Spray Foam Installation – Cellulose is better

Brooklyn brownstone owners are becoming aware of the positive effects of spray foam insulation, also known as Spray-applied polyurethane foam or SPF, to get a nice tight building envelope that does not let heat out in the winter and in during the summer. Examples of SPF are Icynene, Heatlok, Tiger Foam and SUPERGREEN FOAM.

Despite the effectiveness of spray foam to create a tight building envelope, however, most people are not aware of the health issues the spray foam can bring.

Yes current spray foam applications are sort of green because they do not off gas harmful ozone depleting chemicals like the earlier spray foams. And yes they give a very good envelope seal so that the house consumes less energy to heat or cool it.

But SPF are all made from petrochemicals and they all have huge embodied energy (i.e. a lot of energy is needed to manufacture them). On a side note don’t believe the hype around soy based spray foams. It is a bunch of lies. Yes they contain soy but the amounts are miniscule, hovering around 5% of the entire mixture.

Green builders and architects are increasingly specifying SPF for green brownstone renovations, reasoning that the energy saved in a well sealed house makes it worth the energy consumed to turn petrochemicals into spray foam. I disagree but that is another argument.

What is important in this post is that off gassing issue is only now becoming more evident. Up until now it has not been part of the equation because nobody really knew about it.

All manufacturers had claimed their particular SPF did not off gas harmful chemicals. Apparently this is not true. The common knowledge has mostly been the party line very similar to this statement here by Foam Tech. They say:

Urethanes are non-toxic and only require protection for our operators during installations, but the finished product is completely safe and has no formaldehydes.

No formaldehyde yes true. And no nuclear waste or explosives. It is an empty statement because formaldehyde is not the problem with SPF. They throw that in to make the product look greener since everyone knows formaldehyde is bad. It is like olive oil producers saying their product has no cholesterol. Duh. Olive oil never had cholesterol. But it contains fat and lots of it.

Here is the truth about spray foams: SPF foam contains diisocyanates, and dermal (vapors through the skin) or inhalation exposure to these chemicals can cause significant health risks, such as asthma and lung damage, if specific workplace precautions are not followed during product application and clean-up.

Risks also may apply to building occupants who may remain on-site during or re-enter shortly after application.

That is one thing; workers being exposed. But I have found cases where homeowners even experienced negative effects from the spray foam long after it was installed. This is when it gets serious for me. Workers can be trained to be safe by using masks, ventilators and body suits (notice all publicity pictures of people applying SPF have white body suits).

But homeowners have no way of protecting themselves in this way. This applies to children especially who have much more porous bodies than grown ups and absorb chemicals much faster and with much greater effect.

Here is a statement by William Swietlik on the issue, clipped from his much longer comment (No. 11) on the Green Building Advisor site:

I am a member of the Federal Interagency Spray Polyurethane Foam (SPF) Workgroup and Co-Chair of the EPA SPF Workgroup. The mission of these federal groups is to ensure the knowledgable and safe use of SPF, a valuable insulating material.

Spray polyurethane foam (SPF) insulation, both open cell and closed cell, is made from diisocyanates (50% of the formulation), polyol oils, amine catalysts, flame retardants and blowing agents (the other half of the formulation). Dissocyanates are the leading cause of work place asthma and are a well-known sensitizing toxicant to humans.

Once an individual becomes sensitized to diisocyanates there may be no safe exposure level. Sensitization can occur from excessive and/or chronic respiratory and dermal exposures. Diisocyanates are odorless. The amine catalysts (which have an odor) and the blowing agents, can also have health impacts, but these are used in smaller quantities in the formulations.

When installing SPF using high pressure and temperature spraying, unsafe levels of these chemicals are released into the air in the building or home.


