In 2012 some extensive testing began with ICF window bucks:

ICF brands teamed up with the British Columbia Ready Mix Concrete Association (BCRMCA)

"They built and tested six prototype wall panels consisting of ICF concrete walls with different combinations of moisture barriers, bucks, and window installation details. Cascadia Windows, which provided the workspace to construct the panels, also donated and installed the high performance windows for the test samples. The same windows were used in all tests for control.

The eight-by-eight wall panels were tested using industry standard air and water infiltration tests (ASTM E283 and ASTM E331, respectively) and measured for air leakage and moisture intrusion during simulated once-in-ten-year rain and wind events.

"What we discovered," says Hubbs, "was that the window-to-wall interface was quite leaky." The amount of air getting through was of concern, but the amount of moisture was even more troublesome."

Not to toot my own horn but I discussed this topic a year or so ago here on the forum and a few people dismissed the issue claiming that ICF window bucks don't leak and are air & water tight as is. They stated that I was making much to do about nothing, since supposedly "no problem" existed. Well, the building science community studies show that I was correct in my assertions. There are problems and the problems are actually quite "troublesome." There is no long term "track record" out there for ICF homes & window buck sealing and these problems will begin emerging as evidenced by this extensive study.

Key Points Found:

• Vinyl Window Bucks were very leaky
• Commonly used installation methods had lower than expected performance levels
• Innie mounted windows performed better
  
• Mounting the windows directly into the concrete core showed higher load ratings
  

The official report of these tests will be released by the end of May.

Kelly, at BCRMCA, says, " The results of this testing program will form the basis for an ICF best practice guide and the creation of industry standard details and installation practices." He notes that the lab report and guidelines will be applicable anywhere, not just British Columbia, and that this is just the first step in a long-term program of developing generic details for ICF.

The ICF community knew that this study needed to be done. That is why they pooled their money together to have these extensive test done. Amvic, Fox Blocks, Logix, Nudura, Plasti-Fab (Advantage), Quad-Lock, Superform, Arxx, Reward, and The Home Owner Protection Office's Technical Research and Education Branch.

I don't doubt with what this study has initially showed that there will be some rotted window bucks and water damage (drywall, window frames) popping up in the not-to-distant future from ICF homes built back in the 90s. This study also shows us why some ICF homes have poor ACH numbers. The window and door details are the Achilles heel of ICF air-tightness. This study was long overdue but I am glad it's coming out and the building scientists will create some good details for architects to us to help seal up ICF window and door bucks.

From the above link:

"With that knowledge, they moved onto Phase 2, building another six wall panels and testing the assemblies that performed best in the first round, including internal and external wood bucks..."

"In Phase 2 we… exceeded the building code minimum with all of our samples," says Hubbs. "We obtained performance levels normally seen only on high-rise cladding and glazing systems."

Posted By arkie6 on 04 May 2014 11:38 AM
From the above link:

"With that knowledge, they moved onto Phase 2, building another six wall panels and testing the assemblies that performed best in the first round, including internal and external wood bucks..."

"In Phase 2 we… exceeded the building code minimum with all of our samples," says Hubbs. "We obtained performance levels normally seen only on high-rise cladding and glazing systems."

Correct, Phase 1 showed them the flaws in common window buck installs and, "With that knowledge, they moved onto Phase 2, building another six wall panels and testing the assemblies that performed best in the first round, including internal and external wood bucks. "

Don't know if my comment helps in some way....
Coming from Europe, I didn't even know what window bucks are. I've learned that these are necessary to install local windows. Anyway, we are going to build our ICF home soon (Owner Builder) and we are importing our windows from Europe for various reasons. We will not need to have window bucks installed at all. That will save us some money on the window bucks. European windows will be installed directly to the concrete. Now there are different ways to install them. But the current best known way (I believe) is called in Europe an "RAL installation" which is a little more expensive to install but it's said that it will help to seal the window even more. I've googled to see if I can find something that can be understood in English and found the following You tube video: https://www.youtube.com/watch?v=cakA1kc3ICg . These tests are done at ift Rosenheim, Germany. It's an independent organization that tests windows, doors and other construction materials. Don't know if this kind of installation is known in the US at all, but thought to add this into that discussion. We will most likely get our windows installed like that.

