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Which one is better to install the baffles if we're putting radiant barrier foil after the baffles(cardboard) and before R60 blown-in cellulose?

A. enter image description here

B. enter image description here

My pushback on A is that there will be a space between the barrier foil and the baffle and when we blow in the cellulose it will break the foil. While B will have direct contact with the foil to hold the cellulose together. Any thoughts or experiences like this?

isherwood
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Josh
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  • You are asking to compare apples to oranges. Which one is your roof type? With this answer we can help better. Baffles are to allow air to flow. The best one depends on how your roof is made. – crip659 Sep 18 '23 at 19:15
  • Break the foil? Are you using a cannon to install the cellulose? The foil will absolutely not be damaged. Are you laying foil over the cellulose? How else would you get it out to the edges if you don't install it via foam board? I suppose you can attach it at the bottom and leave the top open for access. Please revise to explain that better. – isherwood Sep 18 '23 at 19:32
  • We have an open gable roof. – Josh Sep 18 '23 at 19:34
  • The above image is just an example. I forgot to add that we're just gonna use a cardboard. Some say that the foil will not withstand the weight of R60 insulation. – Josh Sep 18 '23 at 19:38
  • @isherwood we're thinking about the compression of the insulation that can create a force plus the weight to push the foil and break it and start going to soffits. – Josh Sep 18 '23 at 19:52
  • Now I'm even more confused. Gravity pulls the insulation _away_ from the baffles. In fact, homes that are a few decades old tend to have a void below the baffles. What am I missing here? – isherwood Sep 18 '23 at 19:55
  • I would say A is better because it's cheaper, easier to work with, and leaves more room for the blown-in insulation but I don't understand your concern about foil or even why you're bothering with a radiant barrier. – aquaticapetheory Sep 18 '23 at 20:02
  • @isherwood sorry about that, I think it's because of what I got from other answers from my previous post. https://diy.stackexchange.com/questions/281638/insulation-baffles-alternative – Josh Sep 18 '23 at 20:02
  • What I'm getting right now is if we install radiant foil, it will be enough to stop the cellulose from going to the soffits if we have a gable roof? – Josh Sep 18 '23 at 20:06
  • It takes very little strength to hold back blown insulation. Notebook paper would just about suffice. Use what makes sense from an _energy_ perspective. – isherwood Sep 18 '23 at 20:08
  • Comment because it doesn't directly answer either of your questions: If you have soffit vents and gable vents and the attic is unconditioned space, I don't think you should be putting foil foam over your rafters. I assume you're trying to reflect heat coming in through the roof but it's just going to get blown into the attic by the soffit-to-gable air flow. Keep it simple: add baffles to keep cellulose out of the soffits, pile on the insulation onto the floor. It'll get hot in the attic, the blown-in stuff will keep the heat up there. – aquaticapetheory Sep 18 '23 at 20:16

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