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Community and Q&A

Best insulation for indoor air quality?

Carfar96 | Posted in Green Products and Materials on

I cannot decide on a type of insulation for our new home. I want something that is the safest for indoor air quality. I am worried about the off gassing of spray foam, but am also worried about the borate used in blown in cellulose (mainly the reproductive effects of borate). Please help! I want energy efficiency, but indoor air quality is of primary concern. Thank you!

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  1. GBA Editor
    Martin Holladay | | #1

    There are only two types of insulation I know of that sometimes generate smell complaints: spray foam insulation and Owens Corning EcoTouch fiberglass batts.

    For more information on these problems, see:

    Spray Foam Jobs With Lingering Odor Problems

    Smelly Fiberglass Batts

    I have never heard of odor complaints or IAQ complaints concerning any other type of insulation, including cellulose with borates. Remember, if you are building a good house, you will have an air barrier (usually drywall) between the indoor air and your insulation, so the insulation shouldn't be affecting your indoor air quality.

  2. Carfar96 | | #2

    Thank you for your comment! I am not worried about the smell. I am only worried about the toxicity of our air. We are building a tight house, but I am still concerned about having things behind the walls that could be carcinogenic or cause reproductive harm. There are no safer options?

  3. dankolbert | | #3

    Have you read any evidence of harmful effects of borates in cellulose insulation?

  4. iLikeDirt | | #4

    Insulation is the least of your worries. Focus on your HVAC system and its distribution mechanism, particularly if this takes the form of ductwork. Other focus areas should be flooring and baseboard materials, paint, furniture, and appliance fuels (gas ranges are bad bad bad given your concerns). Those all have far greater impacts on air quality than your choice of insulation.

  5. GBA Editor
    Martin Holladay | | #5

    I have never read of any report of medical issues related to people living in a house insulated with cellulose. Living in a house insulated with cellulose does not raise your cancer risk or cause reproductive problems. A house that is insulated with cellulose does not have "toxic air."

    If any GBA readers have any data that support contrary conclusions, please refer me to a paper where those data were published.

  6. Carfar96 | | #6

    The danger of reproductive damage from borates are listed on the material safety data sheets for cellulose insulation. We are choosing greenguard certified products where possible. We do unfortunately have to have a duct system HVAC, but are using HEPA filters, duct sealing, etc.

  7. GBA Editor
    Martin Holladay | | #7

    It looks like you are referring to studies in which rats were fed borates. There are two reasons that I wouldn't worry about this finding:

    1. You won't be eating borates.

    2. The insulation is located on the other side of an air barrier (the drywall). It will not only be hard to eat -- it won't be in contact with your indoor air.

  8. Carfar96 | | #8

    What happens when we need to get in the attic access in the house? There will be cellulose up there. That won't be airtight. If it gets on our floor, clothing, etc.? We have toddlers crawling around.

  9. GBA Editor
    Martin Holladay | | #9

    Again, I have to repeat that a study that shows that rats have some reproductive problems when you feed them borates does not mean that you have to worry if there is insulation in your attic.

    If you want to enclose the cellulose insulation in your attic, you certainly can -- just provide adequate framing and install a plywood subfloor up there. (That's a good idea anyway if you want to use your attic for storage.)

    We have decades of experience working with cellulose -- including the experiences of contractors who work with cellulose daily. I'm unaware of any reports of reproductive issues.

  10. Expert Member
    Dana Dorsett | | #10

    Any risks from the borates would be an occupational risk to the installers, since they are the only ones inhaling it as dust if they're not careful. Even then it's fairly minute quantities. From a an occupational risk point of view it's considered a nuisance dust- not great to be breathing in on a regular basis, but not very toxic. The borates used in cellulose are not volatile at room temperature but become volatile at temperatures found in a house fire *which inhibits the fire.) Even a peak summertime attic temperatures they remain as solids- they stay in place both in your attic inside your walls. The particles are not prone to becoming an aerosol hanging in the for hours or days after installation- gravity brings it all out of the air pretty quickly.

    At the very high air-retardency of cellulose insulation even if you didn't air-seal the walls, you would not end up with measurable quantities of borate particles in the house air even during a hurricane, even though some trace amounts might escape and become detectable in the dust on the floor until the next time you vacuum or mop after a hurricane. If you DO air seal your walls (necessary to meet current code for air tightness) it won't end up inside your living space until the hurricane literally blows your house apart, rendering the "indoor air quality" problem moot.

