Moisture- Should I vent roof for my small building or buy fan? Conflicting answers.

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Starting over.

No you can't vent the roof sheeting as is with out a lot of time and money.
No you don't need to because this is not a heated space and the insulation is in a closed space.
It was the warm moist air in the shed itself that provided the moisture that condenced on the metal light box and fixture.
Venting in both gables would have allowed the cool air out side to cool the air inside the shed. You still might have condensation lower down, if that happens you would just add a couple more down at the floor level.
This a problem with any shed that has been built tight. The roof is not a problem unless you heat on when you have snow on the roof.
It's not a big shed so you don't need large vents but you do need to have air circulation.
 
Thanks so much for going through it Nealtw, where I got confused is SlownSteady said the problem may be from the lack of airspace above the drywall ceiling (which is true) so I thought that was the area I needed to make an adjustment to.
 
If you have ever been in an old barn half the time you can see right thru the wall with all the cracks, they get wet and dry out no problem all they had was airflow to help and they last for ever.
Just don't heat your shed when there is snow on the roof.
 
It's a bit different since it's insulated/drywalled and want interior like a house, but I get what you are saying about needing airflow. No snow, just think morning dew and no roof ventilation could cause issue even with gable vents. Again, not very knowledgeable in this though.
 
What causes a problem with the roof is first warm moist air gets in there that can't get out, can air get into the roof cavities in your roof?
The other problem is when you heat the building, heat willl transfer from the top of the wall to the roof and melts the snow which re-feezes lower down the roof which stops the next melt from running off and then you have a leak.
http://www.luxurymetals.com/freshairintake.html
You can find these cheaper, maybe just one gable and one close to the floor on the other end of the shed.
 
No snow where I am. Re air: A little amount of air does get through drywall/insulation by way of the hole for the 2 lights (shown in previous picture), it is very small when light is covering up hole. I do have a window that provides a 17" opening for shed and will keep it open as much as possible. I apologize for not disclosing I had a window previously if that changes advice, thought my issue was just finding a way to ventilate roof.
 
The only fix he will come with is remove the ceiling drywall add depth the rafters and a ridge vent and soffet vent and replace drywall. Non of which will solve the problem.
After he give you some idea what he wants to do, send him a link to this site and have him explain it me.
 
Okay, yeah I was doing some online research now and eave or soffit vent was recommended as well as air space baffles (don't know how'd that fit). I will update what is recommended and again, can't thank you enough for helping on this.
 
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Hi nealtw and others, solution from contractor was to take the ridge cap off, cut 1 1/2" off each side and cover with ridge vent and new ridge cap. Thoughts?
 
Really? It was one of the only ways left he could think of to vent the roof.
 
Well that would be great if you had a problem with the roof.
A problem with the roof will come up just like a house. Heat from inside a house gets to the outside wall and over time will travel to the surface of the roof, melts the snow and causes an ice dam which causes water to back up into the shingles and leaks into the house. The other problem is warm moist air leaking into the attic space and not finding it's way out. You have built a closed system attic.
No air in no air out, the paint on the drywall is acting as a vapour barrier, there maybe some small holes here and there and a light fixture. As it is now any moisture that was in the roof area when it is was built is what you there now or maybe less.

So lets look at what happens. When you have hot weather the roof will get hot first and the pressure up there caused be the heat will be pushing warm air out. As the rest of the shed warms up any moisture laying around will evaporate and now you have warm moist air in the shed.
Now what happened that caused a problem is a huge temp change in short time and your insulated shed held on to the heat longer than the surface of the roof. The air in the attic cavities condenced and tried to suck air in to fill the space. As warmer moist air tried to squeeze in past the light fixture it was carrying more more than it could will it was cooling and just dropped the moisture off at the nearest cool area. If the shed cools at the same rate as the roof problem solved.
If I had built your shed, it would have had 2x6 rafters with vents at the soffet and at the peak with four inch insulation so you had air flow beacouse that's what we do but there are argurements for a closed system like you have.
You would also have vents of some kind in the shed itself as even if you were using this as an office or living space you need air. because you use it and you give off lot's of moisture.
If you contractor new anything at all, all this would have been dealt with when the shed was built.

A ridge vent will only make things worse as now the inside air will find a good path out when you have a big temp change and that will cause rot.
 
Thanks for your reply. I apologize but honestly still a bit confused on why a ridge vent wouldn't help because you described one of the problems of the current closed system is warm air not finding it's way out of attic, wouldn't the ridge vent solve that?
It doesn't snow where I live. I can leave my window open as much as possible to have air flow.
 
alanrudy said:
Thanks for your reply. I apologize but honestly still a bit confused on why a ridge vent wouldn't help because you described one of the problems of the current closed system is warm air not finding it's way out of attic, wouldn't the ridge vent solve that?
It doesn't snow where I live. I can leave my window open as much as possible to have air flow.
Click to expand...

Ridge vent only works to exhaust air. You have to install intake ventilation along the eaves to allow for air intake so you can exchange air in the area.

Think of it this way, I want you to breathe out until I tell you to stop, don't take a breath till I tell you to......still breathing out? I didn't say stop yet.....


Nope not yet.......



Ok, breath, the area breaths by air in and air out and it doesn't happen through the same vent.
 
Thanks oldognewtrick, so would a ridge vent AND eave vents solve my issues. Pardon my inexperience, but sounds like nealtw is saying gable vents are the only thing I can do short of opening drywall and starting over.
 
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So the conclusion I've reached for now is to do nothing (which is better than $ wasted on contractor ideas that were not helpful) but keep the window open (17"x33" opening) as much as possible. Based on So Cal weather, hopefully won't have an issue 90% of the time, and during the other time I may get a portable heater/ac or maybe one dryer vent. Thanks again all for input, and feel free to add anything.

10993436_10153090912082128_4210140157283327841_n.jpg
 
I would think a small vent would be better as with out an overhang an open window in the rain.
This will only happen when you have a sharp down in temp, how often is that?
 
Usually at most a couple weeks of rain a year but very good point, may add vent. For weather, usually at most a couple weeks to a month a year would be the danger zone where nights sometimes hit 40's and the days can get 70's.
Would you recommend to try to seal/cover any holes of the 2 electric boxes for the LED lights to make it more of an airtight/hot roof so it hopefully can't get cold enough for condensation?
 
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