ICFconstruction
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| 01/20/2008 1:52 PM |
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I have a customer that is getting advise to fur the ICFs with 1"x4" to create an air gap to prevent condensation and for and electrical chase.
What do you guys think? Wasted effort or good idea? |
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Chris Johnson
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Posts:341
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| 01/20/2008 2:22 PM |
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Kinda defeats the purpose of the 'studs' in the ICF doesn't it?
I'll bet the Fire Department doesn't like the air gap, nice chase for the flame.
How do they intent to protect the electrical in the 3/4" chase?, wiring must be I believe 1 1/2" below the surface to prevent being pierced (picture frames, etc.).
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Chris Johnson - Pro ICF
Napa, CA
Come for the wine, Stay for the ICF work |
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Quantum
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Posts:262
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| 01/20/2008 2:55 PM |
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Well; an air gap is advisable behind a cementitious surface like stucco, because when the front of the stucco is considerably colder, the back will condense humidity. Indoors there isn't such a difference in temperature and the EPS is insulation anyway.
Unless you're talking about the Cempo blocks, which is a whole 'nother pile of pancakes. |
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ICFconstruction
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| 01/20/2008 3:40 PM |
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I advised against the furring, the construction manager told me the purpose of the furring was to prevent condensation. The homeowner says he doesn't want grooves cut in the EPS for the wiring.
From what I know, for condensation to form the inside ICF surface temp would have to be below the dew point of the air in the house. I don't see that happening.
Chris you have a good point, does the 1.5" recess for electrical apply everywhere or just at the studs/ties? |
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ICFconstruction
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Posts:81
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| 01/20/2008 3:41 PM |
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| Quantum, what about Cempo/Composite ICFs? |
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dmaceld
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Posts:494
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| 01/20/2008 5:16 PM |
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Posted By ICFconstruction on 01/20/2008 3:40 PM
Chris you have a good point, does the 1.5" recess for electrical apply everywhere or just at the studs/ties?
Actually, it's 1 1/4", and the full length of the wiring in a groove. Here's a couple of paragraphs quoted from the 2006 IRC. Should be pretty much verbatim copy of what's in the NEC. I can find the citation if you need it. You can bet an inspector is going to want to see the 1 1/4" space everywhere along the wire. The 1 1/4" is between the wallboard and the wire, not from the outer face of the wallboard. As said before, the idea is to keep from hitting it with nails driven into the wall.
Bored holes in framing members for wiring shall be located
not less than 11/4 inches from the edge of the framing
member or shall be protected with a minimum 0.0625-inch
steel plate or sleeve, a listed steel plate or other physical
protection.
Where installed in grooves, to be covered by wallboard,
siding, paneling, carpeting, or similar finish, wiring methods
shall be protected by 0.0625-inch-thick steel plate, sleeve, or
equivalent, a listed steel plate or by not less than 11/4-inch
free space for the full length of the groove in which the
cable or raceway is installed.
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dmaceld
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| 01/20/2008 5:42 PM |
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Posted By ICFconstruction on 01/20/2008 3:40 PM The homeowner says he doesn't want grooves cut in the EPS for the wiring. [/quote]Look at using Plastilock boxes and conduit. LINK. For some interesting read find the thread a few months back about conduit vs. grooves for wiring. Strong advocates for both sides. Don't remember the thread subject line. |
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Building house - what a way to spend retirement! |
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ICFconstruction
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| 01/20/2008 5:47 PM |
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Has anyone used these Plastilocks? I had looked at them a couple years ago and dismissed the idea.
The question on condensation is my main interest because I see no problem grooving the EPS for Romex, any the grooves can always be filled with urethane insulation. So what about the condensation question? |
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Quantum
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| 01/20/2008 8:07 PM |
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Posted By ICFconstruction on 01/20/2008 3:41 PM
Quantum, what about Cempo/Composite ICFs?
My opinion? They have less benefit from the thermal mass of concrete because of waffle-grid design, plus they sabotage insulative resistance (R-value) by glueing the EPS together with cement. Less of the two complementary thermal isolation methods that ICF has.
And being shot through with concrete, a higher chance of condensation inside, plus no firring, no hot-knifing, heavier to handle, more expensive, etc.
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dmaceld
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Posts:494
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| 01/20/2008 8:36 PM |
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Posted By ICFconstruction on 01/20/2008 5:47 PM
Has anyone used these Plastilocks? I had looked at them a couple years ago and dismissed the idea.
I haven't yet, but will be when I get started on my house in a few weeks. One big reason is I want as large a box as possible so I don't have to fight wires in tight spaces. The deepest blue boxes are too deep to fit between the concrete and dry wall surface, and the next smaller size are smaller than I want to use. It will cost more but I've decided it's worth it. I'm doing the electrical myself so I don't have the issue of bringing in an electrician to install the boxes and then coming back later to run the wiring.
