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Community and Q&A

Bug Screens

jgwaite | Posted in Green Products and Materials on

I am attaching 3″ of mineral wool with 1×4 furring strips over siding covered with WRB. Most details I’m finding use a product like Cor-A-Vent SV-5 as a bug screen but this doesn’t address the 3″ edges of the mineral wool. Can you recommend a solution that addresses the whole assembly? Is fiberglass window screen wrapped across the bottom (including the rain screen gap) durable enough for this application? What is the maximum hole size you would recommend?

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  1. Expert Member


    Bug screens are prone to damage over time, and very hard to replace once the siding is on. To cover the gaps at the bottom of rain screen cavities we use a perforated flashing similer to this. it stops bugs,rodents and resists mechanical damage.

  2. jgwaite | | #2

    I've looked at this product, and like the Car-A-Vent it only addresses the 3/4" rain screen (between the furring strips). I'm not finding solutions for the 3" of mineral wool which I would think needs protection as well...more from rodents than from insects since it's inherently insect resistant.

  3. Expert Member
    Michael Maines | | #3

    The IRC building code requires soffit screens to be made of metal. They don't specify a type, just "corrosion resistant," but I think it's a good idea to use metal screening at any similar location. Brass, bronze or stainless steel screening would be top of the line, but galvanized should be fine unless you're on the coast.

  4. jberks | | #4

    @ JGWaite,

    This is a good point. I'm doing a similar assembly of 2" roxul and 3/8" Quarrix vented strips. and just expected to find a screen like material for the base. But the rodents or bigger bugs is a concern.

    Sounds like I'll be making a trip to my machine shop afterall. I'll probably get perforated alumnium sheets from Mcmaster-Carr, cut them to 4.75" strips and bend them to create an L Bracket.

  5. Expert Member


    I get all my perforated flashings made by the metal shop at my lumberyard. I only included the Menzies metal illustration as an example. Any sheet metal shop should be able to fabricate any profile, out of any stock you want. An L shape will often leave a gap at the siding. A J shape, rather than a U, makes fastening the flashing to the wall a lot easier.

    A solid base flashing, rather than bug screen, also makes construction of the wall a lot easier. It provides a level platform to sit your insulation and furring on.

  6. jgwaite | | #6

    Thank you all for the responses. I was hoping to find a pre-made solution but it looks like fabrication is the right way to do it.

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