Hi everyone,

          I am having a foam injection company come over to look at adding open-cell foam to the walls of a 1956, 1450 sq ft ranch house in Nebraska.  The foam has an R value of 5.1 per inch and is the non-expanding type.  The 2x4 wall cavity has some original faced but thin batt insulation.  I have also noticed the wall has a fiberboard layer covered by drywall so the total thickness of the surface is nearly an inch.  My basement is currently unfinished and the rim joists are not sealed/insulated yet.  My friend drilled 1 and 1/4" holes in the subfloor at the rim joist from his unfinished basement into the wall cavities of his house and blew in cellulose insulation into his walls.  He said he was able to insert the hose all the way to the top of the wall cavity (not sure if his wall cavities were empty).  So, I was looking at doing something like that in my house only using foam instead of cellulose for a better seal/R value.  I think it would be possible to insert the hose high enough to inject the foam to the top.  We drilled two test holes and were easily able to insert a hose a few feet into the wall cavity (behind the batt insulation I think).  I have a stone veneer exterior and the company said it won't inject foam from the exterior because there is some insulation already in the walls and they are afraid of blowing out the drywall.  The only other way they would do it is to drill 2 and 1/2" interior holes half way up the wall.  That would be a mess!

So, my question is, do you think this method of drilling access holes from the basement rim joist to access the wall cavity is a legitimate/safe idea?

If anyone has had experience injecting foam, would it possible to have the foam reach the top of an 8' wall cavity if we could get the injection hose close to the top?

If the company agrees to try this method (he is coming Wednesday evening), is there anything I should be doing to check if the foam has reached the top of the cavity?  The wall thickness makes it hard to just knock on the walls and hear the foam level.

Thanks in advance for your advice.
Andy

Drilling the holes from the bottom plate is OK structurally, and works for blown fiber, but you can't really do a foam-pour that way- it all runs out the bottom. If you do non-expanding foam pour, it generally has to be from the top.

The difference in whole-wall R value and air-sealing between dense-packed cellulose and a non-expanding pour may not be as significant as you think, and gravity may create more voids than you'd get with blown-fiber under pressure. The hygric buffering of cellulose might also be a worthwhile consideration in a Nebraska 2x4 construction home as well.

The advantages of non-expanding foam pours over dense-packing is that it doesn't pressurize the cavity, and can't blow out the wall during installation, and won't bow it out over time if the wallboard is thin or weak (as dense-packed fiber can.)

The difference in whole-wall R value in a 16" on center 2x4 construction between cellulose or fiberglass and foam with a K value of R5/inch isn't as much as you might think either- at most an R1 difference, despite an R2.5-3 difference center-cavity. If costs are identical the foam is a better deal, but if it's dramatically more there is probably better places to spend the money. Dense packed cellulose (or noo-skool fiberglass such as Certanteed Optima or JM Spider at 1.8lbs density or higher) is VERY air-retardent, and forgiving to install. Voids in a foam pour are difficult to correct once the foam has set up.


BTW: Which product were you looking at? Depending on the product, it may have sufficient internal heat when pouring that the completeness of the fill can be tracked with thermal cameras. (That's a common method of tracking expanding polyurethane pours during installation.) After the fact, a thermal imaging camera will tell all...

I would do the holes in the top half of the wall.  Patching a bunch of uniform drywall holes in a line around the permiter of your house is not that big a deal.  you could probably hire someone to do it for a few hundred dollars if you weren't so inclined.  I would see if the holes could be at 5 to 6 feet or so, so no ladders would be needed.  Fill from the bottom up to the hole, and then the top 2 feet down.  And I would foam the rim joists at the same time.

You can't foam the rim joists with a non-expanding foam pour- it's a different type of product entirely than sprayed polyurethane.

I suspect the product simonzeke is contemplating it Tripolymer (tm) (see: http://www.tripolymer.com/tripolymer/index.html)

It MAY be possible to install it from the bottom, judging by the installation vidi shots:

http://www.youtube.com/user/tripolymer