eugenep
Basic Member
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| 05 Nov 2013 06:33 PM |
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Is there a preference for the bucking material when using ICF? I am using Amvic for my blocks, and we have been going back and forth between the ICF installer, the window installer, and the GC, and we have decided to go with LVL for our bucks. Originally, I was thinking about vbuck, but one big concern was the strength of the vbuck with regards to screw pull strength and just overall compression strength. I am under the impression that vbuck is a relatively thin material with an air pocket for isolation. I am using some big and heavy windows, and so I am worried about the torque on the vbuck when I have the window fully opened. I am using tilt/turn inswing windows. I am also planning to put the windows flush to the inside, so that would put even more force on the edge of the vbuck.
I am guessing I am taking a penalty hit on the R-value of my walls, but I feel that having 1 3/4 lvl for the buck and 1 3/4 lvl for the window box will be way more secure and will give me much more comfort.
I still have some time to decide, and so I was wondering what the consensus was with regards to bucks.
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ICFconstruction
Veteran Member
Posts:1324
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| 05 Nov 2013 09:35 PM |
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Why LVL instead of treated or SPF? |
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| Brad Kvanbek - ICFconstruction.net |
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dmaceld
Veteran Member
Posts:1465
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| 05 Nov 2013 10:06 PM |
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Posted By ICFconstruction on 05 Nov 2013 09:35 PM
Why LVL instead of treated or SPF?
I kind of wish I would have used something like Timberstrand, cheaper than LVL I think, instead of 2 x 6 and 2 x 12 douglas fir for my window and door bucks. The sole reason is straightness. The 2 x 6's tended to twist before getting used. |
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FBBP
Veteran Member
Posts:1215
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| 05 Nov 2013 10:11 PM |
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http://www.greenbuildingtalk.com/Forums/tabid/53/aff/4/aft/81805/afv/topic/Default.aspx |
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eugenep
Basic Member
Posts:144
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| 05 Nov 2013 10:13 PM |
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Posted By ICFconstruction on 05 Nov 2013 09:35 PM
Why LVL instead of treated or SPF?
I prefer not to use treated wood close to the windows because I am assuming that all of the air coming into my house would be "tainted" with the treated wood's toxins. I am assuming treated wood is much more toxic than laminated wood, but maybe it is just an incorrect assumption. We want something that is semi averse to termites, so we aren't looking at SPF. I did a search, and I saw SPF is spruce-fine-fir. I hope that is the correct acronym. |
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dmaceld
Veteran Member
Posts:1465
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| 05 Nov 2013 10:13 PM |
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Posted By eugenep on 05 Nov 2013 06:33 PM
Is there a preference for the bucking material when using ICF?
[snip]
I am guessing I am taking a penalty hit on the R-value of my walls, but I feel that having 1 3/4 lvl for the buck and 1 3/4 lvl for the window box will be way more secure and will give me much more comfort.
I still have some time to decide, and so I was wondering what the consensus was with regards to bucks.
There is no consensus on this board as to which material is best. Have you searched for this topic, or is the variety of opinions the reason you're asking? There has been a lot of discussion the past 6 years here about window and door bucks. If you haven't searched quite possibly the best way is to use Google and add site:greenbuildingtalk.com to whatever search words you use. Buck should bring up a lot. You'll also find discussion of the thermal impacts of bucks, and suggestions how to mitigate heat loss. In essence though, do not obsess about thermal loss through the bucks. It's a small part of the total heat loss in the building. Air leaks and cheap expansive windows will be your greatest enemies. |
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| Even a retired engineer can build a house successfully w/ GBT help! |
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dmaceld
Veteran Member
Posts:1465
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| 05 Nov 2013 10:17 PM |
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Posted By eugenep on 05 Nov 2013 10:13 PM
I prefer not to use treated wood close to the windows because I am assuming that all of the air coming into my house would be "tainted" with the treated wood's toxins. I am assuming treated wood is much more toxic than laminated wood, but maybe it is just an incorrect assumption.
