Question: How effective are ICF blocks if an internal or external house fire occurs? Nudura says it has a 4 hour fire rating with a 6" concrete core. So, are they assuming the wall is fully compromised in a fire down to the concrete from exposure? Also - are they relying heavily on the sheetrock application for the fire rating? Looking at using a pretty good mount of Nudura foam walls with the Plus system. Don't want to create a massive fuel source. Thanks in Advance! CB.

http://www.nudura.com/docs/default-...aJbq83ch9Q


It appears they're looking at a sheetrocked wall assembly.

These tests are done in a total burn scenario as a finished wall (ie, sheetrock is installed). Samples of the finished wall are placed in a furnace and blasted with a direct flame for the duration being tested (in this case 4 hours). After 4 hours, the wall is removed from the furnace and immediately doused with cold water for a dictated time (1-2 mins I think), covering the entire surface. This is to simulate rapid cooling that the way may experience from a fire house. Finally, a close inspection of both sides of the wall is completed to search for any cracks/damage/spawling. If the walls is deemed to be in structurally sound condition, it has passed the test and receives the 4 hour rating.

Sheetrock does not play a crucial role in these tests, as it will typically burn off within 20 min or so, following closely after by the EPS. The bulk of the furnace test is conducted with a flame directly in contact with concrete.

Most/all ICFs use a fire-retardant in their EPS during production to limit the risk of the product catching/spreading fire. Essentially they will not support combustion (unless the fire progresses to generate sufficient heat to exceed the product's ignition temperature) without an external fuel source. In other words, during a fire the EPS would melt/burn, but the concrete is likely to remain structurally sound. This could prevent fire at a neighbor's house from spreading to your home or keep the shell of your home in-tact during a fire inside your house (allowing extra time for family to exit).

ICFBdr is describing the ASTM E119 fire rating test perfectly. A fire rating is given to a wall system or assembly that resists burn through for the testing period, in this case a 4 hour fire rating. It's not hard to imagine that solid concrete sandwiched in between layers of EPS would resist burn through for this test but the EPS would melt instantly when exposed to open flame or the heat generated in a house fire. The drywall would only delay its failure but the assembly would achieve its rating because of the concrete wall. Anything attached to the EPS layer such as lath, drywall, plaster, stucco, cultured stone, etc. would begin to fall as the EPS melted and the exposed ABS webs begin to ignite. Unfortunately all "white block" ICFs (Nudura is a white block with a green tint) will melt when exposed to open flame or high heat and therefore by code must be clad with a fire retardant layer (drywall, plaster, stucco, etc.) to delay failure from fire. If clad properly to resist fire, a white block ICF home or building creates a super strong, super insulated structure.

I would like to point out that ICF must be covered by an effective thermal barrier by Building Code since it is grouped within the broad group of "foam plastics." This leads some to believe that ICF is flammable, produces dangerous/toxic smoke, etc.

Personally, I am not opposed to this requirement, but I am disappointed that in our region, a 6mil poly can be left exposed, which has a lower ignition temp and higher flame spread rating vs your typical ICF (this is a rant for another day)...

Folks - this is very helpful indeed. Thank you.

My intention is to understand how to design a home resistant to external fire source (forest/embers/etc), and internal sources (kitchen/mechanical/electrical/furniture) as well.
However, in my current wall design there would be a good volume of foam to the outside of an 8" concrete core. The concept involves Nudura's PLUS system with both 6" billets, and 6" external laminate panels. This would be done by manually assembling forms using the form extender attachments between both an 8" and 6" web. I want to make sure I'm not placing a massive fuel source in the structure with the extreme level of insulation envisioned. Note: Arctic like climate. So....

A few questions:

Is a double layer of two 5/8" sheet rock panels effective in extending the time before potential ignition/melt from internal surfaces?

If I use metal cladding on the outside of the wall attached to the nailing strips, and it is exposed to sun what is the maximum temp it can reach without affecting the Nudura foam?

