Lets Chat about EPS foam insulation.

So I'm doing a ton of research on wall systems specific to colder climates. I don't really want to stray off into other options etc so much as just good information on EPS foam. The goal is to ultimately decide on the most effective way to accomplish an R50 wall type. Right now I'm looking at a standard stick frame or advanced framing wall with homewrap, 13" of EPS, 1x2 vertical strapping and then a finish layer of siding yet undecided. This should give an R50 wall type at the lowest cost vs performance in my region. The goal is passive house certification. My climate has sub arctic winters with hot (up to 95F) humid summers.

I understand the environmental impact of EPS vs other products and although it is not nearly as good as straw or densepack it is better then many other types including XPS, Sprayfoam etc. This building is meant to showcase performance and be used as a showpiece alongside an R50 strawbale home. So is it the best solution for the world? No, but its a major milestone in progress when compared to the bat and poly status quo we have now.

Just for a quick comparison. Larson truss systems here are coming out significantly more expensive, and the dense pack cellulose is about the same cost as EPS. When balancing labor against materials a densepack at R50 Larson truss type system EPS is coming out cheaper. In face I'm finding the EPS materials significantly cheaper. The basic idea is that the wall system can be 80% completed on the ground and then tilted up with only the corners and tie-ins needing completion.

I am really interested in hearing the negatives as well as positives. However please include the how and why with your negatives including real solutions.

Here is what I'm finding:
-EPS is being found to maintain its R-value over the long term with little or no performance loss. XPS and other rigid foams that require the use of blowing agents do degrade over time and appear to end around EPS levels. From what I've found so far EPS has very good long term performance and durability, so long as it is properly maintained. Maintenance is required for every type of wall system so debating this point is kinda moot.
-Price per R-value is WAY more affordable then XPS etc. You can get a 4x8 sheet or R-X for less then half the cost of a 2x8 sheet of the same R-X, so its half the cost of material and less labor to install.
-EPS is vapor permeable, although it may not have the breath-ability of straw I'd bet it is very comparable when compared to straw properly encased and sealed.
-Due point of the wall will happen inside the insulation itself where there is no organic material to accumulate moisture etc.
-Gaps etc in the sheets are easy to fill with foam

There are still some issues I want to address. Namely thermal mass in the walls. I'd really like to find a way to have mass in all the outside walls, I'm batting around the idea of sand or gravel in the wall cavity up to the first 4' behind the drywall. I'm sure the drywall would be able to withstand the pressure and it would allow a lot of thermal storage in a small area totally unseen.

The big problem with foam is it won't degrade when landfilled--so keep it out of the landfill. I think putting it in a multigenerational house is a good use for it. Sequestering it, so to speak.

Mass inside the insulation is a good idea, not sure the best way to go about it.

I think thick sheets of foam tend to be more recycleable. In fact you may want to seek out salvaged foam from old commercial roofs that are being renovated. Its best practice to use at least two layers that are offset from each other and tape both layers.

If you are building to International Building codes then its pretty safe to assume that the embodied energy of the foam will be recaptured by the saved monthly energy use fairly quickly. There seems to be quite a bit of controversy in the payback of passive house sub slab recommendations though. If buying new foam, try to find some that uses water as the blowing agent.

I forget the perms per inch of EPS but in your thicknesses, there will not be much vapor permeance not that its a big deal with the right details.

As for thermal mass, I think its easy to waste time, effort and money on adding more than what is needed for the building anyway. Put the extra money into windows or PV.

Hi Sean,

Without belaboring your design goals, the only advice/warning I would give, is from a "pest degradation issue." If you have any type of wood ant, red squirrel, flying squirrel, rat, or mouse issue in your area, you much design the wall system to physically exclude these animals. For example, screening or other systems that can withstand there chewing and/or constant vigilance on trapping and removing. Do not use poisons as this is a bait system. Most pest control companies use bait, and in an area where "repopulation" is not a problem it has some merit, but typically because it is a "bait" system, it often attracts more animals in. Good for pest control company, bad for you. We used EPS in the labs as burrowing and nesting medium for these different species. This last building season alone we remove stress skins off a 7 year old timber frame with some panels having 60% to 70% degradation due to burrowing and nesting activity. Many folks will go as long as a decade without incident, then in a single season, incur tremendous damage. Considering the thermal mass issue, if designed well can create a very positive "thermal sink," and keep the structures temperature swings much lower, with a more consistent ambient norm. Since we tend to build traditionally, we are often repurposing older vintage architecture and/or or using traditional windows. and seldom take out original fenestration. We do restore them fully and apply proper textile coverings, such a "window quilts" which will make a vintage window up to 5 times more efficient that a high end replacement window.

good luck,

j

Wow Jay thats some serious problems youve encountered with the stress skin panel example. Would love to hear more detail on the culprits and locations of entry. I would think a true SIP panel would be better protected as the foam is encased by wood on all six sides.

