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FBBP
Veteran Member
Posts:1215
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| 01 Jun 2013 03:06 PM |
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Posted By arkie6 on 01 Jun 2013 01:51 PM
Posted By FBBP on 01 Jun 2013 09:53 AM
How did you seal the wood to the concrete core to prevent air infiltration now and in the future?
Is you rough opening large enough to get sufficient foam between the window jamb and the wood buck to prevent the jamb from being a cold surface?
I'm not sure how ICFHybrid did it, but I inset my wood bucks into the ICF foam as recommended by my ICF manufacturer and distributor. For my 6" core ICF walls 11" overall width), I purchased treated 2x8 lumber for the bucks. I then ripped down the 7-1/4" wide boards to 6" wide on my table saw. These wood bucks had 3" deck screws screwed ~1" deep into the wood on the backside approximately every 8" to help lock it to the concrete after it cures. These wood bucks were then inset into the ICF foam and secured to the foam using 2" diameter EIFS plastic washers and 3-1/2" deck screws every 8" through the 2-1/2" foam into the edge of the wood buck. There will not be any air leaking between my wood bucks and concrete.
If you use flange mount windows and mount your windows externally, you can just mount them on the outside of the foam using long screws through the foam into the edge of the wood buck. Everything is fully insulated that way.
If you use the same flange mount windows but want them inset somewhere near the middle of the window opening, you build your window bucks at least 3" wider and 3" taller than your window rough opening, then come back with 2x framing lumber on the inside of the wood buck to frame out the window attachment point. You can use kiln dried lumber here, but I used treated 2x below the window. Lay down a bead of expanding foam before installing the inside 2x lumber to insure an air tight seal. I did this on my south facing windows, but increased the window buck height to 4.5" to allow me to install a double layer of treated 2x lumber below the window and one (1) kiln dried 2x above the window. This 3" below the window frame allowed me to install a fairly steep sloped sill on the exterior to insure water drains away. I've got a brick exterior and it is ~10" from the face of window to the outside face of the brick.
Did you happen to do a blower door test? I am quite sure that you will have some if not a lot of air infiltration that finds a path between the joints in the outer layer of foam, between the wood buck (which is always flexing and moving due to moisture change) and the concrete core and then through the foam joints or between the foam and buck. Unless you use something like acoustic caulk which remains flexible between the wood and concrete, or between wood and wood, you will have air infiltration over time. I have been back to some of the earlier ICF buildings that we used wood bucks on and without exception they leaked like sieves at that point.
Consider how uptight people get about sealing the mudsill and bottom plates in wood frame construct. Why would it be any different in an ICF building? The wood will still move over time and let air in.
As a rule putting down a bead of foam between two layers and then squeezing them together is a waste of time. The foam works for the most part by the entrained air. Put two pieces together squeezes out the air and you have little left. Putting screws in the back of bucks might help to keep the wood from twisting but does not stop the air infiltration. When you pour the concrete the wood absorbs moisture and swells, depending on the species, between 1/8 and 1/4 inch. As it dries, it shrinks onto itself and the screws wind up holding it away from the concrete.
If on the other hand you use IntegraSpec, Nudura or Fox bucks, the concrete bonds to the foam on the back of the buck and you have a reasonable good seal. You will still have the chance of air infiltration through the joints in the foam if you don't take steps to prevent that. Building up with wood just gives you the same thermal bridging as wood frame construction, which seems a little counter productive to me. |
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arkie6
Veteran Member
Posts:1453
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| 01 Jun 2013 05:56 PM |
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Posted By FBBP on 01 Jun 2013 03:06 PM
As a rule putting down a bead of foam between two layers and then squeezing them together is a waste of time. The foam works for the most part by the entrained air. Put two pieces together squeezes out the air and you have little left. Putting screws in the back of bucks might help to keep the wood from twisting but does not stop the air infiltration. When you pour the concrete the wood absorbs moisture and swells, depending on the species, between 1/8 and 1/4 inch. As it dries, it shrinks onto itself and the screws wind up holding it away from the concrete....
