Hi all! long time lurker, passed a great deal of time reading the forums back then before i commited to ICF for my new house. 3 years later in the construction ..many problems but one more serious arise and now i need your help !! here is situation : - ICF walls 2.25"EPS// 8" concrete // 2.25"EPS - open web steel joists with steel deck flat roof ( also 2 first floors are done this way ..) - roof deck as from 4" to 8" of EPS on it ( slopes) with a EPDM membrane laid on top of it ( glued to parapet on the contour ) and 5" EPS underside the deck ( interior ) - located in Quebec near Montreal ..cold winters This is our first winter, i haven't installed the air exchanger yet as the bathroom vents outside directly and it let it run for some time after we all use the shower ..then still many small leaks around some windows etc to compensate starting yesterday, water strated to dripp from a certain spot in the house, from the roof thought it was a leak ( thought i had worked them all out form the roof ...ahh ..exhausted ) but this morning i removed some part of EPS and notice that the steel deck was all humid with condensation and some droplets forming haven't installed any water barrier other than a thick poly on top of the steel deck before adding the insulation back then ( 3years ago ..ouch ) i've been having -windows leaks ( error from window company ) -roof leaks( never had time to complete the parapet finish and flashing ..so now the Tyvek had time to torn and leaks .. ) and i feel like i've been patching for water leaks for the last 100 hours of work i've done on the house ...and it took me a few months to be able to gather that many hours with the business and other matters keeping me busy so i would really like to know what are your recommendations on what i should do next should i install a thick vapor barrier inside underneath the EPS ?? just verified that humidity is a 40-45% in the room where i had the condensation but yesterday it was raining and it might have been a little higher i can post some pictures if required thanks for your time all happy holidays :)

ah yes also .... we took the time to fill up all the up and down spaces created by the steel deck with 1.5" EPS strips back then
the 5" EPS underneath is screwed through the steel deck, and poly foamed in between each as much as we could
i shoot some polyurethane all around on the perimeter to seal the ICF foam to the roof foam

the seal is not perfect as it was a PITA to fit the 5" foam blocks between the steel joists etc ..but the job is pretty good at the end i believe

Are the steel joists under the roof deck in a conditioned space? If you have condensation, that means you have surface temperatures that fall below the dew point of the air. Which means when the air hits the cold surface, it condenses and leaves water behind. If there is air movement, the problem compounds itself, because you're constantly pulling moisture out of the air. So your options are to raise the temperature of the surfaces around the components that are condensing, lower the dew point (lower the RH) of the air around your steel trusses, and insulate the condensing surfaces to prevent air from getting to the surface.

Pictures I'm sure would help a bunch to figure out what you have going on.

Another thing. You stated that you haven't installed an ERV and your bath fan directly vents outside. When you pump air out of your house, just as much air is going to find its way in though the cracks and crevices. This air is unconditioned, so it could be bringing in excess humidity. An ERV at least exchanges some of the humidity.

here is a quick picture ( sorry for quality ) of the area where i had some dripping last night and where i saw condensation on the metal deck you can also see the roof drain as it was near it, i had to undo the isolation on the drain also to check that it was not only leaking ... then 2nd picture shows a quick view of the wall/roof/joist setup cheers

2nd try seems like this forum is not OPERA compatible :p

The EPDM/plastic/steel acts as an unvented exterior vapor barrier, exactly what you don't want in a cold climate. You could try using a fan blowing outward to depressurize the house to help find any air leaks (perhaps with a thermal camera). You might have to always run slightly negative pressure to keep interior air away from the steel. Exterior air in the wall is tolerable, interior air isn't (it has a high moisture level).

jonr: please explain ...exterior vapor barrier ? there is insulation on top of the steel deck, also 1-2 ply of polyethylene sheet and the EPDM membrane which should be near 100% sealed ...

is the 5" of EPS i installed under the deck a positive or negative ?
when i decided to do so, i thought that maintaining the steel deck at a medium temperature between exterior and interior + having the 5" thick of foam to block air movement under it, would suffice to alleviate any possible condensation ...was i wrong ?

i've started my deshumidifier a few moments ago ( morning ) and it was at 55-60% .... now that i don't really understand...already down to 40% though

i don't see any condensation on any protuding parts of the steel joists though

also please note

right now everything is open, as we have not yet installed any ceiling material
but it will all be suspended ceiling tiles in the next months/years
that will give from ~13" to 20" of free space in between

of course for me this counts as "inside" so i never planned any ventilation in there as it wasn't supposed to be an isolated part of the house
wanted it to be at approx the same temp as the rooms under it ( all bedrooms and 1 bathroom )

what is funny, is that i've had several leaks in the past , 90% on perimeter due to the "parapet" temporary seal failing
but i've never seen any condensation or drips from it except on the 2 roof drain pipes ( 3" abs ) which we now have insulated with airfoil

air leaks are easy, i know all of them

as all my walls are concrete and almost no holes, i have leaks only around the windows
and since i've had a problem with windows leaking, not all finished yet