    If you use damp sprayed cellulose in the attic the borate dust is further constrained from accidentally becoming airborne or picked up by your clothes, but then I suppose you'd want to chase down the volatility and potential hazards of the water activated adhesives.

    The amount you'd pick up on your clothes in an attic visit is vanishingly small (unless you roll around in it and toss it up into the air), and it would come out in the wash. Some clothes washing detergents could potentially add more borates to the clothes than the amount of borate-as-dust it removed.

    While consuming laundry detergent orally or via inhalation isn't recommended either, wearing clothes washed with detergents containing borates isn't a health risk either. This is despite the fact that you have some direct contact between the borates and skin, making it a theoretically higher risk than cellulose in your walls or attic.

    The rat experiments was at daily doses as high as 350mg/kg of body weight. Putting that in perspective, a 150lb human would have to consume nearly a full ounce of boric acid per day to hit those levels. Below 1/4 that dose there was not a measurable problem. A quarter ounce would mean several heaping tablespoons per day for that 150lb human. Within 8 weeks post-dosage (for 30 days at the high dose), residual effects on even the highest dose rats had dropped to nearly that of the zero-dose control group.

    Even a cellulose installer who never uses a mask and who never washed up before eating would be hard pressed to actually ingest a quarter-ounce of borates per day, which is the smallest dose at which the rats showed abnormalities. And while rats aren't a perfect model for humans (save a few select politicians that may actually be closer to the weasel family :-) ), the exposure to even the installers is probably at worst an order of magnitude lower than the lowest observed dose showing a response in rats, and the amount encountered by the occupants of the finished house would be several orders of magnitude below that. No matter how imperfect the rat model might be, it's unlikely that a daily dose that is less than 1/1,000,000 of what showed a response in rats would have a measurable response in humans.

    Bottom line- the toxic risk of borates to the occupants of a cellulose insulated house doesn't even rise to the level of "mole-hill", let alone "mountain".

  11. AlanB4 | | #11

    As mentioned the offgassing of the components, paints and finishes in the house are of much higher concern. Also an HRV will be ventilating the house (presumably) further reducing any concern. Just use a HEPA fitler in the HRV so exhaust from outdoors is kept out (which is much more dangerous then the borates). Your indoors will be safer then being outdoors from an inhalation perspective

  12. Carfar96 | | #12

    Thank you everyone! It is good to know my concerns seem largely unfounded.

    Can anyone chime in about the cooktop? We were considering induction but I am concerned about EMFs. Electric isn't an option (husband likes to cook and said no). Is gas that bad if we run the hood vent when we cook?

    We have a HEPA air filter being installed (media air cleaner). However, the HRV is an additional $3,000. Is it worth it? Are there less costly HRVs that still have HEPA? It is a hard sell for me to my husband especially since the HVAC guy thinks it is useless.

  13. dankolbert | | #13

    Where are you getting your information from? EMF's? There are plenty of genuine and well documented health concerns.

    HRV's are not particularly meant to run with HEPA filtration. They come with coarse filters, good for keeping out large particles, dirt and small children. Why do you think you need a HEPA filter on your HRV? What are you filtering?

  14. Carfar96 | | #14

    EMFs from induction cooktops? I am pretty sure that is well established. Are you questioning whether there is an EMF concern with induction cooktops?

    I would want to filter out dust, pollen, pesticide particulate (we are near a farm field), etc.

  15. AlanB4 | | #15

    An HRV is definitely worth installing in a new tight house, it may sound expensive but its an excellent ventilation system that is unequaled and costs pennies compared to a custom built house. As for EMFs, its likely they have some effects, but research in this area is a low priority because any effects would affect corporate profits from many industries, hence there is incentive to prevent rather then conduct research. However there are very few acute effects, exposure decreases based on distance (squared value is it?) and your putting the load on top of the source, which should minimize exposure. No vent hood will be 100%, you will have some combustion byproducts from the gas floating around your house unless you put the kitchen in a separate building, so frankly from a health perspective the induction would win probably with a landslide. There is a GBA article on the hazards of gas stove emissions.

    You use many EMF producing devices today from motors (fridges, washing machines, dishwashers, air conditioner, fans), light bulbs, computers, cell phones, tablets etc, so you would basically have to give up technology to avoid EMFs. You can try to find info that compare all these sources for reassurance if it will help.

  16. agurkas | | #16

    My wife had been working on cancer research her entire career, heck almost her entire adult life. Degrees from top schools, including Harvard. I bring up these things to her, since she has access to about every piece of research. She is also sceptical as hell of unqualified and under-informed public making claims about something being carcinogen.
    Here is the bottom line: unless you are going to eat cellulose for 3 meals per day, every day, for the rest of your life, you may want to concentrate on other things that actually matter.
    Too often worrying about things/stress is a bigger killer than anything around us.