...Building up with wood just gives you the same thermal bridging as wood frame construction, which seems a little counter productive to me.
The purpose for the spray foam between the window framing lumber was to create an air tight barrier. The polyurethane expanding foam effectively glues them together. The entrained gasses in the spray foam is irrelevant in this application as I am not relying on this thin layer for insulation. What it does do is insure every nook and cranny between the pieces of lumber is filled with foam. I reused some of my ICF bracing for these internal window frame outs and foam came oozing out of tiny holes where I had previously removed screws. I also failed to mention in my previous reply that I wrapped the backside of my treated window bucks with leftover Fastfoot fabric footing membrane. This effectively isolates the moisture in the concrete from the wood bucks. Plus it helps if you start out with dry treated lumber. It helps to purchase the treated lumber in advance and allow it to air-dry before ripping down the bucks to the desired width. Wood bucks inset into the foam are encased in foam on the outside and inside - thermal bridging of the wood here is no more so than the concrete itself. On my inset windows, I installed 2x6s flush with the inside of the ICF wall, then added a layer of 1" thick rigid foam on the outside of those 2x6s prior to installing the windows to provide a thermal break; although, the overall thermal effect of this small area of lumber is small compared to the the 18 sq ft ~R3 window in the wall. The 2x6 alone without the 1" of exterior foam should provide around R7 or more than twice the R value of the double pane low E window. |
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Alton
Veteran Member
Posts:2164
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| 01 Jun 2013 07:33 PM |
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Could untreated dimensional lumber or LVL's be used if totally enclosed in Fastfoot fabric? Trim inside the home and window flanges outside should hide the wrap. |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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ICFHybrid
Veteran Member
Posts:3039
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| 01 Jun 2013 07:55 PM |
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I'm not sure how ICFHybrid did it 2 X 12 treated lumber with big stainless ring shank nails driven through the face of the bucks into the concrete cavity once the bucks were in. Them bucks aren't going anywhere. During the concrete cure, the center of the bucks stayed moist for quite a while and the edges of the bucks did curl markedly away from the wall, but once everything dried, they went right back into place, straight and true. Then, you make a trip around the building with the foam sealant and seal the rough cut edges of the foam to the bucks. This also prevents the concrete from oozing into the space. If the space between the foam and the buck is small enough, you should have a stiff enough mix such that it doesn't leak into there and you can wait to seal up the cracks when you do the rest of the foam sealing. I want to point out that I NEVER got any detectable air leaks between the concrete and the bucks. It is on there like glue, but the foam sealing is insurance and it fills the dead space. I did have a few gaps that were a bit bigger that escaped foam before the pour and concrete did ooze in there. In that case, you need to get out the electric hammer and a chisel bit to break it out. Don't let that happen. Really. Don't. However, even with the electric hammer and the chisel working away in there, you couldn't get the buck to come away from the concrete. You can get away with a gap of up to 1/4". Any bigger and you run the risk of it filling with concrete. If it is a big window, use two treated 2 X 4's for the bottom buck with a gap in the middle so you can pour through. My climate is fairly mild. If I expected long harsh winters, I might have thought twice about using full-width bucks. |
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gokite
New Member
Posts:30
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| 01 Jun 2013 08:52 PM |
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Interesting discussion. New to the board. Building a home this fall with ICFs. I am planning to use either Amvic or Foxblocks and did not see the FB window buck product before (it's not on their website). Anyone know if there is an Amvic window buck product? I can't find one on their website either. Anyone with Amvic experience? I'd like to get some opinions on this block if anyone built with them. Thanks. |
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Lbear
Veteran Member
Posts:2740
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| 01 Jun 2013 09:38 PM |
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Posted By FBBP on 01 Jun 2013 03:06 PM
Did you happen to do a blower door test? I am quite sure that you will have some if not a lot of air infiltration that finds a path between the joints in the outer layer of foam, between the wood buck (which is always flexing and moving due to moisture change) and the concrete core and then through the foam joints or between the foam and buck. Unless you use something like acoustic caulk which remains flexible between the wood and concrete, or between wood and wood, you will have air infiltration over time. I have been back to some of the earlier ICF buildings that we used wood bucks on and without exception they leaked like sieves at that point.
