Chris,

the roofer told me however that because of the roof's pitch a z-closure isn't needed and that it was built "according to book standards"

What do I tell him / what do I do now? Assuming of course that the roof is indeed leaking, which we don't know yet for sure

Posted By Sav on 02 Jun 2012 03:49 PM
Chris,

the roofer told me however that because of the roof's pitch a z-closure isn't needed and that it was built "according to book standards"

What do I tell him / what do I do now? Assuming of course that the roof is indeed leaking, which we don't know yet for sure

Sav;
Ask him to show you the manufacturer's instructions that says it is not needed.
Regardless of wether it leaks or not the "Z" serves several purposes:
1. weather resistance
2.stiffens the ridge cap edge
3.keeps bats and other critters from nesting under ridge cap.
4.Prevents squirrels and field mice from an easy access to chew thru the roof deck into your house.
Wind driven rain will go "up hill" , it is absurd to say it is not needed.

Sav, I'm in Annapolis and am considering a metal roof (Thanks to input from other forum members).  Would you text me separately the name of your roofer so that I can avoid them?

Thanks.-C

thanks Chris that's very helpful and intersting indeed. I never thought about the mice going up there!

Cindi one more thing I noticed on my journey to a new roof: roofers don't know much about insulation. And insulation companies don't know much about roofs. Yet it's one system that needs to be planned correctly. Whos gonna do the planning? YOU or else you'll end up with crap. check out the buildingscience.com website. I think they are biased towards spray foam so I wouldn't take everything as fact what they write. They all have hidden agendas these days, not just the politicians ;-) It's not the cure-all but if you do renovations it may be the only good choice to use spray foam. I found XPS boards are way better. They don't stink, they will last a long time, you can cut them in shape and have as many layers as you like, then spray from a can to seal gaps. You could even do that under the rafters if you can afford the labor involved. Just as with the roofs, estimates for the exact same insulation job can range from 100% to 350%!!!! If you can vent the roof, do that. unvented as in my case: too much risk. The roofers tell you metal gets very hot, that's BS. I have a laser thermometer and can assure you all neighbors here have at least 50 degrees more on their roof than I do (they have asphalt shingles). I highly recommend buying aluminum since you are close to seawater and I would check solar reflectivity ratings. Some nice colors are very inefficient and will make the roof hotter than others. To give you an example, I like to play with my thermometer :) On a random spring day, black surface had 154F, white (the chimney): 87F, cream: 113F and light cream, my roof: 105F and air temp was 78F another recommendation, have someone research all steps in advance and check on the crew as they complete milestones. You'll be surprised some companies hire people off the street to do a mechanic's job! Put in the contract you want your yard clean and free of nails and dirt and if they don't finish on time some kind of penalty in $ so the job doesn't drag on forever. Also add to contract: you want the roof entire tarped at the end of each workday. Did I mention we got stuck with half a roof during a tropical storm? I was lucky, however, the roofer was very responsive and came within an hour to put up a tarp. Lot's of advice you didn't ask for, sorry about that I felt like telling a story ;-)

Posted By cmkavala on 02 Jun 2012 04:15 PM

Sav;
Ask him to show you the manufacturer's instructions that says it is not needed.
Regardless of wether it leaks or not the "Z" serves several purposes:
1. weather resistance
2.stiffens the ridge cap edge
3.keeps bats and other critters from nesting under ridge cap.
4.Prevents squirrels and field mice from an easy access to chew thru the roof deck into your house.
Wind driven rain will go "up hill" , it is absurd to say it is not needed.

Chris, have you seen any metal SIP roofs have condensation issues on the inside?

Chris, have you seen any metal SIP roofs have condensation issues on the inside?




Never

Sav, got it. Thanks for the input!