Rodents and squirrels will invade almost any insulation if given the opportunity. I think foam is a better barrier than fiberglass, cellulose or mineral wool for those type of critters.

Carpenter ants and termites are a different story. While the foam is not a food, it does make a great nest from which they can invade the wood of a home.

I know i have seen pictures of a common pest of bees that has a larval stage that Eats Bees wax, and they have evolved to live long enough to do extensive tunneling in some
forms of insulation ! Some one else want to chime in ! Big AL !

We stored about a dozen sheets of 1" bead board in a no longer used grainery for the winter. It was stored standing vertically sandwiched with a sheet of plywood on each side. By spring roughly 1/4 of the total volume of those sheets was on the floor as loose white beads. The boards themselves looked like a giant version of an ant colony with 1" tunnels everywhere. Needless to say the mice had been busy. And this happened with a good cat population and a door for them to get into the grainery. That was nearly 30 years ago and in the mean time I have seen damage in foam in several other places. Spray foam, extruded and expanded foams have all taken damage. For nearly 20 years I have been expecting makers to begin building building steel mesh into the foam or poison into the foam. I expect this to be a major issue in the next decade or so as builders begin recognizing the problem. Strong precautions should be taken to protect foam from rodents. I have seen some insect damage but it is minimal here so far.

C. Letellier wrote:For nearly 20 years I have been expecting makers to begin building building steel mesh into the foam or poison into the foam.

Our friend C. Letelier, just struck the "common sense" nail on the head! You would think they would do something like that, yet there is so much of what humans do in modern construction that is basically nescient that it doesn't surprise me anymore. I have been harping on this "little gem," for all of those 20 years, here are just some of the "quoted answers" I have gotten from manufactures, builders, and architects:

MANUFACTURE

"We treat the foam to "inhibit" that."

I love it when a manufacture uses the word "inhibit," it is an immediate red flag for me now that something is going on, and they probably don't have a real good way to address it, and/or they don't really feel that by the time it is an issue, it is their problem anymore. Remember folks, most manufactured products only have a 20 year (if that) warranty and that is all most modern construction is really expected to last before major renovations are required...like replacing 50% of your insulative materials. I could write a book on the "Psychology of Architecture" and a full chapter on "human denial syndrome."

ARCHITECT

"It really isn't that big an issue, and is out weighed by the ease of design. Proper pest control management should address it."

I love this one. Another, "lets pass the problem down the road." It is true, proper pest control and management might address it, but that is much easier said than done in most cases. General pest control is one of the largest issues in architecture, is often done unethically, and has become in some ways another "white elephant" that we just don't want to think about. It is easy to not think about, "wee beasties" crawling through our walls, ceilings, foundations and/or little fungus-molds that live on everything inundating our structures. "Out of sight - Out of mind."

CONTRACTOR

"Not my problem..."

"Can't see it from my house..."

"A Good pest control contract will stop it from happening..."

"I have been using it for 20 years, and I have never seen it happen..."

I love the last one, as it is a common answer for a lot of what ills modern construction modalities - "they haven't seen it," - which usually means I don't believe you, or "not my problem." Somehow, "not seeing something" (which we usually don't till it is too late) is suppose translate into, "it isn't going to happen."



To respond to comments thus far, and address questions:

None of these species "eat foam" or wood for that matter, (other than termites - and that is an entirely different topic.) These critters are diggers and chewers, some can even dig and chew through many concretes (especially old concrete and mortar.) Getting through a joint in siding, eave soffit, gable, sill plate, etc. etc. etc. is not an issue for them at all. The timber frame I referenced in my last post was at the corner of both a Flying Squirrel colony, a Flicker territorial boundary and a Red Squirrels "battle zone" with Gray Squirrels. So between the woodpecker using the side of the house as a "sounding drum" (and latter building a "secondary" nest in the stress skin panel) and the Red Squirrels chewing a hole through the soffit, ingress and egress was not an issue at all. Mice and rats both have been observed waiting outside garage and house doors for an opportunity to enter both homes and commercial establishments (like hospitals and restaurants,) coming in and out with the human occupants. Most of our human species is about as "aware" and "observant" as a brick, not to mention our psychological propensity for "denial."

