How Styrofoam Can Be Recycled

Recycling Styrofoam can work. Here’s the Styrofoam made into 16″ x 4′ blocks of insulation.

After moving out of the mountains to the city, because I saw Styrofoam waste almost everywhere I looked, I decided to try to collect and do something with it.

This is a story of how I recycled Styrofoam for the purpose of building insulation.  (I want to make a passive solar shed.)

This topic is divided into three different sections: Research on Styrofoam, How Expanded Polystyrene is Being Used in Building, and this is part 3 – How I Recycled Styrofoam into Building Insulation.

After doing basic research, I approached fast food restaurants that used it, along with several big box stores. (That in and of itself was interesting as I learned about different management systems and levels of efficiency within the respective systems.)


In a very short amount of time, the garage was overflowing with bags of Styrofoam.

By the end of the week, managers at the various stores were saving it for me. I’d pick it up in bags and soon amassed gargantuan, ridiculously large amounts of waste, but clean, Styrofoam.

Take note: Styrofoam is a material that is really easy to obtain. Store managers hate the stuff. A lot of the merchandise on store shelves ship in Styrofoam, but the material doesn’t smash down, taking up lots of valuable space.  Styrofoam is also a material that has great insulating properties.  Why not use the waste to make more efficient buildings?

I originally had the idea that I would make SIPS (structured insulated panels) by using Styrofoam in the core but, this proved to be difficult because the foam came in different sizes and a myriad of shapes. In order for insulation to be efficient, it needs to be continuous. (Imagine how efficient a jacket would be with a bunch of holes in it.)

With my non-building background, I made various models and soon realized that there would be a problem with attaching the Frankenstein-style SIPS to the building foundation.

My next idea was working with traditionally framed with 2 x 4s, in the 16” on-center (o.c.) style of building. I could make a wooden form, then create blocks of insulation that would fit between the 2 x 4 stud walls.

I first built a trial form. It was approximately 16” o.c. and approximately 4′ tall.


An 8′ x 4 ‘ form made out of 2x4s that was the Styrofoam form.

The bags of Styrofoam were unpacked and sorted, then sawed into pieces that were bound together with an adhesive. I purchased a lovely thin, fine saw and went to town. The remaining gaps were filled with expanding foam. After it set for approximately 12 hours, an amazingly, large, thick 4′ piece of insulating foam emerged.

After seeing that it worked, I then moved onto the big leagues of building. I went to the home improvement store and purchased 12 – 2x4s and a 4′ x 8′ piece of OSB (oriented strand board). I has surprised by how heavy OSB wood actually is.

I then measured and cut the wood (with a hand saw) and made a 16” o.c. 4′ x 8′ framed form, backed with OSB.

The idea was to create continuous pieces of Styrofoam that would serve as insulation to be fitted into a traditionally framed house.


Plastic shopping bags were used to line the form.


Instead of using the ¼ inch or even 1 – 2 inch Styrofoam insulation between the 2 x 4s, a nice, big slab of 3.5 inch insulation would be fitted into the frame.

Each section within the wooden form was lined with plastic shopping bags that served dual purposes: The plastic would act as a vapor barrier as well as keep the Styrofoam adhesive and the expanding foam from attaching itself to the wooden form.

The pieces of Styrofoam were carefully fit together. The smaller pieces were sandwiched inside of the larger pieces and bonded together.




I used a foam adhesive and expanding foam to bond and fill the gaps in the Styrofoam.



I used a foamboard adhesive to bond large straight pieces of Styrofoam together, then filled the gaps with an expanding foam.





This thin, serrated saw seemed to be the best option that I used.

I also used a thin serrated saw for the project.  I previously tried both a regular saw and a metal pipe saw.  The regular saw sheared off more of the little, white balls and made more of a mess.  The small pipe saw made a nice, clean cut, but was problematic because it couldn’t follow through the Styrofoam because the larger metal top broke the brittle Styrofoam.


As much Styrofoam and expanding foam were packed together into the form.


I packed as much Styrofoam as possible into the form.

Larger, continuous pieces were used on the outer edges of the form.

When pieces of smaller foam were near the outer edge, cups were cut to make a scale pattern and glued on top to form a type of exoskeleton.




