and are well worth considering. The downsides are well known: they are labor-intensive, and therefore expensive to build if the owner is paying for labor; and they are susceptible to rot and mold at the base unless they are impeccably detailed to stay dry. Monitoring results of straw-bale homes in Canada raise some concerns and indicate the need for more study; the report noted, "It is still unclear how appropriate straw bale construction is for high humidity and high precipitation climates. At the very least, extreme caution should be exercised when straw bale construction is used for walls with northern exposures in these types of climates."

    The GBA Web site includes information on straw-bale construction:

    Alternative Walls: Straw Bale

    Straw-Bale Home in the Minnesota Woods

    How to Insulate a Slab Foundation—With Straw-Bales?

    A Straw-bale Project Aims for High Performance

    Energy-Efficient Straw-bale Home in the Colorado Rockies

    The Baleblock System

    A Near-Zero-Energy House In Upstate New York

    Exterior siding on cob walls

  7. Expert Member
    CARL SEVILLE | | #7

    Martin, Martin...
    I can't believe you just won't trust me on everything. I suppose the implication that cellulose was poisonous was a bit over the top, but I have been collecting information on some ill effects from the use of ammonium sulfate as a fungicide as well as other chemicals that are present. This link on the Healthy House institute brings up some interesting points, although they don't run screaming from it as I might have implied we should:

    My overall point, which was partially tongue in cheek, was that while insulation is generally a good thing, it can also create problems, and rather than move lockstep with the mainstream group think on green building, we should consider various options that help us create better buildings for the future. Some of these may include not using what are now standard insulation products and looking for alternatives that are healthier, more sustainably produced, and make for more durable buildings.

  8. GBA Editor
    Martin Holladay | | #8

    Response to Carl
    I'm afraid the link you provided is pretty weak tea -- an unscientific collection of anecdotes from a Web site appealing to sufferers of multiple chemical sensitivity.

    Since you wrote, "I suppose the implication that cellulose was poisonous was a bit over the top," and that your point was "partially tongue in cheek," I'll except your recent comment as a partial retraction. So we're good.

    Here are some salient sentences from the Web site you linked to:
    - "There are thousands of houses that contain cellulose insulation, yet only a relatively few occupants have complained of health problems as a result of its use. ... some people can be affected by this material ... "

    - "My point all along has always been that, if you build a tight house, the insulation (no matter what it is) will stay in the building cavities, and have no effect on the occupants."

  9. GBA Editor
    Martin Holladay | | #9

    Oh, and one more thing, Carl
    I forgot to respond to the question you used for a title. Since I'm the Q&A guy, I'm happy to help: No.

  10. user-723121 | | #10

    Batt insulation and electrical wires
    A couple of builders I knew in years past had a good method for running electrical wires in stud walls. They would notch a "v" into the bottom of the 2x6 studs about 1" wide, this end was nailed to the bottom plate. Electrical wires were run through the "v" so the batt insulation did not have to be split, the wires were stapled to the bottom plate.

  11. albertrooks | | #11

    Various responses...
    Carl & Martin,

    It's getting confusing as to which one of you is the "curmudgeon". I like this "curmudgeonly self checking"!

    Carl: Regarding cellulose insulation being a serious health concern by its dust or additives.... my goodness, you had to know that this was a stretch as you wrote it. There are much bigger fishes to fry: Like the formaldehyde content exemptions in engineered woods such as OSB, TJI's and the like. I submit that it's a much more serious problem than cellulose dust.

    Never the less, I'll suggest that a solution to the potential "harmful effects of cellulose dust" and other cellulose off gassing issues can be significantly reduced by better air-sealing at the interior layer. By taking the project down to the Passive House requirement of 0.6ACH50 and installing a permanent air barrier behind an un-insulated service cavity, you eliminate the dust intrusion. (Place an appropriate vapor control layer in the climate appropriate position in the assembly in addition to the AB.)

    Gregory, Three cheers for Mineral Wool. The lack of formaldehyde in the European version makes sense. I thought something was missing. Roxul (my fav...) is a European company with only two plants in North America. Those plants probably have not been re-tooled for the new recipe. Got an english version document or source that you can share?

    Aj... Large scale calamity as a solution... Really dude?!?

  12. dU9rsLaVwT | | #12

    I have a problem with the Hawaii comment. The problem there is that everyone seems to run air conditioning all the time, but it makes no sense to try and keep a building cool without insulation to keep the heat out and cold in. What I saw in Hawaii is that, most of the time, the AC running on high with windows and doors open. It made me kind of sad...

    I love the idea of strawbale, but it isn't always practical for every application, I think that is why it gets ignored so much. I wouldn't design a mulit-family or mixed-use building out of strawbale, the engineering, waterproofing details, and liability would be a nightmare. I'm in favor of single family residences with strawbale, however multistory straw bale buildings become difficult in high snow load or earthquake prone areas and you still have to detail how to insulate the floor and ceiling, which to my understanding isn't typically done with straw... at least I don't know if I'd use straw in a floor or ceiling.

    Despite concerns of some of these unhealthy building products, I would be more concerned with the finish materials. These are the materials you are exposed to everyday. Insulation and rigid foam can be well sealed within a wall cavity. The argument then becomes, how "Green" is the product? I'm more concerned with the life of a product. How long will a product last? How much energy and emissions is our building saving compared to the energy and emissions used to create it? Can this product be reused at the end of it's life? And most importantly, can the product be used to retrofit an existing building?

    There is no perfect product...yet, so all we can do is weigh the pros and cons and be logical about real world effects of certain products. As always, I'm in favor of rigid foam wrapping the exterior of a building and I'm hopeful that in the near future, it will become common enough that it will warrant the speedy development of healthier and greener foam products. Of course indoor air quality is important in every building through proper ventilation and supply air .

  13. homedesign | | #13


  14. Expert Member
    CARL SEVILLE | | #14

    Boys, boys...
    First, thanks for all the comments, even those that bust my chops. It's always good to get the conversation going. Second, I am not seriously suggesting that we stop insulating, but this post is an extension of my review of the Building Green book on green materials where I expressed my concerns about chemicals in so many products we deal with daily. With health concerns over SPF, carcinogenic fiberglass, and possibly as yet to be disclosed problems with other common products, it is time to start thinking about alternatives. The traditional methods mentioned in comments above such as straw bale, rammed earth, etc, are reasonable suggestions, but as Martin pointed out, the cost implications of these labor intensive materials make them very unlikely to gain mass appeal. Sometimes I run into problems that appear to me practically impossible to solve and I feel the need to express this frustration.

  15. michael anschel | | #15

    Perhaps what we really need...
    ....Is for Green Building to get serious about the Green part of the process and quick obsessing of the Energy part of the equation. Seriously, it is enough to drive a thinking man insane.