  17. GBA Editor
    Martin Holladay | | #17

    Q. "EMFs from induction cooktops? I am pretty sure that is well established. Are you questioning whether there is an EMF concern with induction cooktops?"

    A. Yes, I'm questioning that. For more information on this topic, see EMFs and Human Health.

    I agree with Alan: "From a health perspective, the induction [cooktop] would win probably with a landslide" compared to a gas cooktop. For more information, see The Hazards of Cooking With Gas.

  18. dankolbert | | #18

    Martin, what's your opinion of putting HEPA filters on HRV's?

  19. STEPHEN SHEEHY | | #19

    Dan: My Zehnder HRV came with MERV 7/8 filters, but Zehnder sells a MERV 13 for the same unit. I'm not sure how one compares HEPA with MERV.

  20. GBA Editor
    Martin Holladay | | #20

    I have no direct experience with installing HEPA filters on HRVs, so my opinion isn't really relevant.

    If a client asked for a HEPA filter on an HRV, my first step would be to contact the HRV manufacturer for advice. Most HRV manufacturers have technical help phone lines.

    The risk, of course, is that the HEPA filter would add static pressure that would reduce the airflow through the ventilation system. Anyone contemplating this idea should verify that the airflow through the system is adequate.

  21. JC72 | | #21


    "The rat experiments was at daily doses as high as 350mg/kg of body weight. Putting that in perspective, a 150lb human would have to consume nearly a full ounce of boric acid per day to hit those levels. Below 1/4 that dose there was not a measurable problem. A quarter ounce would mean several heaping tablespoons per day for that 150lb human. Within 8 weeks post-dosage (for 30 days at the high dose), residual effects on even the highest dose rats had dropped to nearly that of the zero-dose control group."

    -Thank your for pointing out the absurdity of borate ingestion and its link to cancer in rats. It's all too common that context is left out of the discussion as it pertains to how much of "X" is bad for you. I argued it a few times myself while I was earning my BS in Environmental Science.

  22. Expert Member
    Michael Maines | | #22

    Hepa filters are roughly Merv 13-15. If you are in an area with a lot of smog or other fine particulate pollution you might consider that level of filtration, but there is a tradeoff, as Martin said, in system efficiency. It simply takes more energy to pull air through smaller holes. Here is a chart that shows what is filtered at various Merv ratings:

    I am concerned enough about EMF that I would not build a house adjacent to high voltage lines and I would not sleep in a bed with 200A service on the other side of the wall. That said, the small amount of EMF that an induction cooktop creates is orders of magnitude less of a health concern than burning fossil fuels inside your house with a gas cooktop, even with a range hood.

  23. Carfar96 | | #23

    Here is a scientist that does a lot of research on EMFs:

    Another link of interest:

    I agree that most EMF is too low in frequency to cause a problem. However, very high levels of EMFs are generated with induction cooking. I think it is very unrealistic to think you would be standing 1 foot away from the cook top while cooking, especially if you are cooking on the back burners.

  24. Carfar96 | | #24

    Here is an HRV that our HVAC contractor installs:

  25. Carfar96 | | #25

    Also, if we do go with induction, do you recommend a vent hood? How does a vent hood affect the functioning of an HRV system?

  26. pbyar | | #26

    Indoor air quality is a complex issue and might be a good topic for a GBA blog article. In the meantime, it makes sense to me to prioritize the threats based on known toxicity. There is clinical evidence that the following can cause health issues: combustion by-products, volatile organic compounds, including benzene and formaldehyde, mold, and human respiration in the form of CO2.

    Based on my tiny Venn diagram bubble of knowledge, combustion by-products are an ongoing exposure risk, so I plan on no combustion or sealed combustion energy sources and a range hood. Volatile organic compounds are next on my list, so the garage will be detached or connected by a breezeway and I will vet paints, cabinets and floor coverings for vocs. My next house will be designed with an architect, an energy consultant and a builder in order to provide a robust "air-tight" shell which is appropriately vapor permeable for drying. (I've read too many do-it-yourself horror stories on this site.) Drywall is banned from bathrooms. And... I'll continue to sleep with the bedroom door open :-)

    This article seems to present a balanced assessment of the emf issue:

    Edited to add: Carolyn, I did not see your links before I hit "Post".

