# Recommendation for replacing attic baffles...



## VitoB (Nov 30, 2012)

Hi guys,

I will soon be working in the attic to air seal the top plates of the exterior walls.

My current baffles are poorly made from 3/8" OSB and some 1x3s to maintain the air space under the roof sheathing. 

If I were to make my own to replace them, what would you recommend?

Should I use some 1/2" XPS foam? I believe the optimal air space to maintain is 2", please correct me if I'm wrong.

Appreciate the help as always.

Thanks.


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## Windows on Wash (Aug 30, 2011)

Foam board is great as it serves a couple of purposes. I would opt for a foil faced variant if it was me.


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## VitoB (Nov 30, 2012)

Windows on Wash said:


> Foam board is great as it serves a couple of purposes. I would opt for a foil faced variant if it was me.


What is the proper way of fastening it to the rafters? 

Should I cut them as tightly as possible so they fit nice and snug between the rafters and then use some spray foam so they stick to the rafters?

I would assume using 1" thick foam board is good enough?


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## joecaption (Nov 30, 2011)

Any Lowes or HD has them already made and there cheap to buy, slide in place and staple.


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## info2x (Aug 19, 2012)

I did this last year. I was originally going to make my own baffles out of foam like you are thinking. I found that once I was up there cutting foam and trying to fit it all together was a nightmare. I also wanted to prevent windwashing of my insulation because I when I was painting I noticed where condensation had occurred on the interior walls. :furious:

I used these: http://www.brentwoodindustries.com/products/building/roof-ventilation/accuvent-accublock.php

I liked them because they were way tougher then the POS foam ones at Lowes or HD and unlike the heavier ones they had these staple to the top plate to prevent some windwashing.

I have a few more spots to do in the attic and then my plan is to foam the edges to provide a nice seal.

That's my $.02


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## Gary in WA (Mar 11, 2009)

Baffles are mostly used at the house wall perimeter, where the roof is close to the attic floor (ceiling below). Insulation is usually restricted due to the reduced clearance. IMO, use some foam board in the cavities for the chutes as they will not lose heat through *conduction *as a plastic baffle will, if in contact with any loose-fill FG or cellulose, FG batt insulation.http://www.buildingscience.com/documents/published-articles/pa-crash-course-in-roof-venting

Better still, use rigid board at perimeter (to gain maximum R-value) in less height, after air-sealing the drywall (plaster) to drywall joint where there is only paper tape as the air seal- very permeable to air AND moisture from room below, leading to ice-dams on roof above. http://www.buildingscience.com/documents/insights/bsi-046-dam-ice-dam

Gary


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## VitoB (Nov 30, 2012)

Gary in WA said:


> Baffles are mostly used at the house wall perimeter, where the roof is close to the attic floor (ceiling below). Insulation is usually restricted due to the reduced clearance. IMO, use some foam board in the cavities for the chutes as they will not lose heat through *conduction *as a plastic baffle will, if in contact with any loose-fill FG or cellulose, FG batt insulation.http://www.buildingscience.com/documents/published-articles/pa-crash-course-in-roof-venting
> 
> Better still, use rigid board at perimeter (to gain maximum R-value) in less height, after air-sealing the drywall (plaster) to drywall joint where there is only paper tape as the air seal- very permeable to air AND moisture from room below, leading to ice-dams on roof above. http://www.buildingscience.com/documents/insights/bsi-046-dam-ice-dam
> 
> Gary


Thanks Gary, the first link explains how to make the custom baffles really well. They mention foil faced rigid insulation for that purpose.

Would it be OK just to use regular spray foam to hold them in place?

On the perimeter over the top plate of my exterior wall, should I be using foil faced as well or XPS?


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## Gary in WA (Mar 11, 2009)

Canned foam is fine. Foil-faced will act as a small radiant barrier, reflecting the sun's energy back to the sheathing (with the 2" air space) hence warming it for possible ice dams per your location, IMHO. The foam board thickness should stop any moisture from below, the small amount where you didn't air seal the drywall joints, lol...

Gary


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## VitoB (Nov 30, 2012)

Gary in WA said:


> Canned foam is fine. Foil-faced will act as a small radiant barrier, reflecting the sun's energy back to the sheathing (with the 2" air space) hence warming it for possible ice dams per your location, IMHO. The foam board thickness should stop any moisture from below, the small amount where you didn't air seal the drywall joints, lol...
> 
> Gary


Sounds good, canned foam it is then. 