To each his own, but IMO worrying about toxins coming into the house from treated wood that is sealed in the wall assembly is akin to swatting at gnats when swarms of killer bees are headed your way.  |
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| Even a retired engineer can build a house successfully w/ GBT help! |
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eugenep
Basic Member
Posts:144
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| 05 Nov 2013 10:39 PM |
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Posted By dmaceld on 05 Nov 2013 10:13 PM
Posted By eugenep on 05 Nov 2013 06:33 PM
Is there a preference for the bucking material when using ICF?
[snip]
I am guessing I am taking a penalty hit on the R-value of my walls, but I feel that having 1 3/4 lvl for the buck and 1 3/4 lvl for the window box will be way more secure and will give me much more comfort.
I still have some time to decide, and so I was wondering what the consensus was with regards to bucks.
There is no consensus on this board as to which material is best. Have you searched for this topic, or is the variety of opinions the reason you're asking? There has been a lot of discussion the past 6 years here about window and door bucks. If you haven't searched quite possibly the best way is to use Google and add site:greenbuildingtalk.com to whatever search words you use. Buck should bring up a lot.
You'll also find discussion of the thermal impacts of bucks, and suggestions how to mitigate heat loss. In essence though, do not obsess about thermal loss through the bucks. It's a small part of the total heat loss in the building. Air leaks and cheap expansive windows will be your greatest enemies.
You are right. It doesn't make sense to get crazy about it. I was thinking about it because we are discussing it now. I have seen a bunch of threads discussing it, but I was just getting a little lazy. However, most people are comparing PT lumber or regular wood versus some kind of specific ICF buck like vbuck, insulbuck, or the new fox buck. i didn't see anyone mentioning lvl. Or maybe, lvl and pt plywood is used interchangeably. I guess for water issues, I can wrap my bucks with fast foot. I still have quite a bit of it left. I am planning to use LVL, but sometimes, I just want a little confirmation. My biggest concern was the strength of the buck with the heavy windows. I will take the hit on the lower R value. also, my windows will have a connection point already built into the window frame. I am using thermally broken aluminum windows, and so they have already created a special screw hole location to connect to the window box, so the installer won't destroy the thermally broken nature of the windows. This makes the LVL more desirable than the foam bucks with plastic because I can't necessarily contact on the plastic tab because i have no control over the connection point location. I guess my choices are SPF, LVL, PT wood, or some other kind of wood product where I can attach anywhere. Sometimes, I am hoping that just throwing out a question, and someone will have that miraculous solution that I haven't considered or hasn't been mentioned in any previous threads. |
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eugenep
Basic Member
Posts:144
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| 05 Nov 2013 10:40 PM |
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Posted By FBBP on 05 Nov 2013 10:11 PM
http://www.greenbuildingtalk.com/Forums/tabid/53/aff/4/aft/81805/afv/topic/Default.aspx
Hi FBBP, I had actually read that thread before. I am still a little unclear on LVL versus PT plywood. |
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eugenep
Basic Member
Posts:144
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| 05 Nov 2013 10:47 PM |
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Posted By dmaceld on 05 Nov 2013 10:17 PM
Posted By eugenep on 05 Nov 2013 10:13 PM
I prefer not to use treated wood close to the windows because I am assuming that all of the air coming into my house would be "tainted" with the treated wood's toxins. I am assuming treated wood is much more toxic than laminated wood, but maybe it is just an incorrect assumption.
To each his own, but IMO worrying about toxins coming into the house from treated wood that is sealed in the wall assembly is akin to swatting at gnats when swarms of killer bees are headed your way.
Is there a big cost difference between LVL and PT plywood? Am I mistaken about the level of toxins in the two wood products? |
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Lbear
Veteran Member
Posts:2740
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| 05 Nov 2013 11:04 PM |
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ICF bucks (Fox Buck) are new and provide 100% ICF/concrete window and door bucks with no need for wood. I believe that is the best approach.
