# Attic Rafter Ventilation Windstops



## Bud9051 (Nov 11, 2015)

Pick up a bundle of Roxul and use a batt or part of one to block incoming air. It is very dense.

Or fold the first FG batt over to fit tight at the start.

For reaching all the way to the end i use a 2x2 with a 1x3 " TEE " at the business end. The T will have a dozen long bails poi8nting away. You can spike the batts and push the out and then pull the insertion tool back.

Bud


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## Nealtw (Jun 22, 2017)

Build a handle with a piece of plywood and some way of clamping the bat so you can push it out and release it.


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## dtbingle (Jul 19, 2017)

After some more work in the attic, I'm seeing just how many obstructions are in the joist cavity area....blocking, electrical boxes, etc. I'm thinking to do blown cellulose to fill to the top of the truss chord - about 6 inches for R19. Then do perpendicular R30 fiberglass batts on top of that.

In the first picture, the rafter vent baffle isn't pressed all of the way to the sheathing. When any sort of wind stop blocking is installed, it will press the baffle up and leave roughly a 6-8 inch gap. I'm worried that a chunk of roxul or fiberglass plug will eventually fall out and drop the loose fill into the soffit area and then allow more wind washing to occur (see picture).









On the other hand, there's the spray foam route (like this kit). The end goal would be this picture below. However, I can only get about 2-3 feet from the exterior house wall and I'm worried that these spray foam gun kits won't shoot that distance well. Additionally, it looks like these kits require usage every 60 seconds or so to prevent the foam from curing in the nozzle, which would be a challenge to spray one cavity and move all of the boards that I'm laying on over and get set up in the next area.









Last, we had paid for these ventilation baffles to be installed during the insulation removal. Am I wrong in thinking that the area below the baffle and above the wall top plate should have been closed off somehow? I was expecting something like this installed.


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## Bud9051 (Nov 11, 2015)

I think the failure shown in the first picture shows a much higher space between roof and ceiling. A 6" batt folder in half would be in there much tighter plus use longer tails.

The last picture would be nice but you don't have that much space.

A 4' batt stuffed down in there is not going to fall inti the soffit (IMO). Might even need to use 3.5" batts with facing peeled off.

Bud


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## Chris616 (Dec 31, 2019)

I go way beyond what most would do on all of my reno projects, but when I installed the Owens Corning raft-R-mate baffles I didn’t try to staple the flap to the top plate of the wall (which follows the linked instructions). It would have been next to impossible to do (ours is a 5/12 pitch roof which looks like about what you have), and I didn’t think there was much (if any) value to it. If we’d been doing blown in loose fill insulation it would have been critical, of course, to prevent material falling out into the soffit. But for fiberglass batts the only reason to do it is to prevent air moving through the fiberglass itself, as opposed to moving through the less restrictive open air channel between the baffle and roof sheathing. I’d be curious to see any real data on this “wind washing”, but I’m dubious that there would be any significant extra heat loss/gain from the conditioned space below by virtue of the fact that the air that is held in the insulation is getting replaced by air moving in from the soffit. The small section of the fiberglass where that might occur isn’t actually over the conditioned space, but rather over top of the insulated exterior wall.

If you revert to wanting to use batt insulation it would be good to get a shop-vac up there and clean up so that you’re not pushing debris out into the soffit.

Chris


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## SLSTech (Jan 19, 2021)

Pretty cool seeing pics from my site in there: Air Sealing: Attic Baffles (thehtrc.com) --- Quickest fix I can see is get 2" foam board approx. 2' long, rip it to fit the bay width & slide it till it touches the baffle. Then use canned spray foam (get the professional gun) & spray all the edges including where it touches the baffle - between the length of the gun, little extender included with most & your arm you can get it. When moving between bays, just turn the knob on the gun off - worst case is the extender clogs but you probably don't need it anyways. Do not shove to hard or you will defeat the purpose of the baffle. Don't forget to check the other links in that article, specifically the air-sealing portion (linked under "Ice-Dams"). As for batts or blown - blown wins hand down


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## dtbingle (Jul 19, 2017)

SLSTech said:


> Pretty cool seeing pics from my site in there: Air Sealing: Attic Baffles (thehtrc.com) --- Quickest fix I can see is get 2" foam board approx. 2' long, rip it to fit the bay width & slide it till it touches the baffle. Then use canned spray foam (get the professional gun) & spray all the edges including where it touches the baffle - between the length of the gun, little extender included with most & your arm you can get it. When moving between bays, just turn the knob on the gun off - worst case is the extender clogs but you probably don't need it anyways. Do not shove to hard or you will defeat the purpose of the baffle. Don't forget to check the other links in that article, specifically the air-sealing portion (linked under "Ice-Dams"). As for batts or blown - blown wins hand down


Those pictures are very helpful! Sorry if it encroaches on any rights...I thought that by adding the image via URL it would keep the "source" in the picture, but it looks like it just uploads the image without keeping the link. 

I think I follow what you're saying - something like this? I like that idea.










My other thought is to use another foam baffle with the built-in wind stop under what they did, although I'm not sure if two layers of polystyrene next to each other would cause some weird moisture/condensation trap.