Or how about this long list of comments from HowStuffWorks.com giving all sorts of damning evidence, both from studies and personal experiences. A couple of them:

Dan in Atlanta says:

June 30, 2009 at 11:02 am

We installed Icynene under our attic roof on June 11, 2009. It’s now June 30, and we haven’t been able to live in our house since because the fumes were so intense they give use headaches. We’ve be ventilating the house 24/7 since then, and the intensity of the fumes has decreased, but not our headaches.
Our next door neighbor is a PhD research chemist, and he says the ingredients of Icynene are very toxic. If the chemical reaction were 100% completed that would not be a problem. However, he says that a 100% complete chemical reaction is rarely, perhaps never, achieved. That means outgassing of toxic fumes.
We are now sensitized to the chemical, so we may have to replace our whole roof. The company claims you can inhabit your house after 24 hours, but don’t believe it. That’s a problem when your Icynene installation is a retrofit rather than a new build when the outgassing might occur before you inhabit the house.

Heather says:

I had Icynene MD-R-200 sprayed on 2 walls in my basement a month ago and have been having problems with the smell ever since. The dealer has been very supportive and blames the smell on the lack of ventilation in the area. They have installed fans in both of the windows in an effort to increase the air exchange but this has not helped so far.


Bottom line, as a green builder in Brooklyn I have never recomended spray foam insulation to seal the entire house. We use it in small quantities to seal small cracks around pipes or between wood boards. But for the insulation we only install cellulose insulation.

The embodied energy of cellulose is next to nothing compared to spray foam (off the top of my head 600 vs 14,000). It is recycle NY Times newspapers I’m told.

It is true that it is hard to match the airtight quality of spray foam, but if done correctly you can do it with small amounts of foam, tape, caulking and cellulose. The green qualities of doing it this way are much larger.

We also use fiberglass insulation once in a while when we find it being thrown out as overstock from a job. We don’t buy it or use it if it is used, but we will use it if it is new and being thrown out. It has low levels of formaldehyde and also huge embodied energy (12,000 if I remember), but using it is better than sending it to the landfill in our opinion.

About the author: Gennaro Brooks-Church

8 comments to “Spray Foam Installation – Cellulose is better”

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  1. Tony Scarpelli - August 22, 2012 at 1:39 pm

    I have been studying spray foam applications for about 90 days and I decided to consider to get into the foam spraying business. I am very concerned about living green. I am building a zero energy home for my retirement. All the research that I have done leads me to my conclusions that either a spray foam insulation or a hybrid system of spray foam and cellulose would be best for my wallet, health and the earth.

    Embodied energy is a bit deceiving and probably nothing comes close to cellulose. As good as it is, it is not as good as it used to be when everyone bought news papers but today most cellulose does not come from recycled news papers with the advent of e-mail.

    Todays foam chemicals average about 20% recycled and soy/caster content. Also the A&B chemicals are at least 50% petroleum based, much of that content is ‘by product’ that would not be used but discarded if not for this application. I’m not saying foam is green in that sense but it is not as bad as one might think.

    Fiberglass is not even a consideration due to its poor performance actual living conditions of wind of 8 mph or more which reduce its effective R value by 40%. Also cold temps approaching 20 d F make Fiberglass loose nearly half of its effectiveness.

    Cellulose, particularly tight filled cellulose, is superior to fiberglass. The problem with cellulose is that the true effectiveness of cellulose resides to a very large extent with the professionalism and training of the installer. You don’t just dump 10-12″ in the ceiling and fill the wall cavities like we did in yesteryear. That was fine 10 years ago but we know from blower door tests that you must caulk, seal and close every seam, hole or edge of all materials in contact with the insulation to get a tight air barrier.