Say it's 20C inside and -20C outside, the steel is in the middle of the ceiling/roof and there is no air flow. The steel will be 0C, well below the ~9C needed to avoid condensation. So you have to stop all inside air from reaching the steel. An alternative is to go down to 25% for the indoor RH. Or remove the interior foam wherever there is condensation (to allow the steel to heat up).

jonr: should've installed more FOAM on TOP and not foam at all underneath ?

that was my first idea ...before the EPS company pointed to me that it was going to hard to install that thick foam on top
for i don't know what reasons ...

is 5" EPS vapor proof enough ?

i know i have many small leaks ...should i only focus on blocking the leaks ?

what can i do to prevent the inside air to read the steel deck ?

then if manage to do this, won't it make the steel deck even colder and have condensation on other side ?

i seriously dought that i would be able to seal the air completely since we have seal around all of the steel joists

if i have to remove every #$%#$% piece of EPS from underside and redo the top membrane i'll do it
i'm here for 20years + ( unless i die before ) and i don't want to have to be crazy carefull about not taking showers too long etc ..just because of that

how is the concrete in the ICF walls , not causing condensation then ?
it is far from perfectly sealed by the EPS

also we used 2X3 wood pieces on the permiter to hold the ends of the steel deck ( we placed them before the pour of the icf walls so they are "stuck " in the concrete ) and i've already needed to remove
a few because it is getting wet from leaks and or condensation ( althought they are all sealed in 1" + sprayed polyurethane)

i thought i had major leaks but now i'm not too sure if some of the wetting isn't only due to condesation as we haven't had any real leaks during all summer/automn
and now i've got a few places where it is dripping

if i need to remove all EPS foam i'll probably replace all those wood POS with some alum/steel angles

can't stand wood in the walls...everywhere i had leaks it's all started to rot

http://imageshack.us/clip/my-videos/97/9gk.mp4/

quick video i just made to show how the ceiling roof is made

found a few more spots where i is still either humid or traces that it dropped water a some point in the last 2 months
( patterns in the dust on top of the few installed ceiling tiles .. ...again on perimeter only )

Something to consider: make the drop ceiling nearly airtight (probably with plastic). Leave a dehumidifier in the enclosed area above the drop ceiling set to 25% (or adjust it based on outdoor temp). If the area is well sealed, the dehumidifier won't cost much to operate. But the living area can be at a higher and more comfortable % RH (say 50%, depending on window condensation).

jonr: nice idea ...that might be part of a solution what i will need to figure out in the following weeks, is wheter i have to tear everything out this spring and redo the whole roof or i can add material/mechanics to have it possible to leave what is already there if i would be to seal the living air from the EPS/steel deck completely, would it work ? anyway you think i could do it ? is 5" EPS considered vapor/air proof ? i guess it wouldb't be that long to add some reflective vapor proof membrane sticked on the EPS and bridge all the longitudinal gaps the problem would still be on how to seal around all the joists again ..if it is only labor time and some taping/memrbane fitting ... might be worth it if i need to remove insulation from underneath , i'll probably have to empty all of the rooms one by one and seal them off to try and not get foam dust everywhere the foam will probably be 3/4 unusable from all the gluing and i would have to remove the EPDM membrane, redo the drains, remove EPS slopes and add some layers to all that new EPDM ..ouch ouch ouch ouch i don't believe i would be able to have the suspended ceiling all leak proof but i sure can make it resistant to air draft and i was planning to use some FG bats glued on top of the tiles to help with noise propagation then the temperature of the isolated place would probably be lower a bit ..any problem with that or would it be better ?

I think that it is interesting that your drain areas are condensing, and your steel trusses are not. Steel is a good thermal conductor, so the truss should not be a lot warmer than the deck. It seems to me that the drain is going to have outside air in it, so this time of the year is going to be much colder than the rest of the roof, so if something is going to condense it will be the area around the drain (and the drain itself), so you might try something like a spray foam to keep the interior air away from the deck around the drain and the pipe. I would say one more thing about your assembly (jonr has already alluded to it), the deck itself has no real way to dry, so if water gets to the deck it is going to stay there. This means you are going to have to be real careful about roof sealing, otherwise that thing is going to rust and come down on you someday.

I will guess that a couple of inches of cellulose or fiberglass for sound would be OK. More and the ceiling area might get so cold that the dehumidifier would ice up. But that could be fixed by getting some more heat up there.

Even if you move the insulation, you will still have a EPDM exterior vapor barrier. It would require venting to fix that.

If there is a drain/vent pipe that is conducting cold and causing condensation, it might be easiest to wrap some heating wire around it. Warm pipe equals no condensation.

