retrofitting rafter vents?


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Old 10-13-06, 01:39 PM
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retrofitting rafter vents?

We hope someone can help.

We have a cape with vaulted ceilings upstairs and a knee wall with an attic crawl space. We would like to install rafter vents all the way up to the ridge vent with out ripping out our bedroom sheet rock. We can buy some different products to run from the soffit vents to the knee wall.

A friend suggested that he has seen a piece of metal bent at a 45 dgr angle. Perhaps this would not get stuck on the roofing nails jutting down. My wife and I were talking about connecting pieces of PVC like legos to reach the peak. Has anyone delt with this?

Our sheet rock was getting drenched last winter especially right after we had a new roof put on. At first we thought we had a leak and the roofer came back and actually shortened the ridge vent from where we thought the leak was.

The problem got worse and soon we realized there was no leak but condensation turning to frost and then melting. We also dicovered that we do not have soffit vents. (why would any body build a cape with a ridge vent and no soffit vents?)

The roofer came back today and extended the ridge vent almost all the way to the end and next week we are having a 2" continuous soffit vent cut on both sides. We don't want to go through another winter of wet walls. I think we are finally on the right track but we would like to know that the air flow from the soffit to the ridge is unblocked.

Any help would be appreciated.
 
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Old 10-19-06, 08:45 AM
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oh man

What do you have behind the sheetrock now? Any insulation with a vapor barrier facing the warm side? You need those.. Anyway, can you tell if there's a gap between insulation and roof sheathing? If there's no contact all the way up, you may not need to lay out those rafter-mates. Once you get the soffit vents cut out, make sure they are not blocked by insulation and maybe put a rafter-mate in there. This maybe enough to vent out the moisture and prevent condensation. And again, tight insulation and very tight vapor barrier are a must.
 
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Old 01-07-10, 07:39 AM
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I also have the same rafter vent issue. I have vented the soffit already. Has anyone successfully retrofitted the vents in between the ceiling insulation and the roof sheathing?
 
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Old 01-07-10, 02:48 PM
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The only way to do that is to install baffles as the insulation and sheetrock is installed. Air must move from the soffit to the ridge continuously in all bays. Depending on the size of the rafters, you will be limited to the depth of insulation, so there is a trade off.
 
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Old 01-07-10, 03:34 PM
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Before tearing it down, I would buy these at Depot: Berger Building Products Not near the problems as foam - nail rips, 30% less air flow, etc., with or without the Windblocker required from other box. From knee wall side, install one next to roof sheathing, tape another one on top with 2" over-lap (instead of required 2" spacing), taping both sides firmly, extend that one up, etc. The batt should compress enough yet keep the baffles up to roof, losing some R-value.

Be safe, Gary
 
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Old 01-07-10, 04:19 PM
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I don't know, Gary. If the poster has an installed ceiling with insulation existing, how would they gain ventilation over the insulation? Or maybe I am reading wrong.
 
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Old 01-07-10, 04:44 PM
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"We have a cape with vaulted ceilings upstairs and a knee wall with an attic crawl space" ----- I have the same in my 1-1/2 story Craftsman. With 3-1/2' tall knee walls and about 5' deep, I don't like going in there! And it wasn't after I turned 60, either....... lol.
Just hook them together as they shove another 3' baffle in.... They should ride on top of the batts if using the plastic stiff ones, not foam.
Be safe, Gary
 
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Old 01-08-10, 09:35 AM
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Damp sheet rock wall

You are looking at this from the wrong angle.
In all probability you have an un insulated sheet rock wall.
As such it is a magnet for all the water vapour in the room.
Probably this water vapour is merely the breath you breath out that is totally 99% water vapour saturated/humid.
It may be that you leave the bathroom door open, or the kitchen door?
And all the water vapour you produce by cooking, washing, drying towels etc: is finding its way into your bedroom.
Buy an infrared temperature and scan the damp wall.
Then scan the other walls and ceiling to see how they compare.
The damp wall will turn out to be colder than the other walls.