Consider how uptight people get about sealing the mudsill and bottom plates in wood frame construct. Why would it be any different in an ICF building? The wood will still move over time and let air in.
As a rule putting down a bead of foam between two layers and then squeezing them together is a waste of time. The foam works for the most part by the entrained air. Put two pieces together squeezes out the air and you have little left. Putting screws in the back of bucks might help to keep the wood from twisting but does not stop the air infiltration. When you pour the concrete the wood absorbs moisture and swells, depending on the species, between 1/8 and 1/4 inch. As it dries, it shrinks onto itself and the screws wind up holding it away from the concrete.
If on the other hand you use IntegraSpec, Nudura or Fox bucks, the concrete bonds to the foam on the back of the buck and you have a reasonable good seal. You will still have the chance of air infiltration through the joints in the foam if you don't take steps to prevent that. Building up with wood just gives you the same thermal bridging as wood frame construction, which seems a little counter productive to me.
I would be curious to see a blower door test on a 3-5 year old ICF home with wood bucks. Although the sheet rock and exterior finish would throw off the results, as most blower door tests are done prior to putting on sheet rock and exterior cladding. Here is an older article from ICF MAG about window bucks: ICFMAG
"That said, wood does have disadvantages. It's heavy. Boards are subject
to rot, warpage, and splitting. In termite-infested areas, they provide a
pathway for insects to enter the dwelling. Of the five different
materials covered in this article, wooden bucks are the most
labor-intensive material. "
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ICFHybrid
Veteran Member
Posts:3039
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| 01 Jun 2013 11:09 PM |
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The wood and the concrete in my home were placed just about two years ago. I did a good job of draining the footings and it is all dry, dry, DRY. Not even any rising damp. Not only is there no way air is passing between the concrete and the buck, but if you seal the foam to the buck either before or after the pour, there is not going to be any appreciable air that can even get to the concrete/buck interface. |
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FBBP
Veteran Member
Posts:1215
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| 03 Jun 2013 02:39 PM |
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Posted By ICFHybrid on 01 Jun 2013 11:09 PM
The wood and the concrete in my home were placed just about two years ago. I did a good job of draining the footings and it is all dry, dry, DRY. Not even any rising damp. Not only is there no way air is passing between the concrete and the buck, but if you seal the foam to the buck either before or after the pour, there is not going to be any appreciable air that can even get to the concrete/buck interface.
Unless you glue each and every foam block joint there will always be some infiltration into the core. The only place it can pass the concrete core (assuming no voids) is between the wood buck and the core. If you totally detail the drywall to buck connection you might stop it but I have my doubts on the long haul. |
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Lbear
Veteran Member
Posts:2740
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| 06 Sep 2013 03:57 AM |
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With the non-wood buck system like the below. How would one waterproof the window on a recessed install? The window could be installed with screws into the strips or directly into the concrete with TapCons but how does one wrap the window to prevent water intrusion?  |
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Stuie
New Member
Posts:60
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| 06 Sep 2013 08:27 AM |
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I will be excavating next week for my new cottage, I will be using SilverFox blocks and their Fox Buck. I will post pics and/or link to a blog of the build. |
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ICFHybrid
Veteran Member
Posts:3039
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| 06 Sep 2013 09:14 AM |
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Unless you glue each and every foam block joint there will always be some infiltration into the core. Not sure where you are going with this, but it appears you are saying air gets through cracks in ICF block and then can travel ALONG the core (until it gets to a buck, where it gets inside)? I used ring shank nails driven through treated bucks into the empty "core", if that's what it is called. When the core got filled with concrete, it appears to have seized the nails well enough that we detected no air infiltration at any of the wall/buck interfaces. |
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BrucePolycrete
Advanced Member
Posts:524
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| 06 Sep 2013 09:33 AM |