I think to make things a bit easier, I will attach the 2 inch long strips to the baffle so that it's already one piece and then bring it up into the attic and foam it to the rafters.


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## Gary in WA (Mar 11, 2009)

If you have a table saw, cut 3/4 way through (rip) on the line to fold (if using foiled), then hinge each side before installing. Check each one as you may find many different widths in each bay... under-size widths to fit all.

Gary


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## VitoB (Nov 30, 2012)

Gary in WA said:


> If you have a table saw, cut 3/4 way through (rip) on the line to fold (if using foiled), then hinge each side before installing. Check each one as you may find many different widths in each bay... under-size widths to fit all.
> 
> Gary


I do have a table saw. So if I understand correctly you are suggesting I keep them as one solid piece sort of like this:

|_|


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## Gary in WA (Mar 11, 2009)

Tired tonight...... http://www.finehomebuilding.com/item/25504/using-housewrap-for-insulation-baffles

Gary


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## VitoB (Nov 30, 2012)

Thanks again Gary! :thumbsup:


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## VitoB (Nov 30, 2012)

Sorry to resurrect this thread again.

None of my local home improvement stores have 1" foil faced in stock.

I calculated 1" DOW XPS to be around the same price.

Would it be OK to use that instead of the foil faced?


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## Windows on Wash (Aug 30, 2011)

The foil faced polyiso is ideal because the foil works as a radiant barrier to help reject heat. 

Either Lowes or Home Depot will usually have it in a 1 inch variety.


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## VitoB (Nov 30, 2012)

Windows on Wash said:


> The foil faced polyiso is ideal because the foil works as a radiant barrier to help reject heat.
> 
> Either Lowes or Home Depot will usually have it in a 1 inch variety.


The Home Depot in my area carries a product called DuroFoam, it's EPS with a green film on one side and a silver film on the other side. It has a lower R value, R 3.75 per inch so that is why I was hesitating. 

If you search for Plastifab DuroFoam you will find it easily.

Not sure if we are allowed to post links.


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## Windows on Wash (Aug 30, 2011)

That should work fine.


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## VitoB (Nov 30, 2012)

Windows on Wash said:


> That should work fine.


That is what I will use then.

Thanks! Much appreciated.


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## skov (Apr 10, 2015)

Hey guys,

I will need to replace attic baffles, but the problem is that all stores in my area carry pretty much the same product made of foam. For example this one: http://www.lowes.ca/insulation-acce...h-built-in-baffle_g1199778.html?ProductSlot=2 . I don’t trust good reviews. I visited a store and half of them are broken on the shelf. I tried to fold one (how it’s supposed to be folded) and it really brakes! Unfortunately, none of the stores in my area carries plastic baffles and I will need to make something.

So, I have a polyethylene vapor barrier roll and I am planning to cut it to make baffles (very easy – size is just right). I am wondering, does anybody have baffles made of a vapor barrier? Are there any reasons why it may not be a good idea?
Thanks!


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## Gary in WA (Mar 11, 2009)

IMHO, poly should not be used because if the attic air above it is colder (soffit supplied outdoor air) than any air/moisture below it (room heat/air from below conditioned areas), you will have dripping condensation below/on it; "first condensing surface"; Photo 3,4, Fig. 2; http://www.buildingscience.com/documents/insights/bsi-049-confusion-about-diffusion/?searchterm=first%20condensing%20surface

Same with Vito, per his cold location, warming the roof sheathing with foil-faced material is last thing I would do. You want the sheathing colder to prevent ice dams. A thicker foam would separate the warmer attic from colder sheathing. You want the sheathing as cold as possible to ambient temp. Radiant reflects the energy back to the sheathing/roofing shingles (heating them) as I said in Post #8 earlier... not good.

Gary


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## Windows on Wash (Aug 30, 2011)

I think you are over-thinking it a bit. 

I would just use the cardboard ones and be sure to seal that outer top plate really well and get as much insulation there as you can.


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## skov (Apr 10, 2015)

Cardboards from the local stores are very short (around 30-40 cm) and not suitable for my purpose adding blow-in insulation. In addition, I have right now cardboard baffles and they don’t seem working very well – they look like regular cardboard dried out after being spilled (curved uneven surface). I don’t see all of them, but one of them fell off. So, I am looking for something suitable for my purpose and durable.


