Choosing Green Insulation – consider recycled foam board.

In the constant quest for a greener insulation I have considered many options.
– Cellulose is good but messy and dusty.
– Isonyne spray foam or Demilec spray foam is good but not that cheap and quite honestly not as green as they say. It takes huge amounts of energy and petroleum to create the main ingredient isocyanate.
– Formaldehyde free fiberglass is ok but still fiberglass (scratch, scratch).
– Solid foam is good and in my opinion under valued by the green community.

THEN you have RECYCLED SOLID FOAM, which I am starting to think is the way to go.
It comes out at the same price as normal fiberglass batts but is way better R value when you air seal the boards correctly. And it is RECYCLED.

In my opinion normal (non-green) recycled materials is better than new green material. Why make more when it has already been made.

ALSO, foam board does off gas a little BUT almost all of that happens in the first few months or year. And since it is recycled it has already off gassed! Now that is a fantastic side benefit of recycling!

Further info I found on the web

Whether it takes the form of batt, loose fill, sprayed-in foam, or rigid foam, insulation is an essential part of any housing. Insulation slows the transfer of heat (energy) from warmer areas to colder areas. It can also serve to reduce noise. Insulation effectiveness is typically measured in R-value. A higher R-value for insulation is better. A well-constructed insulation system will help reduce air infiltration and heat transfer and help control moisture. All of these factors need to come together to produce a comfortable and healthy living environment. The following analysis examines the relative economic, energy, and environmental impacts of the following insulation types: fiberglass batt, blown and loose fill cellulose, blown fiberglass, foamed-in-place polyisocyanurate or polyicynene, extruded polystyrene, expanded polystyrene, and rigid polyisocyanurate.

Loose fill, blown and batt insulation is more cost effective in walls and attics than rigid board insulation. Foamed-in-place insulation should be used when budget permits, its high R-value combined with excellent air sealing increase the overall performance of the assembly. Look for insulation materials that have stable R-values over time.
Extruded polystyrene (XPS) insulation with CFC or HCFC’s as blowing agents should not be used. Rigid insulation alternatives include: wood fiberboard, (some made entirely from recycled cellulose), expanded polystyrene (EPS), fiberglass board, or cellular glass board.

Insulation Fact Sheet:


cost/sq. ft./R (materials & labor)

energy (R- value per inch)


expected product life (years)

life cycle thinking


fiberglass batt







cellulose blown and loose fill







fiberglass blown







foamed-in-place polyisocyanurate
or polyicynene

not available





requires trained installer

rigid perimeter: extruded







rigid perimeter: expanded







rigid perimeter: polyisocyanurate







Criteria Summaries
Cost: Loose fill, blown and batt insulation materials have a low cost per R-value and rigid board materials. Higher first costs associated with increased insulation thickness of any type may be recouped over the life cycle of the building through reduced heating and cooling costs. Premium costs associated with insulation with higher R-values per inch not only reduce operating costs but also use less material.
Energy: Rigid insulations typically have a higher R-value per inch than batt or blown insulations.
IAQ: If left undisturbed in wall cavities and attic spaces insulation poses no threat to human health. Respiratory masks should be worn when handling fiberglass and mineral wool batts, since they may potentially release fibers into the air during handling.
Expected Product Life: The R-value of most insulation materials decreases with aging. Polyisocyanurate and polyicynene have the longest expected life with the greatest R-value stability. Loss of R-value can be attributed to several different factors. Batt insulation can slump in cavities, or become damaged by moisture. These effects can be limited by proper construction and detailing. Rigid insulation can shrink and or dry over time, while loose fill insulation can settle, decreasing its effectiveness.