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ICFHybrid, Theoretically, any ICF with plastic ties can allow some air infiltration. Concrete does not adhere to polypropylene, so there are always minuscule voids along the ties. This issue does not arise with metal ties. In most cases, the magnitude is not worth measuring, but in cases where you have a sketchy install, it's just one more thing that can go wrong. |
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ICFHybrid
Veteran Member
Posts:3039
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| 07 Sep 2013 09:43 AM |
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Theoretically, any ICF with plastic ties Air infiltration along plastic ties? "Theoretically"? This is not something that anyone should have to consider when selecting a system. In this respect, metal ties would be far more unstable than plastic. |
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BrucePolycrete
Advanced Member
Posts:524
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| 07 Sep 2013 10:21 AM |
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ICFHybrid, don't take my word for it, talk to the Air Barrier Association of America. We did. |
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joasis
New Member
Posts:44
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| 07 Sep 2013 09:01 PM |
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Although I rarely post here, I would not be so quick to assume just because a relative new comer to the market, the Air Barrier Association of America, would be the authority on the subject. I have been building with ICF's for 15 years, dozens of homes and several commercial products, with many passing the blow door tests, and real world numbers on energy efficiency. To sweat out "alleged" air infiltration through concrete, and along the ties is really getting out there. I suppose that if a void occurred, and it just happened to be by a window or door buck, where we take extra precautions on consolidation, you could have an air infiltration...assuming that we don't follow up with sealing the window in as well, but I doubt it. Real world experience will trump anecdotal evidence every time.
A word on the original topic of window bucks: I build by bucks from treated lumber, that with a good design, can be removed easily, and I have yet to encounter any failures, in the 50 plus homes I have built. |
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| Ladwig Construction<br>Hennessey, Oklahoma<br>405 853 1563<br>Residential and Commercial Contractor<br>ICF's and Steel |
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ICFHybrid
Veteran Member
Posts:3039
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| 08 Sep 2013 09:10 AM |
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To sweat out "alleged" air infiltration through concrete, and along the ties is really getting out there. Ha Ha. I was searching for some combination of words that expressed that and couldn't come up with any better. Potential ICF consumers should take extra precautions with someone trying to sell them this concept. |
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joasis
New Member
Posts:44
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| 08 Sep 2013 01:57 PM |
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A start up company selling "training" and "accreditation" to people who don't know any better.
Next, someone will tell us about R values in block, and how the mass of concrete doesn't count. |
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| Ladwig Construction<br>Hennessey, Oklahoma<br>405 853 1563<br>Residential and Commercial Contractor<br>ICF's and Steel |
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ericnh
New Member
Posts:4
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| 18 Jun 2014 03:33 AM |
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My preference will be vinyl windows. Though there are lot of criticisms against it, vinyl windows are very much durable, requires maintenance very rarely and are said to be energy efficient too and also cheaper, www.windowchoice.ca/window-tips/why-do-most-homeowners-prefer-vinyl-windows . My old home had wooden windows which required attention more frequently than I thought. Had spent a lot of money to keep it looks good and out of damage. With all that in mind, when we bought new house, we changed all the windows to vinyl windows before moving in. We used services of professionals, who did their work perfectly. They looks cool and never had as much maintenance problems as wooden windows had. They were cheaper so that our pockets didn't burned a lot. Though I told all these, these kind of things mostly depends on personal preferences. |
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Midsouth ICF
New Member
Posts:65
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| 19 Jun 2014 02:02 PM |
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If you do treated wood, a lot of the commercial projects I have done required Fire&ice barrier. Not sure on the cost comparison with the Fox Buck. But its another option. |
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Ryan Gunn
Owner, Midsouth ICF Builders LLC |
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theInvincible
New Member
Posts:74
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| 20 Jun 2014 09:14 AM |
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http://youtu.be/ZoZlM9l6vN0 |
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