OK guys I need again your expertise! I want to borrow the legal doctrine "preponderance of the evidence" to conclude: yes most likely it's condensation, not a roof leak. Dana, I read what you wrote in other forums about moisture drive through open cell and I compiled a lot of info from other sources, too. I did some experiments with the garden hose and I took down several XPS boards. It really appears to be "moisture vapor drive" driving all that moisture through the OCSPF. Those spots where the XPS had good contact with the OCSPF are likely to be wet. North and east are likely to be wetter than other sides (house is almost perfectly aligned) Where the spray foam wasn't touching, things appeared to have remained dry. Again these are just random checks. Also wetter at the top rather than bottom of roof. Problem: Now I am stuck with $2,000 worth of XPS 2"...What to do next? Possibility #1: Take down just the top row XPS boards to let the vapors exit into air conditioned space. That would reduce the insulation effect a little but at least it would help still, I don't have to take it all down or even trash it. Possibility #2: take it all down, install XPS with a 1" gap away from the OCSPF. Again less insulation efficiency but it will still help shielding radiant heat and avoiding most air contact in the winter with the colder OCSPF Possibility #3: take it all down, put it in the garage, build a new house and use it at the exterior (^_^) The point for installing the XPS in the first place was: improve insulation + sound barrier, cover the smell of OCSPF, and the flakes coming down from the trimmed OCSPF bothered me like crazy HELP! What should I do next?

one more question on moisture drive. If a muggy hot day lets moisture in, wouldn't a hot, dry day suck the moisture back out??
It's an unvented metal roof directly installed on wood planks, no air gaps.

Hello Sav, let’s help you out. Since Maryland, the location of the house, is in Climate Zone 4, a vapor retarder is not required by the code. In the weather conditions you mentioned when the leakage occurred (+ 90°F and 90% RH), there will be a very strong vapor drive from the outside of the building into the interior. However, the metal roof deck is a vapor barrier. The diffusion of moisture would not be a problem, so it appears that it is a roof leak. Repair the roof - end the problem. With a roof leak, Icynene LD-C-50® would allow the drainage of water down through the insulation. When the insulation gets wet the R-value of the insulation is reduced and that’s why the performance of the insulation was not as expected. However, rest assured, the insulation will dry quickly when the rain stops and the high outside temperature heats the roof surface. The application and sealing of the foam board would serve to place both insulation and a vapor retarder on the underside of the Icynene. The Icynene was wet so it would allow the space between the Icynene and the foam boards to heat up. There would be a pressure that develops as the moisture in the space is heated. There should not be a vapor retarder on the inside surface of the Icynene. After considering the information provided, it seems that a leaky roof is the cause of the problem. I hope this helps provide an answer to your moisture problem concerns. Please let me know if I can help you further.

Metal roofing flat against planking is an extreme vapor retarder, so any water that gets under the steel and seeps in there stays there until it can dry through to the interior. When the sun heats up the metal it raises the vapor pressure to extreme levels, but unless there is a ventilation path it still can't get out except through the open cell foam.

By putting up the XPS you're blocking that path, so the moisture between the metal roofing builds up to the point where it's dew point is such that it condenses on the XPS. If you added 3" of open cell foam in place of the XPS it would have the same thermal resistance as 2" of XPS, but it would allow that moisture to dry toward the interior rather than build up.

But the real source of the problem is the amount of rain/dew water getting by the metal roofing in the first place, not water vapor diffusion through open cell foam on days when outdoor dew points are high. If there were a ventilation gap between the metal and the roof deck it would usually tolerate incidental leakage and you could keep the XPS. But with no gap you have to either find & fix the leaks (which may be very difficult), or allow the assembly to dry toward the interior (==no XPS). No easy solutions come to mind.

Icy building Science: "when the leakage occurred (+ 90°F and 90% RH), there will be a very strong vapor drive from the outside of the building into the interior."

That's not a very strong vapor drive- it's quite weak in fact, compared to the vapor drive of a sun-heated wet roof deck, or sun hitting a dew/rain wetted masonry wall. Very little of the moisture coming through the o.c. foam is from exterior-AIR vapor drives.

