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If Ants Like Rigid Foam, Should We Stop Using It?

Rigid foam insulation is routinely used in high-performance buildings, but it also seems to attract carpenter ants

Posted on Mar 28 2016 by Scott Gibson

Writing from the Pacific Northwest, Malcolm Taylor dives into a problem experienced by many homeowners and builders: a carpenter ant infestation in rigid foam insulation.

"I am involved with two projects right now that have carpenter ant infestations — and in both cases they are in the foam," Taylor writes in this Q&A post at GreenBuildingAdvisor. "One is particularly difficult to fix as it is a flat roof with tar and gravel above and a wood tongue-and-groove ceiling, making it hard to get at the nests."

For a season, the owners tried to deal with the problem themselves, but their efforts backfired. Instead of a single nest, there are now "multiple nests across the whole roof," Taylor says. Exterminators brought in to find a solution say that it may take more than a year to get rid of the insects, and of course during that time the ants will continue to damage the building.

"When this topic comes up, typically the responses tend to fall into three categories," Taylor says. "First, ‘don't think about it — [foam] is used all the time so it must be all right’; second, ‘as long as the foam is dry they won't move in’; and third, ‘treated foam is available.’ "

Taylor has found that carpenter ants will move into foam whether it's damp or not. All they need is a source of moisture nearby. As to foam treated with an insecticide, he adds, no one seems to stock it.

"As foam is now increasingly being used as an integral part of many structures, and often in a load-bearing capacity, how wise is it to use a material that is so vulnerable to pest and insect damage?" he asks. That's the topic for this Q&A Spotlight. (To read a previous Q&A Spotlight article on this topic, see “Coping With Termites and Carpenter Ants.”)

Does the foam have to be damp in order for ants to like it?

One person who has some experience with the problem is Building Science Corporation principal Joseph Lstiburek, who recalled his battle with ants in a 2012 . Lstiburek had renovated a barn 15 years earlier, wrapping the building in a thick layer of EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest. insulation. When the ants became an overwhelming problem, he took the barn apart to find out what had happened, and in the process found just two spots where they had made nests in the foam.

"The message here is obvious: keep things dry and you will not have ants," Lstiburek wrote. "By the way, keep things dry and you won’t have a lot of other bad things as well. The dry/wet thing with ants is pretty much proving to be the case in all the ant foam infestation cases I (and others) have looked at over the years."

To Chris M, who cited the article, Lstiburek's story means that having a damp environment near the foam isn't enough to attract ants: "Therefore one could deduce that if 'having water nearby' was the only requirement, then ants would've been found throughout the dry foam as well."

So, dry foam means no ants?

Not necessarily, says Charlie Sullivan. "It might only mean that the ants prefer damp locations. If there were two ant colonies looking for homes, and no wet foam, they might have both moved into dry foam."

"Agree," replies Chris M, "but keep in mind that research shows carpenter ants will live in dry wood but prefer damp wood, so technically there's nothing keeping them from setting up shop in any stick-built structure. So, yes, absent a preferred (i.e. moist) environment, carpenter ants 'may' take up residence in dry foam or wood — or they may just move on."

Ants are a wily adversary

When Taylor built his own house 20 years ago, the only foam insulation he used was a strip covering the second-floor rim joist. Ants found it.

"The nest was on a sunny south wall which as bone dry when I opened it," he said. "Unfortunately, by then they had also eaten a large hole in my top plates (which were not rotten or damp) and able to move down the wall to nest next to a baseboard heater. I surrounded the foundation with insecticides, but the tenacious and alarmingly intelligent colony found the one possible path out to forage by using my power lines and descending the pole on the street."

Although foam seems to mimic the decaying stumps that ants prefer in the wild, Taylor says, they also can be found in wall cavities filled with fiberglass insulation, often next to a heat source such as a fireplace or a wall heater.

"I wonder if the seasonal swings in the moisture of exterior sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. are enough to make them set up shop in usually dry and decay-free wood structures," he says. "They sure like foam, though."

