Treehippy (sorry your geeking out comment and the fact you're an arborist make me imagine you as a raging new age hippy, if only you were from Boulder it would almost be certain truth),

Based on what you've asked about I believe you may want to look at an eifs system like dryvit (dryvit.com). Just a sidenote, insurance companies hate eifs and they might not care if yours is over masonry or not, so your homeowners insurance could go up or they could drop you once they discover you've done this.

Anchoring the eps may be tricky, I would contact the system maker you end up using for recommendations on the eps attachment to a brick/mortar substrate; mortar generally doesn't offer much holding power (think why there is a need to tuck point over time) a hammer drill could blow your brick apart if it's in poor condition. Unless your some sort of super diy'er this is more of a professional job to be hired out, it really is an art and if you watched some good plasterers doing it correctly you would understand why.

Also, anything under 1 perm is a vapor barrier so if xps is .55 perms it is at the point of a barrier.

Good luck with it whatever you decide to do.

If you are going to use 3" or 4" of foam board insulation over brick with a stucco exterior, I think I would do it this way:

1.  Adhere foam to brick AND use mechanical fasteners.  I would like to generate some shear and bond strength through the foam, so this means using a single layer of foam or gluing multiple layers together.

2.  Use a synthetic material directly on the foam to minimize the weight.

I am concerned that if you used conventional (i.e., heavy) stucco over with the foam with a drainage plane (little or no bond between foam and stucco), the stucco is essentially cantilevered out from the brick on the mechanical fasteners.  While this may not actually be a problem, I would be hesitant to do it on my house without some successful examples.  The fasteners would need to substantial and deeply embedded in the brick order to carry the weight of the traditional stucco on a 3" or 4" moment arm.  The foam is soft enough it would provide almost no resistance to the fasteners bending.  It seems this could be prone to movement and cracking.

The detailing around window and openings is a bigger water leakage issue than any differences between conventional and synthetic stuccos.

my €0.02.

Bruce

Thirty some years ago I used 2" urethane over cement block, adhearing it with some special Dow glue available at the time - it was "15" I think - but the point is I used a woven fiberglass embeded in a trowel coat of cement with something in it - epoxy maybe - and then the top coat with color was a powder cement/poly something mix that was troweled on and finished however smooth you want. The system was called Dryvit. I have no idea whether or not they're still in business. Do a search. It has has held up very well. Just don't let water get between the insulation and the substrate.
Peace
Leonard Wallace

@GT: Only slight offense taken at the name-change ; ) We "euthanize" plenty of trees, don't just hug 'em! The wife and I left Boulder County to get away from the SUV-driving Hippiecrites and closet conservatives. I won't say I haven't got hippy tendencies, but I'd like to characterize myself as more old-age than new-age. I've got a mohawk, not dreds, and I'd rather be holding a chainsaw than a crystal. Neither do I count myself a "raging" anything, unless it's beer-snob or occasionally motorcycle-evangelist.

Moving on . . . Our brick is in pretty good shape (appears to have been regularly repointed, or protected by paint for most of its life), and I sort of figured I'd be hitting brick more often than mortar, provided my spacing was intelligent. Is my reasoning flawed here? And here I thought mounting the foam was the EASY part!

I tried (half-heartedly) to get a few quotes on having the labor done, but didn't get ANY callbacks. My understanding is that most stucco outfits around here are pretty uninterested in high-efficiency installations. They'd rather use 1/2" foam for ease of use. So at 2" of XPS I need to be pretty confident in the flashing around windows and doors? Is it worth diffusing worry in this climate to stick with EPS despite the reduction in R-value?

@Bruce: We're sticking with 2" foam maximum, for finishing reasons. Liquid water leakage is a minimal concern, provided the assembly can "breathe" a bit. Denver has WAY more drying days than wetting days, so moisture accumulation is a non-issue. I'm just afraid I'll end up with water trapped behind a class II vapor retarder in 8" of masonry that might not be able to adequately dry to the interior alone.

How much is the actual difference in R-value from EPS to XPS in that thickness?

If the construction industry in your area is anything like my area, you won't get any calls returned unless what you're doing is an absolute carbon copy of what those guys do every day.

