Spray foam insulation in Vented Attic?

Page 2 of 2  


It makes sense. Multipath as mentioned, as well as signal blocking, which occurs wherever gaps between metal are less than a tenth of a wavelength L = c/f, eg 3x10^8/900x10^6 = 0.333 meters (about 1') at 900 MHz. So 900 MHz cellphone signals can only sneak through non-metal paths more than an inch or so wide. And they can't penetrate much past the skin depth in aluminum, d = 3208/sqrt(f) = 0.107 mils at 900 MHz, which is thinner than most metal sidings or foils or paints.
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 1 Jul 2007 06:57:13 -0400, snipped-for-privacy@ece.villanova.edu wrote:

There is a federal law that says thay you can put your antenna outside up to 12 feet high above your roof, regardless of what your homeowners association or building codes or deed restrictions say.
And moving it outside and up will tremendously improve your reception.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

"12 feet high above your roof" - Really? I think not.
http://www.fcc.gov/mb/facts/otard.html Q: What restrictions prevent a viewer from receiving an acceptable quality signal? Can a homeowners association or other restricting entity establish enforceable preferences for antenna locations?
A: For antennas designed to receive analog signals, such as TVBS, a requirement that an antenna be located where reception would be impossible or substantially degraded is prohibited by the rule. However, a regulation requiring that antennas be placed where they are not visible from the street would be permissible if this placement does not prevent reception of an acceptable quality signal or impose unreasonable expense or delay. For example, if installing an antenna in the rear of the house costs significantly more than installation on the side of the house, then such a requirement would be prohibited. If, however, installation in the rear of the house does not impose unreasonable expense or delay or preclude reception of an acceptable quality signal, then the restriction is permissible and the viewer must comply.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Try this on for size: Q: What types of antennas are covered by the rule?
A: The rule applies to the following types of antennas:
(1) A "dish" antenna that is one meter (39.37") or less in diameter (or any size dish if located in Alaska) and is designed to receive direct broadcast satellite service, including direct-to-home satellite service, or to receive or transmit fixed wireless signals via satellite.
(2) An antenna that is one meter or less in diameter or diagonal measurement and is designed to receive video programming services via broadband radio service (wireless cable) or to receive or transmit fixed wireless signals other than via satellite.
(3) An antenna that is designed to receive local television broadcast signals. Masts higher than 12 feet above the roofline may be subject to local permitting requirements.
In addition, antennas covered by the rule may be mounted on "masts" to reach the height needed to receive or transmit an acceptable quality signal (e.g. maintain line-of-sight contact with the transmitter or view the satellite). Masts higher than 12 feet above the roofline may be subject to local permitting requirements for safety purposes. Further, masts that extend beyond an exclusive use area may not be covered by this rule.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
ValveJob wrote:

The reason homeowner associations try to keep them inside is they're unsightly.
--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form snipped-for-privacy@prodigy.net.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@gmail.com wrote: ..

Sorry I missed that part the first time I read it.
Hogwash. I have foil up there and it does not block my TV or cell phone.
--
Joseph Meehan

Dia \'s Muire duit
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Joseph Meehan wrote:

I think you're right. My TV antenna is in an attic with foil and works just fine. Unfortunately, I don't have any good authority or personal "with and without" type evidence that I can cite for the assertion that there's _no_ negative effect.
I suspect a careful analysis of the propagation of the frequencies involved would show that a radiant barrier is transparent to them.
--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form snipped-for-privacy@prodigy.net.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

One data point does not make for proof.
It depends on the installation. The problem isn't necessarily "blockage" of the signal but multipath. The antenna catches the signal, but the foil can also reflect a piece of the signal back onto the antenna. Since the speed of light is not infinite, this second signal arrives a fraction of a second later and tends to damp out the first one (the waveforms are out of phase). The situation can be worse if there are additional reflections from other surfaces.
Depending on the location of the transmitter, antenna, and reflector, you may or may not experience multipath. If you do have a problem you may be able to solve it by moving the antenna to a different location in the attic or switching to a more "directional" antenna, i.e., one with more gain. A higher gain antenna does a better job of "ignoring" the unwanted reflections coming in the sides and back of the antenna.
In short, there are a lot of variables at play.
Back to the topic at hand, I would say applying insulation directly to the ducts themselves is the simplest and most effective solution for the original poster.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@gmail.com wrote:

So if your neighbor has a foil radiant barrier in HIS attic, you would expect poorer reception? It would, after all, create the same sort of multipath.
I think citing some numbers and/or actual experimental results would be a lot more convincing than arguments like this.

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form snipped-for-privacy@prodigy.net.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

http://www.google.com/search?q=tv+antenna+attic+radiant+barrier
About 13,100 results.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@gmail.com wrote:

I clicked on a few. The first one that directly addressed the issue indicated BETTER TV reception after the radiant barrier was installed.
--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form snipped-for-privacy@prodigy.net.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Like I said, a lot of variables. My point is metallic radiant barriers can sometimes be a problem. YMMV.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@gmail.com wrote:

All that is true, but it is unusual for the foil to cause a problem and in fact a neighbor's foil may cause a problem. I would not shy away from foil backed insulation for fear of a problem. It is just too rare an issue. From personal experiences I have had four homes with the foil and never had a problem.
--
Joseph Meehan

Dia \'s Muire duit
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Different people have had different results. A friend who had foil radiant barrier installed saw a negative impact on his TV signal. We do not plan on moving our antenna, and we refuse to take the risk of negatively affecting either or TV or cell signals.
ami
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks to everyone for the recommendations. We've decided to get both the spray-on radiant barrier and insulation added to the attic floor. We'll see how well that works in cooling down our attic before we proceed with the ductwork. We're leaning towards wrapping the ducts in batts instead of spray-on foam so that we have access to clean the ducts.
ami
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Be sure to look at this data, too. http://www.fsec.ucf.edu/en/publications/html/FSEC-GP-66/index.htm
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.