XPS vs EPS Field Practicalities

[NW Architect]

Assuming we start building houses again someday, I want to lobby anew for 3/4" or 1" rigid foam on the exterior of my client's projects. The purpose would be to address thermal bridging in wood framed construction. Location is Portland, Oregon were it is 40deg and wet all winter long.

The challenge is that we build all year round, which means that many structures are built in the rain. We've gotten past green lumber, so at least we're starting with KD before we put it in the rain, and we're in a seismic zone, so walls are fully sheathed, and that sheathing is OSB.

We've also gotten past installing interiors before the framing has dried.

So the sequence is: framing (including sheathing), roofing, windows and doors(while waiting for the municipal sheathing inspection), WRB and siding, WAIT for things to dry to the interior and exterior, insulation (fiberglass), interior finishes.

Putting XPS insulation over rain-soaked OSB (or over WRB on rain-soaked OSB) would trap the water pretty much forever. The better option would be EPS because of its greater permeance.

However, EPS in 3/4" or 1" sheets looks like it would suffer a LOT of breakage during handling and installation, especially on windy days. Some products address this by putting on a plastic facer, which rather defeats the permeance advantage.

Any practical feedback on the relative ease of installation of EPS vs XPS?

Should I give up on the foam idea in this climate and lobby instead for dense-pack cellulose insulation in lieu of fiberglass?

Any studies comparing dense pack with thermal bridging vs fiberglas without thermal bridging?

Anything I'm missing in my thought process?

(BTW I never can keep the acronyms straight, so I've taken to thinking of them as EPS: Especially Permeable Stuff and XPS: Not Permeable Stuff. Anybody got a better mnemonic?)

[frenchie]

Re: XPS vs EPS Field Practicalities

Anything I'm missing in my thought process?

I have one, maybe... In the 2" of exterior foam thread, Dick and I got to argueing code provisions for exterior foam, right? The list from my code book is:

FM 4880,
UL 1040,
NFPA 286,
ASTM E 152,
UL 1715.

I've googled up a few MSDS sheets for EPS, they all mention ASTM D1929, nothing about any of the above. I'll admit I'm pretty vague about what all these standards refer to, exactly... but are you sure code allows the use of EPS in this application?

[NW Architect]

Re: XPS vs EPS Field Practicalities

I'll cross that bridge later.

But since I can put drainage plane EIFS in a house, and that uses EPS, I'm thinking it is permissible.

[Dick Seibert]

Re: XPS vs EPS Field Practicalities

NW, obviously you aren't going Platinum, but in the meantime why don't you wait until an eco-friendly product is available? Dow is working on it now, fireproofing and public image aside?

Dow Chemical is looking at the big picture. It sees a market in the need for low-cost housing and is developing technologies such as eco-friendly Styrofoam used for walls.¹

¹ http://www.businessweek.com/magazine...5/b4019001.htm

[Ted S.]

Re: XPS vs EPS Field Practicalities

Dick is that all you have? I was waiting for a real bomb, you let me down.

Anyway, NW, here in MA, if you frame anything more than a house with metal studs or CMU you are required to provide a min R3 continuous insulation. So I am most definitely in support of your idea.

As for EPS, it is the predominate insulation of EIFS which manufactures an entire line of water management systems. It is also more stable than polyiso relative to moisture - and polyiso I believe is the heart of the Dow SIS we have discussed, intended for exterior walls. So I think you are ok.

I would look at different manufactures; the EPS comes in various densities. I can't cite specifics, I can only say the stuff you buy for EIFS is pretty weak and the stuff that ICF's are made of is pretty durable. So I think you need to spec more than just "EPS"

Personally I'd stick with XPS. For reasons that you are probably going to nail furring strips through it and I'd be leery about doing that with EPS. I think I'd go with 4x8 sheets of "ship lapped" Cavitymate by Dow. I think that would give you more air tightness and would take the furring strips better, but just a guess.

As for that "WAIT" periods you are referring to, maybe with a custom house but forget about it on the mainstream. If you are doing multifamily, I'd start thinking about a 'Moisture Management Plan" which gets incorporated into the specs. I did this for a few architects, you basically develop a plan during construction in which moisture is limited, then the building is measured and dried if required. I wrote it off of the St Pauls Checklist which was a document written for the insurance industry, attached is a copy.

[Dick Seibert]

Re: XPS vs EPS Field Practicalities

Ted:

I find it hard to believe that any legitimate architect would specify EIFS, most of it that was installed is in the landfills, here is a picture of it being torn off a building and the styrofoam is in the landfill of floating around in the Pacific in that sea of plastics twice the size of Texas.

What about the fact that the public considers it cheap crap? I mentioned to a group in Berkeley that they could buy homes in Brentwood for $200,000 that sold for $800,000 a few years ago, one said: "Who would want a new home, they're all built with styrofoam now"; they aren't, we don't use it around here but they've apparently seen or heard that it is being used in other parts of the nation.