Life Cycle Thinking:
• Energy consumption (non-renewable, fossil fuel energy): The manufacturing process for fiberglass and mineral wool batts is energy intensive although less than for rigid products. Where recycled content is higher, energy impacts related to manufacture are further reduced. Rigid insulations have high embodied energy from extraction through production, though they offer higher R-value per inch thickness, and require less material overall.
• Pollutants generated in production: Extruded polystyrenes still use HCFC’s, while expanded and some polyisocyanurates use alternative agents.
• Potential for off-gassing: Not an issue when insulation is not exposed to the interior.
• Durability of the product: Prolonged contact with moisture can cause the paper backing on batt insulation to deteriorate, and also mat down batt and blown insulation, reducing the effective R-value of the material.
• Potential for future recycling: Blown insulation suffers from settlement, but can be recovered easily for reuse. Certain expanded polystyrene rigid insulation products use recycled content in their products (or at least reused waste products).
Practice: With the exception of sprayed-in-place insulations, which require training and professional installers, all insulation types are considered common practice.

Environmental Context
Reducing the amount of fuel to heat and cool also reduces environmental damage and costs. Insulation effectiveness is usually measured in R-value (thermal resistance) – the higher the R-value, the better the insulation value. Other considerations include the amount of recycled content, the ability to reuse or recycle the insulation, the ability to meet code requirements (in Minnesota amendments to the Uniform Building Code and the residential building code), and off-gassing of the products in place. Batt and blown insulation materials will generally have lower embodied energy than rigid insulation materials.

Here is some more info on Rigid Foam Board Insulation from my research

Rigid foam board insulation is a popular mass insulation product used to insulate all parts of homes, metal buildings and commercial buildings against the movement of conductive and convective heat transfer. A high insulating value for relatively little thickness makes rigid foam ideal for insulating roofs and exterior walls. Rigid insulation also substitutes well for other forms of insulation like fiberglass blankets and loose-fill cellulose in attics and floors. The water resistant nature of foam makes it well suited for use under slabs and in the ground around foundation walls.

Types of Foam Board
Rigid insulation is made of air-entrained plastic that is either extruded or pressed into sheets. There are three types of rigid foam insulation: expanded polystyrene (EPS), extruded polystyrene (XPS) and polyisocyanurate (polyiso), each varying in cost and R-value. Boards are available with a reflective foil facing that reduces radiant heat flow when installed next to an air space for total insulation against the three types of heat transfer, conduction, convection and radiation. If properly sealed, foil faced boards can also be used to form a vapor barrier in areas where moisture and condensation are an issue. Alternately, rigid foam can be installed in combination with reflective insulation to add a radiant or vapor barrier.

Insulation is rated by its ability to resist convective heat flow in units called R-value. R-value gives the insulation resistance per inch of material. Construction materials with higher R-value ratings are more effective insulators than materials with lower ratings for the same thickness. The R-value is a function of the material type, thickness and density. The R-value of an insulation system is calculated by adding the R-values of the individual components together to achieve the recommended insulation protection based on climate.

R-value is helpful in comparing different types of insulation as well as different brands of the same type of insulation. Rigid foam insulation has insulation values that are almost double the R-value per inch of fiberglass or cellulose insulation. R-values for rigid foam range from 3.6 – 8 per inch. Note that R-value is not used to rate a material`s ability to resist radiant heat.

Rigid Insulation Type R-value per inch
Expanded polystyrene board 3.6 to 4
Extruded polystyrene board 4.5 to 5
Polyisocyanurate board, unfaced 5.6 to 6.3
Polyisocyanurate board, foil-faced 7-8
(Source: US Department of Energy Insulation Fact Sheet)

State and federal agencies recommend insulation R-values for different areas inside of a building based on local climate conditions with the attic requiring the most insulation. Divide the recommended R-value by the R-value per inch of the type of insulation you want to use to determine the necessary insulation thickness. If you use reflective insulation in combination, you can add in up to an additional 14.5 R depending on whether the reflective insulation has foam, plastic bubbles or fiberglass for its central layer. Foam core reflective insulation (like foam board insulation) has the highest R-value. If you use foil faced rigid insulation facing an air space, you can add an additional R-value of 2.8 without increasing the insulation thickness.