Burke Stoller, another builder in the Pacific Northwest, has run into his share of ant infestations in exterior foam, and it makes him wonder just how deep these insects will live in the ground. The only place he typically uses foam insulation is underneath a slab foundation (full basements are uncommon in his area), and he wonders whether he should worry about subterranean ants.

"I am wondering to what depth we should be concerned about bugs tunneling under our footings and working their way back up to the underside of the slab, tunneling around in the EPS layer?" Stoller writes. "I share the concern Malcolm expressed, as on our PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. projects we are beginning to see architects and engineers approve higher density EPS for structural load-bearing applications, and I, too, wonder if we are looking for trouble down the road."

Is mineral wool insulation a better choicer?

Andrew C is concerned that the widespread use of rigid foam insulation, along with sloppy installation of flashing and other water-management details, will mean a backlash against green building and building techniques in which insulation goes on the outside of a building.

Chris M has the same worries, and suggests that mineral wool batts such as are a better alternative than foam.

"Roxul has never made claims that insects won't bore into their product," he says, "but I'm not surprised, since in my opinion their product is generally sold in climate zones which don't have termites."

John Semmelhack writes that as far as he knows, neither ants nor termites will chew through rigid mineral wool boards, and the insulation is too dense to allow insects to crawl through it. For these reasons, he prefers mineral wool to foam insulation in Climate Zone 4 where he works.

Stoller is another believer in replacing rigid foam with mineral wool. "On almost any renovation project we do with rigid foam on the exterior of a foundation, or on an exterior wall near grade, we find an absolute ant farm," he writes. "They love the stuff, and make incredible patterns to pull apart and view! So, we have completely switched (when we have our say on specifications and assembly design) to only using Roxul Comfortboard IS for exterior insulation detailing.

"It can be a pain for much of the detailing around windows and doors, and for ensuring that all of your rainscreenConstruction detail appropriate for all but the driest climates to prevent moisture entry and to extend the life of siding and sheathing materials; most commonly produced by installing thin strapping to hold the siding away from the sheathing by a quarter-inch to three-quarters of an inch. stays completely co-planar for exterior claddingMaterials used on the roof and walls to enclose a house, providing protection against weather. ," Stoller continues, "but we have learned some tricks over the years to make life easier. Not only does it appear to be totally bug-resistant, but even better is the fact that it is extremely vapor-permeable (+/- 30 perms at 1 inch), meaning that assemblies will dry much better than their exterior foam counterparts."

Other suggestions, and a warning

Among other suggestions from GBAGreenBuildingAdvisor.com readers for controlling ants and termites:

  • From Andrew Bater: Install a removable trim system at the base of a stucco wall to allow inspections for ants, as well as an opportunity to apply insecticides if needed.
  • From Lucy Foxworth: Cover soffit holes with metal screening so insects can't crawl through, and trim trees around the house so they don't form a "carpenter ant highway" into the house.
  • From Christopher Peck: Tape the top and bottom edges of foil-faced polyisoPolyisocyanurate foam is usually sold with aluminum foil facings. With an R-value of 6 to 6.5 per inch, it is the best insulator and most expensive of the three types of rigid foam. Foil-faced polyisocyanurate is almost impermeable to water vapor; a 1-in.-thick foil-faced board has a permeance of 0.05 perm. While polyisocyanurate was formerly manufactured using HCFCs as blowing agents, U.S. manufacturers have now switched to pentane. Pentane does not damage the earth’s ozone layer, although it may contribute to smog. insulation with aluminum tape, on the assumption that termites can't bore through either the tape or the aluminum facing of the insulation.
  • Chemical insecticides are, of course, an option. But one obvious disadvantage of chemical treatment, as Andrew Bater points out, is the disconnect between building a healthy, green house and then having "to douse it with insecticide."

    Further, warns Robert Ohle, there's the possibility that insecticides themselves can dissolve foam insulation. "Twice I have removed siding, where the homeowners had brought in exterminators to deal with ants, to find voids where the insecticide had been applied," Ohle says. "In both cases small holes had been drilled through the wood siding, insecticide injected, then the holes sealed with a dab of caulk."

