I am currently finishing our ICF home.  The house is 6000 sq ft and is icf all of the way to the gables.  We have a hipped roof that is made of trusses at 24 inches o.c.
The exterior roof is 5/8 osb covered with titanium underlayment and ice shield.  The roof itself is a prepainted Englert metal roof that is matte black.  Back of the house faces south east and the roof is covered with solar panels.
the ERV is located in the basement.  We have a two zone HVAC system with one unit in the basement and an air handler in the attic also.

We had our roof decking sprayed with Demilec agribalance open cell foam at 8.5 inches to meet the r-38 code.  My concern is that that we live in zone 4 here in Va. and I am worried that we could have moisture issues in the roof decking.  The foam was sprayed directly to the sheathing without a vapor barrier.  Gable walls are sprayed to r-13.

I am also reading that a fire retardant is to be applied over the foam.  I was told this was not necessary in the unvented attic because the space is only mechanical; however, since I have an air handler up there I am guessing that air is circulated back into the house from the attic.  I am unsure if I need the fire retarder if the returns are all located within the living space.

should I do anything about potential attic moisture and fire issue now, or wait to see how things do when we move into the house?
I doubt we will be in the attic much so I would hate for a problem to not be addressed now if necessary.
Thanks
greg

Have you seen the Demilec "Bee Alert" Technical Bulletin Vol 1, Issue 1?

http://www.demilecusa.com/Repository/File/Bee%20Alert%20Technical%20Bulletins/Bee%20Alert,%20vol%201,%20issue%201.pdf

Does it help answer your question (dunno, maybe it is the source of your question)?

this is the source of concern as I am one county away from zone 5 in west va.  I dont want code to dictate what should be done.  I dont ever plan on moving.

If the steel roof is mounted on purlins and has a decent pitch to it (higher than 2:12) you could have skipped the ice & snow shield and protected the decking by giving it good exterior drying capacity. But with that underlayment the deck now has a vapor barrier on the exteiror, which means you can't safely put a highly vapor retardent material on the interior. The matte-black color may help by cycling the temp on the E,S, & W pitches- but the N side may be still be susceptible. See table 3 in this document:

http://www.buildingscience.com/documents/reports/rr-1001-moisture-safe-unvented-wood-roof-systems

The albedo of matte-black steel is probably closer to that of the asphalt shingle simulation than the light metal, but there's still some risk to the roof sheathing. That risk can be mitigated by keeping the conditioned-space relative humidity between 25-30% (not higher) in winter. It's on the dry-edge of the health & comfort zone, but still meets ASHRAE recommendation. (The simulation maintained 30% when it was below 15F outdoors, but allowed it to rise with outdoor temperatures. See Fig. 4 in that document.)

Since there are both ducts and air communication between the attic and conditioned space you WILL be required to apply an ignition barrier. While there are purpose-specific spray on fire retardents that would meet code, 3"+ of wet-sprayed cellulose or self-adhesive mineral/fiberglass insulation "blown in bag" would in most cases qualify. (Check with the fiber insulation manufacturer about use as ignition barrier.) That would have an additional benefit of boosting your R value above 50.

Unless you put a highly vapor retardent siding or underlayment on the gable ends you should be fine with the open cell foam there, but finishing the interior with a vapor retardent paint on wallboard (or 1" of XPS foam under un-painted wall board) would give it a thermal break on the the studs while reducing interior moisture drives seen by the sheathing.

Looking at it a bit more closely...

Because of the slightly higher density Agribalance has lower perm rating compared to generic half pound density open cell foams (5 perms @ 5" thickness compared to ~9-10 perms @ 5" for typical half-pound SPF). At 8.5" of depth you're looking at ~3 perms, which is open enough for the roof deck to seasonally dry, but tight enough that it won't pick up too much during your relatively moderate winters. From a roof-deck drying/accumulating capacity 3 perms is similar to having 1" of generic 2lb density closed cell foam. In the simulation the R38 stackups with 1" SPF on the roof deck fared well in climate zones 4 & 5, except when under a light colored metal roof (which you don't have) and under the high-humidity profile (which you would be wise to avoid anyway.) I think you're going to be OK here.