But rest assured that it has never been 90% RH @ 90F (87F dew point) anywhere in MD. Dew points that high will occur during the summer extremes in equatorial Africa or the Amazon, but pretty much never in the mid-Atlantic region of the US. (I may have happened at least once past 10,000 years, but not since records have been kept.) The highest dew point recorded so far this year in Baltimore MD is only 72F (on a day when it was in the 90s), and the record max-high dew point for Baltimore is still less than 80F. http://weatherspark.com/#!dashboard;a=USA/MD/Baltimore

Icy building Science thank you for the insight. If you do have some affiliation with Icynene I would like to ask you to PM me your details so I can
forward them to my roofer.


The problem is I am stuck in the middle. The insulation company blames the roof, the roofer blames the insulation and I have no way of proving ****
which is frustrating

Dana, I appreciate your help very much!

On that day I checked weather.gov for BWI it said 34 deg C, 90+ % RH at the moment
Maybe those stats websites you used show a day average or something.

Now regarding the quantity of moisture going through, I was relying on this resource
http://www.numericana.com/answer/gas.htm#perm

which says in the yellow table 135 grams of water can pass through in 24h at 11 perms per sq meter IF 85%RH -> 0% RH at 23 deg C.
I have 170 sq meters total so I figured up to 20 liters => 5 gallons per day is the max. possibility for the entire upper floor.
But the metal roof at the top does block air contact, I agree, so I would also expect less moisture to come in in that case.
I want to finally finish the cathedral ceiling with drywall so spraying even more OC over it seems difficult.....we would need foot long screws....

Posted By Dana1 on 04 Jun 2012 03:29 PM
Metal roofing flat against planking is an extreme vapor retarder, so any water that gets under the steel and seeps in there stays there until it can dry through to the interior. When the sun heats up the metal it raises the vapor pressure to extreme levels, but unless there is a ventilation path it still can't get out except through the open cell foam.

 

Would the above apply to a steel SIP roof with EPS? Or os this issue with XPS only?

Posted By Lbear on 04 Jun 2012 04:38 PM

Posted By Dana1 on 04 Jun 2012 03:29 PM
Metal roofing flat against planking is an extreme vapor retarder, so any water that gets under the steel and seeps in there stays there until it can dry through to the interior. When the sun heats up the metal it raises the vapor pressure to extreme levels, but unless there is a ventilation path it still can't get out except through the open cell foam.

 

Would the above apply to a steel SIP roof with EPS? Or os this issue with XPS only?

A steel SIP roof is a strong vapor barrier, but even if the outer skin leaks, EPS is waterproof- it won't take on more than a very minute amount of water.  There is no wooden roof deck susceptible to rot in the stack up with a steel SIP roof, and completely unrelated to the issues in this thread.

90 degrees and 90% humidity is a 122 heat index. There's no way you hit that! It's gotta be a roof leak. For condensation to occur between the xps and SF the has to be moisture loaded air moving between these components AND the temperatue of the foam has to be less than the dew point.

I agree, the best way to do it is to have insulation at the exterior. that way in the winter the wood planks will stay warm and vapor from inside won't condensate towards the interior ceiling.
The problem was: my roofer wanted $2,500 extra just to cover the area above the kitchen, which was about 250 sq ft. I believe.
So I figured I would have to be Onasis to pay for the entire roof to be covered like that.
Or, I should become a roofer but I am afraid of heights, damn it!

New numbers, today no A/C was used:
Right now 24.1C outside, 41% RH, 22.8C on the XPS surface, at 6ft height, right behind the XPS (the area above is completely open) there is a 1" gap. I measured almost 26C
in the air gap between XPS and OCSPF!
A small different area is covered with only 4" instead of the 6" and when you touch the OCSPF you can feel the warmth coming through.

So I think even if I took the XPS down and re-installed with an additional 1" gap, it should still help a little to keep the room in good temp AND allow the OCSPF to dry towards the interior, provided the top 2ft are left open / exposed with no XPS board.

Jeepster I hope it's a roof leak actually. it would be easier to handle; however, not easy to prove to my roofer. The National Weather Service says the max were 91F and 97% RH (at 10PM). Unfortunately I can't find an hourly graph to see how RH changed during the day