    Our expert's opinion

    GBA Technical Director Peter Yost added this:

    I confirmed with two entomologists that carpenter ants can have satellite nests that are not damp, but that are in materials that are easy to chew and provide shelter and warmth. That is unnerving at best for all of us who have built with and recommended rigid foam on the exterior of wall assemblies.

    There is a relatively new high-density EPS product by Atlas called , which contains Preventol, a Lanxness Corporation insecticide. The ICC Evaluation Service Report (ESR-2918) specifically states that Preventol TM-EPS “is used to treat expanded polystyrene foam (EPS) to provide protection against termites…”

    If you in the PAN Pesticides Database, you'll find more than one product listing. That is, Preventol has different forms used for different applications. While Preventol TM-EPS lists only termites under the pests that it can be used for, a form of Preventol called hs 100cs-50 is listed for use against termites, carpenter ants, and wood-boring beetles. Further, while the active ingredient in Preventol TM-EPS is listed as Imidacloprid in a concentration of 99.8%, the active ingredient in Preventol hs 100cs-50 is Deltamethrin in a concentration of 4.75% and formulated as a soluble concentrate. These two insecticides may share a brand name — Preventol — but they are very different chemicals.

    I tried to contact a leading expert entomologist — Mike Potter at the University of Kentucky — who has proved really helpful in the past, in no small part because the guys at Atlas strongly suggested that I sort out the different behaviors and preventions for termites versus carpenter ants by talking to a bug expert. But I was not able to connect with Mike Potter this time around.

    I think the final cut here is that we have one fairly widely available rigid insulation — Atlas ThermalSTAR — specifically formulated to be used below and above grade to resist termites but not specifically formulated to deal with carpenter ants.

    It sure seems as though if you are building in a climate and wooded site that carpenter ants favor, rigid mineral wool is the safest bet.

    Finally, I can find no evidence that carpenter ants are subterranean, as are some termites. Whether carpenter ants would be able to penetrate or be attracted to rigid foam under an at-grade or near-grade installation (for example, under a slab) remains to be seen.

    I will continue to try and work this through with Mike Potter. Stay tuned.


Tags: , , ,

1.
Mar 28, 2016 12:23 PM ET

So is this all foam?
by David Pfeffer

The article only mentions EPS but seems to imply all foam. Do we have to worry about polyiso and XPS, or are they sufficiently dense to ward off attack?


2.
Mar 28, 2016 2:24 PM ET

David
by Malcolm Taylor

All the foam I've had problems with was XPS. I don't know about polyiso.


3.
Mar 28, 2016 3:42 PM ET

It's not a matter of density
by Dana Dorsett

Until recently one of the guys in my office lived in a nice 1980s post & beam house with 2lb polyurethane core stress skin panels and was constantly battling ants. I've seen carpenter bees & wasp nests in fiber faced 2lb roofing polyiso too.

I would expect aluminum facers on foam to be a pretty good ant-armor if you tape over the exposed top & bottom edges with an appropriate foil tape, but that won't help you for below-grade exterior applications.


4.
Mar 28, 2016 4:44 PM ET

Man vs Nature = Nature Wins
by Peter L

I was told by a wise architect that when it comes to building homes and dealing with pests, it's a never ending battle and nature will always persevere. What one can do is try and REDUCE the threat with ants, termites, rats, bats, bees, mice, etc but in the end it will always be a battle of Man vs. Nature and nature will win.

So I don't believe the problem is rigid foam because termites will eat wood, so should we stop using wood in buildings? Rats and mice like nesting in cellulose, mineral wool and fiberglass, should we stop using it? Every material out there will be used by some type of pest except for maybe concrete and steel. The latter two are great for long term building materials but make for lousy insulation.