Rafi,

If you do not use a window buck, how will the concrete not fill the opening? Also, how will the rough opening be precise?

Alton,

Of course you have a frame for the openings of windows when you fill the concrete, if this is what you mean. Something that will be removed again. I understand that the window buck you are talking here stays and the window will be installed to that? Or am I thinking wrong?

Rafi,
Some methods leave the bucking material in, some don't. You get to decide. Personally, I can't figure why anyone would leave the P/T wood in the window opening on a concrete wall. Common sense seems pretty clear it's a weak point.

Leon,

I am sure you are right for American windows. American windows are different from European windows. The frames and functions are different. I was talking ONLY for installation without window bucks for European windows. I would never suggest to try to do that with American windows.

Leon,

I am not sure if I understood your comment and probably my answer doesn't make sense here. Maybe you tried to say the same and I just didn't get it. Sorry.

Does anyone else find it somewhat bewildering that there are so many different ways recommended to install a buck and window (or a door)? Even when having the same insulating requirements and window frame type.

I suppose that was partially the purpose of the study - to narrow the list of best practices.

However to me it seems that best practices and products would have been more stable by now. I understand new products come out which makes things better (e.g. flexible flashings, expanding foam, etc), so best practices change. However, I haven't really seen anything new in the last 3-4 years in this area other than the ability to purchase ICF bucks (FOX, Gorilla, ...).

In the field, homeowners and architects are partly to blame, with dressing up the window opening with brick or rock which requires tricky and fragile detailing and draining systems.

Posted By sharter on 09 May 2014 09:28 AM

However to me it seems that best practices and products would have been more stable by now.

Building science is always evolving and long-term studies sometimes show that the way grandpa did it doesn't actually work too well in the long term.

The list of things that has changed over the years is quite lengthy. ICF window bucks have been around for about 15 years? That is not that long in terms of building science.

This study will be vital because all the main ICF companies knew that they had to develop a best practice and only an in-depth study would reveal on how to do it properly. As the initial study shows, the "standard" way of doing ICF window and door bucks was not that great because they leaked air and water. The initial tests shocked them because they thought it was a tight detail but it actually wasn't. I had my doubts abut the vinyl bucks being tight and it turns out I was right. They leak a lot around the corners.

It doesn't exactly seem like rocket science IMHO.

Why would someone want to use wood or vinyl bucks? I think that it is fairly obvious why not to. The use of integrated materials will avoid leaks and expand\contract equally - these are EPS and concrete; i.e. use Fox bucks, or have concrete extrusions (holes) in ICF for anchor points. Wood is used for bracing only. Design anchor points for siding, drywall, etc into the concrete, ICF and\or use appropriate anchors or glues (i.e. don't use that as an excuse to use wood).

With expandable foam, flexible flashing material and super good sealants there is no excuse for a window to leak air. Preventing water damage is a matter of proper flashing and sill details. Avoid trim work around the window that require weep holes or extensive flashing, etc. since they will probably fail at some point.

Innie windows can be harder to flash, but do you really want a (heavy) window resting on EPS or a small piece of blocking? Use innies and put a sloped concrete sill afterwards which can also be used as a seat or ledge for plants, and not have a 12"+ ledge on the inside.

Anyway, it would be good to put together a straw man best-practice install of ICF + innies, along with pictures... Hopefully the next study ends with something conclusive.

Why would someone want to use wood or vinyl bucks?

We used treated lumber for bucks and they went together pretty easily. Nearly three years later they are working well.

The inside scoop is that the testing showed that many of the traditional window buck install techniques/details are going to need to be modified because they will develop air & water leaks over time. It will be surprising to some people on how much water and air intrusions were happening.

A solid ICF wall is pretty much air proof, the weak links are always the windows, doors and wall top plate to roof areas. When ICF homes get bad ACH ratings, it's always the window and door areas that are the problem areas. A blower door test with a smoke pencil is the way to test for air leaks. Water leaks are more tricky and one can go for years without realizing that one has a water issue within the window buck area. ICF is forgiving to water issues but the wood bucks and drywall are not.

Proper flashing of the windows and bucks can eliminate any issue you have with wood

Proper flashing of the windows and bucks can eliminate any issue you have with wood