I placed larger pieces near the back, and used smaller pieces toward the top, then covered them with flattened cups to make a scale-like pattern.

Overall, the project worked out pretty well. Well-formed large, continuous pieces of insulation were created out of materials that were bound for the landfill.

As the project was gathering inertia, I accepted a job in New Mexico teaching film. Much to both my dismay and relief, it cut the building project off short.

Originally, I was going to use my retirement from my previous job to make a passive solar shed using the recycled Styrofoam blocks. Instead, I used it to relocate to the desert of New Mexico. Now that school is back in session, it has curtailed writing time on this magazine. (But I’m getting the hang of it and catching up with articles on

Does recycling Styrofoam work?


There’s an abundance of the waste material that makes it really easy to collect. Doing this type of a project does take some time and patience. With an assortment of pieces of Styrofoam, it took me about 8 hours to make approximately 6 – 18” x 4′ panels.

The recycling Styrofoam project did work.

Imagine what the world would be like if we could all start doing crazy projects like this to make better insulated homes and keep Styrofoam out the landfills.

It’s a hope of mine that they stop using Styrofoam altogether. While it is readily available, instead of throwing it away, why not utilize it? It’s possible.

A big THANK YOU! To all the people in the various stores and restaurants who saved the expanded polystyrene for me. Thank you for listening to my crazy idea, then saving it so I could try this project. You all are awesome.


Here’s an image sent in by a reader (see comment below) who used recycled Styrofoam in her build.


The reader used old Styrofoam boxes in wall cavities to renovate a room.


P.S. Notes on building and using recycled Styrofoam.

I’d recommend putting a liner of plastic on both sides of the Styrofoam because it does give off a smell.

Styrofoam insulation used in building has a thin layer of plastic on each side.

Note that the type used in building does come with a thin layer of plastic that is a vapor barrier.

When transporting the bags of Styrofoam from the collections points, there were times when the large amounts of Styrofoam in the enclosed space of my car made my eyes water.

It’s good to work with it in a contained, yet well ventilated area (not outside), as it goes everywhere. When Styrofoam is sawed into, it releases tiny little balls of expanded polystyrene everywhere.

I worked in a hot garage. I fainted once. I think maybe because it was hot, but the fumes may have had something to do with it. While Styrofoam is a somewhat noxious substance, we continue to eat and drink from it regularly. Along with the need to use the masses of the stuff that never decomposes, perhaps other materials could be sought out, developed and used?

Just somethings to think about.  🙂



Keya Lea

Keya Lea likes to spend time outside, enjoying the sun.

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33 Responses

  1. Thanks for doing this.
    Styrofoam gives me anxiety, and this could be a fantastic way to get rid of it. But is it really non toxic in the walls of a home?
    Would have loved to have read more.

  2. Kieran says:

    Looks great

  3. Kieran Sullivan says:

    Hey how’s the performance of this method holding up? I don’t understand why more people aren’t doing this.

    • Keya Lea says:

      Hi there Keiran! It did take a lot of work. Collecting all of the styrofoam, and putting it into a mold really took a lot of time. (I even fainted once in the hot garage I was building it in. But thank goodness, it styrofoam, so I did not get hurt when I fell down.) It would be really, really awesome if someone or some company could formalize the process to make it profitable, or if someone/a business had time, I’d definitely pay them to do it.

  4. Jeannine Andr’e says:

    Thank you for this article! I googled and found it because I need to insulate underneath my cabin as well as a barn shed. I have some fairly large sheets of styrofoam from packaging, so had the idea of using them for insulating, but wasn’t sure.
    I especially appreciate the conversations about it outgassing and being a petrochemical. This is a real big issue for me, so will be using the plastic, or some type of barrier.
    Much appreciation!

  5. Larry says:

    I’m not an expert on this. However, the thought of the toxic gasses and flammability of styrofoam scares me. Vapor barrier in home construction is a solid unbroken piece that prevents moisture from condensing in the wall resulting in mold. Unless you prevent the movement of warm moist air through the wall you will create condensation when that air meets the cold outside walls. MOLD!
    Years ago we had urea formaldehyde foam put in our home. A few years later we had to remove the brick and siding to have it removed and neutralized. I would encourage everyone to do the research to protect your health and your home.