Moisture Considerations
Preventing condensation in building cavities is a major consideration for an insulation system. Rigid foam board insulation resists absorption of moisture from the atmosphere in the form of humidity and also has a low water vapor transmission rate. However, rigid foam alone cannot be used as a vapor barrier. A vapor barrier should have a permeance rating of less than 1. The permeance of 1 inch of expanded polystyrene is 2 and the permeance of 1 inch of extruded polystyrene board is 1.2. In contrast, the permeance of aluminum foil is .001. Reflective insulation or foil facing is commonly used in combination with rigid insulation to create the vapor barrier necessary to keep moisture out of the walls and ceilings where it can cause rot, mold, mildew, odors, condensation and dripping. To create the vapor barrier, all seams are tightly sealed with aluminum tape.

Moisture also creates a heat transfer problem of decreasing efficiency when insulation gets wet as water is a good conductor of heat. Rigid foam board has been shown to retain its structural integrity through freeze-and-thaw cycles. It retains very little moisture in comparison with other types of insulation like fiberglass or cellulose. The Energy Division of the Minnesota Department of Public Service found that Expanded polystyrene used in exterior foundation insulation showed moisture levels of only 0.13% after 7 years of use. They concluded that the damp insulation board still maintained between 95 and 97 percent of its original thermal efficiency and compressive strength.

Benefits of using Rigid Foam Board Insulation

* Density – Density provides hi R-value with minimum thickness making rigid insulation more resistant to air and water vapor movement than fiberglass batts or cellulose.
* High compressive strength – rigid insulation provides a solid structure under the roof deck that can withstand the weight of both equipment and light foot traffic.
* Low weight makes rigid insulation boards easy to install and less expensive to ship.
* Resists outside air infiltration when joints are sealed with tape or caulk.
* New products are made without ozone depleting chemicals for virtually no global warming impact.
* Can be installed with full coverage over studs instead of just between them to eliminate the heat loss path through framing members.
* Non-hazardous to install – no fibers or fumes to inhale, non-irritating to skin.
* No deterioration of R-value over time – rigid insulation does not lose R-Value over its service life.
* Green – A manufacturing study showed that the energy required producing polystyrene foam insulation is 24 percent less than the energy required to make the equivalent R-value of fiberglass insulation.
* Rigid insulation “breathes” instead of trapping moisture like fiberglass or cellulose and therefore does not require the venting methods used for other insulation materials to prevent trapped moisture within walls, ceilings and roofs.
* Highly resistant to mold
* Not a food for insects
* Good acoustical insulation properties
* Can be used in structural insulated panels or for insulating concrete forms.

Expanded polystyrene (EPS) or beadboard, has been used as common household insulation since the 1950s. EPS is environmentally friendly as it is not manufactured using CFCs or HCFCs- both ozone-depleting chemicals. In addition to insulation, EPS is commonly used to make coffee cups and packing peanuts for shipping.

EPS is closed-cell foam made from polystyrene (a type of plastic) beads mixed with pentane and steam, used as a blowing agent, to expand the beads under pressure into foam, which forms thousands of tiny air pockets in the finished board. As air is a poor conductor of heat, these tiny air pockets will block the transfer of heat through the foam and trap expanding warm air.

EPS is molded into large sheets with R-values ranging from 3.8 to 4.4 per inch, depending on the density of the material. However, air spaces in EPS can accumulate and retain water. Because water is a good conductor of heat, some form of moisture barrier may be required to prevent this problem in high humidity areas, especially when EPS is used around foundations. To make the insulation more waterproof, EPS boards are available with optional thin foil or plastic facings.

Extruded polystyrene (XPS) or blueboard, is also a closed-cell foam insulation made from polystyrene plastic beads mixed with chemicals to turn them into a liquid before using a blowing agent to turn it into foam. The foam is forced through a shaping die, cooled and cut into panels.

XPS is more consistent in density and has a higher compressive strength than EPS making it better suited for use in roof assemblies and structural insulation panels. Higher density makes it more resistant to moisture than EPS, and XPS has a slightly higher R-value of R-5 per inch. Because of its superior properties, XPS is more expensive than EPS.

