vented ridge cap

[yukon cornelius]

We have been battling condensation on our ceiling. we just have fiberglass between rafters and tried covering that with thick plastic. Our ceiling is still unfinished and will be for a while.  condensation remained after the plastic so we ended up adding this vented ridge today. This is not a total cure but a fix until I can spray foam insulate the whole ceiling.

Pretty simple install and not only made in USA but made a 20 miles from our old place.

[yukon cornelius]

pictures not loading....

[yukon cornelius]

 

  her is the only one I can get. basically just cut the sheathing back 3/4 inch on each side of the ridge. place ridged vent over it and place ridge shingles back over it. the moisture is already drying up and there is a lot of warm moist air exiting the vent area.

Success for now.

[POSTON WIDEHEAD]

I don't get on ladders.  ;D

[yukon cornelius]

Bologna! goats can and will climb anything. ours were in a tree once! Im starting to think your not a real goat  ;D now a turtle on the other hand....they don't climb :D

[Brucer]

Attic and roof venting has been more of a black art than a science (until recently). I've concluded that a really, really tight seal between the insulation and the heated room is absolutely essential. For venting, the ridge vent is the way to go.

[Peter Drouin]

If you get snow the ridge vent will not work with snow on it. Also put in gable end vents, For me in NH they're the best.

[21incher]

For those ridge vents to work there has to be unrestricted airflow between the insulation and the roof sheathing from ventilated eves up to the vent. They make a extruded vent pocket that you staple to the underside if your roof sheathing to make a path for the air before you put the insulation in place. Also if you add poly over faced insulation be sure to slash the vapor barrier on the insulation so moisture does not get trapped on the warm side and form mold. 

[47sawdust]

Unless you have a continuous air flow from vented soffit to the ridge a ridge vent alone will not work.Insulating the rafter bays is the least desirable method.It is much better to insulate the ceiling and install gable end vents and fully vented soffit.

Also cellulose ,say 18'',would be cheaper than comparable spray foam.Not knowing your construction details though,that is just a guess.

[Bruno of NH]

Ridge vents work best in combination with soffit vents .
Is the ceiling vaulted ?
Jim/Bruno

[Autocar]

On our place we have a 14/12 fall on the roof I had sawed 2x8's twenty four feet long and used six in insulation leaving a two inch air space between the roof and ceiling. With vents at the over hang and at to top of the ridge we have never had a issue with condensation.

[yukon cornelius]

We are fully vaulted ceiling as in the rafters are the ceiling. once I can afford the foam it will be a continuous  sealed area where the indoor air will never meet a cold or hot surface until then venting it is my only option. fiberglass insulation was never in the plan to begin with because I think it is one of the worst forms of insulating compared to the others available. this house is being built with cash in hand so I regrettably stepped downgraded to it. my situation now is to remove the moisture that is in it currently and work extra hard to buy the foam.

[Chuck White]

My garage roof has a vented ridgecap and when it snow or rains with wind, the weather will end up in the garage.  It's a steel roof on perlins spaced at about 8 inches, no insullation.

Eventually I will be redoing the roof and it will be OSB covered with felt paper, then the steel, but the ridgecap will be sealed and I'll be putting attic vents on the gable ends of the building!

[sawguy21]

If you get snow the ridge vent will not work with snow on it. Also put in gable end vents, For me in NH they're the best.

That was my first question when I saw them, not much good in snow country. If you have gable vents why bother with the vented ridge cap?

[Peter Drouin]

When you build A house you want to vent the roof all you can in the north with the cold.

[Gadrock]

I have put up a bunch of this venting ridge row stuff in the past. We aimed at 6 to 8 complete airchanges per hour for the ceiling area.

Not likely to see me building any of that stuff up North, as I reserve that area for visiting only.

And I do not allow goats on my roof, even if they wanted to be there.

David G

carry on

[Don_Papenburg]

That turtlegoat might be OK up there though

[Peter Drouin]

My garage roof has a vented ridgecap and when it snow or rains with wind, the weather will end up in the garage.  It's a steel roof on perlins spaced at about 8 inches, no insullation.

Eventually I will be redoing the roof and it will be OSB covered with felt paper, then the steel, but the ridgecap will be sealed and I'll be putting attic vents on the gable ends of the building!

