Dow Great Stuff BIG GAP filler question
 

GREAT STUFF? Big Gap Filler

Got this insulating foam at HP and plan to use it under my boiler,
to keep down the heat loss into the basement floor.

I see it says "One 16 oz. can = up to 24 tubes of caulk"..
I have four 16 oz cans, so that's = to 96 tubes of caulk?? WOW!

Preparations:
I have drilled a small hole in each corner for the plastic tube,
and have sealed the bottom edge cracks with adhesive sealer.


But, I'm not sure if the can is used upside down or rightside up??

Some pics I've seen, show it upside down..

http://www.familyfeatures.com/releas...lec.Outlet.jpg

Is this how is works? Like whip-cream? (No inside tube like spray paint)??

Edit:
Never mind! I just watched a few movies... :)
GREAT STUFF
It works like a whip-cream can (which I know a lot about using, because of my ice cream addiction).

I'll post my results after application..

Upside down it is to excrete the foam. Very nasty if you get it on ya. Be careful the foam well swell pushing weak flexible stuff a part.

I heard ya! I'm planing to wait at least 24 hours for the adhesive to fully cure before pumping in the foam.

I used some of the regular crack filler foam a few years ago, when installing
a big (powerpig) 18,000 BTU in-wall AC.
I was amazed at it's expansion. It seemed like I was just using a small
amount, but it expanded so much that, when I came back from lunch, half of it was hanging outdoors.
A lot of trimming was needed.

The space to be filled is about 1.2 cubic feet . I hope the void will be mostly filled.
If not, 4 cans of foam should still cut the heat loss a good bit. Some is better than nothing.

I have used three different types of spray foam. The first is the polyethelene GreatStuff. It has to be sprayed upside down, which is a problem if you are trying to seal something above your head. It dries to be rigid.

The second was also GreatStuff brand, but it was a urethane based foam. It stays flexible when it dries, so it is good to use around windows and doors. It can be sprayed in an upright position, at least when the can is mostly full.

The final type was also flexible when dried and seemed to provide fewer closed cells. Like the urethane foam, it remained flexible. I can't remember what it is called and haven't seen it in the stores since I bought it the first time three years ago. The main thing that I liked about it was that it is easy to clean up.

Until it dries, you can remove it with acetone. It doesn't take long for a small dab of it to dry, though. Only a couple minutes. That's more likely what you'll get on you if you do.

I love this stuff for sealing gaps. It's perfect for keeping rodents out. ;)

I expect you'll get the space mostly full with 2 cans. You might get better results applying it in 2-3 inch layers instead of all at once.

Well, we got almost a cubic foot of over-flow. :(

The first 2 cans seemed okay. I waited about an hour and probed inside the space with
a steel rod. I found that there was still gooey foam and some liquid gunk under the boiler.

I think this stuff works better out in the open air.. Not inside a tight space,
where their isn't any air coming in..

After 2 hours, it was still mushy under there, and some dirty brown liquid came out of one of the holes.

So, about 4 hours into the job, I squirted in the last two cans. No over-flow at first,
then later, about one cubic foot of over-flow came out..

The next day, I cleaned and wrapped the bottom stand in insulating tape.

The bad news:
Today, the temperature of the floor around the boiler is slightly higher than yesterday.
The heat from the boiler seems to be going into floor faster now.. :mad:

My guess:
The sealer that I used around the steel skirt, might be conducting heat into the concrete floor, more efficiently..
Wasting more fuel.. :confused:

We are getting a bit of sun today, so maybe I'll see if the other insulation
(on the pipes) is going to help limit the normal losses.

They call the foam in a can like this one part but to cure it really needs a 2nd part and that part is water, normally it gets that water from the air, thus on humid days it will expand and cure faster, get some on your hand and it will cure fast, because of this you have to layer it or it will never set up.
For going under something like a boiler I would think that a 2" thick foam sheet would work, as long as it did not get to hot of course, for higher heat use fire brick or insulating concrete.

I had some polyurethane glue that said to spray the parts with water before putting them together to get the glue to cure. Seems counterintuitive, but it worked.

I sprayed on a mist of water where the foam was over-flowing under cracks.
I'm wondering if the seal job was just too tight and the first can 'ate' all
the moisture and the rest just remained in a slowly curing liquid state.?.
Maybe in a gooey liquid state, it's conductive.?.

Whatever happened under there, I think this part of the project was a bust..