    Spray foam does not get a free ride either. While it gives a much better insulation job than anything else, doing four things at once: water proof plane, vapor barrier, Exquisite R value per inch the highest in the insulation world and a complete wind/air block. It is equally dependent on a knowledgeable, professional, trained and certified installer to get the job done right. With the explosion of home building through 2007, every manner of installers showed up to get rich quick. They sometimes can buy chemicals from less than reputable distributors without the required training and certification. Spraying foam is a very complicated business basically operating a ‘plastic manufacturing plant’ out of a 20 foot box truck. You must have a chemical reactor/proportion-er, 50 KW generator, 35 CFM at 175psi compressor, 2- 3 gallon per minute supply pumps for the A and B chemicals which must be maintained at 100 d F no matter the outside temps. The chemical must be delivered exactly 50%/50% proportion at 130 d F(or whatever each manufacturers chemical data sheets require) to the Fusion gun which sprays the correct air and chemical to get the proper foam reaction. All this has little margin for error yet it is easy enough to maintain with proper training, equipment and preparation. The foam must be installed with minimum humidity or use $4k air dryers for the compressed air to keep the moisture below 5% within the system. The substrates must be 50 d F or warmer for normal blends but there are special blends for Winter that spray 28 d F substrates. The installers must be completely trained and certified to guarantee a good job.

    With all this said it is easier to get a ‘great insulation’ job with Spray foam than with any other medium of insulation.

    If the job was not done correctly, and this is very unusual as it is highly unlikely that any trained spray tech would let thousands of dollars worth of chemical be applied to create bad foam, knowing the likelihood of having to go remove it at 3x the work as well as costs of putting the customer up in a hotel. And when correcting the foam is as simple as changing the digital thermos setting for the Drum heaters or reactor heaters, or the heated hoses up or down a few degrees or adjusting the 1100 psi or 1300 psi air to get the perfect spray.

    It is true 97% of off gassing occurs in the first 10 hrs after applying, the home should be ventilated for 24 hrs and the EPA has said you can reoccupy a home 24 hrs after the job is completed. 99.97% of all jobs are done without the issues of oder after 24 hrs. If there is any smell or oder that is 100% due to a poor job of installation not the chemical or the product. Just like any untrained cellulose installer might not bother with caulking the stud walls to the floor or ceiling, or to the sheathing or the drywall as well as foam fill every hole for the electric wire, cabling, plumbing that goes through every stud will end up with a very unsatisfactory insulation job. With other forms of insulation the cost is invisible in that is only higher utility costs over the life of the system. With Foam, a bad job warns you with smells immediately or rewards you with exception performance.

  2. Gennaro Brooks-Church - December 31, 2009 at 1:20 pm

    I am not sure since I am not familiar with New England or your house. I do know that cellulose does not rot under normal humidity situations. And if the envelope is sealed against water getting in that is the most important aspect. Because New England is cold your humidity issue is going to be on the inside of the insulation where the warm air of the house condenses on the cooler insulation and gives off humidity.
    So the main areas are places like a bathrooms where there is a lot of humidity in the air to condense. Again, your best measure is to seal as much as possible so that humid air doesn’t get trapped in the wall cavity in the first place.

  3. Peter Houk - December 31, 2009 at 8:33 am

    I live in a small two-story wood frame house that’s 90 years old and I’m thinking about insulating the walls and replacing the old windows. Seems this will involve pumping something into the stud bays from the outside of the house. I live in New England. How should I be thinking about the vapor barrier issue? My understanding is that presently I don’t have a problem with moisture because there’s so much air infiltration through the walls that any moisture that accumulates in the wall cavity will evaporate quickly. What happens when I fill the cavities with foam or cellulose? Will I then create a moisture/mold/rot problem? How can this be avoided?

  4. Gennaro Brooks-Church - December 7, 2009 at 8:07 pm

    Fire retardant paints are another issue. They may not burn but that says nothing of their health effects…sort of like trying to eat something light because you ate too much. I am not aware of fire retardants being required in residential Brooklyn buildings. Would they prevent off-gassing? I think a more accurate way of saying it is that they would slow the off-gassing, which depending on how you look at it is good or bad. I like second hand kitchen cabinets that are more than a year old because most of the formaldehyde off-gassing from the cabinets happens in the first year. If somebody had tried to seal the cabinets I wouldn’t be so crazy about them anymore.

