Replies

1. GBA Editor
   Martin Holladay | Apr 01, 2013 05:35am | #1

   Bruce,
   Plenty of people use cardboard ventilation baffles. You can buy them:

   J&R - Cardboard Attic Baffles

   Bafflo baffles

   As with any ventilation strategy, the usual warnings apply: pay attention to airtightness, and make sure that the R-value of your insulation is high enough. More information here: How to Build an Insulated Cathedral Ceiling.

2. 
   snfh | Apr 01, 2013 08:07am | #2

   Thanks Martin. I'm familiar with both manufacturers and many others. There are flaws in the designs of all these products and most are not long enough to be installed in a single pass. So, I plan to make my own as long as I can be assured that the cardboard itself poses no risk (moisture/mold) as long as it is properly installed.

3. GBA Editor
   Martin Holladay | Apr 01, 2013 09:26am | #3

   Bruce,
   If you are installing cellulose, the question is simple: will the cardboard be stiff enough to resist the pressures induced by the blowing machine?

   If you are installing fiberglass batts, then the cardboard is certainly stiff enough -- but you still have all of the inherent disadvantages of fiberglass batts.

4. 
   snfh | Apr 01, 2013 12:43pm | #4

   I am installing cellulose and will test cardboard on the next house. Our test chutes are fairly rigid (if stapled close to the crease of the flap) and seem like they will withstand the pressure of a blowing machine . I guess the only way to know for sure is to test it.

5. 
   mrgregpittman | Apr 03, 2013 09:49am | #5

   I found one of the article on the Yahoo! Voices that might help you to understand more

   http://voices.yahoo.com/how-install-choose-baffles-attic-1427873.html

6. 
   Foamer | Sep 17, 2013 09:56am | #6

   Bruce,
   I came across your question while browsing for a better baffle - a search that is ongoing. We have installed pretty much every baffle out there and I don't like any of them. Cardboard is adaptable and plenty strong at the time of install but does not hold up well over time. Styrofoam is too flimsy and require additional work to block the eaves. Site built systems are very labor intensive. I did find a product that installs like a cardboard baffle but is made of fluted plastic. If you can swallow the cost, this may be your best option (http://www.dciproducts.com/html/smartbaffle.htm).

7. 
   user-917856 | Sep 17, 2013 01:52pm | #7

   Bruce,

   I saw these baffles at EEBA in 2006. They are recycled plastic, very durable (can't be torn) and they offer a "high energy" version for deeper attic insulation. Call them and see if you can get some free samples.

   http://www.brentwoodindustries.com/spg/building-products/index.aspx

8. 
   snfh | Sep 18, 2013 12:05pm | #8

   Torsten,

   Thanks for the feedback. My experience is pretty much the same as yours. I wish I could see some 30-50 yr old cardboard baffles to see how they are holding up but that will probably never happen.
   I did order a box of the smartbaffles and experimented with them. They work for standard spacing and are a bit of a pain for non-standard spacing. Anyone could make smartbaffles with a sheet of corrugated plastic for less money.

9. 
   r5portals | Oct 29, 2016 10:27am | #9

   Here are photos of cardboard baffles at thirty years of service:
   https://drive.google.com/open?id=0Byj-qncyomXmRjhVcUN3QUtYVEU

   Perhaps coated cardboard lasts longer. I doubt it, where bare cardboard side exposed, may curl more. Manufacturers do not offer a service life guarantee.

   Let's emphasize plywood as the best solution. Where most bird block is like that in the photos, know tiny hole area demands placement in every bay.

10. 
    user-5946022 | Aug 31, 2020 03:19pm | #10

    What about making rafter baffles out of 4x8 sheets of 1/2" polyiso the big box sells. These have foil on one side so with the foil face down they could also serve as a radiant barrier.

    Has anyone ever done this, and is the scored polyiso strong enough to resist both the force of blown cellulose and the raves of time (that photo of the 30 year old cardboard baffles is scary...) If so, other than the fabrication time, is there a downside? You could fabricate them so you get the full 2" depth or more that some articles advocate.

1. Expert Member
   BILL WICHERS | Aug 31, 2020 05:50pm | #11

   1/2” polyiso is used for this all the time. The foil side facing up helps as a radiant barrier to keep the attic a little cooler, but I wouldn’t use polyiso just for this. Facing the foil down doesn’t do anything if it will be pressed against some other type of insulation since a radiant barrier needs an air gap to work. Polyiso is rigid enough to spray insulation against unless you try to span something a lot more than the standard rafter spacing.

   Polyiso holds up pretty well. I just pulled out some in a renovation in part of my house that is about 40 years old. It is just like new except for the exposed polyiso on the edges being yellowed. It’s still rigid, in one piece, and insulating just fine.

   Bill

1. 
   user-5946022 | Aug 31, 2020 08:45pm | #12

   Thanks for the reply. Did you insert a block into the rafters, glue something to the polyiso, or just score and bend it? I'm considering this solution over the expensive DCI Smartbaffle. It would get the full 2" of vent space.

   I'd put the reflective side down; per other articles here putting it up it gets dusty and eventually does not work. Only a small part of it would be in contact with the insulation under it - the rest could act as a nice radiant barrier

   Working in an existing condition so I'm trying to avoid as much in place work as possible; I'd like something I can just slide it in there and secure with a staple on each side. A baffle created by scoring polyiso relies on the foil side polyiso to hold the thing together - I'm concerned it would tear either from the cellulose pressure or over time.
   Taping the score does not seem like a good option as I presume the attic heat would eventually overcome any adhesive. Any easy way to fabricate these so they are sturdy and stay and work in attic is limited?

   I watched this video: https://www.finehomebuilding.com/2016/06/29/rigid-foam-vent-baffles. Thought I would use the same system but stop the scoring 4" short of the high end. I'd score that last 4" on the other side and fold that section the other direction to use as a staple flange.