Does Mylar block cell phone signals?

Thread Starter

jpanhalt

Joined Jan 18, 2008
9,392
This statement was made by a member in another thread that was locked for good reason. It raises an issue I was not aware of:
just wrap your house in mylar to make it a faraday cage. I had a friend who just had a new house built with special roof decking/siding,etc.. that had mylar backing.. He couldn't get a cell phone signal in is new house so he had to pay to have repeaters put in so he could use his phone in the house. His attic was never hot though
I just put a new roof on my house a few weeks ago. There are several new underlayment products on the market. One is trademarked, Titanium. It appears to be a polyester film (i.e., Mylar) reinforced with (carbon?) fibers. I didn't even think it might interfere with cell phones; although, I went with a different product for other reasons.

Can anyone report first hand experience with modern building materials interfering with cell phones. I suspect that the manufacturers may not have thought of that possibility either.

John
 
Last edited:

SgtWookie

Joined Jul 17, 2007
22,210
Our home was built with steel studs in the walls. I barely have any signal level when inside the house. That's OK though - if I'm at the house, I don't want people calling me on my cell phone, and I don't make outgoing calls on it, either. That's what the "land line" is for.
 

studiot

Joined Nov 9, 2007
4,998
I was about to ask for more details of the mylar stuff, when Bertus locked the thread so thanks for starting this one.
 

beenthere

Joined Apr 20, 2004
15,819
I just did a quick and dirty experiment. I have sheets of 5 mil mylar on hand for laminating. We are in a low signal area, usually one bar, occasionally 2. With a 300 deg wrap around and over the cell phone, I saw no loss of signal strength. The mylar was oriented so as to be between the phone and the cell tower.

I wonder about mylar wrap on a house, from a cost standpoint. The usual stuff is woven tyvek. Our house is wrapped in it, and we have a metal roof. Tyvek is not conductive - http://www.tyvek.lu/what_is.html
 
Last edited:
100% mylar should be pretty transparent to RF, it was probably metalized mylar used in the OP quote. That would make sense as it would be a good infra-red reflector, which is what the metalized layer on modern car windscreens is for.

I'm currently working in a building on the south coast of England, with a steel roof and steel sidings, and built into the side of a cliff. The mobile reception can be problematic, and often a French base station will be picked up before the local ones. FM radio reception is noisy in stereo, but clean in mono. I've worked in steel buildings on flatter terrain before, and the mobile reception wasn't too bad, so unless the signal is weak anyway I wouldn't worry about a shielded roof. And like you say, there's always the repeater workaround.
 

zero_coke

Joined Apr 22, 2009
294
Get a cardboard box, and put your cellphone inside it. Then, wrap it very nicely with Mylar so as to leave no gaps. Then use your landline to call your cellphone. See if it will work? Try different kinds of Mylar, like ones with aluminized or coated ones as PackratKing mentioned.
 

zero_coke

Joined Apr 22, 2009
294
So you're saying to wrap your house with aluminum (on top of the drywall/plywood) and then apply the stucco/siding/brick and it should make any device that uses radio communications to seize working?
 

t_n_k

Joined Mar 6, 2009
5,455
If the mylar were "aluminized", or coated with some other sort of metallic deposit, and then grounded in turn, there is a good chance it could be an effective faraday cage ...
Just wondering ....

Does a Faraday Cage need to be grounded to prevent RF penetration? Is it actually a Faraday Cage if it's not grounded?
 

Thread Starter

jpanhalt

Joined Jan 18, 2008
9,392
It has been shown pretty conclusively that the antenna for 2.4 GHz, but not 72 MHz, cannot be placed inside a carbon fiber/epoxy composite fuselage of a model airplane. It does not need to be grounded to cause severe loss of sensitivity.

Let me refocus this question a little. We know that radio reception can be problematic inside a metal building. The question was basically whether modern construction materials (e.g., Mylar with fibrous support or an IR blocking coating, coated windows, etc.) and construction practices interfere with cell phone (=>2.4 GHz) transmission. I suspect the term Mylar was used rather loosely in the original comment, as "pure" Mylar would not be expected to interfere. But as one looks are various products "engineered" to improve heat efficiency or longevity, I was struck with the question of how exhaustively they had been tested for use in our modern society.

Experience has taught us that many building materials have been introduced without adequate testing only to find out years later that they cause serious problems and expenses for the unlucky homeowner. Examples include formaldehyde-urea resins in particle board and laminates, imported drywall from China, aluminum wiring, certain types of foam insulation for insulated concrete foundations, and some insulation practices for foundations and moisture barriers.

John
 

mcgyvr

Joined Oct 15, 2009
5,394
I'm the one that made the comment about the mylar.. I did use the term mylar loosely.. I believe it was a metalized/aluminized mylar material and not just plain mylar. I believe it was made by dupont. He used their Enercor wall radiant barrier and also a similar product for the roof/attic space. So essentially his whole house was shielded by this causing a loss of cell phone signal strength to the point he needed the repeaters installed. His heating/cooling bills were very low and he has never been contacted by aliens. :)
 
Top