You'll still need an ignition barrier to meet code, and a purpose-rated wet-spray fiber blown-in-bag is still likely a better value than a spray fire-retardent approach. eg:

http://www.specjm.com/files/pdf/T07-020JMSpiderIgnitionBarrierV2.pdf

http://www.amerrock.com/PDFs/ThermalBarrierAnnouncement.pdf

thanks for the response.  I spoke with the spray foam company and I was told that since the system is a sealed system i dont need the ignition barrier.  I am told that all of my air exchange occurs within the living space so I dont have "air exchange" in the unvented attic.  I was also told that wood catches fire at around 400 degrees and the foam protected wood at about 1000 degrees.

for me, the million dollar question is do I leave the envelope as is or make changes.  I did put in humidity controlled fans in all of the bathrooms that can be adjusted.
I know that my wife will not want to live in a dry house in the winter and have flaky skin.
would it be of any value to add a dehumidifier to the conditioned attic space to reduce the moisture on the roof decking in the winter.
thanks,
greg

My Hvac contractor suggested putting a dehumdifier that ties into my condensate line in the attic that runs independent of the hvac to control moisture in the attic with the open cell foam.
I would like to be able to maintain comfortable air quality in the house  while not risking moisture problems in the attic.  the studies I read suggest air humidity no greater than 30% in the conditioned space.  I dont want to battle low humidity in a tight icf home.
I am getting very puzzled with all of this as I am having ice dams form on the edge of my metal roof now that has no gutters.

what is the approximate cost of spraying in some fiber over the open cell to provide a fire barrier?  since I have a vapor barrier on the exterior of the roof sheathing does spraying a material on the underside of the attic foam create a double barrier?
thanks,
greg

The IBC calls out for a reduced rating for the ignition barrier in accessible attics with ducts, but where there is no air exchange, but it still requires an ignition barrier. The ignition point of the wood or foam isn't the issue- it's the toxic smoke/fumes coming off the foam in the presence of flame/heat. There are sometimes local variances with the code, and plenty of inspectors who will ignore it in low-risk applications, but it can become an issue at point of resale, or with insurers in the event of a fire. IIRC 3/8" gypsum is acceptable, but there are many spray-on

As long as you maintain the conditioned space air to an absolute humidity of dew point of <40F ( which is 34%RH @ 70F) whenever it's below 20F outside you will be fine leaving it as-is. At 30% RH at 68-70F comfort and health issues are just fine (definitely not flaky skin and static territory the way <20% is.) Unless you somehow built in a vapor retarder between the attic and conditioned space the attic air's absolute humidity (=dew point) will track that of the conditioned space. Latex ceiling paint on gypsum, not a problem. Alkyd paint on gypsum, sometimes. "Radiant barrier" foil-faced gypsum or poly sheeting, big problem. As long your attic floor is reasonably permeable to the fully conditioned space and has no insulation between the floor joists, you won't need an attic dehumidifier. In a tight home you can control the interior RH in winter by putting the HRV under dehumidistat control. Keep it between 30-35% and your roof deck will stay happy. Put pump it up to 40-45% all winter, maybe not.

Allergists & other health professionals recommend keeping it 30-50%RH year round, ASHRAE says 25-65%. But above 60% in summer can lead to high mold-spore counts, and above 50% allows dust-mites to thrive. IIRC much below 30% it becomes an increased virus transfer/sinus susceptibility issue, not so much a dry skin thing.

If you're wet-spraying fiber blown-in-blanket as the ignition barrier it is still highly permeable, allowing the modest winter-moisture accumulation to seasonally dry. Gypsum is also highly permeable. You'd have to read the specs for any other spray-on ignition barrier for perm ratings- keep it >5 perms if you can- <1 perm becomes a real problem. The cost of using ignition-barrier rated fiber insulation as the ignition barrier varies a lot by the particulars of the job- you'd have to get some quotes. It'll very likely be more than a non-insulating spray on barrier, but the difference in cost will likely be cost-effective in an NPV analysis on fuel savings. Try to find a contractor who knows what is/isn't a qualifying ignition barrier for foam- not all wet-spray or blown-in-blanket systems meet the spec.

