Roof Ridge Vent And Attic Soffett "Channels" (raft-r-mate, etc.)

Hello:
Have been looking into whether we want, or need, a ridge vent to be installed when we get a new roofing job. Anyway, we noticed that the insullation in the attic has, over the years, crept over the soffett ventillation holes, thus making them probably useless.
It was suggested that we use those thin plastic channel pieces that go between the roof rafters in the attic, and that then serves to channel the air flow from the outside soffetts toward the ridge vent. These would also stop the insullation from migrating backover the soffetts holes.
The mfg's web sites say to use the whole 4 feet up the underside of the roof. As they are 4 feet in length, so, for our roof, would be perhaps 2/3 of the way up toward the peak.
They would also stop the insullation (once moved back) from re-migrating over the soffett holes.
Started thinking about these channels that supposedly provide "better" attic ventillation than just using a ridge roof vent without these channels. Two of these channels are called Raft-R-Mate and also one by ADO Pro Vent.
I'm obviously missing something here.
Wouldn't the ventillation of the whole attic be better if these channels Weren't used ?
I would think that you want drawn in air from the soffett (by the slight negative pressure caused the hot air flow out the ridge vent) to mix with the complete attic's air volume (and then out).
Not to just channel the drawn in air up and out, without any real attic air mixing.
What am I missing here ?
Thanks, Bob
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wrote:

I"m not a pro, and I can't see the wind, and I don't spend enough time in the attic to be intimately acquainted with airflows, and I've only had one configuration anyhow, but...
This sounds a little bit like shampoo, rinse, repeat. Where "repeat" might double sales (although it does get the hair cleaner, so it has no body)
It seems to me that all the thing has to do is go above the insulation, maybe 6 inches (since you're probably not going to be able to get it all the way down to the bottom even if you tried.) So then you would only have to buy 1/8 as much.
I believe tehre is another product out there that is only a U-shaped piece of wire, that goes in one wire at a time to keep insulation in batt-form out of the space between the rafters. I aassume that no one uses more than one or two per space.
I guess one question to ask oneself, If I could well circulate the air that is immediately below the roof (in these channels they sell), would the air in the middle of the attic get hot.
Well, the answer might be No if the channels went all the way to the top, , but won't the bottom of the roof radiate heat into the entire attic everywhere the channels aren't?** Doesn't that even include the rafters themselves? Doesn't all that radiate heat? Let's see what others say.
**In your case, the top two feet. But wait a second: If 4 foot channels go 2/3rds of the way to the top, are you saying your hole house is only 6 feet, times 2, from front to the back, or side to side? Only 12 feet? Is a number wrong somewhere?

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Hi,
Oops
Not too good with the math, I guess.
You're right, of course.
Just have the typical roof pitch for a typical 3 bedroom split.
Bob
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