Come on ground! Thaw out so I can dig and pour!!
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Building house - what a way to spend retirement! |
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Chris Johnson
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Posts:341
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| 01/20/2008 8:58 PM |
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Condensation will not be an issue, never once have I seen frost work it's way through an ICF wall and thaw on the inside. Without looking it up, thermal mass is the key component going on here, cold air is on the outside trying to push in, warm air on the inside is trying to push out, somewhere in that mass of concrete they eventually meet, never in the foam area.
Cut the electric wires into the foam, tell the client you can furr out the walls, how much do they want to spent, why are they re-inventing the wheel? ICF manufacturers have paid for all the studies which proves what they want is not neccessary. |
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Chris Johnson - Pro ICF
Napa, CA
Come for the wine, Stay for the ICF work |
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ICFconstruction
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Posts:81
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| 01/20/2008 10:55 PM |
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dmaceld,
I recomend the electrician use 4" x 4" x 1 1/8" box and a mud ring for a single outlet or switch. Plenty of room, still has insulation. I don't like the idea of Plastilocks because of weaking the forms, clogging up the wall cavity with conduit and that much more to deal with before the pour. |
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walltech
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Posts:469
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| 01/21/2008 10:53 AM |
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ICF construction: I also would not use Plastilock in ICF. Home depot sells a carlon single gang box that is a screw on model that is 18 cubic inches and 3" deep. These work great for ICF's with 2 1/2" of foam but they don't address a double gang box. The idea of furring out is a huge unnecessary expense and there will be no frost, or condensation on the interior of a ICF wall. As stated above it will violate the electrical codes also.
How many ICF's have you guys built?
Dave |
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GRickard
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Posts:38
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| 01/21/2008 1:20 PM |
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| dmaceld, The boxes that walltech mentioned are what I just used on my house and they work great. They are made to screw to the face of a metal stud. Anywhere I needed a 2 gang box or just more room, I used a 2 3/8" deep 4 square with a plaster ring. With the deep box you can screw it to the concrete with tapcons, just keep in mind that if you use a metal box, you have to put a ground pigtail on it. |
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Opus
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Posts:51
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| 01/21/2008 11:09 PM |
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| For those interested, it does not meet code to put a hole in a plastic box in the back and tapcon it to the concrete. If the box has tabs on the outside ( as the plastic boxes for exterior use have) you can use those. Otherwise use a box with a flange made to mount to a stud and screw it to the ties. |
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dmaceld
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Posts:494
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| 01/22/2008 12:13 AM |
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Posted By Opus on 01/21/2008 11:09 PM
For those interested, it does not meet code to put a hole in a plastic box in the back and tapcon it to the concrete.
It sure looks like those are molded in punch outs (one is circled) for mounting holes in the attached pic of the Carlon square box.
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Building house - what a way to spend retirement! |
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ICFconstruction
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Posts:81
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| 01/22/2008 7:42 AM |
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| We use a hot knife to make a 4" x 4" x 1 1/8" cutout and our foam glue or PL300 to glue the metal box in and it's done, never had to fasten boxes any other way. Add a mud ring and there is lots of room for wires. |
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Opus
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Posts:51
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| 01/22/2008 8:37 AM |
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dmaceld,
Check with your electrican- he will tell you. You are not allowed to put a screw through the spot you have circeled on the box. The boxes are insulated. Once you put a screw through the back you have a path to ground in the box. I beleive this voids the UL listing on the box. I will try to find the exact section of the code tonight. Your inspector might overlook it, but it does not meet code. |
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GRickard
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Posts:38
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| 01/22/2008 10:12 AM |
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| Just to clarify things, the 2 3/8" deep 4 square box that I mentioned above is a metal box. Iam not sure if anyone even makes a plastic box that deep. However I do like the idea that ICFconstruction has, but I didn't have a hot knife. I used an eighteen volt chainsaw. Opus, You are correct about the plastic boxes. NEC article 314.43 states "Provisions for supports or other mounting means for nonmetallic boxes shall be outside of the box, or the box shall be constructed as to prevent contact between the conductors in yhe box and the supporting screws." Greg |
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dmaceld
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Posts:494
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| 01/22/2008 1:57 PM |
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Thanks for the clarifications. I see the problem with a screw inside the box now. Interestingly, that restriction is not copied over into the electrical section of the 2006 IRC. Almost all of the rest of the NEC pertinent to residences is.
Looking at HD last night I find that the Carlon B232B-UPC would work for a 2 gang box. It has the metal adjustable flange on it and is 3" deep. You might have to cut or bend back the back edge of the metal bracket and the screw.
For 3 & 4 gang there are the B344AB, 2 11/16 deep, and the B455A-UPC, 2 1/2 deep. They both have the plastic flange but also captive nail ears. Now, if the inspector is willing to overlook missing nail ears those boxes would probably work good.
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Building house - what a way to spend retirement! |
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