No matter what you use, one cannot "build it and forget it" when it comes to pest protection. One has to remain vigilant and keep up the battle with nature. I got mice in my garage this winter and if I didn't address & attack the issue then the mice would make their way into the home. It's a constant battle. Welcome to nature and mans struggle with the earth. Don't get me started on battling weeds in my vegetable garden ;)


5.
Mar 28, 2016 5:00 PM ET

nesting in mineral wool?
by andrew c

Peter L, while everyone has seen mice in fiberglass batts, I haven't heard of mice in mineral wool, especially the denser version that come in board form for exterior use. Is this common? I also wonder about dense pack cellulose as well; properly packed, it would seem like it would take an awful lot of effort for mice to tunnel into.

I understand your general comment that nature tends to prevail in the long run and material selection is not always simple.


6.
Mar 28, 2016 5:34 PM ET

Insecticide Stability
by Tim C

My concern with the insecticide treated foams - how stable are the insecticide compounds? If they're going to decay in 10 years and leave you with non-insecticidal foam, they haven't gotten you very far.


7.
Mar 28, 2016 6:54 PM ET

Edited Mar 28, 2016 7:00 PM ET.

Animals do nest in mineral wool, at least the less dense stuff
by Christopher Welles

Apparently birds like to nest in the less dense CavityRock boards at least: Wrapping an Older House with Rock Wool Insulation

And mice seem to like the batts: Mice nesting in Safe and Sound

I don't know how resistant the significantly denser ComfortBoard might be, but apparently rock-wool isn't really pest proof. If pests like plastic and glass, perhaps they do like rock when it's been spun into wool. I'd love some more solid information on this myself.


8.
Mar 28, 2016 8:42 PM ET

Andrew and Chris
by Malcolm Taylor

I guess for me the distinction between battling rodents and insects is that you have a fair chance of building a mouse-proof exterior, but I can't imagine being able to build an envelope tight enough to keep out ants.


9.
Mar 28, 2016 10:18 PM ET

Rodents vs insects
by andrew c

Malcolm, that's a good distinction. I've moved a lot, and while looking at houses at some point I decided that if there were no signs of mice, it was an indicator that the house was reasonably built (at least by normal production builder standards).

I do appreciate that this thread was chosen for a Q&A Spotlight. I look forward to any additional expert input (from the bug people), and to more articles on how to detail with rigid exterior mineral wool. I've heard that some people have techniques for getting good rain screens that allow for straight forward cladding installation...maybe using panels instead of just fiber cement siding...


10.
Mar 28, 2016 10:19 PM ET

Edited Mar 28, 2016 10:26 PM ET.

Andrew C
by Peter L

Yes, most definitely, mice, rats, birds, etc. can and do nest in mineral wool and cellulose.The dense packing means nothing since a rodent will simply just remove the cellulose and create a nesting pocket.

In my area pack rats will actually gnaw their leg off in an attempt to escape a snap trap. I've seen snap traps with only a rodent leg in it and no rodent and a 3 legged rodent running around. They nest in thick brush packed with twigs, cactus and rocks. So mineral wool and dense packed cellulose house walls is the Hilton resort for them.

Mineral wool is susceptible to infestation. Posts and articles here on GBA and what I have observed and read about shows that it does happen. Even birds have been observed nesting in mineral wool. I've personally seen squirrels and rats nesting in cellulose and mineral wool.

I quote:
"One slightly amusing problem that we did not anticipate: birds like to nest in rock wool! As soon as we installed insulation above head height, the word got out to the bird community that there was some prime real estate to squat in! The birds would quickly burrow clean circular holes to claim their own little condo.

In the few weeks that it took to install the insulation and await delivery of the metal siding, there were a dozen or so uninvited guests in our wall assembly. ..."

Read more: http://lakesideca.info/blogs/dept/guest-blogs/wrapping-olde...


11.
Mar 29, 2016 2:08 AM ET

Maybe they need to add
by Alan B

Maybe they need to add diatomaceous earth to the mix when making foam?
Would it work?


12.
Mar 29, 2016 2:30 AM ET

A green home in all sense
by kINGSTON GA

While building homes , we should ensure that they are sustainable and healthy . I f this foam is leading to accumulation of ants then we might as well avoid using it . A green home should be environmentally stable in terms of the materials being used and the energy it consumes.


