soffit vent baffle installation

[Fueler]

Gathering up steam to redo my 50+ year old attic.
Today's pondering is Soffit vent baffles. This attic doesn't have a proper versions.
I have seen examples of a single baffle used running 4 ft up.
I have also seen examples of running them all the way up to the ridge vent.
Your thoughts?
Pros and DIYers welcome.

 

[Rusty Musket]

We will need some more info. If you are insulating the attic floor, the short baffles are used to provide a clear air channel from traditional soffit venting through the insulation layer and into the open space above. If you are insulating the underside of the roof, you may need continuous air channels from the soffits to the ridge. It all depends on how your attic is ventilated now and what exactly you are trying to insulate.

 

[Fueler]

Single story Ranch style house with Gable roof lines.
Floor of attic will be re-insulated. Pulling out all the collapsed original. It's in pretty bad shape.
No plans at this time to insulate the roof line.
I am considering adding some of that reflective material to the roof while I am at it.

They did ok for the time period. Non of the soffit vents were covered. Just trying to modernize and improve it while I am at it.

 

[12ozd]

We will need some more info. If you are insulating the attic floor, the short baffles are used to provide a clear air channel from traditional soffit venting through the insulation layer and into the open space above. If you are insulating the underside of the roof, you may need continuous air channels from the soffits to the ridge. It all depends on how your attic is ventilated now and what exactly you are trying to insulate.

Very good explanation !

To the OP - "If you are insulating the attic floor, the short baffles are used to provide a clear air channel from traditional soffit venting through the insulation layer and into the open space above".

 

[sands35]

OP - a detail that matters is to ensure that the end of the insulation is sealed from air penetration. You don't want cold (or hot) air forced into the end of the insulation.

http://www.epa.gov/indoorairplus/technical/moisture/wind_baffles.html

Take the time to ensure the baffles are sealed against the trusses and top plate with expanding foam.

If there is an air leak, you can get condensation on the interior of the wall or inside face of drywall in cold weather.

There are baffles with a return flap that is designed to be stapled to the top plate and there are baffles that do not have that. Get the ones with the return flap for the row that runs along the top plate.

For my garage, I had a bunch of leftover EPS foam sheet from the foundation and used that to seal off the end above the top plate. Two cans of expanding foam later and it was air tight for the insulation, but still had the required vents into the uninstalled attic.

 

[Fueler]

Yup, agreed. I already figured to build a foam board /right stuff dam. Just makes sense.
I was just curious why some folks run that baffle all the way up. Personally I don't see the advantage at the moment.
If I add the reflective material I essentially accomplish the same thing as the long baffle deal.
Perhaps also a gap in the reflective material near the bottom for air to push across above the insulation?