Polyisocyanurate or Polyiso, has the highest R-value per inch of thickness of the different rigid foam insulation types with an average R-value between 5.6 and 8 depending on the facing material. Facings such as plastic or aluminum foil increase its resistance to both moisture and radiant heat transfer. Polyiso is commonly used in roofs and cavity walls because of its thinness.

Polyiso is touted for being an economical choice. Its higher R-values per inch allow for savings on other building materials like thinner walls and roofs and their associated shorter fasteners.

According to the Polyisocyanurate Insulation Manufacturers Association, polyiso is a completely green building product as it no longer is made with either of the ozone depleting chemicals – CFC and HCFC. In addition, construction site waste can be recycled. Other beneficial characteristics of polyiso include its resistance to solvents in common construction adhesives and high fire test ratings.

Foil faced polyiso insulation has the highest R-value per inch of any type of mass insulation currently produced. When installed facing an air space of at least 1″, the R-value will increase by 2.89. ASHRAE assigns a 1″ air space R- 2.77. The Masonry Advisory Council adds an additional R-2.89 to polyiso insulation for a foil facing.

Rigid foam insulation boards used to insulate the interior of masonry walls do not require an additional vapor barrier. Wood strapping is attached to the wall and the insulation is installed over the strapping. If a foil-faced board or reflective insulation is used also, the foil side should face the room and an additional layer of wood strapping is needed under the drywall to create an air space. Fire safety codes require that at least ½-inch thick gypsum board (dry-wall) be placed over rigid foam insulation. The drywall is then attached to the wood strapping or underlying masonry with nails or screws. For insulating an unventilated crawlspace, rigid insulation boards can be glued directly to the wall.

About the author: Gennaro Brooks-Church

18 comments to “Choosing Green Insulation – consider recycled foam board.”

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  1. Jerry Young - February 7, 2014 at 8:58 pm

    I found your site when searching for info on ground-up recycled XPS as sub-grade insulation. So far I have come up empty. Any ideas?

    We are owner-building a sustainable, off-the-grid home for $35 sq ft, not in the boonies, but as an urban infill where codes matter. A tight budget and codes mandate creativity. For instance, we are using wall trusses from recycled lumber confining 10″ of rice hull insulation with minimal thermal bridging ( And we are harvesting the summer sun for winter heating ( which requires sub-grade insulation, hence the interest in recycled XPS that is available from a local vendor as odd scraps or ground up. If it would work, it would be dirt-cheap compared to new 4 x 8 sheets.

  2. lee kottke - July 5, 2012 at 2:31 pm

    surely you all know about and it’s mushroom-based bioboards very recently in actual production. Unfortunately way too expensive for me at this point, a 2 x 40 x 16 inch board going for $90. sounds like you’d be interested.

  3. Chuck Kottke - July 29, 2009 at 4:20 am

    That’s a good observation, 50pascals! from mullein to corn, there’s many cellular space-filling plant materials; and if growing algae for bio-diesel is being tested, then perhaps plant cells for closed-cell board products would be a worthy consideration as well in large culturing operations. Desert flats, cooled glass-covered boxes with pith tissue growing sheets within – water, air and nutrients in, foam-board out!

  4. 50pascals - April 1, 2009 at 11:35 am

    Been paying attention to this thread and it got me thinking. There are MANY plant that grow foamlike cellulose-based (I assume)structures inside them. Stuff like corn.

  5. Gennaro Brooks-Church - April 1, 2009 at 11:02 am

    I definitely think you are going in the right direction.

  6. Chuck Kottke - April 1, 2009 at 10:52 am

    Brainstorming foam products obtainable naturally:
    -foamed natural rubber
    -foamed natural resins & waxes
    -foamed polylignin
    -foamed cellulose
    -cultured bark cells (cork)
    -cultured pith tissue cells
    -cultured siliceous cells (club moss cells)
    – dried blue-green algae formed into flat boards

    Nature makes an amazing array of things, we have yet to unlock the mysteries and possibilities..