If not doing Fox, the other option would be to use NON-treated wood bucks with a capillary break between the wood and concrete. Treated wood tends to split, warp, bend, twist and overtime it will develop air leaks. Spray foam doesn't help because as the wood moves the seal breaks between the spray foam and wood.
I am not big on the vinyl bucks but they are widely used and most reported no major problems with them.
#1 - Fox Bucks (best solution - 100% concrete/ICF and no wood)
#2 - Non-treated wood with a capillary break between wood and concrete
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dmaceld
Veteran Member
Posts:1465
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| 06 Nov 2013 12:17 AM |
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Posted By eugenep on 05 Nov 2013 10:47 PM
Is there a big cost difference between LVL and PT plywood? Am I mistaken about the level of toxins in the two wood products?
Since I've never obsessed about toxins I can't give you a definitive answer. Toxins is the primary reason you can't buy old fashioned CCA treated lumber. ACQ isn't a significant toxin, if at all. The biggest problem with PT, as I'm sure you've read, is it's propensity to twist and split. That's why I used untreated doug fir 2 x's. I was surprised, and disappointed, by how much they twisted. Splitting was not an issue. As far as cost I suspect LVL would be the most expensive, followed by Timberstrand, plywood, PT, and untreated. If you're not familiar with it, Timberstrand, and I'm sure there are other brands like it, is basically OSB formed into dimension lumber. Builders use it where they do not in any way want to contend with twisted and bowed framing, e.g., kitchen walls. Untreated wood, like Lbear says, needs to have a capillary break between the wood and concrete. This is not because of moisture migration from the ground, but because of thermal differences of the wood and concrete leading to potential condensation on the concrete surface. I used sill seal between the buck and concrete, wide enough that I curved it into the block exterior so that concrete would push it up against the ICF foam and the buck. Not everyone here agrees with Lbear about foam between the window frame and buck. There is foam made specifically for sealing windows with the characteristic of staying flexible. The foam won't pull away from the wood. I had absolutely no hesitation in using foam to seal around my windows. |
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dmaceld
Veteran Member
Posts:1465
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| 06 Nov 2013 12:23 AM |
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Be aware Lbear has done a lot of research into ICF building, but hasn't yet built his house. If he has he hasn't told us about it yet! Experience sometimes corroborates, and sometimes contradicts, research knowledge! I did quite a bit of research plus I have built the grand total sum of one house, so I write with at least some experiential knowledge in hand. Quite a few of the guys here write from the standpoint of a lot of experience, and even they don't always agree!
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| Even a retired engineer can build a house successfully w/ GBT help! |
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Lbear
Veteran Member
Posts:2740
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| 06 Nov 2013 12:55 AM |
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Dmaceld - "Be aware" is always better than "beware"  Aside from my research, I have observed quite a few ICF builds personally, and I know a few ICF pros. My house design is also ICF and while it hasn't been started, there has been A LOT of research. That is for sure. As you mentioned, ICF guys disagree on this topic, probably the most debated topic among ICF builders. My objection to the spray foam is from the studies conducted by Building Science experts on this exact topic. The rigid spray foam is guaranteed to break the seal over time. The semi-flexible spray foam is better but the jury is still out whether over 10+ years that foam seal is still intact or broken. If broken, that is another potential air or water leak. What works better is Tremco ExoAir Expanding Foam Tape. The 100mm width has an R-Value of R-13 and it is a Polyurethane foam impgregnated tape with a synthetic resin. It is an air and weather barrier and when exposed to rain and wind, it is 100% weather proof and air tight. It will expand and contract along with the window and framing area, indefinitely. SEE VIDEO HERE The Building Science community really loves this tape as it is easier, faster and better at sealing than spray foam and other similar products. It remains 100% flexible, indefinitely. The other issue at hand is WHERE to install the window within the window buck area? Most US made windows are flush mounted (outie) but there is scientific data that shows a 20% improvement when windows are inset and installed as "innie" windows with over-insulated frames. (see study from Thorsten Chlupp) |
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ICFHybrid
Veteran Member
Posts:3039
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| 06 Nov 2013 08:37 AM |
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I am assuming that all of the air coming into my house would be "tainted" with the treated wood's toxins. All what air coming into the house? It's supposed to be sealed against air leakage, isn't it? |
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eugenep
Basic Member
Posts:144
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| 06 Nov 2013 12:18 PM |
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My window installer brought a tape guy to my site, and they recommend siga products. Of course, the tape guy was a siga trainer and application advisor. He will give my GC and ICF installer some training on the siga products. he was showing how to do flashing and other things around the window opening. They also have some kind of house wrap.