  5. Gennaro Brooks-Church - December 7, 2009 at 8:07 pm

    I asked some of my green building colleagues about your claims since I am very interested in being accurate in this area. I turns out you don’t have a leg to stand on unless you can back up your claims with refferences. Bottom line, I can see where isolated situations call for small amounts of spray foam, caulk, take, fiberglass and glue as a supplement to the major players: cellulose. For most of Eco Brooklyn’s residential insulation needs we see cellulose as the best option.

    See my fellow green builders’ comments below:


    This sort of comparison (as presented by the commenter) is flawed on several additional grounds:

    (1) what is a building’s lifetime–how come is it so easily specified?
    (2) a residential building doesn’t really consume oil, or even gallons-of-oil-equivalent fossil fuels. The occupants of the building have a lot more say-so about what they use to heat and to what temperatures they choose to heat than this framing implies.
    (3) What wall thickness is assumed? I suspect if the two hypothetical buildings featured thick enough walls (higher R-values) the absolute numbers would look very different, and perhaps the relative ones too.

    Reuben Deumling


    There are so many factors as to make these comparisons somewhat meaningless. Is this with an equal R-value applied of cellulose and foam? Is it loose or dense pack cellulose? Is it open cell or closed cell foam?
    I mistrust and dismiss all such claims without detailed supporting information.



    Obviously this depends on what R value and what airtightness is achieved.
    The payback in oil for a spray foam of around 2-4″ is regularly measured in months of winter weather (not years) when I have done the calculations.
    A competition between cellulose and spray foam is a a false one of course.
    Cellulose is great, low cost insulation but it does not stop water vapor, or air or rain water. Spray foam can do all those things.
    As in almost all things HOW you use something is more important than WHAT.

    Just FYI: I used a boat load of spray foam on the exterior of my own home, a larger volume of cellulose in ceilings and attic, (as well as rockwool batt and various foam boards). I always try to use the best product for an application, and have yet to find one product that is best for everything.

    Dr John Straube, P.Eng.



    What’s the defined lifetime–10 years? 100?
    Why does it have to heat on petroleum oil?

    Useless comment.

    Jason Holstine


    Assuming that the wall thickness, and the duration are the same,
    this would be a comparison of Rvalues. Since a great deal of
    the heat loss/gain of a house is through factors that are unaffected
    by the insulation (windows, doors, framing, and infiltration to a
    lesser degree), perhaps, 2/3rds of the heat transfers might be
    effected by the insulation Rvalue. For that 2/3rds to make that big
    of a difference, over cellulose, would require foam with an Rvalue
    of nearly R14/in, or almost double the Rvalue of the better foams.
    So, he is not just wrong. He is very wrong.

    -Laren Corie-


    If the two houses are insulated to the same R value, and the cellulose house has careful sealing (Foam does a good job of sealing air leaks) then the energy use should be about the same, all other things being equal (windows, thermostat settings, occupant habits etc.) . That might mean they have different wall thicknesses if the insulation is different. If that is true, then the cellulose wins because it isn’t made out of oil.



    I agree his comments are poppycock. But one can assume (hope?) that he used the same lifetime, heat load, etc. for both cases. So the key thing he assumed is approximately 1/4 as much heat loss with the foam as with the cellulose. Whether that was due to a different R-value of cellulose vs. foam, or he applied some air-leakage loss, we can’t know. If he’s talking about dense-pack cellulose, I believe the air-sealing properties are often underrated.

    In any case, in the absence of a great many more specifics, he’s just trolling.

    Finally, if you went along which this specious near-information-free analysis, you could argue that the foam insulation has a 9:22 ratio of oil “input:savings”, whereas the cellulose has a “near-0:6”, which equates to near-infinite Oil-COP, which means simply adding more cellulose blows away foam.