    We build unhealthy structures and we pack them full of unhealthy stuff. The asthma rates in the US are higher than anywhere, even China where coal pollution is a part of every day life. We build homes that struggle to last 20 years as technology after technology fails.

    My favorite line from Building Science Corporation's Summer Camp a few years back came from Jan Kosney from the Fraunhofer Institute in Bavaria who said "Buildings work just fine until you insulate them. Get rid of the insulation, and you eliminate the problems"

    Insulation should be used judiciously, and it has a value, but our first priority should be the health and safety of the folks making the stuff, installing the stuff, and living with the stuff.


  16. michael anschel | | #16

    I think the onus is on Martin to prove to us that Cellulose is completely safe. In order to do that he will have to prove that the fungicide, fire retardant, stabalizers, and all the other additives are harmless to humans in all stages of the products life. Last I heard there was a big blow out because big box retailers were selling cellulose that used Ammonium Sulfate and homeowners were complaining that their homes smelled of cat piss. ... wait, in order for that to happen the cellulose must have been getting wet... and since insulation slows the drying potential the insulation can stay wet... and then... THE REMODELERS GET RICH REBUILDING HOME AFTER HOME THAT WAS INSULATED WITH CELLULOSE BECAUSE HOMES LEAK.

    Yeah, cellulose is so awesome.. like blue jeans. I like to wear blue jeans when I shovel snow because they dry out so fast.. I should make insulation of those too....

  17. wjrobinson | | #17

    Father of LEED: Humans ‘blissfully unaware’ of coming climate cr
    a snippet.... along my population thoughts....

    “There’s a perfectly safe fusion reactor [93 million] miles from the planet. We know when it’s going to start up and power down,” he said.

    He added: “The planet does not need you…there is absolutely nothing we can do to this planet that, in a million years — two ticks of a second to the planet — won’t be obliterated. We need to get over ourselves.”

    It starts by using that most unique of human abilities: the capacity to plan. If we take this information and use it intelligently — instead of ignoring it — we can stop ourselves from being the “villain” and instead “be the hero in our own movie,” he said.

    If we don’t, and climate change reaches “a tipping point,” we’ll no longer have the power to change things.

    “We do not have recourse,” he said sternly. “We cannot negotiate with nature.”

    And another from the comments....

    "Watson, like most environmentalist doesn't have the courage to just flat out state that we are breeding ourselves out of existence - certainly out of existence as we have known it in the last 150 years. Or, state that the only universal environmental solution to anthropic environmental problems and non-sustainability - is the reduction of the human population. Anything else is just a token effort. This is the over-whelming denial factor that will ultimately result in self-correcting solutions (as Watson points out) to the human over population problem - just like it does with every other species."

    My last thoughts on the matter at hand....

    All our green building ideas to date can't put a nick in the real deal problem, which is the fact that no one but the Chinese seem to understand... population lowering is the one and only way to get us through this next century or two reasonably unscathed.

  18. GBA Editor
    Martin Holladay | | #18

    Response to Michael Anschel
    So, what's in your attic?

  19. Jesse Thompson | | #19

    Mineral Wool
    For all the fans of mineral wool, have you ever actually worked with it?

    It's fairly miserable to be around, much more similar to fiberglass than not. It itches like crazy on unprotected contact, the rigid stiff "boardstock" (Roxul Drainboard type) is rare and expensive, the soft type (standard Thermafiber or Roxul) is soft and floppy just like fiberglass batts are and installs just as poorly, and the US stock seems to have levels of formaldehyde in it that wouldn't lead me to put it inside an air-barrier in a building that people use.

    We specified it on a recent project and the contractor really wasn't thrilled with it. I heard the same thing from Solar Knights in California when they started it using it on their Passivhaus retrofit after being around too many Euro building slide shows just like us.

    Perhaps in a few years after the commercial sector starts using it in greater quantities these issues might get solved for us, but we'll stick to cellulose for our current projects, and work really hard to make sure we find out if our new construction buildings leak before we close up the shells on them.

  20. Expert Member
    CARL SEVILLE | | #20

    Michael, about your comment...
    "enough to drive a thinking man insane" seems to imply that you are both a thinking man AND sane. I know several people who would argue with at least one of those points about you.

  21. jbmoyer | | #21

    Cellulose Insulation
    Uh, what's wrong with cellulose insulation?

    Just make sure it isn't treated with ammonium sulfate.

    Green Fiber and National Fiber are just 2 U.S. manufacturers treat their product with borates which, from what I gather, is pretty benign stuff.

    And about the whole durability and insulated buildings thing...

    BS 101: Make sure your building enclosure controls heat, moisture, air, and yer all good.

  22. albertrooks | | #22

    Mineral Wool density

    It't true that the Solar Knight PH project had issues with the mineral wool board to warp the exterior. However to be fair to the product, the issue was density. The boards come in density ranges from 4lb to 8lb off the shelf. The mistakenly ordered low density boards compressed when the battens were applied. The higher 8lb density will not do that.

    There is also a fastener issue. The double threaded countersunk heads will let the fasterner drive in, set the head flush, without as much compression on the insulation board as with the normal SIP, ledger lock etc screws. Works great on external foam too.

    And yep, it's not fun to work with. I agree!

  23. Gregory La Vardera | | #23

    re Mineral Wool to Jesse Thompson
    Jesse, You must be commenting on thermafiber's products. Roxuls wall batts are nothing like fiberglass blankets. Anybody who has handled both would know. I've handled the Roxul material and it caused no itching or discomfort on my skin - nothing like fiberglass. And this is the difference, and why it installs so much better than fiberglass. No drooping, no sagging. Its a totally different dynamic from fiberglass batts. If there are no wires in your cavity mineral wool will fill voids better than blown in cellulose.

  24. user-988403 | | #24

    Nice discusion
    You guys need a comment on a comment on an exiting post like this. So to Micheal `s comment "...quick (or did you mean quit) obsessing of the Energy part of the equation". Obviously that is the difficult part and you need some engineering skills to solve it. I am sure Jan Kosney from the Fraunhofer Institute did not suggest to NOT insulate buildings? We have to improve the energy part of green building significantly in order to make a change. As we all know 50% of the energy used in the US is used by building and 90% of this by buildings operation. In fact I believe (when my idealism comes out) we should build net-zero because we CAN. If our children`s - children`s ask why we ruined the planet and the answer is that it was too expensive....NOT COOL.

    Of course I have not all the answers so it is also of my concern what type of insulation is environmentally safe and healthy. From an environmental standpoint I found the recent blog ( very helpful. I especially liked that Excel sheet. From an health prospective this blog including the comments is also very informative. I also hope that new products come soon. I know in Europe they use hemp and sheep wool. Even Vacuum Insulation Panels seem to be quite sustainable (just not to your wallet).