There are several solutions.
Paint the wall with gloss/oil based paint, this will stop the water vapour from getting into the wall, but you will then see condensation on the surface.
One buy and fix some two inch thick polystyrene sheet over the wall.
Then cover that with some more sheet rock, this will make the wall warmer and stop the water vapour condensing into the sheet rock.
Pull the sheet rock off the studs and fill the gaps between the studs with polystyrene sheets, put enough in between the studs to fill the space, maximum thickness six inches.
Polystyrne can be cut with a knife and should be a tight fit with no gaps, then replace the sheet rock
 
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Old 01-08-10, 10:41 AM
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Check this link out:

Cape Cod Roofs
 
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Old 01-09-10, 04:18 AM
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Check this link out:
Cape Cod Roofs

Jclaar, this is a well written article. It should be compulsory reading for all people undertaking a conversion.
The very best solution to most of these problems is sprayed in polyurethane foam, as it will attach itself firmly to all surfaces and completely fill the space. It does cost a lot of money!
However, it does have a downside, if sprayed on the underside of the roof, if the roof should leak at some time, the wood will become rotten long before one discovers the problem. By which time the solution will have become vastly more expensive and difficult to correct.
 
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Old 01-20-10, 08:15 AM
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I have a craftman style house with extended roofline (no rain gutters) and no soffits. I.E. you look up from outside and see the rafters and roof sheathing. The interior is basically a cape style house - vaulted ceilings upstairs and a knee wall with a side attic crawl space. The house has end vents as well as a ridge vent. It is insulated on the floor of the side attic, kneewall, and the angled ceiling that follows the roof pitch and above the top-flat part of the attic.

Now on to my questions:

Q1: Since there are no soffits, should I add some kind of venting under the eaves into the side attic spaces? How would I do this without having to add actual soffits? I don't want to spoil the look of the house by adding soffits. The junction of the roof overhangs and the exterior vertical walls is finished with a large facia type of moulding. I have peeked from the inside and if this facia were removed, there would be an exposed opening to the outside. Again not wanting to spoil the look of the house, is there a product that would allow venting but still not allow me to see it from the outside of the house?

Q2: Do I need to add the baffles if there is already air space above the insultion? ie. from inside the side attic space, looking up toward the ridge there is existing insulation on the angled ceiling and there IS visible air space between the insulation and the roof sheithing.

Thanks!
 
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Old 01-20-10, 09:08 AM
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This actually installs under the shingle for rafter ventilation. You still need some sort of baffle in between the insulation and roof sheathing.



Smart Vent
 
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Old 01-20-10, 09:12 AM
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Condensation? Insulation? Drafts?

Bungerlowdog, this is a complicated subject.
Perhaps best viewed from the point of:
Do you have a problem, that need to be fixed?
Or is it just an idea?
Perhaps you have read an article and feel you'd like to do something?
The basics are that, there is a lot of miss understanding about attic ventilation and why people do it!
The two starting points are:
There is condensation in the attic.
The room in the attic is cold.
Or do you have a unique issue?

The bottom line is why consider spoiling a lovely home, when the solution is elsewhere?
 
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Old 01-20-10, 12:23 PM
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jclaar: Cool product. I just had the house re-shingled 3 years ago. Not sure I'm readly to go to the extent of pulling shingles to install this. I'll keep it in mind.

Pery525: "Perhaps you have read an article and feel you'd like to do something?" - that's pretty much it :-) There is no condensation. The upstairs does get very hot in the summer. Also I'm trying to prolong the life of the roofing shingles.
 
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Old 01-21-10, 04:11 AM
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Hot attic, missing insulation?

We have a starting point: The attic gets too hot in the summer.
It follows on from there that the existing insulation in the roof is either missing or of low standard and this means you are wasting heat during the winter.
There is only one thing you can do to help shingles last a bit longer and that is to paint the roof a light colour or preferably paint it white, this will do two things, it will reflect the suns heat back into space and will make the inside of your home cooler.(Its the sun that kills shingles.)
If you want to improve the insulation?
Then the way forward it to pull the ceilings and knee walls down and fill the spaces between the rafters and studs with sheets of polystyrene, if you pack at least three inches of polystyrene between the rafters and studs (taking care to leave a gap between the polystyrene and the underneath of the roof of no less than one inch, preferably two inches) and then place another two inch layer across the underneath (inside of room) of the rafters and studs, (all this needs to be a tight fit) you will end up with a really cool room in summer and a cheap to keep warm room in winter.
A roof made up as indicated will be warmed by the rooms downstairs to about 19 to 20C thats 66 to 68f and you will probably only ever need additional heating on the coldest of winter nights.
 
 

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