What about the fact that all insurance companies (selling in California anyway) not only prohibit EIFS but won't insure a contractor who has installed it within the last 10 years? (see attached) If it's worth anything at all why would the insurance companies refuse to sell insurance to contractors installing it? Somebody ought to tell the insurance companies that styrofoam isn't only behind EIFS but is showing up behind other siding materials so they can specifically exclude from coverage not only EIFS but styrofoam itself.

If NW does specify it how's he going to handle the waste? Portland banned styrofoam in restaurants 18 years ago and was a leader in banning it. If it's got no place in temporary usages like plates, it's certainly got no legitimate use in a building that is suppose to be permanent. If you get a leak, and you will, the styrofoam is destroyed and ends up in the landfill, if you remodel the building you are tearing it off and it's in the landfill.

In today's environmental world sustainability and quality trump energy efficiency.

[Ted S.]

Re: XPS vs EPS Field Practicalities

Thats' better Dick.

[NW Architect]

Re: XPS vs EPS Field Practicalities

#6: Facts not in evidence, counsel. Never said I specified EIFS. Said it was done and used that as a logical fact to indicate that EPS in a NON-EIFS application would be code acceptable

#5: "Wait" actually works in our winter climate. It may be raining, but the air is relatively dry. In multi-family, one just delays the insulation and finish crews about 30 days behind the siders. Cost of money is cheaper than the cost of heat. In single family, sometimes the opposite is true. The HVAC guys are using up a lot of that interval anyway since they don't install their stuff except in dry weather or in a dried-in enclosure.

In either case, nothing goes into the inside until the framing and sheathing have been tested and the WMC is 19% or below.

[NW Architect]

Re: XPS vs EPS Field Practicalities

#6, more: The styrofoam food container ban had to do with recycling. Foam contaminated with food stuf is not recyclable. Construction foam IS recyclable (don't know if it is being done, though, since it may or may not be a profitable enterprise)

[Dick Seibert]

Re: XPS vs EPS Field Practicalities

NW, to date nobody has figured out how to recycle it, it's too light-weight to manage. I mentioned before that a student in Canada has developed a process to biologically degrade it, if his invention pans out I guess our dumps will have special sections dedicated to degrading it over a few months' period of time' so we'll have huge cesspools in every dump degrading it. You will have large amounts of waste from cutting it and just breakage, my recycle container has instructions on the top prohibiting it from the container.

I never accused you of specifying EIFS, but I did accuse Ted of the dastardly deed. What about your reputation as an architect if you specify something as cheap as styrofoam? What if a building's siding leaks, what happens then? A disaster like the EIFS disasters?

[Ted S.]

Re: XPS vs EPS Field Practicalities

I never accused you of specifying EIFS, but I did accuse Ted of the dastardly deed.

My reputation was one who was able to make EIFS work.

Since you keep bring up the junk EIFS of 1995, which I am very familiar with, why don't you go back even further to war torn Germany where it was originated and see if you can figure out why many of those installations are still just fine.

Then you will be on a level where I can talk EIFS with you.

[NW Architect]

Re: XPS vs EPS Field Practicalities

If my building's siding leaks the WRB is there to deal with it. If the WRB can't keep it completely out, the building's hygric capacity and drying potential are there to deal with it.

If all that can't handle the leak, its a BIG EFFING LEAK that no building envelope system would be intended to cope with (meaning its a contractor error that I didn't see when it was being built, or somebody put a big hole in the wall after I left)

Thanks for not putting me on the EIFS bandwagon. FWIW, though, I think drainable EIFS is a very workable product - just too much stigma attached to it, and too many contractor policies that won't allow them to touch the stigma.

[NW Architect]

Re: XPS vs EPS Field Practicalities

#11: Can I play???

(Answer: Masonry structure)

Do I win anything?

[NW Architect]

Re: XPS vs EPS Field Practicalities

Looks like styrofoam IS recyclable. This is from MissionRecycling.com, located in Pomona, CA.



In the ongoing effort to attain zero waste for our communities, Mission Recycling is pleased to begin offering an exciting new service - Styrofoam Recycling.

Styrofoam or polystyrene is pervasive in our society and is a considerable environmental hazard as it is not biodegradable. While it is not heavy by its nature, it is space consuming which is a serious problem for our already overburdened landfills.

Mission Recycling has invested in new technology that will allow it to compress styrofoam in a 50:1 ratio thereby producing blocks of styrofoam weighing 19 lbs. per square foot.

This technology has made the recycling of styrofoam economically viable and when such programs expand, they will greatly reduce material currently taken directly to landfills.

If you are a company that generates or produces large quantities of Styrofoam/Polystyrene and are interested in recycling this material, thereby lowering your regular waste hauling expense AND helping to save the environment, please contact us for a consultation.

We will come to your location anywhere in the Southern California area to give you a presentation that will go over how to set-up a styrofoam recycling program and detail the benefits to your company.

[NW Architect]

Re: XPS vs EPS Field Practicalities

OH, BTW, I hereby throw the yellow flag, blow the whistle, and charge "THREAD DRIFT".

Now away with the environmental and EIFS stuff, and back to my original inquiry, please.