  25. GBA Editor
    Martin Holladay | | #25

    Another response to Michael Anschel
    You wrote, "I think the onus is on Martin to prove to us that cellulose is completely safe."

    And why is that? Let me recap. Tens of thousands of homes have been insulated with cellulose, for decades. Carl Seville decided to write a blog in which he wrote, "There are concerns with the dust and additives used in cellulose insulation, raising some suspicions about that product’s green credentials ... Do we stop insulating buildings to avoid being poisoned by them?"

    And suddenly the onus is on ME? I think the onus still rests on Carl's shoulders. This isn't my blog.

    It isn't as if cellulose is a new invention that just came out of Dow or Monsanto. It's ground-up newspapers and borate.

  26. Jesse Thompson | | #26

    itchy mineral wool
    Greg, you must be tougher than me, after this thread started I went to look at the chunk of Roxul Drainboard (stiff 8lb density) we have in the office and my fingers were itchy for a few hours after the brief contact.

  27. wjrobinson | | #27

    "If our children`s -
    "If our children`s - children`s ask why we ruined the planet"

    The "children" are the problem. Have 0-1 offspring and you will be doing the only real thing you can do to make the future world livable for those that live then.

    That and all kinds of new tech will do the job.

    And toxic cellulose? What next?

  28. JustHousing | | #28

    MSDS on cellulose
    Granted, this is the materials data safety sheet for just one product, but I think that most cellulose insulation could be categorized as such. So, I'm not Martin or Carl, but it is so easy to check the "safety" of this material, that I'm joining the conversation.

    Michael, you can find insulation made from blue jeans. Here's just one company:

    Carl, you ask if integration is the answer. You bet! But not the kind you refer to. Integration is how we make good buildings. I think that green building is a 3-legged stool, with energy, occupant health, and building durability as the legs.

  29. Expert Member
    CARL SEVILLE | | #29

    Throwing More Stones at Green Building's Glass House
    I really appreciate all the comments, it is a great feeling to generate so much conversation on a subject.

    To address Michael and Martin's discussion about cellulose - we might consider the precautionary principle - rather than have to prove that something is toxic to eliminate using it, maybe we should start requiring materials to prove that they are completely safe before they are allowed on the market. Regardless of whether or not cellulose is safe, as Michael pointed out, it is one of the most challenged insulations when wetted. And while we are all working to build better, I've been in construction long enough to acknowledge that things go wrong very frequently, and as building science has determined over the past few decades, insulation and moisture don't mix well. Add health concerns from many of the insulation materials we use, and I think that it's worth reconsidering how we build and insulate. I would love to see buildings with safe, structurally integrated insulation, but I do recognize that it is not financially viable in our current economic model.

    Regarding the comments on the merits of mineral wood batts - it does appear that their fibers are large enough so as to not to be considered carcinogenic, but I will argue that in day to day practice, batt insulation is problematic. There are a small, select group of professionals that can install it effectively, but the vast majority of the time it is poorly installed, regardless of what it is made out of. I do like the idea of notching studs and running all wires along the bottom plate, but there are still electrical devices, plumbing, and numerous other obstructions that make any batt installation challenging at best.

    As to the title about continuing to insulate our buildings, I am not seriously suggesting that we don't insulate, but we need to reconsider how we use our living space. As Steve Mouzon pointed out in his book and blog, The Original Green,, humans are capable of easily withstanding about a 30 degree temperature range, yet we heat and cool our buildings to about a 2 degree range. This is costly, wasteful, and very often, not particularly successful. So maybe it's time to reconsider how we use our buildings and look at conditioning the people rather than all the enclosed air within our buildings. Not that I have a way to effectively accomplish this but it is worth taking the long view and rethinking how we do things.

  30. GBA Editor
    Martin Holladay | | #30

    Conditioning people
    I know of two ways of conditioning people in a heating climate:

    1. The first is to install microwave emitters in the ceiling of each room, so that occupants are cooked just like the food in your microwave oven. This was suggested by a military engineer, Dr. Eleanor R. Adair. I wrote an article about the proposal for the Journal of Light Construction. There are a few problems -- melting chocolate, the tendency for metal objects to arc -- that need to be worked out. Suffice it to say that few green builders want to heat occupants with microwave radiation.

    2. Wear a snowmobile suit containing electric-resistance heating wires hooked up to ni-cad battery pack that you wear on your belt. (Milwaukee is already selling a heated jacket that operates this way.) Just swap out your ni-cad battery pack every few hours and you're good to go. At night, just pile on the quilts really thick. Of course, you still need to keep your house above freezing so your pipes don't freeze.

  31. Expert Member
    CARL SEVILLE | | #31

    More Northern Bias from Martin
    Martin - I appreciate your comments on heating people, but, once again, you show your northern bias by not even mentioning air conditioning. Time to remember the rest of the country. buddy.

  32. GBA Editor
    Martin Holladay | | #32

    Conditioning people down South
    Here you go:

  33. user-884554 | | #33

    In the interest of full disclosure, I work for large, dare I say the word, fiberglass manufacturer with production facilities around the world. I suggest you read more closely the recent report on carcinogens. You state "inhalable fibers are listed as a carcinogen". Your statement is out of context and does not accurately reflect the actual report language. What you do not state is that only certain inhalable products were listed as carcinogens. In fact, the report actually states "not all glass wool fibers cause cancer". Those "certain glass fibers" that were mentioned in the report are specialty fibers that are not used in the manufacturing of building insulation products. These specialty fibers make up less that 1% of all fibers produced. Traditional fiberglass building insulation products comprise the most tested building product in the building community...and guess what, the most recent testing points out that it is safe to use.
    Knowing that you are not a fan of fiberglass products, I don't expect to sway your opinion. However, in fairness to your reading audience and in the interest of accuracy, I offer these comments.
    Tongue in cheek or not, your reference to fiberglass building insulation as a carcinogen is simply not correct.

  34. michael anschel | | #34

    Rachel, I am all too familiar with bonded logic and have witnessed the stuff in action. I think my favorite installation so far was the one Carl and I looked at in Carmel California. A stunning 9 million dollar home built on what we guessed was a 5 million dollar lot. This LEED certified "green" house was boastfully insulated with blue-jean batt insulation. And, like ever other batt installation, this one was crap. Compressed batts, sagging batts, 80% full wall cavities... Also, no air barrier on either side and no moisture retarder on either side (although it is coastal CA so they are in a somewhat neutral state of existence)

    MSDS sheets disclose some information, but tell us little about the compounds themselves. If Cellulose manufacturers were to agree to ban the use of Ammonium Sulfate in their products, perhaps that would be a start but it is still commonly found. Often installers don't even realize they are installing it.