13.
Mar 29, 2016 8:07 AM ET

Law of conservation of toxicity
by Charlie Sullivan

Just as proposals to remove toxic flame retardants from below-grade foam are being seriously discussed, we have to consider adding another toxic substance to them.

An organization promoting the first change has a webinar about it tomorrow and is asking for letters of support by April 1st.


14.
Mar 29, 2016 9:00 AM ET

What a depressing article. I
by Jay S

What a depressing article. I am nearly ready to build my dream home and after all my study I have decided that SIPs are the way to go in my zone 7 area, but this area definitely has carpenter ants. Back to the drawing board?


15.
Mar 29, 2016 9:21 AM ET

interior insulation
by Sharon Secrist

A reason to insulate on the inside.


16.
Mar 29, 2016 9:23 AM ET

We're generally talking exterior insulation are we not?
by John Clark

If so I don't see how birds or rodents could physically get into a rain screen and set up shop in dense mineral wool board.


17.
Mar 29, 2016 9:30 AM ET

Edited Mar 29, 2016 9:31 AM ET.

Response to Chris M
by Martin Holladay

Chris,
I don't have enough experience with mineral wool to know whether rodents or birds like to nest in mineral wool.

But it's obvious to me that rodents can get there if they want to. Rodents have teeth. The word "rodent" comes from the Latin rodere, "to gnaw." Rodents are gnawers.

Different species of birds have different behaviors, of course. But a woodpecker can make a hole you can put your fist through.


18.
Mar 29, 2016 2:51 PM ET

Chris & Martin
by Peter L

In my area I joke that woodpeckers have created an alliance with rodents. The woodpecker pokes a hole in the soffits & walls and then the rats, mice and even squirrels then make their way into the homes walls. It's a team effort to break and enter into your home ;)

That's why I believe and stated that it's an ON-GOING due diligence effort that must be undertaken by the homeowner to watch over the house and see what pests are attempting entry. You can build a better pest resistant home but you CAN'T build a pest proof home. Unless you want a home made of concrete and steel with no insulation, one will have to deal with insulation which by nature is soft, warm and provides a safe haven for pests like termites, ants and rodents.

Fact is NO insulation material is 100% pest proof. All have their pros and cons but NONE are 100% pest proof.


19.
Mar 29, 2016 4:14 PM ET

Mice?
by stephen sheehy

My old farmhouse, built when the Founding Fathers were just getting started, had mice. My new, super tight (.59ach50) house has had a few. Lucky I have a cat.


20.
Mar 29, 2016 4:48 PM ET

Don't give up on SIPs
by David Jones

Jay Stewart

I have built with SIPs, spray foam, cellulose for 25 years. In my opinion, SIPs are relatively protected from insects because the foam is completely sealed in wood. The article correctly pointed out that carpenter ants can get into virtually any building material, so you don't eliminate the danger by using a different material. Ridged foam behind a rain screen wall is an insect superhighway. Ridged foam at ground level (exterior foundation insulation) is just begging for problems. I have seen only a few minor instances of ants in SIPs and I have seen plenty of ants in wood framed houses. Moisture is the enemy of all building materials. Control moisture carefully and your risk of ants is low. FYI, many SiPs are available treated with borates , (non-toxic to humans).


21.
Mar 29, 2016 8:30 PM ET

Edited Mar 29, 2016 8:31 PM ET.

Thanks David
by Jay S

That's a little encouraging, but my plan was to build an ICF-style basement and put polyurethane foam blocks under the basement floor. Foams are wonderful insulation. Nothing can touch them in R-value/inch. It never occurred to me that ants would love them and destroy them.


22.
Mar 29, 2016 8:55 PM ET

ICF and ants
by David Jones

Jay,

I am proponent of foam, but I have always considered ICF to be scary product because they were so difficult to protect from insects, that I have never used them. I am not worried so much about the ants getting to foam below grade, but the foam provides a hidden path from the ground to the rest of the building. I often use a pre-cast concrete foundation that comes on the inside surface of the foundation from Superior Walls.