I have used foams when specified in a design, I avoid them when I can, and typically only use urethanes, or "Aircrete" when I do, and I design both mitigation systems and management plans for myself and clients to address these issues. Pretending it doesn't or can't happened is not a plan. Foam is not a better barrier, and in some ways attracts them because it is an optimal nesting material. Yes this can happen in cellulose insulation (not so much with dens-pack that is treated) as well, especially with rodents, and if the insulation gets damp, (which the so often do because of the bloody "plastic wrap" we are throwing up on everything.

The pest tunneling is a problem regardless of the insulation media. Aircrete is more resistant only because it is harder so they dig slower (or move to easier digging like your wood structure!). Mice will chew through metal siding/roofing, modern stucco mesh doesn't even slow them down. You can't poison the foam with anything that would repel termites without making it kill the construction worker first.

Found IT! L@@K in forum thread >Moths that Eat Plastic ! (bugs forum at Permies !) Any one want to Debunk this ! Big AL !

Late note, who wants to keep this family alive after the demise of the bee's maybe fed them out of mans waste stream, and then feed them to chickens like
'Black Soldier Fly Larva ?! A. L.

We raised those in the lab also, but I always thought they tunnelled into the material for purposes of pupation, nothing more. It would make sense that they could perhaps, if desperate, eat it as well to some degree. I will have to read the posting.

Thanks for that

This may be an odd point. When the stuff burns what are the toxins released? I will do some research maybe someone already knows the answer.
I am bringing this up for the reason that homes have a significant fire hazard. I have never been in a home fire, but I have nearly been the cause of one when I was a kid learning about fire and matches. 37 years of no home fires. Knock on wood. I know there are fire resitant treatments for such occasion, many of them are water solluable and get washed off or degraded when fire fighters spay them with water. Maybe this is a useless point. If the house is on fire saving it vs keeping other structures from burning is the fire fighters job.

Great point Seth. Burning any plastic is terrible for the environment and a serious inhalation threat. I know some green builders specify cast iron and copper to avoid any plastic plumbing for this reason. Fire is one of the more serious threats our homes face and its one of the many reasons I prefer all-electric homes to eliminate the increased risks associated with combustion apliances.

I have been trained as a fire fighter. One of the major reasons we are required to wear the air tank system at fires regardless of being inside the structure is released toxins. However the bulk of those toxins come from furniture etc inside the house more so then the structure itself.

One if my major responsibilities at work is fire rating structures. Your best bet is to choose a fire rated drywall over standard board on the interior. It's not a guarentee the building won't burn but it can buy you those vital few minutes to escape. Fire walls etc are horribly lacking in residential system design.

I'm proposing the use of eps on the outside of the structure in a remote wall configuration so the fire would meet to be well on its way before hitting the insulation. That said once a building is engulfed in flame all bets are off. Kitchen fires or other small fires aren't really a theat to the EPS. Most fires are contained unless the result of ignorance or incompetence. Most home fires in my area are due to poor building practice in old structures and lack of electrical maintenance. Attached garages are risky as well.

Brian, is correct, all the foam, especially XPS and EPS are extremely toxic in fires. Some fire departments have lobbied to ban there use for this reason alone (unsuccessfully.) Some volunteer fire departments will stop a response in some cases if these materials are noted in the fire load. I'm not sure an all electric house is any kind or justifiable solution to stopping fires in any substantial way, since 10% to 15% (NFPA) of domestic fires are electrical if you just count the wiring harness malfunctions. If you include all other electric items that cause domestic fires this number jumps to ~55% to 65%. The breakdown of domestic fires causes in order of highest to lowest:

1. Cooking, electric or gas ovens left on, grease fires, combustibles falling on burners, etc.

2. Children playing with fire.

3. Smoking.

4. Heating systems that aren't maintained, especially electrical space heaters, and open flame kerosene.

5.. Electrical system.

6. Candles.

7. Fireplaces - Wood stoves.

8. Dryers electrical and gas, but since most are electrical this is a root cause and can effect the statistics for electrical fires which can jump to ~65% if you combine 1., 4., 5., and 7.,

9. Flammable liquids in house, lamp fuels, alcohol, cooking oil, lubricant oils in basement shops, finishing oils on rags, oil paints, etc.