If the Nudura foam will move from melting to combustion at a certain temperature, what is that temp?

Has anyone placed a layer of Roxul (stone wool) between the Nudura foam and inside or outside cladding?

Thanks again! Sure appreciate the very detailed responses so far.

Regards,

CB.

Posted By cbryndal on 07 Aug 2017 05:23 AM
Folks - this is very helpful indeed. Thank you.

My intention is to understand how to design a home resistant to external fire source (forest/embers/etc), and internal sources (kitchen/mechanical/electrical/furniture) as well.
However, in my current wall design there would be a good volume of foam to the outside of an 8" concrete core. The concept involves Nudura's PLUS system with both 6" billets, and 6" external laminate panels. This would be done by manually assembling forms using the form extender attachments between both an 8" and 6" web. I want to make sure I'm not placing a massive fuel source in the structure with the extreme level of insulation envisioned. Note: Arctic like climate. So....

A few questions:

Is a double layer of two 5/8" sheet rock panels effective in extending the time before potential ignition/melt from internal surfaces?

If I use metal cladding on the outside of the wall attached to the nailing strips, and it is exposed to sun what is the maximum temp it can reach without affecting the Nudura foam?

If the Nudura foam will move from melting to combustion at a certain temperature, what is that temp?

Has anyone placed a layer of Roxul (stone wool) between the Nudura foam and inside or outside cladding?

Thanks again! Sure appreciate the very detailed responses so far.

Regards,

CB.

A double-layer of sheetrock would likely extend burn time.

As for the Roxul question.  I don't know of anyone who has.  Others might.

As for the rest of the questions, you're probably better off talking to Nudura directly.  Because you're essentially asking MSDS/implementation questions.

Based on your first sentence in your question: "My intention is to understand how to design a home resistant to external fire source (forest/embers/etc), and internal sources (kitchen/mechanical/electrical/furniture) as well." it appears that you might want to look elsewhere for an ICF that does not burn. All "white block ICF" made with EPS will melt, vaporize, and burn when exposed to open flame or extreme heat. The only ICF made with EPS (recycled) that does not burn is "gray block ICF". Gray block ICF, or insulating composite concrete forms (ICCF) is 100% recycled EPS ground into aggregate and mixed with Portland Cement. The cement coats the EPS and makes a fireproof block. Full disclosure: I am an ICCF manufacturer and we routinely demonstrate how ICCF block held in our hands holds up to a MAPP gas torch at 3600 degrees F (3 times the temperature of a house or forest fire) for several minutes of exposure to the flame. If you haven't made the block purchase, you might want to do some research into high insulating fireproof alternatives in your region of the country. Heat from the sun on metal cladding on furring strips with an airspace will have little or no impact on the foam underneath but will easily radiate an extreme heat to the foam in a forest fire. Drywall is a great "interior" thermal barrier to flame but it will only delay heat penetration, not stop it in a prolonged fire. Stone wool layer added to your walls? It seems to me that you could add a number of fireproof materials to your white block walls to make the assembly fire resistant but the added labor and material costs to do so seems unreasonable. IMO, seek a fireproof wall block.

Looking into an ICCF, as described, may increase your fire-resistance, but would likely not yield the high R-value you are looking for (feel free to correct me if I am wrong, RickICCF).

You will not be able to fasten a metal cladding to the exterior with the wall assembly you describe. The 6 inches of laminated EPS on the outside of the form means your fastening strips are now 6.5" (+/-) below the surface. A better approach would be to request custom-cut insert billets from your Nudura dealer to the desired insulation thickness. If this billet is 12" thick, you could use unassembled panels with webs and connectors to create a thick enough core to allow for the 12" billet and required concrete thickness to remain. This would keep the fastening strips near the surface for mechanically fastening interior/exterior finishes.