I see a lot of guys do that . Add heat and it will rain inside when it's cold out.

[Chuck White]

I have no ceiling in the garage, just strapping!

[Peter Drouin]

I have no ceiling in the garage, just strapping!

Had a farmer did that with a barn. I told him the board the roof F paper then tin. He just strap it then tin. And when he put the cows in it rained. Every one likes to skip a step with a roof.
An open shed is ok. But if you box it in, put on a real roof. And OSB will sag between the rafters over time. Go with CDX 5/8. Good luck

[Chuck White]

I have no ceiling in the garage, just strapping!

Had a farmer did that with a barn. I told him the board the roof F paper then tin. He just strap it then tin. And when he put the cows in it rained. Every one likes to skip a step with a roof.
An open shed is ok. But if you box it in, put on a real roof. And OSB will sag between the rafters over time. Go with CDX 5/8. Good luck

My garage is unheated, so it doesn't rain in there, and when the reroofing is done, the roof will be solid boarded or OSB will be installed on the existing 1x6 perlins!

[thecfarm]

Vents are VERY important is having a cold roof. The air in a vented roof should be almost the same as the outdoor temp,seem like only 10° difference?? Been over 25 years since I did all this.

[Peter Drouin]

I have no ceiling in the garage, just strapping!

Had a farmer did that with a barn. I told him the board the roof F paper then tin. He just strap it then tin. And when he put the cows in it rained. Every one likes to skip a step with a roof.
An open shed is ok. But if you box it in, put on a real roof. And OSB will sag between the rafters over time. Go with CDX 5/8. Good luck

My garage is unheated, so it doesn't rain in there, and when the reroofing is done, the roof will be solid boarded or OSB will be installed on the existing 1x6 perlins!

You don't have to yell at me Chuck, I was just trying to help so you don't have to it a third time.

[Chuck White]

Not yelling, by any means Peter.

Just letting you know my options!   

[Brucer]

Some comments on other comments.

Venting is done for two purposes. One is to keep humidity from building up, or to evaporate moisture inside the roof. This prevents molds and fungus from building up, and keeps the wood from rotting.

The other purpose in the snowy north (where I live) is to keep the air beneath the roof surface from getting above freezing temperature. If the surface temperature gets too high, the snow starts to melt from the bottom, the water runs down to the eaves (which are cold), and then it freezes and forms ice dams. No amount of insulation will stop heat from flowing up into the roof spaces -- it only slows it down. Snow also acts as an insulator so it tends to push the temperatures of the roof spaces up above freezing.

Eave vents combined with gable vents do a decent job of keeping the humidity down. It's been my experience that this isn't enough for dealing with ice damming in snow country. The problem is this. As the air under the roof slowly warms up, it starts to rise. The rafters (or the top chords of trusses) form channels that conduct the warm air up to the peak, but prevent the air from moving sideways to vent out the gables.

If you just try to direct the warm air out the sides of ridge vents, they will get blocked by snow (as Peter points out), and may also let the weather in (as Chuck points out). The solution is to have a ridge vent that only discharges warm air out the ends. In other words, it acts like a duct above the tops of the rafters or truss chords and vents lets the warm air trapped there get out.

The vent will also have to be insulated on top (a half inch of insulation board will be plenty) to the warm air flowing out the vent doesn't melt the snow on top of it.

I have seen a commercial ridge vent that is insulated on top and open only on the ends. For long ridges these vents can be connected to a prefabricated chimney-like tower that extends well above the roof line (and hopefully above the snow line).

Two years ago a neighbour was doing renovations on his house and discovered a lot of rot in the roofing system, caused by inadequate ventilation (the house was built the same year I built mine). When the roof was being rebuilt, the owner had the contractors build an insulated ridge vent (about 8" high and two feet wide) that was vented only at the ends. The roof is 50' long. There has been absolutely no sign of ice damming or snow melt during the winter.

When I built my house, I put in 4 times the venting specified by the building codes. I still had ice damming. Fifteen years ago I increased the venting by another factor of 4. I still get a modest amount of ice damming. Next time the shingles need replacing, I'll be putting in a ridge vent.

[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.