Worst case, cheapest & easiest option would be just using a big fiberglass batt plug and stuff it in there.


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## SLSTech (Jan 19, 2021)

No worries - as long as you got it from my site I am glad it helped, now if you got it from another one though please let me know 
Well if you can attack it from that side go for it - I was thinking from inside the attic you could still pull it off but yes that is what I propose
You can always swap but I think that would be harder but might be worth a try


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## Nealtw (Jun 22, 2017)

Or just do this with fibreglass.


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## Bud9051 (Nov 11, 2015)

As a footnote, if you use one of the spray guns with a larger can of foam I was able to attach a plastic tube to mine to allow me more range when adding foam. You have to attach it securely. I also have a6' nozzle on mine. I can did it out if you need more details.

Also, be sure to pick up several cans of the cleaning liquid, takes a bit of time and effort to clean when done. But I found it held well between uses.

Bud


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## dtbingle (Jul 19, 2017)

SLSTech said:


> No worries - as long as you got it from my site I am glad it helped, now if you got it from another one though please let me know
> Well if you can attack it from that side go for it - I was thinking from inside the attic you could still pull it off but yes that is what I propose
> You can always swap but I think that would be harder but might be worth a try


Sorry the foam arrow was misleading - everything will be done from attic side. Slide foam board along top of top plate/drywall until it meets the baffle, then spray foam gun from inside attic to fill any gaps between the foam board and baffle.



Nealtw said:


> Or just do this with fibreglass.
> View attachment 650428


This is a good option also, but I'm saving it as a last resort. It will definitely block the loose fill from falling into the soffit, but lacks a bit as far as providing as much R value in that little space and preventing any airflow through the insulation.



Bud9051 said:


> As a footnote, if you use one of the spray guns with a larger can of foam I was able to attach a plastic tube to mine to allow me more range when adding foam. You have to attach it securely. I also have a6' nozzle on mine. I can did it out if you need more details.
> 
> Also, be sure to pick up several cans of the cleaning liquid, takes a bit of time and effort to clean when done. But I found it held well between uses.
> 
> Bud


I was thinking a similar idea with the tube, but couldn't think of what extension tube would be straight/rigid that would fit nicely to the metal spray foam gun tip. Even with planks laid out and my head about 2" from the nails in the roof sheathing, my extended arms are still about 3 feet from being able to reach the exterior wall.

What did you use for the extension tube? I have the Great Stuff Pro 14 gun. They also have a Great Stuff Pro 14 xl gun with 46" barrel, but it's close to $100.


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## Nealtw (Jun 22, 2017)

dtbingle said:


> This is a good option also, but I'm saving it as a last resort. It will definitely block the loose fill from falling into the soffit, but lacks a bit as far as providing as much R value in that little space and preventing any airflow through the insulation.


Do you understand the concept of the air chute, this is the one place in the house where you want heat to dissipate before it gets to the roof above. there is not enough room to get the needed R value there.


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## Bud9051 (Nov 11, 2015)

"Great Stuff Pro 14 xl gun with 46" barrel " They didn't have that when I went creative, would have been in my truck in a heartbeat. Especially when tools can be cleaned up and re-sold so many ways.

Bud


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## dtbingle (Jul 19, 2017)

Nealtw said:


> Do you understand the concept of the air chute, this is the one place in the house where you want heat to dissipate before it gets to the roof above. there is not enough room to get the needed R value there.


Not sure I follow what you're getting at. This my understanding from some of the energy efficient home articles online:

Rafter ventilation baffle allows air to flow from soffit up ridge vent to minimize issues like condensation, extreme heat buildup, ice dams, etc.
The cross-section area just beyond the exterior wall should be filled with a material that is suitable as an air barrier, which is intended to provide two functions
Prevent any insulation material in attic from falling into soffit (mostly geared towards loose fill insulation)
Prevent wind from blowing through the attic insulation
Loose fill insulation can be blown around to create low spots over time
Fiberglass batts become less effective when very cold air passes through them, and also accumulates dirt/debris which degrades efficiency over time


Yes, the height over the exterior wall is not enough for proper R-value. However, maximizing the R value over this area does still help prevent heat transfer and reduce chance of ice damming. The two main ways I'm seeing this done is (1) to use the foam/plastic rafter baffles with the end flaps that fold down to the exterior wall and then you can insulate all of the way out to the exterior wall with loose fill and (2) spray foam this gap to provide most R value / inch.

With all of that said, I'm still sort of skeptical on how much not having an air barrier in this area actually reduces the effectiveness of the insulation, but I would hate to go through this terrible job and go with the fiberglass plug option if there's better options available in term of insulation efficiency.



Bud9051 said:


> "Great Stuff Pro 14 xl gun with 46" barrel " They didn't have that when I went creative, would have been in my truck in a heartbeat. Especially when tools can be cleaned up and re-sold so many ways.
> 
> Bud


Very good point - the problem is that I don't get rid of anything "just in case"


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## turbo4 (Jan 30, 2021)

Letting insulation spill out onto the soffit can be a disaster.I had 10 ft ice sickles once from it.


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