Foam under a basement floor is not likely to have an ant problem. Ants have to travel a long way under ground to get there, there is no food source down there, and that foam doesn't provide an easy path the rest of the building. Foam makes sense there.


23.
Mar 30, 2016 7:52 AM ET

ant won't travel far......
by Brad Hardie

I was told by a scientist once that ants won't go further than 10' feet from a source of moisture. So there is truth that they burrow in dry foam (poly-iso, XPS, EPS, PU), but if ants are on a roof there is a leak somewhere high.

Once I heard this from the scientist, it really helped me during investigating for leaks/causes. Not that I should assume, but based on that statement, once moisture was removed, the ants would retreat. I haven't ever gone back to look at any situation where corrective action was taken though to see if that was truly the case. All I can say is that I never heard complaints post leak remedy.


24.
Mar 30, 2016 10:33 AM ET

Bituthane
by Buzz Burger

Some ICF proponents claim that a Bituthane barrier will block access to termites (and I assume ants). Any experience or opinions on that?


25.
Mar 30, 2016 11:48 AM ET

Edited Mar 30, 2016 11:49 AM ET.

This is a rather depressing
by Rob Myers

This is a rather depressing read through - I find it amazing that more is not known about the problem. Years ago I had ant problems in my geodesic dome which had EPS insulation in the wall. It seemed to be related to tree branches contacting the house and vents that allowed easy access to the foam. Once I took care of these, the ant problem seemed to go away. More recently I found that ants had chewed into a section of XPS foam that was left with wet OSB in contact with it (it was also exposed to sunlight so it was warm). There were no problems with any other areas on the foundation but it was disconcerting to say the least. These were very tiny ants (not carpenter ants) - I should have kept a few to identify. Strangely, I have never seen an infestation in a scrap pile of foam - perhaps they prefer finished houses!


26.
Mar 30, 2016 5:16 PM ET

styrofoam? dense packed cellulose with fire retardant?
by David Goldman

Are those two insulators susceptible too? Styrofoam would seem to be too hard for ants to penetrate--unlike the cellulose. But are they attracted to either?


27.
Mar 30, 2016 5:19 PM ET

Under-slab Insulation
by Steve Young

So, what is the solution? Insecticide impregnated foam? Rock wool?
There does not seem to be a clear remedy for bugs/rodents in foam. Perhaps it is not as much of a problem? Have there been serious problems with GeoFoam in highways?
I have seen on this site that someone used Roxul Confortboard CIS (maybe renamed to Comfortboard110) under a slab but there seems to be no documentation that this an approved use of the product.


28.
Mar 30, 2016 7:43 PM ET

Steve.
by Malcolm Taylor

Martin did a blog on sub-slab mineral wool. I think Roxul has approved it for that application.
http://lakesideca.info/articles/dept/musings/sub-slab-miner...


29.
Mar 31, 2016 7:41 PM ET

Edited Mar 31, 2016 7:42 PM ET.

AAC + Rockwool?
by Ethan T ; Climate Zone 5A ; ~6000HDD

This article again makes me question the soundness of the idea of relying on thin films, tapes, membranes, etc to ensure building performance over future decades, particularly as we face climate change which may bring unanticipated pests to a building which cannot migrate north. The idea of building with autoclaved aerated concrete + rock wool, as Dan Levy has done, is increasingly attractive as it seem to follow the directive of the third little pig who built his house out of masonry units so the wild forces of nature couldn't knock it over.


30.
Mar 31, 2016 9:53 PM ET

Ethan
by Malcolm Taylor

I think it's a good exercise to think about who does the bulk of the renovations in our neighbourhoods. Are they building science buffs who will understand and respect the meticulously assembled envelopes that we are encouraged to build?


31.
Apr 1, 2016 11:17 AM ET

Interior Insulation x2
by Melina Boukis

Avoiding insulation on the outside has more advantage than just keeping the pests out. Keeping the weather barrier layer (sheathing/WB/cladding) pure from the insulation layer will simplify construction, reduce maintenance, simplify future remodels and repairs. And yes, if those pesky varmints want to get into the walls to nest, they will. However, a pure, quality weather barrier layer should drastically minimize that (with the vigilant care mentioned by others).