  35. michael anschel | | #35

    Of children and wallets
    Phillip, I like your contribution to the discussion. We could easily look to European buildings from the last thousand years and point to straw bale and lime rich plaster with large overhangs as a model of smart home design. But since we began importing the Tuscany and the California Modern into MN, ignoring its climatic origins and created an industry set on volume and speed, that model died with it.

    I have to point out though that in the first paragraph you ask us to consider the value of human life, and in the second you reverence wallets. To my way of thinking, the cost of using building materials that pose NO THREAT is irrelevant in the equation of life.

    To that end, the out-dated "three legged stool" of green building, is the most ridiculous thing I have ever heard from the energy and HVAC camp. I think Mark L. and David J. are great dudes, but I want to slap them every time I hear this referenced. No green building program in the world with its salt would ever reduce the concept to this base an irresponsible an equation. CASBEE (cool), BEEAM (old) , GreenGlobes (decent), even LEED all understand the concept to be far more complex. To quote Bill Reed (one of the authors of LEED) green building is about developing our relationship with nature.

    PS. Phillip. Your stats on energy are close, but not entirely accurate. 48% of total US energy use goes to buildings. Roughly 50% of that is in homes. 76% of the electricity used in the US comes from operations in buildings. The amount used in homes is guesstimated at less than 40% of that or roughly 30%. This would be more in line with global emissions reporting that attributes around 4% of GHG emissions to homes. Hardly seems worth putting our families at risk, or spending oodles of cash pursuing so-called net-zero energy homes (They need to start calculating GWP).

    And once again.. Energy Source is the issue. NOT Energy Efficiency.

  36. Beideck | | #36

    This article is shameful
    This is the type of piece that I really hope the green building advisor doesn't run again. Carl is clearly just trying to stir the pot, see his comment, "it is a great feeling to generate so much conversation on a subject. "

    The reader has to wade through all of the comments to find out that Carl was making comments "a bit over the top" and "partially tongue in cheek". He has admitted that he had no justification for his claim that insulation is poisoning occupants. The issue of what insulation is "best" can be complicated as there are different points of view to evaluate them. I would much rather see a piece that has a goal to illuminate the situation rather than cloud it so the author can amuse himself by creating controversy. Thank you Martin Holladay, Philipp Gross, Rachel Wagner and others for trying to bring some reality into this. I just hope others took the time to wade through all the comments after Carl decided to muddy the waters.

  37. GBA Editor
    Allison A. Bailes III, PhD | | #37

    Martin's right.
    The answer to your question is an emphatic NO, Carl. Martin's comments are spot on. Unless you can convince everyone to stop conditioning buildings as well, insulation should not and will not go away, despite some flaws in the materials used.

    I understand your desire to be provocative with this article, but it may lead some to think that there's actually a debate here when there is none.

  38. PeterTroast | | #38

    Dammit Carl.
    Dammit Carl. I know this forum is us talking to ourselves, and that you're being provocative, but you and Anschel continue to be the nattering nabobs of negativism. It's time to stop it. We're struggling enough trying to get traction for building efficiency. When experts cast doubt, it amplifies the already difficult challenge of the under-educated consumer. It injects paralysis at a time when we can't afford it. Time to start seeing that glass as half full.

  39. GBA Editor
    Martin Holladay | | #39

    Thanks for the support
    Daniel Beideck , Allison Bailes, and Peter Troast -- thank you.

    At a time like this, when millions of American attics desperately need 12 to 24 inches of cellulose on top of whatever thin layer of poorly installed insulation happens to be up there, Carl's blog isn't going to help.

    The climate of our planet is at risk. It's all fine and good to write humorous articles that are "a bit over the top" and "partially tongue in cheek," but the topic of this blog is a serious matter on which many things hinge, including a potential planetary catastrophe.

  40. Expert Member
    CARL SEVILLE | | #40

    Response to Chris Brown
    I appreciate your contributing to the conversation, however you are mistaken that I am not a fan of fiberglass. I happen to like it in blow in form (and like all products, when installed correctly). My earlier post taking batt insulation to task did not specifically target fiberglass, it included all other batt products.
    I was very disappointed to read in the report on carcinogens that glass fibers were included as I recommend blown fiberglass products to many of my clients. Regarding your comment that I should read the report more closely, I have and this is what I found:
    "Inhalation exposure of F344 rats to FG insulation fiberglass with binder (4 to 6 μm in diameter and > 20 μm long) significantly increased the incidence of mononuclear-cell leukemia in rats (males and females combined). Glass-fiber-related pulmonary and tracheal-bronchial lymph-node le- sions were observed but were less severe than for exposure to special- purpose fibers. As with the findings for Tempstran 100/475 glass fibers in this strain (discussed above), these findings were considered to be exposure-related (Mitchell et al. 1986, Moorman et al. 1988). Intraperitoneal injection of MMVF 11 glass fibers caused mesothe- lioma of the abdominal cavity in male and female Wistar rats (Roller et al. 1996, 1997), and intraperitoneal injection of MMVF 10 glass fibers increased tumor rates in male Wistar rats (Miller et al. 1999)."

    While I am not terrified of fiberglass and I will continue to recommend it, I don't believe that this report exonerates it from being a potential carcinogen.

  41. Expert Member
    CARL SEVILLE | | #41

    To My (Now Possibly Former) Friends Who Have Commented Above
    Yes, I look to stir things up in my posts and I certainly have done so with this one, even more than I would have ever expected. I am surprised that those who know me, and even the casual reader, would take seriously the suggestion that we stop installing insulation. I have been a long term proponent of high performance construction and recommend various insulation products to my clients on their projects. I have been a fan of most types of insulation including spray foam, blown in fiberglass, mineral wool, and cellulose. I do believe, however, that as concerns are raised about products, including health concerns from diisocyanates, formaldehyde, and fire retardants, global warming potential from blowing agents, and carcinogenic properties of fibers, I think it is very important for us to consider how they will affect our decisions in both the short and long terms. We used the miracle product asbestos for many years before it was banned from most products. Lead was a major component of most paints for many years. DDT was regularly sprayed where people lived for decades. BPA is still being used in plastics and likely causing health problems in millions of people. While we need to make our buildings efficient, we cannot do so in a vacuum and if we can't bring up concerns in a forum like this, where can we?

  42. Expert Member
    CARL SEVILLE | | #42

    Shout out to Peter Troast
    Nice reference back to Spiro T Agnew on the "nabobs of negativism" quote, although I believe the word was actually "negativity." And it was written by the late William Safire, writer of the wonderful column On Language in the NY Times Magazine for many years. I miss his wit.