    This argument is as specious as his, so I wouldn’t go far down that road: it doesn’t explicitly address the air-leakage issue — if he is assuming that cellulose always leaks, then that assumption will sink the more-cellulose approach.

    I suspect in an ideal world we might use a very small amount of foam very judiciously (after all, most building materials are perfectly good air barriers: we’re just trying to stop infiltration at the cracks between them), and then finish with cellulose. Few installers use both technologies. Those that do, use a simpler/faster approach: an inch or two of foam everywhere for air sealing, and finish out with something else (normally fiberglass, since the prep work of dense-pack makes it problematic).



    and cellulose will not cause cancer if you breath it in, and it
    settles less (or none if you get the right installer), and it can get
    wet, and, and, and….

    Benjamin G. Pratt, Professor, Design


    Some embodied energy numbers (MJ/m^3) for some insulation materials (Cole
    & Keenan) for a rough comparison:

    Cellulose – 112
    Straw Bale – 31
    Mineral Wool – 139
    Fibreglass – 970
    Polystyrene – 3770

    So unless the cellulose insulation is of a composition that somehow makes it twice the R-value of the same thickness of fibreglass, “No”.

    An “excellent air seal” will not be achieved simply through the use of one inch of foam insulation.
    The foam can be used as component of an effective air barrier strategy *if* an effort is made to detail it properly. ie If it is installed in a manner that leaves gaps at junctions and/or penetrations, then the installation will still be air-leaky.

    And one inch of foam insulation can be used effectively to retard vapour diffusion but the need for that function is seldom an issue in low-rise residential construction and when implemented, is often done in a manner that can have deleterious consequences.

    I’d say that if we spent the time to prove or disprove all of the useless, meaningless, illogical claims made on the WWWeb like the above by Rude Guy, that time would be wasted, lost forever.

    Rob Tom, Architect

  6. David Peabody - December 7, 2009 at 5:30 pm

    This is the first I have heard about off-gassing problems with foams, and it adds to other growing concerns I have. Thanks for putting this out there.

    Has anyone done any studies on whether the fire retardant paints that are increasingly required over foams work to encapsulate the foams and prevent off-gassing?

  7. Gennaro Brooks-Church - December 6, 2009 at 9:08 am

    Insults aside, here are your numbers for oil usage:

    Foam: 900 gal
    Cellulose: None

    That I believe. 900 gallons of oil to foam insulate a small house! Versus recycled material that consumes no oil.

    But then your numbers get wacky for oil saved over the life of the insulation:

    Foam: 22,000 gal
    Cellulose: 6,000 gal

    So according to your calculations foam saves 15,100 more gallons than cellulose. Ok…..show me the sources of these claims. I don’t believe them. You are claiming that spray foam insulates three times better than cellulose? But R values don’t reflect that. R value test show very similar insulation values.

    And you are not addressing the real concerns about chemical off gassing. They don’t exist right? Party line.

    Show me your sources please.

  8. Fitz Abercrombie - December 6, 2009 at 1:39 am

    Gennaro indulges in poorly thought through half arguments such as safety precautions during the manufacture of foam. It would be the same thing as if we were to hone in on the bleach used in the paper manufacture of his beloved cellulose. Fact is that people need to wear protective gear while spraying foam as the material is highly atomized during this process. Just like paint sprayers need to wear masks during the spraying, so do foam applicators. Foam cures entirely without leaving reactive residues (only soy-based foams don’t react entirely, but this is only the soy which is harmless anyway). Insulation a 2000 sq.ft home consumes about 900 gal. of oil. During its lifetime, this building will save about 22,000 gal. of oil. The cellulose consumes almost no oil during production. In the same house, it will save 6,000 gal. during its lifetime. I think I prefer foam.
    My advice: keep installing your cellulose but don’t talk about foam. You don’t know anything about it.

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