Moisture accumulation at ridge beam, Solution? ridge vent ?
Hey everyone,
I have an issue on my latest project that baffles me., I can really use your collective thoughts and recommendations on this.
One room in the house, the bedroom is 14 x 13 with ridge beam at center and 12 ft high. The floor is concrete with hydroponic water, heating the slab. thermostat is set at 68. The finish on the ceiling is 1×6 t&g fir directly nailed to the bottom of the rafters. Cathedral style. Between the joists (2×6) is 5″ thick rigid insulation. The rafters are covered with 5/8″ plywood and on top of that is “Tyvek Roof Liner, premium roofing underlayment”. The finish roof surface is standing metal roof and the color is dark bronze. The metal roof has been on for at least six months. We have been through many bad rain storms here in California and not a leek in the place. Last Tuesday I get a call from the client his ridge beam is wet in the bedroom he noticed it at approximately 2:30 in the afternoon. it has never appeared before. I head over yep, about 2 to 3 inches down from the ceiling is moist and is the length of the beam except about the last 3 feet at the north end is dry. the following morning I return to see that it is now dry. I do a short investigation, remove vent cap to notice no moisture entering from the exterior. the client arrives haome later that same day and texts me, ‘It’s staring to get wet up there again, damn.” I reviewed the pictures taken of the project and no water lines are in the vicinity of the beam. There are no roof penetrations. I have posted a video I’ve taken showing what I have done to investigate , but I’m a carpenter and not a film editor so it is not of the best quality but should give hopefully enough information for a possible solution. The video may be viewed here.
The video is to help you with your thoughts and recommendations . After ruling out that no water is entering from the roof, there is no water pipe leaking inside the ceiling cavity. and remember that 3feet of dry beam at the north well there’s a roof from the other part of the house over that area of the bedroom roof. The only possibility I can come up with is atmospheric, the moisture in the ceiling cavity is condensation caused by a closed ceiling cavity. the architect did not specify any ventilation, ridge vent, in addition to lower vents at the bottom of rafters, possibly, as it would deter from the clean architectural look she was after. So now for corrective measures, a ridge vent running the entire length of the ridge is doable. Do I need to have vents at the bottom of the rafters to create a flow of air or does the heat accumulating and rising, exit the roof vent on it’s own .
Thanks in advance, Mox
Replies
I'd want to know the humidity in the room. Seems to me the moisture is either coming from inside or there's, eg, a leak farther down the roof and rain is getting in and being conducted up to the ridge. It's not "atmospheric", I don't think.
I don't think adding a ridge vent is a good idea. For a ridge vent to work there'd have to be a source of incoming air (eave vents) and suitable channels up the roof to the ridge.
Plus it doesn't make sense to do anything until you've identified the source of the moisture. (Have you considered the possibility of a leak in the hydronic heating?)
(BTW, a "hydroponic" system is used for growing weed, not heating. If there's really a hydroponic system here then that's likely a source of several problems.)
Dan, Thanks for that hydro correction. So I gather you think the roof vent is useless if no incoming air is available? there are no leaks in the roof or the tubing in the radiant floor heating. so moisture then needs to be entering the ceiling cavity simply by hot air rising and accomulating at the ridegmaking it's way throught the ceiling T&G boards into the ceiling cavity. if there was a roof vent would not this rising hat air continue through the cavity and out the roof vent? and sorry for posting in two categories, new here.
The moisture's coming from somewhere.
Like I said, you need to know the humidity inside the room. For that much moisture to be coming from inside the humidity would have to be pretty high.
How do you know the floor tubing isn't leaking? How do you know the roof isn't leaking?
bought a cheap hygrometer. the room measured 48% at 72 degrees he likes his house hot. is 48 high in the humidity?
consider this morning here in venice it did rain. the day it showed on the beam was 8o+degrees and was for 4 to 5 days, no clouds and dry off shore winds
What's the night-time temp there? Dark roof, clear sky, the metal roof will get 5-10 degrees colder than ambient at night. If it gets down to, say, 60, and the roof gets to 50, that's below the dew point for 48% air at 72 degrees.
Asked and answered
over at JLC, but...
The addition of a ridge vent could make this worse by making the beam even colder. I think what you're imagining is that the moisture would dissipate out the top, but the cold air outside would simply chill the beam more quickly. And, it sounds like the venting you're talking about would be an air leak straight out of the building.