Not sure what forum this question fits in. I am interested in constructed the exterior walls of my passive solar house with a vapor barrier foil on either side. I have heard from someone who had a foiled faced sheathing on their house, they were not able to use their cell phones in the house from interference from the foil envelope. Wondering if this is true and whether Wi-fi would be disrupted as well. Has anyone ever heard of anything like this?

True, metal foil is bad for RF, although wifi is usually internal only (ie, doesn't need to pass through it). Why do you want foil?

Does "...with a vapor barrier foil on either side..." mean foil on both sides, or only one?

Foil on both sides would create a moisture trap, and be an extremely bad idea. If you put any strong vapor barrier on either side you have to be very particular about the stackup to guarantee that it doesn't collect too much moisture seasonally. In general in a heating dominated climate if you have a strong vapor barrier it needs to be either on the interior side of the insulation or at an intermediate point in the R where it's average temp during the winter season is at or above the dew point of the interior air, so that the interior finish can be left fairly vapor open for drying to the exterior, and the exterior side can be left fairly vapor open to dry toward the exterior. (Back-ventilated/rainscreened siding on the exterior will aid drying of the wall assembly IMMENSELY, if the exterior side is still reasonably vapor open, but only protects the siding if there's a foil on the exterior.)

Cell phone is microwave, and gaps as big as windows provides easy paths through the foil, but it's possible to orient a foil clad house so that it's optimally bad for cell phone reception in particular locations. Strategically placed passive antenna feed-throughs could be installed to get the signals in & out of the "bad" corner of the house if that became an issue, but those would be the very rare exceptions rather than the rule.

Spending your worrying-energy on how to build resiliance into the assembly stack-ups than about the RF translucency of the shell is a far better use of your time.

Actually, the wall system is very nice and has a good price point. Check out: www.raycore.com They have a very nice product that works well. Please review and tell me your thoughts regarding the foil faced walls. Thanks.

Posted By Myrtleboone on 13 Dec 2012 10:00 PM
Actually, the wall system is very nice and has a good price point. Check out: www.raycore.com They have a very nice product that works well. Please review and tell me your thoughts regarding the foil faced walls. Thanks.

Lots of thermal bridging through the studs and plates with that design.  There is no insulation over the studs and plates.  There is no way they are getting R26 whole wall with a 3.5" wall panel due to thermal bridging of the wood.  I'm not even sure how they came up with R26 just for the foam which is R6.5 per inch at most (R6.5 x 3.5" = R23).  They must be counting on the radiant barrier providing that extra R value.  The foil on the inside provides virtually no thermal benefit if drywall is attached directly to the studs because for foil to function as a radiant barrier, it needs an air space.

I suspect that you can beat the price and performance with a normal stud wall + cellulose + rigid foam + a taped air barrier.

Posted By Myrtleboone on 13 Dec 2012 10:00 PM
Actually, the wall system is very nice and has a good price point. Check out: www.raycore.com They have a very nice product that works well. Please review and tell me your thoughts regarding the foil faced walls. Thanks.

Where do I begin?

I guess I'll start with "what arkie6 said", followed by "what jonr said".   The whole-wall performance isn't anywhere near what their promotional literature implies.

The foils are still a moisture trap for the structural timbers within the panels, but the extemely low vapor permeance of the high-density polyurethane is almost as vapor retardent as the foils.  It's not easy for moisture to get in, but once there it never gets out. If they don't build with kiln-dried timbers it could still be a real problem even without moisture leaks from nail penetrations, etc.

But then there's the worse stuff:

It's all done with closed cell polyurethane foam, the vast majority of which is blown with HFC245fa, that has more than 1000x the greenhouse potential of CO2, and more than 50 years worth of the greenhouse gas emissions of the energy use it's offsetting.  While there are some very low greenhouse potential blowing agents being developed for polyurethane they are not on the market yet, and they don't have a track record for how well the perform on long-term shrinkage issues that has plagued closed cell polyurethane goods- it's a touchy chemistry.

If you're going to build with SIP type panel system, go with EPS cores, which are blown with pentane, not HFCs.  Pentane-blown EPS has less than 1% of the lifecycle greenhouse potential of a polyurethane-core version of equal performance.  It will be ~50% thicker than a polyurethane SIP, but even an R50 SIP is only about 12.5-13" thick.

EPS has long term shrinkage issues too, but those aren't much affected by blowing agents, and there is now a 20+ year history on pentane-blown EPS, and it's no worse than when it was blown with ozone-layer damaging HCFCs- if anything the switch to pentane has been an improvement regarding aging issues.

A few manufacturers (eg Huntsman) make structural polyisocyanurate core panels which have nearly the same R-values as polyurethane at a given thickness, but like EPS most polyiso is blown with pentane these days, not HFCs.

They have a staggered stud design with 1 3/4" foam for a thermal break from outer surface to stud. I need more r-value anyway so I'd be adding foam sheathing on the outside of it to decrease its thermal bridging even more.

I would be interested in your costs for such a wall.

A quote for my home is actually very competitive to a "build on site" stud wall with the same while R-value including labor.

But the environmental cost of the massive volume of HFC-blown polyurethane is more than it's worth, no matter what the quote price is.

When they can deliver a product blown with the (soon to be released) Honeywell Solstice™ or similar or a water-blown product that may change. (The new stuff delivers only ~ 0.5% the greenhouse gas punch of HFC254fa, which is currently nearly universal in the closed cell polyurethane biz.)

Even the staggered stud version has the issue of the thermal bridging and air leakage at the plates and the framing between the panels. The whole wall-R is still well under the advertized clear-panel R.

My house was built in the late 80s and I have horrible cell reception. At first I thought it was only where I live at but I get less dropped calls outside. Well they ripped the siding off to add vinyl and to build my addition. What did I find? Foil lined 1/2 inch foam over the outer side of the wall.

The cell issue is easy to overcome if you have cable or DSL. All the major cell companies offer FEMTOCELLs which are similar to the many PICOCELLs that are in place in large sports arenas, remote office buildings, and some subways. I have sprint and they provided me an Airave 2.0 for free. About a year after I got that it stopped working. Sprint then exchanged it for an Airave 2.5. The 2.5 no longer has the GPS issues and can provide coverage up to 5000sft. The guys working on my siding noticed the beeps on his phone when he was talking on it outside. I get 5 bars most everywhere in my house, 3 in the addition on the opposite side of the house on the other side of the foil, and 2 bars in the crawl space.

My last house had steel siding and I had no issues.