32.
Apr 4, 2016 7:44 PM ET

I have been flip/flopping
by Jonathan Lawrence CZ 4A New Jersey

I have been flip/flopping between MW and EPS and now leaning towards MW again.


33.
Apr 4, 2016 10:50 PM ET

Mineral Wool Densities
by Burke Stoller

I think the distinction between the different mineral wool products needs to be reinforced. The typical batt products used in framing cavities definitely pose no difficulty at all for mice, ants, termites or birds to nest in. Same as fibreglass or blow-in cellulose. The Roxul Cavity Rock MD, as referenced by Peter L. in his post about the deep energy retrofit project (http://lakesideca.info/blogs/dept/guest-blogs/wrapping-olde...) I think also has a low enough density that nesting would be pretty straightforward, as the author discovered from the birds. That product almost seems to have a thin layer of higher density material on the outside, and then just a slightly more dense batt attached to the backside of it.

Roxul Comfortboard IS, however, is a totally different beast altogether. Conventional batt products are soft and fluffy. I'm even tempted to nest in them some days at work! The Comfortboard product, however, is very dense in comparison, and has a far scratchier, grittier texture. When working with it, you will have a pile of dark green sand at your feet afterwards. It really is nothing like other mineral wool products at all. It really makes it obvious that mineral wool is indeed made of rock and steel slag. I would be very surprised to see any kind of rodent, bird or insect have anything to do with the Comfortboard. Not saying it's impossible, but of all the insulation products available, Comfortboard would by far by the most resistant to pests, in my opinion. It also seems much more hydrophobic than other mineral wools. When used in a vertical application, water does tend to bead and roll down it, unless it gets completely hosed down, at which point it will begin to absorb. It does dry out quite easily, however.

Buzz Burger- If I was building an ICF foundation, and was concerned about possible connecting paths for pests between the exterior foam and other assemblies in the building, it would be a no brainer to install a continuous sheet of self-adhered waterproof membrane (bituminous peel-and-stick) from the top of the concrete stem wall, over the top of the outside layer of EPS, and all the way down connecting it to the concrete footing. I have used Bakor Blueskin and their paint-on Blueskin on top of foam before, and it works very well. Astoundingly, it does not melt EPS or XPS foams, and provides a tenacious grip for the peel-and-stick. Of course it should be used anywhere you are sticking the peel-and-stick to concrete as well.

To further add to Malcolm's comment (and Martin's article) that Roxul Comfortboard is supported in under slab applications, here is a link to Roxul's technical document regarding it:

I haven't yet done a cost comparison between Roxul and EPS for under slab applications to see how they stack up. One thing of note, however, is that the Comfortboard is NOT commodity pricing. EPS is sold for the same price per board foot, no matter the dimensions ordered. Roxul gets wildly more expensive as the thickness increases. For example, when I priced out two different thicknesses from our local supplier, the 1.5" Comfortboard IS was $8.58 per cubic foot, and the 2" product was $12.24 per cubic foot. Quite a difference, so beware! It may be less expensive to install 2 layers of a thinner spec, and actually get a higher r-value than one thicker layer, but for less money! (Comfortboard IS comes in 1.25", 1.5", 2" and 3" thicknesses, all in 2' x 4' pieces.)


34.
Apr 4, 2016 11:03 PM ET

Burke,
by Malcolm Taylor

Thanks - that was both interesting and very helpful.


35.
Apr 4, 2016 11:20 PM ET

vermin
by brian carter

I had always found rotten wood in association with any carpenter ant problem, but I know they will use adjacent foam as well. Thinking from the ant's view, I wonder how they happen to find suitable substrates to nest in. It may be that they are able to follow a chemical (odor) trail to mold or fungus colonizing wood. They definitely hunt during swarming behavior, and it seems it would be a great advantage over wandering randomly across a landscape.

I've found nests in stacked, covered lumber that got wet and punky, yet they didn't bother a pile of Iso stacked nearby. I believe using XPS at ground level is not too risky if it is covered or encapsulated to below grade, Carpenter ants definitely do not tunnel into soil.


