I’m looking for some advice or a possible solution an ongoing problem. I have a residential remodeling company and we built a addition for a customer. The addition is a single story family with kitchen. We built the addition with a cathedral ceiling. The cathedral ceiling was built with 2×10 rafters , structural ridge, insulation , proper vents, ridge vent, and soffit vents.
The first sign of trouble was the first winter, the house/addition has vinyl siding with vinyl soffit vents. The customer first called to say she was seeing brown staining in the ceiling in certain spots. My first thought was a roof leak, but there had been no rain or snow. When I went to take a look I noticed that the soffit vents had dirty icicles hanging from them. I opened the soffits up and noticed a thin layer of ice on the under side of the sheathing. My first thought was that the proper vents were blocked somehow so i removed a portion of the ridge vent and took a look down to see if it was open all the way to the soffitt and it was. The next thing I did was to remove the ridge vent and replace it with a larger vent and to replace the vinyl soffit vent with 2 rows of 2″ wide aluminum soffit vent, thinking that there was not enough air flow to control condensation.
Unfortunatley I received another call saying that the stains in the ceiling and the icicles were still happening. Scratching my head I called a couple of people in the field to come take a look and maybe see something I hadn’t. The first was a home inspector, the second was the local builing inspector, third the owner of the lumber yard I use, and the fourth was my roofer. They all said the same thing everything looks ok. The Home inspector recommended that I set up a hygrometer and a thermometer in the room to see if maybe there was a high humidity in the room due to the kitchen or anything else. All readings came back normal.
The problem is still occuring and seems to occurs with tempreture changes. I have built a number of cathedral ceiling projects for other customers and never had an issue. I’m looking for any suggestions or someone who might be able to diagnose the problem for me to fix. I have no problem fixing the issue for the customer , I just don’t know what to fix.
Replies
What I would like to know is, was there a vapor barrier installed before putting up the interior sheeting. Also are there any recessed can lights in the ceiling. or any other penetrations from a ceiling fan or other hanging lights?
Virginbuild
Where is the house?
Andy Engel
Senior editor, Fine Woodworking magazine
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Andover, MA
I was called out by a well known local contractor to look at a similar situation this past February.
A nice large home with a central large room with cathedral car sided ceiling....leaking in cold weather as the sun came overhead to the northwest side.
Several errors in building practice were observed...
Master bath w/large jacuzzi and shower vents with the fan directly into the attic space that adjoins the higher pitched cathedral ceiling system....
crawlspaces are unvented and unconditioned and only partial poly barrier....and moist.
And the great room insulation was installed to the I joist by stapling to the side of the bottom chord rather than the flat and the insulation was not continuous, nor was there a continuous ceiling vapor barrior, nor was there drywall w/tape intalled prior to the installation of the car siding.
Summation....heated, humidity ladened air seeps through all the cracks in the cathedral ceiling, and from the house's side wings with heavy use bath areas and/or open crawlspaces and the the humidity is "thermosiponed" into the rafter bays where it frosts on the interior side of the roof sheathing during the cold evening hours until the sun rises and shines...then it rains in the great room!!!!
First remedial action...vent the bath fans through the roof, seal the crawlspace dirt floors..and hope this will correct the problem.
We will have to wait until next winter and a good cold spell to see if that is enough.
I suspect the contractor will bite the bullet and have to remove the car siding and reinstall the insulation correctly, plus a continuous vapor barrier, taped drywall and then replace the stained car siding in a 36x40 great room. Probably a $20K mistake!!
My clients relative humidity was (40%RH)~ normal....but you might check yours out! Things that contribute to excess humidity are: houseplants, acquariums, water fountains, spa's, steambaths, unvented to the outside clothes dryers, bath and kitchen vents, and ventless fireplaces/heaters , as well as gas appliances that are improperly vented.
Sorry to rain on the parade....but it may be serious!
..................Iron Helix
couple of things, no bath vents in this room, both bathrooms are in another part of the house. I did check the humidity for about 3 weeks last april. highest reading was 44% , also had another meter in another room in the house to compare too and they were with in 3 or 4 % of each other. Addition was built on Sona tubes. the bottom of the joists are sealed with plywood and insulated, there is air flow under the room. There are a couple of recessed lights in the ceiling , but the staining is over certains area not close to the lights. Kraft face insulation was used on in the ceiling and I can not remember if is was stapled to the sides of the rafters or on the front.
Just a few points to ponder
1)Is there any pattern to the "brown spots" on the ceiling?
Are the localized or all over the place?
All in the same rafter bay?
Low and close to wall?
Near the ridge?
2) Is the opening in the roof sheathing at the ridge adequate?
3) Any outside sources of water vapor nearby? Dryer, power vented furnace or power vented water heater?
Mike
It's O.k. to think out of the box, Just don't walk off of the plank!
If there is ice, you are in a cold climate. What did you use for insulation? If it was fiberglass, there is no way that you can get enough in a 2x10 rafter to prevent large heat loss. The warm, perhaps moisture laden air, is escaping and condensating.
My gut tells me you need better insulation. Heat rises and can get trapped in cathedral ceilings. Is there a fan to move the air back down? Did you use a vapor barrier? Do you have continuous propa vents the whole length of the rafters?. If there is that much moisture up there, it has probably wet the insulation too, reducing it's value.