  7. Chuck Kottke - April 1, 2009 at 10:31 am

    Well believe me, after learning about the chemicals used to make conventional polyisocyanurate (ie – phosgene gas, used in WWI – chemical warfare), and thinking about chemical releases and giant industries, I’ve been looking for something else for a long while! When we define “green” in energy terms alone, we miss the point (and after working with petrochemical plastics, most of the stuff is nauseating to work with inside the plants). I think of risk to workers and to people living near the production plants, and I most dearly wanted to find a solution!
    After testing a piece of pith tissue from a mullein plant, it has the following properties:

    * Density – rigid cells, approx. 7.5 lbs/cu.ft.
    * High Compressive Strength (greater than the pink or blue board, and thus suitable for use under roof decks, walls, etc.)
    * Resists outside air infiltration as a solid board product
    * Made with no ozone depleting chemicals 🙂
    * Non-Hazardous to Manufacture!
    * Probably no deterioration of R-value (R~4 per inch)
    * Non-hazardous to install
    * A True Green Product (encompassing all aspects)
    * Acts as a carbon sink, taking CO2 from the air as the culture grows in the sun. 🙂 (carbon negative, I believe that’s called..)
    * can be treated to resist insects through treatment with boric acid (ie – borates – common minerals from salt lake deposits), or with silicates
    * As any rigid foam product, probably good acoustical properties
    * comparable to sustainably grown balsa or cork as an insulation board
    * Glue-able using conventional non-toxic adhesives
    * Rigid enough to be fastened or fastened to with either nails or screws
    * Preliminary tests suggest a lower flammability than either polyisocyanurate or polystyrene board products
    * Made primarily using solar power (it simply grows!)
    * Disposal poses no threat – it decomposes into natural humus (try that with petroleum-based foam boards once!)

    * not a vapor barrier
    * slowly wicks water; not suitable for damp locations
    * not market-ready yet
    * slower to produce (wait 1-2 weeks for sufficient growth)
    * space required for growth is significant

    * Cost per sheet (this could be less)
    * Actual values
    * Rate of production
    * Long-term studies
    The ability to grow a reasonably flat pith layer is still a question to be answered, although one should be able to accomplish this, as the plant does so within the stem with little trouble.
    The color might be green, if dried quickly so as to preserve the chlorophyll pigments, but otherwise pith without chlorophyll is a light tan color.
    One could argue for the use of more sustainably grown cork or balsa wood as an eco-alternative, but demand is high, so I’m thinking we can only grow so much of these trees.
    It is quite rigid, but does not recover like cork or petrol based foam-boards from compression if high pressure is applied; it’s like a cork that doesn’t “spring back” when a thumbnail is pressed into it. Of course, it takes a lot of pressure before it “gives”, so this may not be an issue.
    I will check on growth rates for pith tissue, and come up with some estimates for how rapidly it could be produced; one thing, though, is that pith is normally cultured without in-cell chloroplasts, instead it’s grown on growth mediums (sugar agar gels). Adding chloroplasts to pith cells for solar energy growth I would think would be fairly strait-forward, as they are compatible with plant cells, and only lacking in undifferentiated tissue (pith) because of the non-necessity there. Although, by what mechanism are they excluded from pith tissue? (maybe just by the exclusion of light?) This would require research. Perhaps an easier solution would be to grow a layer of chloroplast-containing differentiated tissue on top, akin to how a plant does it.. Actually, if one were to follow the general plan of layout, the bottom inch could be pith cells, then woody-type cells, then chloroplast-containing cells. When dried, the upper layer would add strength and rigidity, which could be a useful property.
    …more to discover!

  8. Gennaro Brooks-Church - March 29, 2009 at 3:32 pm

    Chuck you might be on to something.

