No worries about the wires, they will be fine when fully encapsulated by the foam (only the old knob and tube type wires must be in open air). But the boxes are another story. I've found that if there is even the slightest opening, the foam will get into a box. Best to kill all the power to the affected boxes while installing and then open every receptacle, light switch and ceiling box afterwards to check and clean out any foam that got in.

However, I would also carefully check that 60 year-old wire before enclosing it. If you see any corrosion of the wires, I would strongly consider replacing them now, before you fill the cavities with foam.

Isn't it the job of the foam guys to check this stuff???

Come on, Pete. Be realistic. How many of them do you think are going to bother?

If I understand the way this stuff works, I wouldn't want it in my home. There are two reasons.

One is that I remember the unexpected health effects of earlier foam-in-place insulation products, and I'm leery of anything similar that has chemical reactants.

The second is that I have enough trouble fishing cable in walls with blown-in cellulose and fiberglas insulation. Foam-in-place has to be much harder to get through. Or am I missing something?

Actually I don't find it particularly difficult to fish wires through foam. The fish tape moves rather easily through the foam right next to the drywall, and pops right out into the box opening, when you're lucky anyway. Occasionally I have a hard time with it, but no more than snaking through any other type of insulation.

We use foam for some applications (mostly Tiger Foam), and the new stuff is much better than the old. The manufacturers claim it is the most fire resistant insulation out there, even better than fiberglass, and when installed correctly it is amazingly effective, as it seals the wall tight to any air infiltration. It's polyurethane based, and essentially only gives off steam as it is applied. We'd use it more but it is very expensive, and other types usually beat it out on cost. But in some cases, where you need a very high R value per inch or want to insulate walls without opening them up, it's the best way to go.

"How many of them do you think are going to bother?"

I am doing my second renovation where they are using Icenene(sp). The shoot the stuff on the underside of the roof. The only real issue is at the eves where the foam will actually meet the ceiling.
I strongly feel it is the responsibility of the foam people to look into, if not provide an MSDS, about the reaction of their product with other compounds.

I was told there is no harm to any wiring with the stuff they are using. And they asked if any fixtures or enclosures needed to be boxed around that I did not want foam infiltration.

The fish tape moves rather easily through the foam right next to the drywall ...

Tried it with lath and plaster lately? ;-)

Other than income property, I've only owned one home with drywall, and that was many years ago.

Jeez, david, sorry about that. Hope you can afford a new home someday! (Jess kiddeeng.)

Fishing behind plaster and lathe is hell, no matter what insulation is behind there. Used to do it a lot when I worked in San Fran, but haven't worked with the old wood lathe for 6 years now that I've moved further north. New plaster jobs use the metal lathe, which doesn't grab the fish tape like the wood would, but it's still a royal pain.

BTW, we've been using the durorock paperless drywall exclusively for the last 2 years, and though it's not fun to work with (lots of fiberglass fibers in your skin) it does seem superior in pretty much every way. We often put a smooth drywall compound skimcoat over it to mimic plaster, and it looks pretty darn good. No popcorn for us.

Fishing with lath & plaster is a pain even when there's NO insulation. It's also all kinds of fun to cut holes in plaster for old work boxes.

That's part of the price I pay. Financially and otherwise, old houses probably cost me more than new ones. I still like 'em, except for income property.

I suppose I'm being annoying and pedantic - but "lath" is the correct spelling. Adding the E makes it a machine for turning wood or metal. ;-)

Here is a link that might be useful: Lath in the dictionary

Dang, now I gotta look up "pedantic" too!

We use a cutoff wheel in an angle grinder to cut through LATH and plaster; works much better than a sawzall, and doesn't shake the wall apart.

I knew how to spell it. I was just testing you.... (Yeah, that's the ticket, just testing!)

If your wiring is that old I am going to guess that it has no grounds. Consider rewiring before you fill the walls with foam.

We use a cutoff wheel in an angle grinder to cut through LATH and plaster; works much better than a sawzall, and doesn't shake the wall apart.

Interesting! I've used a rotozip with the rpm cut way back (otherwise the lath chars and fills the house with smoke). It's slow. Does the cutoff wheel avoid that problem?

David: Yes! It works great. No vibration, easy clean and quick cuts. We've also used small circular saws (like the little battery-powered ones) with various types of masonry or metal-cutting blades, and that works pretty good too. Works best to plunge the blade/cutoff wheel in and then pull out, and then plunge back in as you work your way around the cut, rather than plunging in and trying to cut along a straight line. It also works well for cutting out old boxes so you can pull new wires in, and then install a handybox using the E-Z-IN box supports. Cuts right through any nails or brackets holding the old box. Try it. You'll like it.

My walls are not true plaster (some kinda wallboard skimcoated?) I dont think. The wall covering is 7/8 of an inch thick and is not drywall, but doesn't truly appear to be wet plaster (no lath of any sort). Although the ceiling where I can see from the upstairs may have some sort of lath, its pieces of gypsum about 3/8 thick with paper on both sides.

Any how I am definitelly considering rewiring first. The lower lever receptacles would be easy because of the basement, same with the light switches. Getting to light fixture is gonna be a PIA in the two bedrooms and the hallway. The upstairs also shouldnt be hard as I can bring a wire up next to the plumbing vent.
I am thinking of removing or somehow reusing the existing box or putting a new box where I removed the old one as to minimize patching, and abandoning the old wire inside the walls. I am going to have to look upstairs some more to refine my exact plan (the house started out with 4 fuses when it was build, fuse 1 north half, 2 south half, 3 two kitchen receptacles, 4 basement receptacle.)
The original panel is now a J box and each circuit from that connects to a breaker in the basement.