  43. GBA Editor
    Martin Holladay | | #43

    Carl - wrong again
    Google before you guess. "Nabobs of negativism" was the original phrase spoken by that disgraced criminal, Spiro T. Agnew.

  44. Expert Member
    CARL SEVILLE | | #44

    Or Maybe Not...
    Didn't guess, I did check it on google. Of course the reference could be wrong.

    Penned by speechwriter William Safire, the "nattering nabobs of negativity" was the phrase used by former Vice President, Spiro Agnew, to refer to the "liberal" media. Agnew had reason to discourage press scrutiny: not only was he in the Nixon administration, but he would later be convicted of tax evasion and money laundering in connection to bribes he took as governor of Maryland.

  45. Gregory La Vardera | | #45

    If you have DrainBoard in the office, then you know its not the same consistency as fiberglass batts. Roxul's wall cavity insulation is not as rigid as DrainBoard, but its closer to that than fiberglass batts. If fiberglass comes in blankets, mineral wool comes in loaves. You even cut it with a bread knife.

    Fiberglass makes my skin irritated - you have the sense that there are thousands of tiny shards stuck in your skin. Mineral wool by comparison just feels like sheep's wool to me. It does not bother my skin at all.

  46. GBA Editor
    Martin Holladay | | #46

    Google results
    Number of Google results:
    "Nattering nabobs of negativity" = 57,700 results
    "Nattering nabobs of negativism" = 349,000 results

  47. Expert Member
    ARMANDO COBO | | #47

    WOW... green commandos again...
    It’s to bad this thread is going from good to wako, as this is a typical example of political correctness going wild. For crying out loud!!! This is why sometimes “Green Commandos” and “Green Police” turn people off to green building, energy efficiency and high performing houses. Most of us have known Carl for many years, and if you think he meant to “not insulate houses”, well, either you don’t know him or you don’t understand his blogs, or maybe, you are a literal Curmudgeon.
    Most of us who design and build homes for a living, in the real world, know that every single product that goes into our homes is made with some kind of natural or man made component that may cause some harm at some point, or at least has the potential to. Yes, some products are better than others; and in the case of insulation, as far as I know, there is no insulation that is 100% safe or has no issues when installed incorrectly. I choose combinations of cellulose and foams, open and close. I choose not to use FG batts because it is hardly ever installed right and I want to avoid fixing, reinstall, and inspection delays. Also, I expect every subcontractor to follow OSHA rules in their installations. That’s all we can expect.
    Finally, there is more bad stuff in all the chemicals, furniture, automobiles, pets and clothing that people bring into their brand new healthy house than most products used to build it. Maybe we should concentrate our commando comments to that.
    Carl… hang in there, buddy…I’ll be your only friend if you need to… ;-)))

  48. Kopper37 | | #48

    Isn't It Ironic?
    Here's a bit of trivia for you Carl ;-)

    The captioned picture asks, "Will something like autoclaved aerated concrete (AAC) emerge as one of the safest forms of insulation?"

    For almost 50 years, AAC was produced in Sweden using alum slate deposits. Unknown at the time, the rock deposit also contained uranium. And somewhere along the radioactive decay chain it produces radon gas. They didn't stop using the alum slate until 1972.

    Don't get me wrong. I've built with AAC, and it certainly has its place. But the captioned picture reminds me of the saying that "no good deed goes unpunished."

    Insulating is a good deed, but it does carry a potential liability.

  49. Expert Member
    CARL SEVILLE | | #49

    Awesome Info on AAC
    Daniel - I think you may have just proved my point and then some. Maybe we should just stop building altogether, it seems like everything we touch may somehow be hazardous.

  50. GBA Editor
    Allison A. Bailes III, PhD | | #50

    Still a friend...
    Carl, I know you well enough and could read the qualifying statements in the text, so I knew you weren't seriously proposing not to insulate houses. You've got a big reputation in the green building community, and GBA gives you a huge platform to amplify your writing, though, so something as seemingly innocent as a blog post title can have serious ramifications.

    I guarantee you that, based on the title of this article alone, some people will go out and start claiming that you, and thus GBA as well, advocate not insulating houses. Look what happened with your post on batt insulation. You didn't actually state definitively that batts should be outlawed, but that's how a lot people represented your article.

    Now, if batts went away, that would actually be a good thing. I jumped into this discussion, though, because the same does not hold true for insulation. Take away insulation, and houses start getting new problems, the most obvious being high energy bills.

    Another is that many uninsulated houses in humid climates didn't have problems from lack of insulation - until they installed air conditioning. Put in the AC, drop the temperature of that uninsulated floor over the vented crawl space, and suddenly it's a biological wonderland on the wood. I've seen it. You've seen it. That problem isn't from lack of insulation; it's from air conditioning.

    Yes, you're absolutely right that it's fair to discuss the safety of the materials we use and recommend. I'd say it's even incumbent upon us to do so, and that's a great discussion to have. My main problem with the post was the logic-defying leap you made from materials safety to getting rid of insulation.

    I don't think any of us ever escapes writing or saying things that bring us grief and that we wish we could take back or modify. You correctly called me on my uncritical review of heat pump water heaters last year, and I modified the article as a result. I applaud your adding a note at the top to help people understand the context better and what your true intentions and beliefs are.

    Anyway, I wouldn't dump you as a friend over something as silly as this. Now, if you ever made fun of me and told me I have a girl's name, them's fightin' words!

  51. GBA Editor
    Martin Holladay | | #51

    Carl, if I'm still your friend, I can still tease you, right?
    Thanks for the Author's Note, Carl.

    You stirred the pot a little deeper than usual this week, but eventually the broth will clarify.

  52. michael anschel | | #52

    Positivity reigns!!
    I think it is great that we can tell homeowners that rather than spending all their hard earned cash pursuing an overly complicated, potentially health threatening, potentially more polluting, and low return on investment, that they can use that cash to enjoy life. yay!!

  53. user-988403 | | #53

    Bad bottom line
    At first I thought this was kind of fun but know I can see the concerns of recent posts that people with selective hearing (or reading) could get the wrong message. I will keep this short because I have to plan some super insulated houses.

    GWP: As mentioned in my last post the tool provided here ( shows that people who are not afraid of overcomplicated stuff are actually thinking about this and helping others understand (given that they can do simple inputs and can read a graph).

    Health: Eat healthy, do sport and live in a house with a mechanical ventilation system (HRV or ERV to be energy efficient too)

    To the common debate "Energy Source is the issue. NOT Energy Efficiency": My opinion is that we have a Energy Source problem that we can only (maybe) fix, if we become more Energy Efficient. Everything is interconnected and unfortunately we life in a complicated world....

  54. homedesign | | #54

    Please Raise the Bar for the South
    Instead of advocating less insulation I think we should all consider MORE insulation....
    Especially us "southerners"
    "We" are more of a "problem" than our yankee friends
    We seem to be building more houses AND we are Cooling Dominated

    WE are using more SOURCE energy per household than the Northeast !

