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Community and Q&A

Attic Foil to Block RF

pico_project | Posted in General Questions on

We’re in the middle of a remodel and have the attic totally cleaned out. Before (or after) the insulation goes back in I want to install some attic foil to block RF signals from a nearby tower (and neighbors Wifi). 

I’m in northern Michigan, and this website recommends a super-perf for cold climates laid on top of the insulation.

From an install standpoint, it seems easier to staple to the rafters.

Since I’m looking for mainly the RF blocking properties of aluminum, is it safe to staple the super-perf version to the rafters? Or should I go with the original version?

Or is it best to avoid having it on the rafters altogether?

Mainly concerned about shingle life, moisture issues, etc…

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  1. Expert Member
    BILL WICHERS | | #1

    If it's perforated, it won't be a moisture issue. If you just want to block RF signals, you can use aluminum window screen too -- you don't need a solid surface. The ability of a mesh to block/reflect RF signals is related to the size of the aperature of the mesh in proportion to the wavelength of the RF signal, and regular window screen with about 1/16" mesh is good up to well above 12GHz, which is right around where direct broadcast satellite services operate. Wifi and regular cellular signals don't get much above about 5GHz.

    Note that installing something like this only in the attic isn't likely to do much about RF. RF signals will go through walls and windows too. To really be effective, you would need to shield the roof AND WALLS of the home, and you'd need to do something about the windows too. It is true that every bit of shielding does attenuate (reduce) the signals, but you'd accomplish more shielding the walls and windows than the roof since most terrestrial signals aren't coming in at high arrival angles, they are coming in at lower angles where they'll mostly be entering through vertical surfaces like walls.


    1. pico_project | | #2

      Thank you for the reply.

      The house had aluminum siding and it was actually worse than with the siding now removed. Seemed to trap the signal in house or some other crazy physics that's over my head. Haha.

      We have Rockwool in the walls now and I'm hoping blocking at the roof will help a little.

      Using super-perf on the rafters will there be any issue with the shingles getting too hot? We're installing soffit baffles as best as possible (low pitch roof) and the foil would go over the top of those. So I'm thinking the airflow should be good?

      1. Expert Member
        BILL WICHERS | | #3

        There isn't usually an issue with the shingles getting "too hot". I would suggest looking into aluminum screen though, which is much more open but will work fine for RF shielded. Note that you don't need electrical connections between panels, either, an inch or two of overlap is fine. You get enough capacitive coupling with an overlap to keep the shielding effective.


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