June 14

How to Choose Healthy and Safe Insulation for Your Home

Here is an extensive review of healthy insulation options for your home.  If you are in the process of building a new home or renovating an existing home then you know that there are a lot of choices you need to make throughout the process.  As the homeowner you are tasked to choose lighting, flooring, cabinetry, countertops, bath fixtures, exterior finishes, and much more.  It's a bit overwhelming. 


Now imagine adding in the research to make sure you are buying products that are not going to off-gas harmful chemicals into your home.  This takes countless hours of research.  And on top of the products you have to choose, your contractor is also making choices on what building materials to use such as roofing, insulation, drywall, subflooring, and adhesives.  The product list is endless and the quest to find healthy, non-toxic options can be too time consuming to bear.  

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I know first hand that trying to choose safe, healthy building materials is a daunting task.  I have been selecting products for my home renovation for eight months now and the research is exhausting.  

I want you to reap the benefits of a healthy home without having to go through the struggle of researching all those healthy building material choices.  I don't want anything to come in your way of making the healthiest home possible for you and your family.  

What I am Looking for in a Healthy Building Insulation

  • Hydrophobic (Repels or does not mix with water)
  • Natural fire resistance or lack of harmful flame retardants
  • No off-gassing / VOC's
  • Low embodied energy (Does not take a lot of energy to create the product)
  • Sustainable sourcing
  • Easy installation
  • Low to moderate cost

Types of Building Insulation​​​​​

  • Rigid Insulation: Usually a plastic foam product such as EPS, XPS and Polyisocyanurate.  EPS and XPS are contributors of greenhouse gas emissions and should be avoided if possible.
  • Semi-Rigid Insulation: Formed boards made of fibrous materials such as cork, mineral wool and hemp.
  • Batt Insulation: A roll or sheet of soft, fibrous insulation that fits between wall studs and floor joists.  Fiberglass and mineral wool are two common types.
  • Blown-In Insulation:  Fibrous insulation that is blown into attic floors and wall cavities.  Fiberglass, cellulose and mineral wool can all be used as blown-in insulation.
  • Spray Foam Insulation: A polyurethane foam insulation created by mixing chemicals and spraying them onto a surface where they foam up and harden.  Spray foam should be avoided because the blowing agent is a greenhouse gas contributor and the product is highly toxic during installation.

My Top Choice for Healthy Building Insulation

Mineral Wool Insulation

Mineral Wool Insulation


Mineral wool is a stone wool insulation made from at least 75% recycled content.  The insulation is naturally hydrophobic (it will not hold water) and fire resistant since it is made of rocks.  

Why I like the product

  • Made of natural, recycled materials
  • Hydrophobic (does not hold water) which is critical in keeping mold out of walls
  • Naturally fire resistant so there are no added flame retardants
  • Easy to install - The insulation is really easy to cut with just a large serrated knife (basically a bread knife)
  • Dense - It fits snuggly into each cavity wall bay, which blocks air from moving up the wall cavity
  • R Value is R-4 per inch.  A 5.5" batt that fits into a standard 2x6 cavity wall has an R-Value of R-23, which exceeds latest building codes.
  • Readily Available - Carried at big box stores
  • Available in both batts for interior installation and semi-rigid boards for exterior installation.
  • Has low embodied energy because it is a waste product



  • Rockwool brand contains a small amount of formaldehyde as a binder
  • Need to wear respirator while installing because of the silica sand - tiny particles that get into your lungs
  • Do not have exposed skin while installing as the sand irritates skin



Fiberglass is the cheapest insulation you can buy and the price of mineral wool is about 25% to 45% higher than fiberglass.  We paid about $1.15 /sf of R-23 mineral wool batt from Home Depot.  

One thing to keep in mind is that even though mineral wool is significantly more expensive than fiberglass, insulation in general is a small percentage of the overall cost of building or renovating a home.  So the cost of mineral wool is not a huge impact on the overall budget.