  55. Gregory La Vardera | | #55

    watch a Mineral Wool install
    Here is a short video showing the factory fab of wall panels in a typical Swedish factory. The isulation segment takes place in the first minute, so go watch it:

    Things to note:

    • The material cuts easily, into definitive rectangular blocks that fully fill stud cavities - BETTER than any blown in insulation.

    • The mineral wool is cut with a big bread knife. Its not compressed when its cut the way fiberglass is cut a drywall knife. It is not a blanket, but a block that can be measured and cut precisely.

    • The workers have a cutting jig, which allows them to cut the mineral wool precisely to fill off-size stud cavities. Its a simple device, nothing clever here, but makes a good installation easy.

    • When the wall is done every void is completely filled with Mineral wool. Dense batts fill every cubic inch. Nothing sagging. No gaps between pieces. 100% fill, no convection spaces. And this is not some demo staged by an insulation manufacturer. Its this easy to install well, its rote. They achieve this quality of installation on ALL their houses. That is the point, is it not.

    • This install is fast, and easy. As fast or faster than any blown in install, especially when you figure the prep. And your subcontractors already know how to do this.

    • And last, but not least - note that the workers here are not wearing gloves, nor respirators. Aside from Jesse above, mineral wool is not itchy and does not irritate the skin like fiberglass.

  56. homedesign | | #56

    Gregory La Vardera is on a good track
    I noticed that you did a good job of challenging Martin recently.
    I also think you have some very good ideas posted at your site

  57. Expert Member
    ARMANDO COBO | | #57

    Balloon Framing
    Yeah, let’s try to do that with field-framed houses, especially in scorching summers or freezing winters. I can see a lot of issues with his Swedish techniques, and besides, no one has to go to Sweden to learn that… you could have study Balloon Framing or “Chicago Construction” right here in the good ol’ USA, made possible by the invention of factory produced nails, and it had less thermal bridging too.
    George Washington Snow constructed the first balloon frame structures in Chicago in the early 1800s, a warehouse, 1832, and St. Mary's Church, 1833. Houses were smaller and you could do such “engineering” of resting floor joists on 2” thick ledgers. Today with larger spans, many trusses and TJIs require 3” bearing. Framing floors with trusses allow using them for mechanical, electrical and plumbing runs, thus no having to build furr-downs (which have issues on their own).
    So slap rigid foam outside the wall and roof sheathing, OC foam on rim joists and cellulose on the walls, just no batts, please. I call it good here in the South & SW and I leave the double walls and Larsen truss walls for folks up-nowth.

  58. homedesign | | #58

    moving to the Q&A
    Sorry about changing the subject...(Thread Drift)
    I started a new topic at the Q&A

  59. Jesse Thompson | | #59

    Air barriers
    One more key detail the swedish platform framing video shows that would be critical to using mineral wool (and other batt insulations) in cold climate low-energy buildings with their colder exterior skins:

    The Swedish system relies on a warm side air barrier (the plastic sheeting) shown sandwiched between the 2x8 & 2x strapping and breathable exterior sheathing (looks like gypsum exterior sheathing in the video?). This is why they can get away with a batt insulation in high-R walls without moisture damage, voids and gaps in the batt insulation are much less dangerous when any moisture that enters the wall can easily dry to the outside.

    Replicating their system with typical impermeable US OSB sheathing on the exterior in a high-R wall system would be much riskier in a cold climate.

  60. Robert Swinburne | | #60

    A quick summary after slogging through all the comments above instead of doing my work:
    There is no perfect solution.

  61. user-910182 | | #61

    Spray Foam
    This has been a great discussion but little discussion on spray foam. I used to think that it was the way to go if you could afford it, but am seeing problems on almost every job I see it used on. My instructor at my IR training showed many examples of problems with spray foam and stated that he has yet to see a foam job without problems. That said what is the alternative?? Batts are out of the question which leaves SIPs, cellulose and foam. Foam is out because of issues mentioned above. SIP buildings are the leakiest new buildings I have done air leakage tests on and have seen some catastrophic moisture problems due to concentration of air leakage and subsequent moisture problems. That leaves cellulose as the preferred choice. The drawbacks on cellulose mentioned previously center on flame retardants. That problem is solved by using 100% borate treated material. I use Canadian material which is all borate and meets a more stringent corrosive testing standard than required in the US.

  62. MGHbHtTyUE | | #62

    Another side of insulation . . .
    One item I have not yet seen discussed on this site is the concerns of flammability of insulation. Foam plastic insulation (EPS, XPS, Polyiso, spray foams, etc.) is combustible and produces very thick smoke - and remember it is smoke that kills more people than fire does. Fiberglass insulation melts in a fire; the kraft facings are highly combustible. For these reasons, as well as the reasons provided in this article, I am increasingly more impressed with products like AAC and rock (mineral) wool insulation - highly stable over time and temperature and good R-values to boot. I think Mr. Seville is on the right track without even looking at the fire-hazard of insulations.

  63. zt88TUzzpw | | #63

    Don't forget about existing buildings
    Carl brings up some good points. While structural material with integrated insulation may be a good suggestion for new construction, ti's not practical for rehab projects. The options are a bit more limited especially when money is concerned. We've compiled a number of options, noting the pros and cons of each.

  64. user-347767 | | #64

    Flamability and Combustion Products
    I would like to second the post by Edward Dueppen. My wife and I are planning a new, highly insulated house in Wisconsin. After seeing first hand how fast a residential fire can spread, and doing some research on that subject, fire proofing became a top priority. Most of the fire deaths occur due to inhaling hot and toxic gasses -- not the flames themselves. Foams appear to be much more dangerous in a fire situation. I am looking hard at rock/mineral wool insulation (along with metal roofing and fiber cement siding) for that non-flamable feature. It really seems to satisfy all of the green building demands except one -- it's commonly available only in batt or board form.

    Would the dislike for rock/mineral wool go away if a blown in product was available? Or does that have other problems. I have not been able to find anyone that installs blown in rock wool, and few around here even want to do batts. I will likely end up doing this job myself just out of frustration.

  65. user-988403 | | #65

    Fire hazard
    Karl, I am sorry to hear about the first hand experience. I do not think mineral insulation comes as a blown in application. There are several points/advice I want to give you.

    1) Most deaths occur to the fact that fire burns the oxygen you need to breath. That would be my bigger concern than the toxic gases released by foam (I don`t like foam and I am would not suggest it anyhow)

    2) The largest potential of fire spreading in your home is the interior accessories (Curtains/ sofas furniture etc.) not the construction material. The structure could be build to such a high level of fire safety, that there would be no more oxygen to breath before the fire gets to the insulation.