How do you fix it if this is the problem? If you need more insulation, there are three ways to do it. 1.) Re frame a second, lower cathedral and remove the existing sheetrock ceiling and insulation. 2.) Remove the existing sheetrock ceiling, add depth to the rafters and re-insulate and re-sheetrock, 3.) add 2" of extruded foam to the existing ceiling and re-sheetrock over that. One more option might be to remove the existing sheetrock ceiling and fill the rafters with spray foam. I don't have much experience with the foam so I don't know what R values are achievable. In my cold climate, R-38 is the minimum for ceilings.
I'd also be questioning the effectiveness of your vents. Most structural ridge beams are fairly wide and ridge vents aren't. Some types of ridge vents don't work that great, especially the roll out style. Tight nailing of the cap can close them off. I wonder if those smoke guns they use to test houses for tightness could be used to test your vents. Even the best vents should be combined with adequate insulation.
Beat it to fit / Paint it to match
R-30 Kraft face insulation with proper vents the entire rafter. We made sure when we installed the 2nd ridge vent that there was good air flow. There is also a ceiling fan in the room.
Just more questions...trying to fit the pieces together! Something is missing!
Are all the rafter bays showing signs of moisture w/ icicles in the winter?
If not all then how many, and where are they located?
When you married the addition roof to the present house was there a plumbing stack that was buried in the valley framing?
Did you cut an opening from the new valley attic into the existing attic area?
If the attics are connected what appliances, etc might be vented into the existing attic.
Are the leaks still happening in our now warmer weather?
What was the RH in the winter months?
How many windows are present...did they sweat during the winter?
What is the house''s heating system....do they have a ventless fireplace?
Did you confirm that the clothes dryer was properly vented?
When the vinyl siding was installed did you use any tyvek or similar product?
Describe the wall construction system.
.................Iron Helix
From the symptoms (water stains, visible moisture (ice) present in the rafter bays, it's obvious that moisture is getting into the rafter bays. In a cold climate, as you've discovered, that's a bad thing.
So, the vapor barrier...my opinion? If using FG the only decent (or least worse) VB would be poly, from plate to plate, with any seams overlapped and sealed. Still, that's not the best.
Any holes in the ceiling? You answered that weith the comment about can lights and a ceiling fan (hole from j-box). Right there you have holes in the VB. Even with careful detailing.
While the relative humidity checks you did aren't terrible, cathedrals are animals to be always held at arm's length. They'll bite you if given the chance.
You know how the roof and addition was framed. So step back and have a thought or two. How can moisture be getting into the rafter bays from inside the structure, or from within the framing itself (example, think balloon framing). If the framing is tight with no continous paths, then the moisture is getting into the bays from the interior space.
It's coming through the drywall itself or through cracks and holes (can lights and j-boxes). The vapor hits the cool sheathing, condenses, then freezes. Then drips down, staining.
For cathedral ceilnigs my personal preference is for rigid foam board insulation to be applied to the faces of the rafters. Gap the sheets during install, then foam the gaps with canned foam. That is a vapor barrier.
Furr over the RFBI, then drywall.
I'm not a fan of track lighting, but I'd can the can lights and use surface mounted track lighting with the wiring hidden in the gap provided by the furring strips. Protected if required. Sure their are air-tight can lights, but still, it's not just the air infiltration, but the heat, as well as the hole in the ceiling. For the ceiling fan I would have built down and surface mounted the box. Essentially, no penetrations in the foil-faced vapor barrier.
In your case, it's too late for a "what I woulda done" dissertation, instead it's "what should I do" time.
From your measurements, it sounds like the moisture isn't excessive in the house. If there is no way that moisture is being short-circuited and being drawn into the soffit vents from the outside, then it comes down to addressing the issue of a compromised VB on the interior.
Either demo to the rafters and redo, or perhaps you can apply a proper VB right over the existing stained ceiling. I'd prefer the former to the latter. Take it down to the framing. But that is messier. But more thorough.
There are code issues as to how a cathedral can be detailed, look into it. Embrace the code or see if you can work within it, and with your inspector, to get what you want.
You need to prevent moisture from getting into the rafter bays. and what vapor gets in there, you need to prevent it from hitting dew point where it can condense and cause problems.
You have choices regarding vapor barriers, you have choices regarding insulation choice (cells) as piffin mentioned in an earlier post. One thing I've learned over the years...FG is a compromise.
Andover...memories of an old girlfriend...not sure if they're good memories or bad ones, though...<g>
Edit: did a google to see if I could give you something more substantial, here's link that might be helpful: http://www.buildingscience.com/housesthatwork/cold/minneapolis.htm
Edited 4/18/2005 8:49 am ET by Mongo
Other than the vents, the two most importnat parts of this package are missing in your description. You need very good insulation and a vapour barrier on the interior face, uninterupted.
All you say is that you have insulation in a 2x10 space with propavents.
If this is fibreglass batts, you have the worst choice in insulation. if you neglected a good VB, you are inviting moisture into the space to make the condensation problem.
Better insulations include denspak cellulose, BIBBs, spray foams, or a sandwhich with a sheath of foil covered foam over the insulation - on the interior surface under the sheetrock.
I have done catherdrals with the spray foam, the BIBBs, and the foam over batts. The latter is most prone to potential condensation.
I did do one house with catherdral with 2x12 insrtead of lesser framing, and used batts with vents, and with haevy plastic for a VB. This was before i knew very much about this issue, and was working for another company at the time, and it has had a minor drip in a valley location where the venting is probably not effective, but otherwise it is doing OK to the point that there are no water signs showing inside. When I went into things to investigate that one drip, I did find a minor dampness to the plywood roof sheathing in several places, and I increased the size of the soffit vents.
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