  6. Sharon G says:

    I’ve had success cutting styrofoam with a heated knife. Not sure about gases released during this process, but a much smoother cut edge is achieved this way.

  7. Jeff says:

    I’ve been considering a styrofoam-as-insulation project much like yours to weatherize my detached garage. Thank you for the real life proof that this is doable!

    Instead of using a saw or knife though, I’m going to make a hot wire cutter, which is what crafters/modelmakers use when working with this stuff.

    Seems easy enough to make one for little or no $. Just google “diy styrofoam cutter” or “diy hot wire cutter”.

  8. Steve Nordquist says:

    No. Never. Not unless you enjoy losing the insulation at maybe a half-life a year, outgassing pretty toxic stuff from the usual formaldehyde to styrene specials. Not a way to do it. I have seen this stuff used as an essential component to separate earth overlay of an enclosed garage from the support tiers, but it becomes essential to make outgassing barriers or yes, the foliage set in the earth overlay and the soil biota suffer amain.

    If you recycle styrofoam, just reuse it a bit, then put it in a green chemical loop that can reuse it.

  9. Fay Patterson says:

    Some companies pump insulation into double brick walls, which are otherwise poor for insulation. My plan: chop up Styrofoam, remove a brick at the top of the wall, dump it in. Probably without a stabiliser as running services would get pretty hard. Any off-gassing should be sealed off. l have a couple of light switches, could pull these off the wall, disconnect wires, slip a flexible plastic hose over and replace. Termite proofing wouldn’t be affected. Oh, and bread knives are great for chopping up Styrofoam without creating those loose beads!

  10. Annie says:

    I started my little project back in 1996! It’s actually a 16×20 barn with a loft. Never got it finished cause I started having grand babies and became a baby sitter while mommies and daddy’s worked!

  11. Annie says:

    I Am very interested in what Ed Watt has done. I’m no builder nor intelligent at all but I sure would like the recipe for mixing the concrete and styrofoam!

    I actually started insulating my little barn for a weight room. Never got it finished but I could tell that it was cooler from the little I got done. But I just glued styrofoam to the wood walls!! Guess that was wrong 😳 lol!

  12. Ed Watt says:

    A consideration I failed to mention is to capture the foam in something like sackcloth / burlap bags. I have been blessed with
    many other low energy solutions. for heating and cooling , drawing water out of the air for free, etc.

  13. Ed Watt says:


    Shredding Styrofoam through a yard derbies shredder and mixing
    it with a little water and cement can create a material to be used to create any desired shape. Drips dry and is as strong as the Styrofoam before shredded.
    Greater amounts of cement lend to different applications.
    IT IS FIREPROOF ! Regardless of what you may think, this material when placed in a wood stove for hour still does not burn only the cement remains with little pockets where the Styrofoam used to be. Beyond the outer surface the Styrofoam is still in tact.
    It does NOT work in a cement mixer at least this has been my experience.

  14. Judith Johnson says:

    If I’m not handy that way, how else do I recycle it? Do you have any suggestions?
    Judith Johnson

    • Keya Lea says:

      It can be recycled in some areas. I found a place in Denver that recycles it. They don’t take any styrofoam that has been around food, but they took clean styrofoam used for packing.

  15. John says:

    I have still found no good answer to the question, does this give off deadly gasses in case of fire. Someone at my local Home Depot says it should not be used for house insulation.

    • Keya Lea says:

      It’d be interesting to hear the reason the Home Depot worker has that opinion. They often sell it in sheets for insulation there. There is a thin layer of plastic on both sides that act as a vapor barrier. Styrofoam does give off gas not only in intense heat like fires. It’s debatable as to what constitutes a deadly amount of off-gassing from styrofoam, as it is a petrochemical, but I I’m not aware of specific levels and conditions.

  16. Ange says:

    I was looking into this for my treehouse insulation. I have a couple of questions:
    1. Is there a tremendous amount of off-gassing?
    2. I am considering using acetone/styrofoam plastic for the joining instead of liquid nails, et al. Any thoughts on this idea?
    3. What about fire retardant?

