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Community and Q&A

Vinyl Downspouts as Baffles in Rafter Bays

CRHawk | Posted in Energy Efficiency and Durability on

Hi!  I have a 1970’s contemporary in Zone 5 (Massachusetts)  It has a vaulted ceiling with 2×6 rafters, R19 fiberglass, and no baffles.

The attic has has mold issues before (before we bought the house this summer) and I want to make sure they don’t come back.

I started with air sealing, and have most of it done, mostly from the interior due to the cosmetic beams.  Will finish the rest soon.

I figure I should still have baffles though.   I was looking at the vbaffle for retrofits, and they look great, but they are on infinite backorder.

I came across the idea of using vinyl downspouts.  So I took a 4″ x 3″ downspout and ripped it into a 4″ wide 1.5″ deep U shape.  I then slid it down the rafter bays.  It worked!

My questions:

Is there any reason doing the rest of the rafter bays is not a good idea?

I figure the outside of the U will get condensation on it as it is cold.  Should I drill some holes through to allow the condensation to vent out?  Or will it go into the sheathing and then wick into the baffle space and vent out that way?

Eventually I plan to add a interior layer of polyiso and drywall over that.


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  1. user-5946022 | | #1

    These are only 4". How many are you planning on installing in each rafter bay?
    Why don't you just fashion a baffle out of polyiso and side it in there the full width of the rafter bay?
    If this response seems like I did not understand the question, please post back with a photo or a drawing explaining your question.

  2. ecodude | | #2

    I’m in the west, so it’s a little different…? I’m using black 2” in pipe down past the top plate and attaching them with metal plumbers tape to the rafters… it all depends on how wide the opening in is via the soffit…(I’ll have to add blocking with smaller pipe or stuff insulation) If the pipes metrics don’t add up?

    And, that top plate needs to be covered with insulation, the highest leak point in a houses shell!

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