  9. Chuck Kottke - March 29, 2009 at 3:28 pm

    I’ve got it!! It’s simple to grow your own foam board – it’s simply pith tissue!! Searching the fields today, I ran across a mullein plant, and busting the stem, I realized the pith tissue dries into a solid closed-cell foam core!! Since we can easily culture pith tissue in flasks with basic cell growth mediums, it should be relatively easy to add chloroplasts to the cells and get a growing layer of pith on a large flat tray, set in the sun with enough humidity and air, and just wait a week or two – in time,voila’ – a sheet of foam board! True green too – color and composition. The sheet would need to be dried in the sun, then treated with a little boric acid, and then ready for use. I’m not sure if anyone’s thought of this, but that seems to be be a more natural way, instead of the usual stuff made with phosgene gas and other risky chemicals.

  10. Gennaro Brooks-Church - February 24, 2009 at 2:15 pm

    Hi 50pascals, thanks for the comment. I can’t find it in the post but if I said Polystyrene is any better than fiberglass, I mis-wrote. I agree they both consume lots. What I maybe wanted to say was that recycled Poly is better than new Fiberglass.

    I would try Ultra Touch if it was less costly. But I read somewhere that contrary to the cuddly image of cotton T shirts, making cotton is also a really nasty process….

    Either way, I think we have a LOT of stuff in the world already and if we set up our salvage and recycling structures better we can run on quite some time with what we have made already. This is true the US at least since poor countries already recycle and re-use extensively due to simple need.

    A great example of our potential resources is the Gotham Forest: vast amounts of wood in all the NY buildings. For the most part the wood just gets thrown out when they renovate, unless I can get my hands on it!!

  11. 50pascals - February 24, 2009 at 1:52 pm

    Sorry – It’s ultra touch. Also a real PIA to cut. We insulated a whole house with it.

  12. 50pascals - February 24, 2009 at 1:51 pm

    Hi – Found your search googling “salvage foam insulation board”

    Comfort touch (cotton denim batts) are made in Arizona. Hence trucking to SoCal much cheaper than to Brooklyn. Even truckload price in NYS is more than I can install wall spray cellulose for.

    I disagree with the embodied energy of fiberglass vs. Polystyrene. Don’t get me wrong – fiberglass is garbage. has good embodied energy info.

  13. Gennaro Brooks-Church - January 7, 2009 at 8:51 am

    I think I got it from this site:
    But they don’t seem to say where they got it.
    Apparently academics we are not 🙂

    Try asking them. Let me know!

  14. Bob Charron - January 7, 2009 at 8:26 am


    In your above report you include the following bullet point:

    * Green – A manufacturing study showed that the energy required producing polystyrene foam insulation is 24 percent less than the energy required to make the equivalent R-value of fiberglass insulation.

    Would you be able to provide me with the source and title of that study? I’d be very interested in seeing it.

    Many thanks!


  15. Gennaro Brooks-Church - November 25, 2008 at 8:19 pm

    I wonder why it is so expensive here? I would use it if it were comparable to cellulose. It has the same sound attenuation capacity as cellulose, possibly better. But cellulose is just as good for R value and costs 25 cents a square foot. Last time I checked the cotton cost $1.50 a square foot.
    Another reason I don’t like the cotton insulation company is that they support child labor as seen on their advertising photo:

  16. Rebekah Collins - November 25, 2008 at 8:00 pm

    Because where I live ( N Cal ) it is equal to or only very little more than a roll of the regular nasty fiber glass insulation – the contractors I worked with loved it because everyone hates getting fiber glass on their skin – they were impressed with the price and were not ‘green contractors’. I am happy to learn about the recycled rigid you have been using – I sent them an email for a price I will use it under the floor and spread the word – Thanks.

  17. Gennaro Brooks-Church - November 25, 2008 at 5:49 pm

    I think blue jean insulation is a total waste of money. You can get salvaged board like I have or blow in cellulose that does the job just as well (board is higher R value though) but is three or four times cheaper.
    How come you chose it?

  18. Rebekah Collins - November 25, 2008 at 4:28 pm

    Hi – What about the ‘blue jean insulation it is competitive with conventional rock wool now . . . Thank you so much for your post on recycled rigid -that’s exciting and I agree that keeping materials out of the land fill is greener thatn new manufacture even if it is green ….

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