Rockwool (formally Roxul) - makes batts and board, residential focused, multiple cavity depths, does not have a formaldehyde free option

Owens Corning Thermafiber - now has formaldehyde free, batts only, makes both wood stud and steel stud widths, commercial focused

Other Healthy Building Insulation Options

Fiberglass Batts

Fiberglass batt


Though the cheapest, this is not my favorite option because the insulating capabilities of fiberglass batts are not as good as mineral wool and cellulose.  Fiberglass batts lose their thermal effectiveness when compressed so if they get shoved into a wall cavity and smooshed by other building materials, they won't really be doing much.  The other problem is that they are not very dense so air travels very easily through them and the wall cavity.  

Fiberglass batts are not hydrophobic.  If the insulation gets wet, it will stay wet, and mold could potentially grow within it.

And don't forget the itchy-ness factor during installation.  Do not install with skin exposed.

What to Buy if Choosing Fiberglass Batts

  • Formaldehyde Free - This option is becoming readily available for fiberglass batts.
  • Look for high recycled content, at least 50%
  • Choose unfaced batts - The intention of Kraft paper faced batts is to have an insulation and vapor barrier product in one.  But the design falls short of being effective.  And since sometimes you don't want a vapor barrier on the inside of your wall, it is best to avoid the paper faced batts.
  • If you have 2x6 wall construction be sure to select R-21 batts rather than R-19.  (Both options are offered for this stud size).  R-19 does not meet the prescriptive energy code for most climate zones. 


Certainteed and Johns Manville both carry formaldehyde free fiberglass batts.

Cork Insulation

cork cladding


I love cork insulation but it is a more expensive product.  That is about the only downside I have for cork.

  • Cork is a 100% natural insulation product.  
  • The semi-rigid insulation is installed on the exterior side of your home.  
  • It is naturally fire resistant  
  • It has the ability to dry out when wet.  
  • Cork is harvested from biodiverse forests, and the finished product has a negative carbon footprint.  
  • It has an R-value of between 3.7 and 4.2 per inch.  
  • Cork is great at absorbing sound.  
  • I think the coolest part of cork insulation is that it can double as the siding for your house.  Cork starts off as a light brown color (just like a cork wine bottle stopper) but will eventually darken when left exposed. 

Blown-In Cellulose

blown in cellulose


Cellulose has become controversial for a few reasons.

  1. Cellulose is made of naturals fibers, usually recycled newsprint, which is obviously not a natural flame retardant.  A borate treatment is added to the fibers for fire and water protection which some experts believe is very toxic while other experts do not think Borate poses a threat to humans.  Since no one can agree, I'll err on the side of caution and stay away from it if possible.
  2. The dust from blown in cellulose gets into the air and contributes to respiratory problems.  

So should I use it?

I think installing cellulose in places like attics that are sealed from the rest of the house and where no one ever goes is ok.  But there may be a better option available for us all relatively soon...

Two companies, UltraCell and Nature-Tech, are working on a new formula for cellulose insulation that uses clean, recycled cardboard instead of newsprint which makes the insulation more robust, and "instead of mixing dry fire retardants into shredded fiber, a new "wet" process along with a fire retardant blend it calls "Celluborate" results in reduced dust and the potential for higher R-values."  See the full article by Scott Gibson at Green Building Advisor.  

Hemp Insulation

hemp insulation


Though hemp insulation is not yet available to the US market, it looks like it may be available soon.  Hemp is a great mostly natural insulation material, made of 88% hemp fiber and 12% polyester fiber.  There are no VOC's in the product.  The semi-rigid insulation R-Values are comparable to fiberglass and mineral wool.  One brand, MEM, makes R-20 hemp insulation for a 2x6 wall which meets the energy code for many climate zones.  If hemp insulation gets wet, it will dry out as long as the faces of the wall cavity are vapor permeable.

I like the potential of this product and will keep an eye out for its US availability.

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