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## skov (Apr 10, 2015)

Gary in WA said:


> IMHO, poly should not be used because if the attic air above it is colder (soffit supplied outdoor air) than any air/moisture below it (room heat/air from below conditioned areas), you will have dripping condensation below/on it; "first condensing surface"; Photo 3,4, Fig. 2; http://www.buildingscience.com/documents/insights/bsi-049-confusion-about-diffusion/?searchterm=first%20condensing%20surface
> 
> Same with Vito, per his cold location, warming the roof sheathing with foil-faced material is last thing I would do. You want the sheathing colder to prevent ice dams. A thicker foam would separate the warmer attic from colder sheathing. You want the sheathing as cold as possible to ambient temp. Radiant reflects the energy back to the sheathing/roofing shingles (heating them) as I said in Post #8 earlier... not good.
> 
> Gary


Thanks for letting me know!  This is exactly what I meant - unexpected surprise with moisture. It’s especially important for the climate in my area (Alberta, Canada). Double digit change in temperature in just one hour is a common thing. 

I have to think. I have very limited number of options. Even those Durovent baffles are not available – all stores in the city have in total 10-20 good pieces (I was in all stores).

I also doubt about Durofoam mentioned above – it seems not easy to work with it. I will need something easy to staple.


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## Gary in WA (Mar 11, 2009)

Use some unfaced foam board at the eaves, in the cavity and on the top plates (due to reduced clearance without reducing R-value there). Or- for baffles, use fanfold on the rafter bottoms, leaving a small gap at the eaves and another at the peak to vent the bulk of attic. OR, just fanfold (need the FB for more R-value on walls) at the bottom- 12" above the blown-in and rafters bare on up. Cover the blown-in with housewrap to prevent wind-washing/convective looping. Air seal the drywall/plaster ceiling/wall joints next to the top plates everywhere, no sense feeding the stack effect; http://www.wag-aic.org/1999/WAG_99_baker.pdf

http://www.google.com/url?sa=t&source=web&cd=23&ved=0CCUQFjACOBQ&url=http%3A%2F%2Fapps1.eere.energy.gov%2Fbuildings%2Fpublications%2Fpdfs%2Fbuilding_america%2Fba_airsealing_report.pdf&rct=j&q=foam%20board%20in%20attic%20require%20thermal%20barrier%20with%20drywall%20already%20installed%20on%20other%20side%20of%20kneewall&ei=IvqWTveuIKW0sQK3zPzwBA&usg=AFQjCNHwd56o0AxLi8-V03E5cMUmwWATQw&cad=rja

Interesting immediate turn-around answer for; "I think you are over-thinking it a bit. ". lol

Gary


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## Windows on Wash (Aug 30, 2011)

Gary in WA said:


> Interesting immediate turn-around answer for; "I think you are over-thinking it a bit. ". lol
> 
> Gary


I will confess to not having considered the foil facing and rejection of the heat back to the roof surface. Something to think about in the case of a cold climate like Canada.

We have make our own baffles here on several application and found the foil facing to work perfectly as well as meet the ignition barrier best practice. The uncovered side of the foam is filled to the brim with insulation so covered in this case. 

Would the roof deck be getting that much radiant energy from the son if it were covered in foam (i.e. the very condition that we would need to concern ourselves with if we are thinking about ice dams)?

As we both know, an overwhelming (i.e. hugely disproportionate amount) of ice dams are a result of lost heat from the attic and not solar warming. We do see more than a handful of posts on here about bad valley and roof designs but the vast majority are as a result of heat/air loss. 

Good points either way. Something to think about in the future and thanks for pointing that out.


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## Gary in WA (Mar 11, 2009)

Found it; "thanks for pointing that out." Thank you.

Gary


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## Gary in WA (Mar 11, 2009)

It is a fine line between ice dams or not. Ventilation plays a role. You can figure mathematically if you have enough ventilation or not... this formula does not include daytime solar loading or nighttime radiational cooling. You would also need to figure 10*F warmer for a radiant barrier, supplying extra warmth to the sheathing. Granted, it is a small amount but it just may be enough to put you into ice dams; http://www.erdc.usace.army.mil/Portals/55/docs/CEERD-RV/CEERD-RR-H/BuildingTechnology/ResearchPapers/MP-02-5778,%20Guidelines%20for%20Ventilating%20Attics%20and%20Cathedral%20Ceilings%20to%20Avoid%20Icings%20at%20Their%20Eaves.pdf

Gary


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