36.
Apr 6, 2016 8:18 AM ET

ICF and pests
by Jake Vierzen

I have been building ICF homes in Michigan for 12 years. About 80 completed homes now. We have not experienced a problem with ants, termites, birds, or rodents (yet.) All foam must be completely covered from footing to truss. Below grade, we use a combination of Delta-MS and the manufacturer's own peel and stick. Then a synthetic stucco laps that and extends just under the siding. Siding covers it from that point on. If an air gap is used under the siding, the bottom of course must not be left open. Annual monitoring of the transition area between grade and siding is necessary.
At least one manufacturer now has a metal shield that can be installed while stacking blocks to prevent insects from migrating upward into the foam.
I think the point made that all homes are susceptible to damage and must have a plan to mitigate the risks cannot be overstated.
Nobody mentioned the more certain risks of what happens when you don't use exterior insulation--namely interior cavity condensation--this isn't dependent on the whims of critter--it will happen every winter in many climates. Perfect interior vapor barriers are rarely seen.


37.
Apr 7, 2016 9:58 PM ET

Jake,
by Burke Stoller

Great points!


38.
Apr 8, 2016 10:42 AM ET

Mineral Wool and SE U.S (Zone 1-3) mixed humid and humid
by John Clark

Since these climate zones are considered termite-land and some of us opined mineral wool as a substitute for foam I wanted to put this out there. Linked is BSC study on moisture durability of sheathing with vapor permeable exterior insulation (mineral wool) and a reservoir cladding (Brick, Stucco, Cement board, etc).

Good stuff!!!


39.
Apr 11, 2016 10:45 AM ET

Edited Apr 11, 2016 10:45 AM ET.

Ants in a SIPs house
by Fred Greenhalgh

We have a SIPs house - small 550 sq. ft structure, 10 years old. We have battled ants constantly with borates, DE, and most recently insecticides - don't really love the poison, but they certainly do the trick. Right now we have a handful of ants roaming through the house - so they're clearly around, but are they a problem? We're at the point where the population seems under control, but hard to fight them any further since there is not enough activity to trace back to where the nest is.

Would love to chat about/swap carpenter ant war stories w/ anyone off list. [email protected]


40.
Aug 5, 2016 10:36 AM ET

ants moving in after less than a year
by Charlie Sullivan

I found today that carpenter ants have moved in to EPS just below grade on my foundation, after only a year of having it there. It's covered by cement boards and stucco, but there was a crack between boards that was hidden by a rock, and the ants found it before I did. Fortunately, they quickly found the boric acid sugar syrup bait put out and are industriously carrying it back to the nest.

It is near one of the damper corners of the house, where I had been planning on improving the grade.

We used a foot of mineral wool on the top foot of the exterior of the foundation partly in hopes of having the foundation wall dry better, but I am also hoping that will help keep the ants away from the structural wood. Maybe I should tear open this section to see where they got to, and whether the roxul successfully blocked them.


41.
Aug 6, 2016 6:55 PM ET

Charlie
by Malcolm Taylor

Just met a couple who moved into my neighbourhood last year. They found their house was infested with carpenter ants - something that was missed by the pre-sale inspection. The remediation costs topped 100Gs! This one wasn't foam related.


42.
Aug 15, 2016 2:54 AM ET

ants
by Sherry Litasi

I have been experimenting with ant killers and find that Splenda works really well. I sprinkle it in their path and the ants take it to their nests. Presumably they die. I'm found a new trail in my adobe building. Hopefully they didn't just move to another building.


43.
Aug 15, 2016 5:38 AM ET

Edited Aug 15, 2016 5:40 AM ET.

Response to Sherry Litasi
by Martin Holladay

Sherry,
Scientific studies have disproved the urban myth that Splenda (aspartame) kills ants. Here is a link to a relevant paper:

The researchers wrote, "Our current results strongly oppose the rumor that aspartame-based sweeteners are effective lethal poisons for ants."


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