We will probably be using these products on my openings and possibly use some of the other stuff for the roof deck and building sheathing.
I forget what kind of foam they were discussing to seal and set the window.
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eugenep
Basic Member
Posts:144
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| 06 Nov 2013 01:44 PM |
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Posted By ICFHybrid on 06 Nov 2013 08:37 AM
I am assuming that all of the air coming into my house would be "tainted" with the treated wood's toxins. All what air coming into the house? It's supposed to be sealed against air leakage, isn't it?
I guess my builders won't be as good as you, and I don't think I will attain zero air infiltration. I would prefer to have as few toxins in my house as possible. I guess you don't care, but some of us would rather err on the side of caution versus assuming that any place that we will have toxins will stay in that location for the entire time we live in the house. At least you are consistent with your condescending attitude. I would love to see your house, and see how well it performs with regards to a blower test. I presume with your comment it is the best house in the entire world, because I think everyone else is assuming some air infiltration especially at the doors and windows. |
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eugenep
Basic Member
Posts:144
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| 06 Nov 2013 01:47 PM |
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Posted By ICFHybrid on 06 Nov 2013 08:37 AM
I am assuming that all of the air coming into my house would be "tainted" with the treated wood's toxins. All what air coming into the house? It's supposed to be sealed against air leakage, isn't it?
Also, if you aren't going to provide anything helpful, can you keep your condescending attitude to yourself? You sit there on your pedestal and you wonder why people get mad at you. |
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ICFconstruction
Veteran Member
Posts:1324
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| 06 Nov 2013 03:09 PM |
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Posted By eugenep on 06 Nov 2013 01:47 PM
Posted By ICFHybrid on 06 Nov 2013 08:37 AM
I am assuming that all of the air coming into my house would be "tainted" with the treated wood's toxins. All what air coming into the house? It's supposed to be sealed against air leakage, isn't it?
Also, if you aren't going to provide anything helpful, can you keep your condescending attitude to yourself? You sit there on your pedestal and you wonder why people get mad at you.
The point is that around windows and doors should be flashed with peel and stick tape on the outside, expanding foam and or insulation filled to prevent air infiltration. Since you will have no infiltration elsewhere in the ICF walls you can concentrate your efforts at these openings.
We usually use the method of GT plywood and 2x6 ripped at 22.5 degrees and turned to "hold" onto the concrete. My second favorite buck is 2x SPF with something between it and the concrete. |
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| Brad Kvanbek - ICFconstruction.net |
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Lbear
Veteran Member
Posts:2740
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| 06 Nov 2013 03:42 PM |
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The issue of window bucks and how to solve the issue is boiled down to the issue of dissimilar materials in a single area. You have of course the concrete but then introduce wood or vinyl, and this creates two materials moving/expanding at different rates. As one ICF expert stated, “one of the last unsolved challenges of ICF construction.” EPS expansion rate is basically ZERO. The same cannot be said for wood or vinyl.
The best solution is to always KEEP THE SAME MATERIAL. That is why the EPS window and door buck is a huge step in confronting this issue. You are not introducing dissimilar materials. It's like the ICF wall; EPS and concrete.
Another thing with ICFs that have exposed ties (bad idea). The plastic ties that are exposed will move due to the thermal movement of plastic is much higher than EPS. If you used stucco on the exterior, the areas where the exposed plastic ties are will crack because they move while the EPS does not.
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