    • Keya Lea says:

      Truthfully, I didn’t do a lot of research into it. Styrofoam does give off gasses, especially when it’s heated. I was planning on placing a vapor barrier on both sides of the styrofoam when building with it.

      I don’t know about other types of adhesives as I only used the one mentioned in the post above.

      In regard to fire retardants, it is a product that is extracted from oil, so it will burn.

      There’s been other things that have been mixed with it. There was a comment made by someone who mixed it with concrete and had good results. I would think that if it were mixed in that way, it raises the insulating properties of cement, but that’s not an ideal building material for a treehouse.

      Let us know how it goes and best of luck!

  17. johndowe1950 says:

    I have an old house and barn .. instead of trying to glue in the pieces .. I used a electric rototiller turned upside down with a box built around it to shred the eps – Styrofoam. then cut a 12′ strip from the sheetrock at the top of the walls .. then mixed the eps with Portland cement. slightly moist and a bit crumbly .. kinda like little pieces of light weight playdo then pour in the top … it fills the cavities and then when dry is a solid piece .. very little sound and much wamer house . and Portland cement is also very fire resistant .. at the top, I pack the “insulation” in and trim with trowel .. screw the sheetrock back on and paint over screws … done .. warm .. quiet ..

  18. andrea says:

    Would you use it in a chicken coop under plyboard?

    • Keya Lea says:

      If could definitely be used under a chicken coop as long as it was protected by something like plyboard or plywood so the chickens couldn’t peck at it. Otherwise, little balls of Styrofoam will be everywhere.

  19. Linda says:

    I think this is a excellent idea and I’m definitely going to start collecting styrofoam from my place of work for a few of my own projects. 🙂

  20. thermofoampk says:

    Thanks for sharing such valuable information. I am very lucky to get this tips from you.

  21. Jeff B says:

    I am planning a different use for the ubiquitous styrofoam. In our yard, we have large spaces that require mulching and plants. I don’t want to plant continuous or large planting. I was contemplating purchasing boulders, however, current price in my area is $400/ton plus delivery cost plus renting machinery to place the boulders or pay someone to place these monoliths. There is also associated damage to the grass due to the machinery.

    I ran across several You Tube videos addressing hypertufa. There are several videos that address applying a dry concrete mis to pieces of styrofoam to create rocks at a fraction of the weight and a fraction of the cost. The other positive is you can create a rock that fits you existing landscape.

  22. Karen Hansen says:

    I have used old styrofoam boxes in wall cavities when I renovated a room. I figured if it is used in refrigeration panels, it would work in walls. I put in a small double glazed north facing window at the same time to allow light in and aid ventilation, as the room was horrible, dark and musky. I just used my filleting knife and liquid nails, overlapping at the joins to ensure no draughts, and filled the cavity.

    The first summer came and we had a day of 42 degrees outside, inside the main house it was 32 degrees, and in the room that was insulated, it was 24 degrees. (I don’t have any form of aircon). In winter, the room does not drop below 10 degrees (with no heating in it) even though it often gets to zero here, and my wood heater struggles to heat the remainder of the house.

    pic of the styrofoam going into the walls

    • Keya Lea says:

      You are so awesome! Nice job on the renovation with the recycling of old styrofoam boxes in the wall cavities! It’s brilliant, and more efficient than piecing together cups and random containers. It’s amazing what insulation can do. I like that you included the outside, indoor, and insulated room temperatures. Thank you for sharing!

      (I’m guessing that your degrees are in Celsius, rather than Fahrenheit?)

    • Nikole says:

      I’m confused. You seem to indicate
      You like the styrofoam insulation but if the room is that much cooler in the winter… isn’t that bad? Never mind I see it was summer and cooler is good lol

  23. Laurence says:

    I have done the same thing but I went the veg box and cut with a sharp carving knife, re sharpening every few mins !

    I used it as the insulation under the slab wrapped in Builders plastic, about 4 ” thick,

    Don’t know if I would put it in walls as it is a fire risk, and you found the off gassing, here in Australia, we have termites that eat wood, They love to live in Polystyrene in cool dark damp conditions….

    Well done


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