  27. STEPHEN SHEEHY | | #27

    Whether you need a vent hood (and how powerful) or not depends on what type of cooking you do. Frying and high heat sautéing or anything that generates a lot of smoke will create more of a need for powerful ventilation than most cooking.

    We cook a lot. We get by fine without an outside vent, just boosting the HRV when we cook anything a bit smoky or smelly, like frying an onion. It's necessary to locate the HRV grille well away from the cooktop, to avoid clogging the HRV with grease.

    An HRV doesn't substitute for a vent hood. The HRV air flow is much lower than the smallest vent hood. Our whole house HRV is 72cfm, whereas a big hood fan can be ten times that and even a small one is 300cfm.
    Given your concerns about contaminants, you really need a good whole house ventilation system, whether or not you install a vented hood for the cooktop.

  28. JC72 | | #28

    Carolyn here's a good start. These guys are professionals. (I'm not affiliated with them, I just like how they explain what you should consider when buying a hood).

  29. GBA Editor
    Martin Holladay | | #29

    It would be nice if the FAQ page included this one: "Where does the makeup air come from?"

    But, like almost all range hood manufacturers, ProLine appears reluctant to discuss that issue...

  30. Expert Member
    Dana Dorsett | | #30

    Humans aren't very electrically conductive, and the amount of induced current is something like 8-10 orders of magnitude lower than the induced current in a metal pan on the same cook top. But at 20-100 kHz induction-range frequency you could cook somebody in 5 seconds if the intensity were high enough (but it's nowhere near that intense). EMF hazards are more of an intensity than a frequency issue.

    But the hazards to humans at induction range levels is extremely small. Again, it's a dosage issue.

    The IEC 62233 standard is extremely conservative even from an occupational exposure perspective (are you working at the RF power end of a radio broadcasting station?), and for very low duty-cycle and intermittent exposures such as you would experience in home cooking exceeding that limit by even 100 when leaning on the cooktop reaching for the back burner several 10s of seconds per day would have immeasurably small effects. (And they're not 100x the very conservative limit, not even 25x.) Occupational limits are set to presumed safe levels for constant exposure for 8 hours/day for decades. That's simply not going to be YOUR exposure.

    By way of analogy, while going out in the mid-day sun for a few 10s of seconds per day without sunscreen won't harm you, the UV intensity of mid day sun is still more than 1000x higher than occupational exposure limits would allow.


    "...the National Institute for Occupational Safety and Health (NIOSH) recommends that the time of exposure to an intensity of 100 microwatts per square centimeter at wavelength 254 nanometers not exceed 1 minute. When averaged over an eight-hour work day, this value is 0.2 microwatts per square centimeter. "

    So the NIOSH recommended limit is averaging 0.2 microwatts per square centimeter for 8 hours/day, every day.

    The UV intensity of mid-day sun is 0.4-0.6 milliwatts per square centimeter, which 400-600 microwatts per square centimeter. That's 2000-3000x higher than the NIOSH prescribed limit. Not merely 100x more intense, more than 1000x.

    OK, don't stand out in the sun all day every day, but don't be concerned at all about walking to & from the car in broad daylight multiple times a day. The EMF exposure for the tens of seconds or even tens of minutes per day of cooking at 10x or 100x the occupational exposure limit is still but a fraction of the dose of UV experienced daily relative to the occupational UV exposure. The cooktop radiation is really only of concern to somebody who spends 8-10 hours per day standing next to it, and even if it violates the standard by 10x or so it's not a large risk even to that person. Occupational standards are VERY conservative.

    So, if you taped your kid's head directly to the cook top and ran it on high for a year or two I suppose there's a realistic chance you might actually do some biological damage. But it would pale next to the damage from the emotional trauma and elevated stress hormone levels- it might be hard to detect. :-)

    Bottom line, there are many MUCH bigger hazards in life to worry about about than EMF exposures in a residential setting.

  31. JC72 | | #31


    Agree, but IMO there are just too many variables to consider (How tight is the house, what other appliances do you have, mechanic ventilation, etc). other than a blanket statement regarding the possibility of needing makeup air.

    BSC has some good documentation on range hoods and the required make up air.

  32. nvman | | #32

    I believe Venmar has HEPA filters for some of its HRVs.
    I would also stay away from Certainteed fiberglass insulation has it precipitated lung problems for my wife.

  33. Expert Member
    MALCOLM TAYLOR | | #33

    Dana wrote:

    "So, if you taped your kid's head directly to the cook top and ran it on high for a year or two"

    Could it be my nephew instead?

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