Attic insulation questions

[the_tool_man]

Hi all:

My house is about 15 years old. The center of the house has a cathedral ceiling two stories high. On either side of this area, the ceilings are standard 8'. The vertical wall separating the attic above these spaces from the room with a cathedral ceiling is insulated with what appears to be R-19 fiberglass batts. The walls are studded with 2x4's, which leaves some of the insulation protruding on the attic side of the walls. The builder used clear polyethylene plastic, stapled to the studs, to hold the batts in place. After 15 years of attic heat (I live in South Carolina), the plastic has begun to literally fall apart. Very little of the insulation has shifted, but I am concerned that it will. I can see the paper vapor barrier against the back side of the drywall, as is typical in my climate. Presumably, the paper is stapled to the studs on the drywall side, but I can't tell for sure. Even if it is, there are a couple of places where the insulation is separating from the paper, so I need to find a way to support the insulation.

I want to replace the plastic, but I am concerned that if I use plastic sheeting, it will become a second vapor barrier, which I understand is undesirable. Also, I don't want to be doing this again in another 15 years. I found some plastic anti-bird netting at a local home center that is supposed to be UV stable. It's essentially a 5/8" square mesh made from plastic. I thought about stapling this over the insulation to hold it in place, but I wonder how long it will last. I guess I could use metal chicken wire (poultry mesh, if you're PC), but wouldn't that interfere with radio and cell phone signals? Do they make a product specifically for this application? If so, what is it called? Any other ideas?

Thanks in advance, John.

[dpb]

the_tool_man wrote: ...

Either will work fine--I'd expect the plastic mesh, particularly if it is fiber-reinforced, to last quite a while. The wire would, of course be permanent.

It won't be significant for RF attenuation owing to the porosity.

I'd think a simpler and probably cheaper solution would be to simply use some light wire on about 18-24" centers stretched across, however. I don't think you need anything near a full areal coverage to do the job adequately although it would, of course be certain.

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[the_tool_man]

Possibly, but since the insulation protrudes from the studs by about 2 inches, I would think a mesh solution would work better without compressing it very much. Wire might kink it enough to reduce its efficiency. I'm headed to the store now to get a look at the anti- bird mesh. I'll report back with what I find.

Regards, John.

[BobK207]

John-

imo the fastest, cheapest, easiest & longest lasting would be "stucco line wire" (similar to DPB's suggestion)

I'd start a few inches down from the top & nail in a row of dry wall nails across the wall studs......repeat the process about even foot or so....ending with row, again, a few inches from the bottom.

After all the nails are in starting from the upper left (if your right handed) wrap the wire around the first nail. Continue across the studs, givining the wire a wrap or two at each nail.

At the far end, don't cut the wire, just jump down to the next row of nails. If you're concerned about wire breakage (in the future or want the make the wire runs more independent...nail down end of row nails once the wire is wrapped around them.

This will be super fast, never need to be redone & cheap. :)

I don't remember the diameter of line wire (like 18 or 20 gage ?) ......something like 1/32"? but anything you can buy cheap in the .030" to .040".

The stuff is dead soft & easy to work with.

cheers Bob

[dpb]

...

I don't think it would be a problem--any compression is pretty localized and wouldn't have to string the wire tightly, anyway (in fact, wouldn't want to).

But, another thought -- take either the netting or the chicken wire and cut it into narrower strips -- it'll have sufficient surface area but be less costly.

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[dpb]

BobK207 wrote: ...

...

That works and similar to my thoughts, certainly. Since it's a vertical wall (I think?), my thought would be to start at upperleft (say) and go diagonally across to opposite corner or at 45 or less angle depending on the wall length -- that gives a longer area across each wall cavity the wire runs.

I'd also probably use only the two end nails initially (although they would have to be heavier to hold the load) then stretch it not very tight (just enough so it doesn't sag much) and then use a stapler w/ decent-sized staple to fasten down the middle. That saves the wrapping around the nails in the intermediate runs which saves both time and (some) wire...

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[the_tool_man]

I went ahead and bought a roll of the anti-bird mesh. It appears to be a grid of plastic fibers that are melted or bonded together where they intersect. I attempted to rip it apart with my hands, and couldn't, so it's pretty strong. For about $20, I got a roll that is

14' x 45'. If I cut it into 1' wide strips, and space them apart, it's more than enough to do the whole house. Thanks for the suggestions.

Regards, John.