    3) Mineral wool batts put in right are a good way of insulating your house. As a belt and suspender approach I would suggest to have two air barriers (interior and exterior) to minimize convection potential.

    4) To really improve the fire spreading potential of your new house you should consider.

    -Two (or one thick) layer of drywall.
    - No air gabs between critical rooms
    - Fire safety door where there are potential fire causes (mechanical room etc.)

    This is not standard practice and does not have to be. But I totally understand that you would want that after your experience.

  66. GBA Editor
    Martin Holladay | | #66

    Blown-in mineral wool
    It's possible to install mineral wool as a blown-in insulation. Unfortunately I don't have supplier information.

  67. user-347767 | | #67

    Philipp Gross,
    Thank you for your reply, your points are well taken. Just to be more clear than my original message the house that burned was a neighbor, not my own. After watching that tragedy (I was the second person to call 911 as smoke was seeping out around the garage eaves) I started doing a lot of research into building fire safety. I hate scope creep as much as anyone else but if "green building" means safer for people and planet then I think that fire safety needs to be added to list of considerations for any building material and system.

    I'm not an expert but after looking at all the various insulation alternatives I've landed on borate-only celulose and rockwool as the two best. I think between the two all of the insulation bases are covered. Are they perfect? No, but the rockwool in batt or board form can work if the installation is done properly and the green goodness of cellulose insulation has been covered quite well here.

    The rockwool fills the green checklist in that it is inert, water resistant, insect and rodent resistant, fire proof, made with widely available material, decent R-value, available in many forms and densities, and should last 100+ years with reasonable protection. Am I missing something? In this area rockwool is used only for commercial and industrial buildings. It seems that rockwool was common in the past until fiberglass batts displaced its use due to lower cost.

    Another item that I'm looking at is residential fire sprinkler. I think that between fire safe building materials and the fire sprinkler system I would feel well covered.

    Martin Holladay,
    Thank you for the reply. My general contractor has called around and can't find anyone local who does that - or has even heard of blown in rockwool. Maybe this is a great opportunity for someone.

  68. hCMByaNRpd | | #68

    Hi Martin and Carl (and
    Hi Martin and Carl (and Albert too),
    This is an interesting subject indeed. Though I am not at all interested in abandoning insulation, far from it. I am deeply challenged by it in some ways that Carl touched upon. I live in the Pacific Northwest and actually met Martin on his trip to Washington this past March. (I even had the honor of buying him a beer.) Anyway, as Martin has observed in another post, blown-in-fiberglass is more common out here than cellulose. I just used it on a house that I designed and built this past year.
    Having become increasingly interested in building science over the past few years I was excited to use a material that seemed better than the standard batt insulation typically put in 2x6 walls. (My clients had initially wanted to use wool batts till I got some price quotes.) I researched both blow-in-fiberglass and cellulose, but none of the insulation contractors in my area were as comfortable with cellulose. They clearly used it far less often and they even expressed a greater concern over its durability in our climate. So in the end I went with the blown-in-fiberglass.
    Though I believe it will perform as advertised as far as energy goes, I have regretted the decision ever since. It went in in November, right as the stormy and cold season really kicked started here. We needed to have the windows and doors mostly closed, and everyone who worked in the space suffered for weeks and weeks. It was not until every surface was covered and every inch was vacuumed multiple times did people stop coughing. I have two little girls and the thought that the insulation that i myself specked and had installed in a house project might actually shorten my time on this planet with them really disturbs me. I have read convincing "scientific/medical" literature that points both ways as to the potential of fiberglass to be a carcinogen, and I had been convinced to the contrary prior to specifying it this time. But it was so unpleasant, I really wonder - and worry even.
    So this is what struck me about this discussion. For all of my fruitful reading of the GBA site last year - which has generally inspired me to design and build much more highly efficient and hopefully better houses - there was very little discussion about this dimension of the materials that make a home perform of not perform. But if I, or anyone else, ends up getting sick from them, who cares about performance. There is something wrong with the picture. I will definitely choose cellulose next time, no doubt. But I really felt let down by my decision and I had felt that I had researched pretty well the pros and cons. The general feedback I got from the GBA was that both forms of dense pack perform similarly so go with either. But there is definitely more to consider, which is what Carl's article brought up.
    The aspect of the conversation that he started that has not been developed very far is how else might we be building? Is there an overall better way? Carl's sighted Autoclave blocks as an example of a different approach all together. He reminded me of my hope for years that this material would become more common. They represent something totally different than our wood cavity filling approach that is considered so normal to us who live in the US. But really, we are among the few who build this way. I have often wondered if the buildings that we build, despite all of our efforts to the contrary, will seem pretty short lived in a few generations. The autoclave blocks represent a more integrated wall material: durable, firesafe, insulative, tight, and without a dew-point problem. Having traveled in Europe when I was younger I have always remembered those long lasting masonry buildings that are so normal there with their very limited use of wood. So though I too agree that Carl was exaggerating a bit regarding cellulose at least, I appreciate his thoughts about the pitfalls of they way we currently build things. I too sometimes wonder why they can so easily end up toxic and relatively short lived too.
    Thanks for all of the very interesting discussion.
    Chris Morris

  69. GBA Editor
    Martin Holladay | | #69

    Response to Chris Morris
    It was good to meet you in Washington -- and thanks again for the beer.

    I've always preferred cellulose to fiberglass, for a variety of reasons, and I was surprised to discover that builders and insulation contractors in Washington state are relatively unfamiliar with the product.

    I'm sorry to hear that you and other workers suffered from coughing spells after you insulated with fiberglass. It's probable that your lungs won't have long-term damage, although any future research that leads to a different conclusion would just provide one more reason why cellulose is a better insulation.

    It sounds like this was your first insulating job. I worked with fiberglass batts for years, like most residential builders, and I have experienced the itching and occasional coughs that come with working with fiberglass. However, residential construction work is often unpleasant, and it's important to distinguish between discomfort and a serious health threat.

    On most job sites, builders get itchy, sweaty, mosquito-bitten, scratched, and exhausted almost every day. It's hard work. Although I didn't enjoy installing fiberglass batts, especially overhead in a crawl space, it wasn't my worst construction job. (The worst, if you are curious, was scratching tar-and-gravel roofs. If you ever have to repair an old tar-and-gravel roof, the first step is to take a big scratch bar -- a heavy chunk of steel that looks like an ice chopper -- and scratch off all the gravel until nothing but asphalt is exposed. This job raises large quantities of asphalt dust which irritates the eyes and is quite painful, especially during the winter in dry, windy weather. The only cure is hard liquor at the end of the work day.)

