vented ridge cap

[yukon cornelius]

All my insulation is now dry  8) now I will leave it this way with nothing covering it until I can get the foam. Or if it never comes back.....maybe I can leave it this way???? I do need to check a few places to make sure there is no mold. That would be $1000 or more in my pocket if I can leave it. So far, SUCCESS! What a relief

[69bronco]

Ridge vents and gable vents are a good thing, just not together. The idea as stated by someone earlier is to pull air through the rafter bays to properly ventilate. If you combine gable and ridge vents you are going to pull outside air from the gable and directly out the ridge.

[Peter Drouin]

Ridge vents and gable vents are a good thing, just not together. The idea as stated by someone earlier is to pull air through the rafter bays to properly ventilate. If you combine gable and ridge vents you are going to pull outside air from the gable and directly out the ridge.

Would you tell me how that works Or why it works that way??

[sawguy21]

I don't get that either. The air outside the gables and the ridge is the same temperature, why would that cold air be drawn in? The vents are to disperse rising moisture laden warm air from the house, if the ridge vents are covered with snow that air has to go somewhere.

[hacknchop]

Really want have fun install a whirlygig or two that will draw air.

[Brucer]

... The air outside the gables and the ridge is the same temperature, why would that cold air be drawn in?

Exactly.

... if the ridge vents are covered with snow that air has to go somewhere.

Which is why it's best to have the ridge vents exposed at their ends (or to a central "tower") rather than along their sides.

Flat whirlygigs don't work too well when they're squashed flat -- which is why you don't see them much in snow country. :D

[yukon cornelius]

Update again....failure. damp insulation again. I gotta work harder to buy foam but not enough hours in the day. What if I cut out sleeping. those are wasted hours. ;D

[Peter Drouin]

You need a foam soffit vent from the soffit to the ridge stapel to the roof sheathing.
Then the insulation will be dry.
Try it on 3 or 4 bays with the soffit vent between the rafters.

[Bruno of NH]

Like Peter said , you need to have proper vents stapled under the roof deck for air to go from soffit vent to ridge vent .
Jim /Bruno

[Bruno of NH]

I don't like poly on a ceiling .
I use kraft faced insulation on ceilings and have better luck with it that way .
Just my 2 cents .
Jim/Bruno

[Warped]

My thoughts
You said you have a vaulted ceiling? I'm guessing you didn't use scissor trusses? If not, gable vents can't even be used. You must vent every rafter run at the ridge from the soffit. Boxed in skylight channels need adjacent rafters drilled to allow air exchange to vent below and above the skylight.
What size rafters?
What R-value insulation?
A 2x12 rafter (11.25') should have at most R-38 (around 9" when lofted, don't compress insulation). This gives around 2" of air space which is cutting it close. You absolutely want the air on the underside of sheathing as close to outside air as possible always. Summer heat isn't good for asphalt shingles.
     Styrofoam baffles can be added for security to make sure the channel is not restricted blocking air flow from soffit to ridge, but they are fairly expensive. I would drop to R-30 especially since the first inch is 80% of insulating value.
     Aluminum ridge vent is bent and stamped to allow warm air to escape along it's entire length, and rubber plugs are available to keep rodents out of the ends.
     You do not need to run it to the last gable end run (the eave), but certainly cover the last rafter run (the outside wall)
Screw them down or use long roofing nails into rafters or they WILL pull allowing wind driven rain underneath.
Shorter eaves will cut down on ice dams. Obviously, snow melt drops off sooner giving less time to freeze
You can also use shingled roof vent such as Cobra Vent.
I personally would not fill it with spray foam.
If my long winded response doesn't pertain to your situation, ignore me.........most do :D
Good luck!

[Warped]

Forgot to mention, you may simply need a dehumidifier. Then you have mineral free water for batteries and radiators, not distilled, but hey!

[yukon cornelius]

Warped, we have just simple 2x6 rafters 24"on center and R-19 kraft face covered with 6 mil. plastic. We have 24" overhang all the way around. I heve watched closely for ice damming but have only noticed the overhangs melt at the same rate as the rest of the roof. Our walls are also 2x6 with the same R-19 kraft faced. We have concrete slab floor insulated underneath. We heat solely with wood but it rarely gets dry for static electricity. we don't use/don't own a clothes drier and dry our clothes either a clothes line but (sometimes) .or around the wood stove (most commonly). no vent in the bathroom yet. hand wash and dry dishes. simply stated....We may just need a dehumidifier.