It sometimes takes ~R50+ to be fully rid of ice dams on unvented cathedralized ceilings in my neighborhood, but heat leaks aren't the full story- temperature differences on the roof can be generated by direct solar gain through different depths of snow causing a localized melt with re-freeze lower down. The black roofing may be a contributing factor, exaggerating sun-derived temperature differences that might be absent or much reduced on a lighter colored roof. (Mounted on furring or purlins with reasonable venting between the metal and roof deck the temps might have been more even too.) I've seen one instance of a home with large overhangs where the column of air warmed by the sun shining on the south wall created a little melt-zone just outside the top of the wall, that re-froze into an ice dam, but it didn't usually back up to the point where it leaked inside, but it got under the shingles out on the overhang causing some minor local damage. (I should have taken pics- it was a weird one. The same construction on the E,W, & N sides didn't have that issue.)

I am now wondering that if I just locate a register and a return in the attic and condition the entire house I could rid myself of humidity worries.  this may be high on energy costs, though.  If the proper ignition barrier is installed I think I can do this.
this gets confusing with the term conditioned space.  My hvac contractor refers to actual air exchange in the attic within this conditioned space.  The sprayfoam installer refers to the attic as conditioned once sprayed without air exchange.
I also have an erv, not an hrv.
by the time I run the woodstove in the basement the air will be dry and all of this will be moot if we dont cook ourselves out of the house!!
I thought the code reads that no ignition barrier is required if the conditioned attic space is for mechanical use.
Clearly if I put registers and returns up there I need the barrier.
this is my final build and we wont be moving.
what is the best way for me to actually monitor the attic humidity levels.
It really does not stay below 20 degrees here for days at a time often so I am hoping with the erv and open cell I will be ok.
Thanks for all of your input and knowledge.
I really appreciate it.
greg

If all of the insulation is at the roof deck, fully conditioning the attic with air exchange has zero effect on energy use. "Conditioned space" refers to the enclosed volume inside the pressure and thermal boundaries of the building. These two boundaries are not always identical, but in this case they are.

ERV or HRV, the wintertime humidity can still be controlled by the ventilation rate, but with ERV you can run somewhat higher average ventilation rates while keeping it down to 30-35%.

Apparently revisions have made to the IBC in 2009 now waives ignition barrier requirements in attics & crawl spaces if the material met some other testing on assemblies representative of actual construction: http://www.sprayfoam-mag.com/articles/foam-plastic-insulation-has-a-special-place.aspx So, you may be OK on that front, provided those updates are supported by your local building codes. (I was unaware of that revision, but I'm sure foam installers are all over it!)

You need not monitor the RH in the attic- anywhere inside of conditioned space will do. The air in the attic will have the same dew point as the rest of the house, independent of the air temperature in different locations. A woodstove doesn't change the absolute humidity (dew point), even if the RELATIVE humidity drops in the overheat room with the stove running full blast. There are sub-$20 relative humidity monitors available for keeping tabs on it, as well as more expensive versions wiht higher accuracy, but the cheap ones are good enough, eg: http://www.natlallergy.com/prod/1890/acu-rite-indoor-humidity-monitor-thermometer-model-00325.html
http://www.amazon.com/dp/B0013BKDO8/ref=asc_df_B0013BKDO81418622?smid=ATVPDKIKX0DER&tag=dealt453766-20&linkCode=asn&creative=395093&creativeASIN=B0013BKDO8

Get a couple, make sure they agree with one another when in the same room for an hour, then place them where you deem reasonable. Somewhere where it's 68-70F most of the time (and not with highly variable in humidity sources like bathrooms with showers) would be reasonable. If it's 68-70F, and under 35% RH it's coldest out, you're good. If it's above 35% at those temps when it's below 20F out you need to crank up the duty cycle of the ERV a bit.