    Anyway, as I said, construction work can be irritating. But we must distinguish between irritation and serious health threats -- for example, asbestosis or lead poisoning.

  70. hCMByaNRpd | | #70

    fiberglass dust vs autoclaved blocks
    Are you implying that you are convinced that there are no dangers to fiberglass dust inhalation beyond the itch? I am less certain, but hope you are right. ...especially for the young Latinos that seem to be the ones sent out to install it all day every day.
    And how about those autoclaved blocks? Have they taken off anywhere in the US? How about in Europe? I wonder if they have they achieved a significant market position anywhere.

  71. GBA Editor
    Martin Holladay | | #71

    Response to Chris Morris
    Contractors have been installing fiberglass insulation for over 50 years. If regular exposure to fiberglass insulation causes serious health concerns, I think they would have shown up by now. There is no evidence yet that fiberglass causes problems similar to tobacco smoke or asbestos fibers.

    Of course it would be foolhardy for anyone to label a building material "harmless." I think it's wise to wear a dust mask when working with fiberglass batts, and I avoid fiberglass these days in favor of cellulose.

    Autoclaved aerated concrete blocks have an R-value ranging from to R-1.1 to R-1.3 per inch -- That's not much. To get an R-40 wall, you'd need to build a wall that was at least 30 inches thick. That's expensive, and it's hard to put a window in such a thick wall.

  72. hCMByaNRpd | | #72

    Autoclaved blocks and their cousins
    Thanks for the reality check on Autoclaved blocks. I did not realize their R-value was so modest. I could live with a 16" thick wall, no problem - love them actually. But 30", that is pretty massive.

    It is hard to beat masonry for durability, though. What do you think of the Faswall and Rastra type ICFs, Martin? I sometimes wonder about their durability. I have seen some pretty crumbly samples of Rastra and I worry when I see people using the Faswall in foundation walls that are backfilled, since they are made with wood. Faswall is now produced in Oregon, so it is actually possible to get from my region, which I like.

  73. GBA Editor
    Martin Holladay | | #73

    Response to Chris Morris
    Rastra is another low-R wall assembly. Tests performed in 1996 by Construction Technology Laboratories, Inc. (CTL) showed that the R-value of a Rasta wall is between R-6 and R-8. (That's not the R-value per inch -- that's the R-value of the whole wall.)

    Oak Ridge National Laboratory measured the R-value of a Rastra wall and determined that the whole-wall R-value was R-7.7.

    I'm not sure of the R-value of Faswall walls.

  74. xqHJbbzZNR | | #74

    Help! Cellulose Insulation problems
    My landlord installed cellulose insulation 3.5 months ago. For the first couple of days, the smell of ammonia was overwhelming and I was experiencing shortness of breath. The intensity has gone down some, but the smell is still there -- coming out of the air vents every time the A/C is on. It smells like cat pee.

    Unfortunately, it does not smell at all in the attic, so the landlord does not believe me that the insulation is the problem. Can someone please explain to me how it could be that the smell comes out of the A/C vents but there is no smell in the attic? I need to be able to explain this to him.

    Thank you!

  75. GBA Editor
    Martin Holladay | | #75

    Response to Abigail Davis
    It's impossible to diagnose your problem over the Internet.

    I'm just speculating here, but it is possible that a long-standing odor problem in your house just became obvious after weatherization work tightened the thermal envelope of your house.

    The first step is to identify the source of the odor.

    The second step is to determine whether your house has adequate mechanical ventilation -- in other words, a fresh air supply.

  76. DVMf3LNpGw | | #76

    Think on THESE materials!
    I am a layperson who has been struggling along on the building trades learning curve for many years now, as I attempt to reconstruct a disassembled hand-hewn dovetail, old-growth cedar log home. It's considered new construction in my county and still in the planning stages. I began this as a salvage project, having salvaged many other components as well, and have been on the "green" track from the get-go searching for the materials and systems that make up the rest of the house (e.g., have had 12" AAC walls slated for the bathroom addition.) Over the years I have come to rely heavily on the BuildingGreen site for more in-depth information, reviews, discussions, etc. Okay, that's a bit of an introduction to what I want to say...

    I agree with the person who expressed an interest in seeing more "natural products" (not just natural structures, e.g., cob, strawbale, etc) listed, compared and discussed. Personally, I have been very interested in rice hulls for insulation after doing a fair amount of research, though it was awhile ago. (My county would surely take me to task on this one!) From what I recall, rice hulls are an agricultural by-product, fire-resistant, pest-resistant and mold-resistant, and a natural fiber. I cannot recall how the Texas professor (I think) filled his wall cavities. But this is one such example, along with hemp --only briefly mentioned above.

    Pumice is another natural insulation (or does it have more thermal properties?). Yes, unconventional "earthbag homes" make use of pumice in both shaping the structure and insulating. These items may be too out of the norm for professionals in the field to take seriously. But aren't we trying to pinpoint the best options, with the least hazards, and look to other sources? The more we individually investigate some of the raw materials or agricultural by-products, the greater the chance our choices will broaden.

    Another insulation product no one mentioned, though a manufactured one, is Foamglas, which I have slated for the sub-slab air-floor insulation (it's friable so would be painted). I'm always weighing out the embodied energy, health considerations, recycled or by-product contents, efficiency, etc. Anyway, I would love to hear from any, and all, who may have some experience or opinion about these 4 insulation products/materials as well as any other lesser known materials.

    With thanks.

  77. servant74 | | #77

    Concrete domes?
    You could go to the domes (that don't have to be dome shaped when done), like Monolithic Domes ( ) does. Their method is blow up a plasticized fabric dome (they sell these), spray foam on the inside for 4" of insulation, then put up reinforcing and spray 4 to 8" of concrete on the Inside.

    If you insulate the slab similarly, it makes for a VERY well insulated structure. Little on the inside to burn except furnishings.

    It may not be stylistically what most folks want, but it is 'an answer' especially for those that can't have un-natural materials on the inside.

    Yes, you can put doors and windows in it, sometimes very attractively, sometimes not. Check out their web site for more info.

    I am just interested in their stuff, other than that, no attachments to them.

    ... even considering this, the outer cover only lasts 5 to 10 years, so before 5 years, I would consider putting on a 'permanent roof', like stucco. Just my thoughts.

  78. GBA Editor
    Martin Holladay | | #78

    Response to Jack Coats
    I'll let other people comment on whether they want to live in a spray-foam dome.

    I'll just comment on your last paragraph: Stucco is not a permanent roof. It isn't even a temporary roof.

    Stucco is a type of siding, not roofing.

  79. Growin_woman | | #79

    Maybe straw bale construction?
    With all the concerns about insulation I wonder what you think about straw bale construction, expecially for simple buildings like shops? Would this method address the health and sustainability concerns?

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