10. Christmas Trees (electric lights, etc.)

Last is arson.

Interesting points.
I am interested in knowing if the boards could be treated for fire resistance before they are installed. In the instance of a structure fire I would think that the ability to save the structure is limited. The key being to save the structures around the burning building. Although For the building in question, I can understand the point of toxins being emmited from the other products in the building. The products may not have fire ratings of any sustantial usefullness.
In the idea that a coating could be added to the EPS board: Would the EPS board be compromised? Would it have a significant effect when the building is so far gone? Hard to know case by case basis.
This is a good topic. So far I am still convinced the pros outweight the cons concerning better insulation.
The toxicity is still a factor, yet the toxicity of the mass pollution from over generation of power is still extreme. It is a difficult idea to work with.
Sean the over all power savings vs. the cost is huge. Better insulation is still the key. Basically it is the right track.
Brian are there any comparable products made from natural materials with a similar thickness and cost that could provide the same R value? That are less toxic and similar in cost?

Insulation and fire: I have used foam insulation and most install specs require "sealing" the insulation away from the living spaces with "non flamable" skin - ie. taped sheet rock of one sort or another. This is purely a fire safety spec AFAIK. Dense pack treated w/fire retardant IIRC will not carry a flame at all on it's own.

Fire retardant skins seem to help considerably saving the building structure. My parents had a good hot fire in 1-1/2 bedrooms on the 2nd floor of a 3 floor wood frame house from 1902. The ceiling directly above the shorted heater that started the fire w/the bed burning remainded intact and the joists above were charred on the surface but not more than 1/8" of their surface was compromised. The whole house was "smoked" and 1/2 the wall/ceilings had to come off because fire related damage but the building structure was fully sound. This was old plaster/lathe; not sure how standard sheet rock would have fared.

Can speak from personal experience that "lodgers" of all sorts are endemic to buildings. In an urban neighborhood on the border of Chicago my sister and I are presently trying to evict a nest of flying squirrels and probably also one or two of grey squirrels from my sister's house. Most annoying, time consuming and expensive. Way mo' betta to do everything reasonable in the beginning to make a building unattractive to varmits. Count out 5-10 years and it'll be much cheaper...

Insulation repair: Not sure but it _may_ be easier to repair dense pack (still not cheap) by simply repacking after locating problem areas.


Rufus

Jay, great list but combustion appliances are included in 1, 4, 7 and 8. I doubt the percentages add up to an insignificant amount. Also curious why wildfires didnt make the list but I guess thats a different sort of beast to your list.

Seth, No. There is no natural competitor to foam sheet goods in terms of R per inch and costs. As for toxicity, I feel natural insulations are not necessarily more friendly than foam. Anyone interested in this thread should see this one started by Seth.
https://permies.com/t/30310/green-building/Toxins-Energy-consumption

Foam, like all valuable resources, should be used judiciously and strategically. There are many situations that natural insulation makes more sense. I think cellulose is often a great choice for permaculture philosophy. Mineral wool also seems to be emerging as a good product despite its higher embodied energy due to its ability to be used as continuous insulation like foam is best used for. I like many aspects of strawbale and very small structures are probably fine with less R per inch and overall lower R values.

I also dont think EPS is a clear winner over other foams. Two drawbacks compared to other foams is its tendency to absorb more moisture and shrink which can make it difficult to tape the seams. It depends on the situation and the details.

Sorry for resurrecting this old thread but i feel the title deserves a little more attention.

Due to the ways our modern world operates, industrial products and byproducts are made available more readily than other (more natural) materials and sometimes at a considerably lower price / performance.
Case in point is EPS.
At a price / performance ratio there's nothing close.
I am leaving the other considerations aside for a moment so stay with me.
A natural-ish alternative is mineral wool.
It has same thermal properties and almost none of EPS's issues but is costlier and can be used mainly on walls but not as bearing layer like under a self bearing floor.

And here's the crux of the matter.
It was discussed until now about using it in wall systems where fire is an issue.
But what about underground, horizontal usage, where there can't be any fire ?
I'm thinking of putting a layer of EPS200 over a well packed gravel layer and a natural floor over it.

The badness of EPS could be diminished by the service it's doing and long lasting life in this usage scenario.

Only one issue remains : pest damage (mainly rodents).
That could be mitigated somewhat depending on the build.

So what about using EPS like this ?
What to be aware of (the wolf in sheep's kin)?
Advantages / disadvantages / etc ?