I am open two any advice/products to make things easier.

I am thinking first I should get a general idea how the existing wires are run in the walls.

Also I know would have to add receptacles and do some things differently to meet modern codes. So I thing I will find out what version of the NEC my local code is based on then get a copy, or should I spring for the latest model? What about those code check books? Anyone ever used those?

We icynene'd our new house and did not find the foam getting into the electric boxes to any significant degree (open low voltage boxes are another story). It does apply to the underside of the roof sheathing, not to the attic floor, so wiring in the attic is wide open and cool. They also completely covered double insulated recessed cans without an issue. I can't imagine how one would snake inside a foam wall however unless they did not fill up the cavity.

Our 1922 wood frame home has the original knob and tube wiring and NO insulation. We recently got a quote from a contractor that said they would use Retrofoam insulation and we were not to worry about the existing knob and tube wiring, that they use the foam with homes like ours all of the time. Should we believe them? If not, what are our options???

According to every professional electrician on this site,knob and tube CANNOT have contact with insulation. So it sounds like you better get it changed before insulating.

see below

Here is a link that might be useful: NEC reference

What about moisture inside the walls causing mold? My 1914 stucco house has no insulation in the walls. Was recently rewired but I think there were a few areas in some places they could not rewire and am a little worried there may be a little knob and tube left. Instead of them drilling on the outside they are going to try to drill into the walls from the basement to at least get the first floor and then they will spray where the floor joist meet the block in the basement. Does the stuff in the walls expand and possibly crack the plaster?Biggest concern is mold in the walls,cracked plaster, and worst fire. Do I need to worry. Should I have them spray the joist and forget the walls?Thanks,Todd.

You need to make sure there is no live knob and tube. Properly installed there should be no issues with plaster cracking. Plaster is much stronger than than drywall and most modern house sheathing products so I can't imagine a problem.

Mold should be less of a problem than now.

I have an MSDS sheet from retrofoam. it shows that it contains .3% formeldahyde. NOT GOOD. Now I know why you can't find the MSDS sheet online anywhere. Also if you look on there website, it doesn't say anywhere about "does not contain formeldahyde" but it states many other things it doesn't contain. Not sure about the US, but in Canada, this is a big problem if you put it in your place, as now when you sell you have to disclose that you have formeldahyde insulation in your house. Can you say another UFFI situation. I also know that they do not have a CCMC or ULC listing yet, due to the fact of the formeldahyde in it. What I would suggest to look at is airkrete insulation. Alot better benefits than both retrofoam and icynene. Iceynene is still urethane based. I have talked to many installers about it.

For plaster om wood lath I set a Rotozip to barely touch the wood and run it around the desired opening.
I then use an angle grinder with a slitting saw blade to cut though the lath.
The section often just falls into the stud cavity at that point, but if it stays in place it can be gently pushed in.

If expanded wire mesh is near the desired opening I use a Sawzall with a minimum 10 inch blade.
This allows a very shallow entry (I use a 'blind start') into the plaster and avoids the jacking back and forth of the wood lath that occurs with a more perpendicular cut.

In either case Durabond makes a solid repair around the box if required.

In regards to foaming over knob and tube wiring, which has already been stated you shouldn't. In my experience with one house that I've owned with it, there will be bare wires somewhere in the runs if it's old enough. I found sections that were inches long where the insulation had deteriorated. Of course the house was built in 1911, so it was pretty old wire. I also found switch boxes that the studs had been chared where the boxes were attached. Good Idea to replace that stuff.

Sparcky,
You sound like a fella that's does his homework...
what's your opinion of Air Krete?

I had no problem with the icynene guys.
The darned stucco guys on the other hand will fill any opening you can find. You're well advised to place covers on the boxes before they get to them.

SPARCKY above says the RetroFoam MSDS sheet says it has formaldehyde in it. But I am considering this product for my home and when I visited the website for Retro Foam Of Michigan under benefits, it states NO FORMALDEHYDE.

Mary in Camden, MI

Here is a link that might be useful: Retro Fit Of Michigan (FORMALDEHYDE)

in Canada, this is a big problem if you put it in your place, as now when you sell you have to disclose that you have formeldahyde insulation in your house.

Yep, the clause is still there despite high Court rulings--including an eight-year trial test case--that UFFI is not a proven health hazard.

I was a real estate broker here at the height of the hysteria.

Here is a link that might be useful: UFFI clause has outlived its usefulness

I have serious concerns about spray foam on the undersides of roof decks. Despite their claims of 'open cell', I have yet to see a sample that water will pass through (like a sponge). All roofs eventually leak and with this foam, the leak water will end up trapped between the foam and the wood deck material, causing rot that might even compromise the trusses before there is any evidence of a problem. I think that foam should be relegated to walls and undersides of floors only. I see a huge problem looming down the road with the sprayed roof decks....

When you say roof deck, you mean the underside of any sort of roof, sloping or otherwise? An interesting point you make, I don't know about open cell or not, but most commercial spray foam I know of will act as a moisture and air barrier, so you are right, any moisture between it and the roof is trapped til it finds another way out. I was reading a discussion about reflective barrier products that go on the roof underside directly, could be a similar problem.

As of Feb 2009, Retrofoam has been banned for use in Canada, by Health Canada due to its UFFI based content.

here is the link

Here is a link that might be useful: retrofoam banned in Canada

I have old tube and wiring in the walls. the braker box has been changed over to switches. One of your retofoam agents says it can be insulated. But everthing I have read says knot and tube wiring can't have any insulation touching it, it has to breath and cool.