For commerial construction in cold country it is standard procedure to insulate roof drains. The pipe insulation should have a vapor barrier. Depending on location, vents, especially if there is a horizontal run near the exterior termination, may also need insulation.

Bruce

Posted By JinMTVT on 23 Dec 2011 10:14 PM
jonr: nice idea ...that might be part of a solution what i will need to figure out in the following weeks, is wheter i have to tear everything out this spring and redo the whole roof or i can add material/mechanics to have it possible to leave what is already there if i would be to seal the living air from the EPS/steel deck completely, would it work ? anyway you think i could do it ? is 5" EPS considered vapor/air proof ? i guess it wouldb't be that long to add some reflective vapor proof membrane sticked on the EPS and bridge all the longitudinal gaps the problem would still be on how to seal around all the joists again ..if it is only labor time and some taping/memrbane fitting ... might be worth it if i need to remove insulation from underneath , i'll probably have to empty all of the rooms one by one and seal them off to try and not get foam dust everywhere the foam will probably be 3/4 unusable from all the gluing and i would have to remove the EPDM membrane, redo the drains, remove EPS slopes and add some layers to all that new EPDM ..ouch ouch ouch ouch i don't believe i would be able to have the suspended ceiling all leak proof but i sure can make it resistant to air draft and i was planning to use some FG bats glued on top of the tiles to help with noise propagation then the temperature of the isolated place would probably be lower a bit ..any problem with that or would it be better ?

JinMTVT - You have an number of problems and by not solving them one at a time you are driving yourself nuts!
First - finish the roof so you are sure all flashings and caps are properly installed. This should have been done by the roofing contractor.
Second - make sure your ventilation is running properly. Even though you live in a fairly humid area (and it was wet when I was out in October) the cool outside air coming in should easily drop your r.h. to below 40%.
Third - Your have used tapered insulation on the roof deck. The 4" areas will only have R20 max. This does not meet code so you have added the eps underside. This brings you close. The areas with 8" are close with just the above deck eps however the steel deck and owsj conduct heat away. Also the air can leak through many areas of the below deck eps. Any air reaching q-deck or exposed steel will have the potential to condensate on them.
Yes you can tear everything apart and start over but that might be a little extreme. If you have the ventilation working and still have moisture problems on warm days you need to check for more leaks. BTW is your basement floor poured? Is there a v.b. under the concrete? If you have no leaks on warm days and you have no leaks when it is raining (or you run a hose up there) then the dripping on cold days is still condensate. You need to seal the air from reaching the cold materials plus you need to improve the R value of the owsj to code minimum (R40 I believe in your area but it might be a little less.) Both these objectives can be reached with spray foam. A minimal layer over all the eps you have placed under the deck should air seal it. Spraying 3" of foam an all the exposed steel web would get you close to code. It might be cheaper to line one side of the steel web with rigid foam and than spray from the other side. But it has to be air tight!
Also all the foam both walls and ceil has to be thermally protected. The building inspector might allow for a suspended ceiling to be the thermal protection if there is no ventilation in the space. Other wise you will probably have to spray it with fire fluff. I'm not sure what the R value for fire fluff is but it might act as part of your R value for the open web steel joists. It might also be sufficient air seal right over the existing underslab eps so that you would not have to spray foam it first. We use them to get required fireratings in commercial buildings so you should be able to find someone in you area that does this and has the info. It might be part or all of the solution you need.
Also make sure any sanitary vents and rain water leaders are insulated to at least 10' from the roof penetration.
Bob

Thanks Bob for your time and effort.

Update ..
since i am having no help from the person that told me to do as this ... i will need to proceed on my own

i've not invested too much time yet on this as since weather is warmer we had no condensation of course ..

so now i was looking at a few solutions ...
but the only one that seems logical is to completely remove the 5" EPS from underside of the deck
and then redo the complete roof assembly ( !@!##$%!@#$ 2000sqft ) by adding the required EPS and vapor barrier on top of the steel deck

right now, on trop of the deck resides 3" EPS + 0.5 to 4" EPS tapered .. so how much foam should i add on top to meet code and have the best
isiolation VS foam price ratio ?

i guess that code is r40? that would mean around 10" total of foam
i do not think it would be easy to add 7" of foam ..as there is a door on the roof that is only 3-4" from the membrane height ..
also would need to add some height to the "parapet" all around which won't be up to 42" anymore

what do you guys suggest as best membrane on top of steel deck before EPS ?

i guess we have to glue everything together if we don't want to puncture it ??

should i try to work with some aluminum reflective barrier to also help with insulation ?
there are soo many products available today ...

beeing here on greenbuildingtalk :) new question for you guys . since redoing all of the roof system .. WHAT is the best way to insulate a steeldeck flat roof that is going to be used as a terrace in very cold climate ?? (we get down to -35c during winter i believe ) just to know if there are new things i've missed in the last 5 years or so :)