I would suggest a non-combustible finish on the exterior (eg, stone veneer, etc), which could have embers burn out directly on the veneer without damage. Areas with combustible appliances (ie, kitchen stove, mechanical room, etc) could use a similar interior finish (eg, tile backsplash in kitchen, cement board in mechanical room, etc.).

The Roxul could work, but you would need to use a non-combustible framing (eg, steel studs) rather than a wood framed false wall. Personally, I think this would not be money well spent, since you can achieve similar ratings by methods listed above.

Referencing the R-value of "gray block" ICCF to "white block" ICF. Most gray block ICCFs are referred to as "screen-grid" ICF by the International Residential Code (IRC) because of its post and beam internal cores for concrete grout. Because of this design ICCF uses much less concrete than "flat" ICF (there are some "screen-grid" white block ICFs) and because of the grid in the ICCF block you will have full block thickness of fireproofed EPS in the areas between the cores to add thermal resistance to the ICCF wall. The R-value of an ICCF wall is equal to or greater than an ICF wall. Both white and gray block ICF have an added "thermal mass" multiplier to the grouted wall from the internal concrete.

RicklCCF - thanks for the suggestion. Could you suggest a product I might want to research in this category? My goal is a challenging combination of structure (concrete/steel), extreme insulation level (arctic), and fire resistance. One thing I considered was a double layer ICF wall. Like house within a house, thermos style. I modeled it with some blocks we have. Calculating the volume, not being able to create an actual vacuum, etc.. are design challenges so I returned to the single wall concept.

ICFBdr - thanks again. Excellent info. The billets are in the current design, using un-assembled panels and web joiners to get the 8" concrete core + 6" billet design. I'd spray foam the webs during assembly to avoid the concrete infiltration in the web assembly. While the internal webs could sized/extended to get more billets inserted (thereby moving the nailing strip to the outside/optimal location), the billets are a different foam type than the Nudura panels, and have a lower R-Value. I'd need to check my notes on the detail there. On the mockup I setup with just blue board as the outside panel equivalent, it seemed like a 6" screw plus some attachment depth would not be unreasonable for corrugated siding. The concern would be in what firing strip material to use. The building shape is a simple rectangle, so no funky roof lines or walls.

Ahh....more to think about & research.

Thanks fellers! Good stuff.

CB.

cbryndal - I would like to help you make an informed decision on the type of construction materials to build with for your specific needs in anyway I can. So as not to breach any rules of this forum by referencing names or websites you are welcome to call me, Rick T. at six two three - two seven one - 11 seven three. My curiosity is piqued, I'd like to hear more about the thermos style house. Call me anytime.

You might check out Durisol blocks as they are a product with Roxul inserts available. They are a type of ICCF that uses mineralized wood chips and have excellent fire rating. If you are in Canada the shipping would be cheaper as I believe they make them in the Toronto area.

RickLCCF - I'll give you a ring Thursday to discuss. Feel free to remove or edit your post above to remove the phone number, so the BOTs don't latch onto ya. I wrote it down.

AlwayslikedICF - interesting! Breezed through their site, will read more soon. Thx!!

Building will have internal dimensions of 16x64, 2-stories, and basement/walkout. ICF/Wall, etc would be in addition to those dimensions. Due to snow depths, and views living areas are on second/top floor and bedrooms on main level. Basement is 1-car garage, mechanicals, storage, man-cave, etc...

CB.

RickLCCF - I'll give you a ring Thursday to discuss. Feel free to remove or edit your post above to remove the phone number, so the BOTs don't latch onto ya. I wrote it down.

AlwayslikedICF - interesting! Breezed through their site, will read more soon. Thx!!

Building will have internal dimensions of 16x64, 2-stories, and basement/walkout. ICF/Wall, etc would be in addition to those dimensions. Due to snow depths, and views living areas are on second/top floor and bedrooms on main level. Basement is 1-car garage, mechanicals, storage, man-cave, etc...

CB.