[beenthere]

So what is the vented ridge cap actually venting? The room (living space) or the space above the insulation between the R-19 and the roof sheathing?

[Warped]

R-19 is indeed for 2x6 walls. For rafters it is too thick as it leaves zero air space. I used 2x6 rafters in my cabin, but used r-11, could have been r-13, I forget. If I recall the loft is only a quarter inch or so difference if any. When I get time I'll check unless you find out first.
You don't want to hear it I'm sure, but I would replace it with r-11. Carefully remove it and roll it up and tape it for future use somewhere else. Maybe even put it in garbage bags for protection.......MICE!
Always unroll insulation and let it expand (overnight?), then measure its thickness.
You could also add wood strips to rafter bottoms to increase their thickness to gain air space so r-19 would be acceptable. This would be even easier if you used collar ties on the rafters instead of wall ties, or considered installing them. Sometimes they also make finishing the ceiling easier I've found.
Anyways, that's my input......for what it's worth.

Your not placing a pan of water on your stove are ya? If nobody has a nosebleed it dry enough! lol
Another concern is todays homes are wrapped so tight there's no air exchange.......off topic, I know

[Bruno of NH]

I would remove the poly.
Having two vapor barriers could be the problem .
The moist air is locked between them.
Try it it might work .
When you poly a house up tight you need an air exchanger to remove the moist air .
Jim/Bruno

[beenthere]

Usually the paper barrier on bat insulation is not a good vapor barrier, so IMO I wouldn't remove the poly.
But so far, we don't seem to know just where there is condensation.

In the OP,

battling condensation on our ceiling.

I think the ceiling is the insulation and plastic, if I read it correctly.
If there is condensation on the plastic, then the insulation is not keeping the plastic from getting cold (causing condensation) for some reason. 

A bit of a dilemma.

[Holmes]

 Double vapor barrier can be a big problem, but it depends how it is done. If the moisture is not able to escape the building it can make a lot of condensation.  If the kraft face is up toward the cold it is backwards.

[yukon cornelius]

the poly went up 6 or so months after the bats. no change It was a suggestion after we had already been battling the moisture. the moisture is between the sheathing and paper on the insulation causing damp spots on the paper in low sagging areas. It is 2x6 rafters with r-19. on 24 inch centers it causes a bit of insulation sagging between the rafters. this in turn creates a void cavity between the fiberglass and sheathing. im am certain the house is not too tight as it is still under construction and has lots of cracks and crevasses t seal up. I spoke with the local lumber yard owner who built a similar house and had the same issues. he spray foamed an inch of foam and says it fixed it. It certainly wont hurt it. the kraft paper is to the interior then poly over that.

[yukon cornelius]

What are the negative sides of using the foam on the underside of the sheathing to try to stop the condensation?

Also maybe a dehumidifier is the answer. last night we had a flooding rain and water came shooting in the conduit our water line comes through the floor in and our bathroom floor was flooded so checking the humidity in the house today wont be accurate. it was 50% anyway. the shower floor rarely dries by morning after showers the night before. that should a sign of high humidity.

This business of carving a place for yourself in the wilderness on a steep hillside using a tiny budget is for the birds. As I was digging up the side of the manhole up the hill where our water line shutoff/ outdoor water spigot is at midnight to install a drain I was wondering what the heck I am doing this for. (I knew it needed done but just low priority till water is spewing in the house) Off topic but I am a little frustrated with this project.

[beenthere]

Is this home on a slab? or on an elevated floor with crawl space below?

[yukon cornelius]

it is a slab

[beenthere]

Vapor barrier under the slab? 

Sounds like moisture coming up through the floor, keeping humidity high. Not sure what the answer will be, but don't think the foam insulation will help much over what you have now.
Air exchangers maybe, to bring in air and flush out moist air. But really don't know.

[yukon cornelius]

we did install vapor barrier and insulation under the slab. also the concrete is sealed if that matters. my plan is not to foam over but remove the bats. then an inch of spray closed cell foam to make it seamless then possibly replace the bats. we might leave bats out.

[VictorH]

The inch of foam will help greatly.  I would re-install the batts and run a dehumidifier.  You may find that once things have been dried out you won't need it.  I spray foam and should tell you that fire code would dictate that is needs to have a fire barrier over it.