Treeguy,
The dryvit system I watched going on was 2" eps. I have never seen eifs on xps but I dont know if its a cost/budget thing or because you cant. To add arches, quions and bands they adhere additional foam to the base 2", (drive around and check out newer commercial buildings with alot of different layers at the soffits and around doors/windows, alot of times that's just built up foam not even framed out) Their foam came packaged in bags from dryvit, in fact everything related to the installation had a dryvit logo on it, I'll be back at the job today and I'll snap a pic of the stucco with the banding and other details so you can reference it.

Are you calling stucco guys or are you calling eifs guys? You want eifs guys. Also check out that website I mentioned but by the time you get this all figured out you probably could have worked the extra hours instead and paid a pro to do it.

I found this link awhile back and bookmarked it.  It sounds like a similar project.

http://compassionatespirit.com/Superinsulation-Process.htm

http://compassionatespirit.com/Superinsulated-Retrofit-Overview.htm

Hope this helps,
Kenny

@Kenny: Thanks for the link. I'd come across that before. That guy's in Denver as well, if I remember correctly! Alas, his house is a very simple rectangular box without a lot of interior corners. He's adding near 6" of assembly to the exterior of his place. No big deal if you're not having to finish around doors that are already 3" from the adjacent wall WITHOUT insulation!

@Jelly & Greentree: I believe the difference is R3/inch versus R5/inch. Not a huge difference numerically, but it's an R4 change in 2" or 40% less from XPS to EPS. If I'm going that way, I may as well use 1" of xps to save a little money and headache. It's the vapor retarding capacity of xps that has me worried. I would assume that XPS would be BETTER at bearing a load, since it's more rigid. I did a little checking on Dryvit, finding several companies that would apply it to commercial properties, or for builders, but none who listed it in the "Residential" section of the website. I also can't find a site that will sell Dryvit directly to a consumer. They want you to be certified and trained with their application methods (probably a CYA measure against the eifs lawsuits).

I fired a few emails and made some more calls, but got no responses. Looks like this is gonna be strictly DIY, just like the "superinsulated retrofit" guy. I'm going to have to find a way to use traditional stucco (perhaps 2-coats) without it pulling off my walls . . . Will talk today to a Kiwi friend who spent 3 summers stuccoing in NZ. Perhaps he'll have some ideas.

Here's the latest bright idea to ponder: I'm thinking about putting a rough-cut 2x4 above the TOP of my insulation and using it to "hang" the wire lath from. I'd still anchor the lath to the foam (and tarpaper or whatever we use) with the long screws, but I'm thinking that hunk of wood might be enough to hold up the layer. How much concrete goes on a 10x10 space, by volume, anyhow? I'm wondering if I'm overreacting to the question of "weight bearing" in this assembly. . .

Dryvit isn't your only polymer modified option. Look into STO products. You should be able to get them as a DIY'er.

Just checked out the STO website. Looks promising. The Denver area supplier looks like a wholesaler, but they'd probably be a good place to start . . .

i see you need some enlightenment over the matter, well check this out guys,
Brick has a nice appearance, but is more difficult to build. Stucco is easier to build and maintain, and will take a coat of paint nicely. If you live in an area that is prone to earthquakes, brick may not be a good option as it is less stable.
I prefer brick to stucco because stucco can break fairly easily and is hard to repair. Brick is easier to work with, is a better insulator,and is easy to repair.
in the long run ___it's your taste that has the final say right!___ check out this site if you want some visual to your taste guys... have a great time
www.besttorontostucco.com ---yipes mod alert!

I've put 1/4" Sakrete Bonding Cement (has lots of fibers) + acrylic admixture (adds flex) over roughened XPS without any problems. If I did it again, I'd try using a hopper gun to save some of the troweling.

I am still looking , I have a friend who told me about a fastener he used for foam to block in Europe all the time. It is not metal so rust is not a problem.
Drill hole through foam into block/ masonry, slide fastener in to hole and drive home with hammer.

http://www.styro.net/RigidFoamInsulationFasteners.html
Above are up to 4" I am looking for 9" but the right idea

With all of the problems associated with using foam over brick not to mention the unnecessary extra costs, I recommend stucco directly to the brick. It's easier and less costly and you won't have nightmare's with the inevitable water problems that will follow with a foam over brick installation. In this manner you will eliminate the weight and cantilevering effect that is so problematic.

The foam is insulation. Know what that is for?