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Retrofit Soffit Baffles

pico_project | Posted in General Questions on

Question about two options I have for soffit baffles on our renovation. More about if one way would be considered ‘better’ enough for the amount of work.

The original plan to put in Accuvents didn’t work as the rafter spacing/soffits openings vary quite a bit, especially on the small size. So the plastic ends up just getting crushed.

The insulation contractor wants to put up foam vents, seemingly pressure fit and then do the blocking with fiberglass. This seems like the easiest since both would form to the openings a bit better. My general understanding though is that most people don’t like the cheaper/flimsy foam baffles.

I was thinking about buying a few sheets of 1″ faced foam board to see how much work it would be to create my own baffles and do the blocking with the same foam board and a foam gun. I can see this taking some time as there are about 160 bays to fill. I figured about 30 sheets of 4×8′ foam board. Is this even realistic?

Another option would be to just trim the thinner plastic Accuvents with scissors and then fill any gaps with can foam.

Any feedback would be greatly apreashiated. I really want to the soffits right as we have all the soffits off right now and insulation out of the attic.

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  1. Expert Member
    BILL WICHERS | | #1

    Yes, you can build your own baffles. 1/2” polyiso works great for this because it’s reasonably stiff while still being thin enough to cut through with a regular knife. You don’t really need to seal it in place if it’s just keeping a vent channel clear, because anything that leaks around the baffle will just get carried away by the ventilation channel.

    What I like to do is to use some 1x2 furring strips, which I nail up against the sides of the rafters tight to the underside of the sheathing. This goes fast with a Brad or finish nailer. Once you’ve done that, cut the rigid foam to fit between the rafters and either press fit it in place or tack in in place. The furring strips will ensure the vent channel is open and evenly spaced. You can use a bit of canned foam or caulk to keep the baffles in place too.


  2. charlie_sullivan | | #2

    Check out the dci smart baffles made from coroplast. The fold makes them adaptable to variations in width. I ended up making my own from generic coroplast, partly because I could make them in a few variations of width, and partly because I bought the wrong ones intially. I'd make a batch of 20 or so in three different sizes, take them up to the attic, and put the best fitting size in each bay. Then I'd make more of whichever size I ran out of first, so I could have them all fit well without doing a full measurement and custom cutting project.

    I do think some effort at sealing the perimeter is worthwhile.

    If you happen to have the roof off for other reasons, it's much easier to install them from above.

    Do you happen to have 16" OC spacing? That's the size I initially bought by mistake and I still have them sitting around, although I'm not sure whether it's feasible to ship them to Michigan for a reasonable cost.

    1. pico_project | | #3

      I was thinking about buying 1" faced poly foam board and then scoring them to have similar flanges to screw/nail into the side of the rafters. Seemed to be the same amount of money?

      1. charlie_sullivan | | #4

        I think the difference is that typical facing is much thinner than the plastic on one side on the coroplast. So the coroplast will spring outward and hold itself in place, whereas I expect the facing would be too floppy to do that. But I haven't tried it.

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