Fill crawl space with foam?

[JoeSpareBedroom]

The dining area of my kitchen is built over a crawl space that's enclosed by cinder blocks like the rest of the house. In the basement, there are two openings to this crawl space, but they're only 6" high x 18" wide. I assume they were put there for ventilation purposes, since they're useless for anything else. The area in question juts out from the main kitchen, and is

12x12 feet.

In winter, the floor is ice cold, so that dining area is useless. I believe the traditional first step for dealing with this is to lay a plastic vapor barrier on the soil underneath, followed by fiberglass insulation. The vinyl flooring needs replacement, so I could also rip up the wood underneath in that area and have total access to do the work. Replace the sub-floor afterward, install new vinyl or tile, and it's done.

BUT: Someone suggested an interesting alternative: When the vinyl flooring is removed, drill access holes in the sub-floor and pump the space full of foam. It's already a form of plastic, so it should form its own vapor barrier. And, it'll insulate. Progress could be checked via the access slots in the basement. Makes sense, but there's always a "gotcha".

Your thoughts, please.

[Robert Allison]

Did you know that termites find that foam is a perfect pathway to get to what they like to eat without being seen? They just love it and it is so easy to make their little tunnels through, that you probably won't even notice anything until the floor falls through.

[JoeSpareBedroom]

That's a sobering thought. Does this also apply to the foam sometimes used in small amounts to insulate crevices around doorways & windows?

[S. Barker]

Here's another thought. (oh and btw, i don't see where a cold floor makes a room useless). Put a heating duct into the crawl space and there, you have radiant heat on the floor. Done.

s

[JoeSpareBedroom]

I'm not talkin' chilly. I mean "Holy shit - you could freeze fish fillets on this floor."

[Robert Allison]

Expanding foam, foam board, spray foam, all of it. There is a reason that code requires it to be kept 6" from grade.

[Robert Allison]

As to your original problem, you should just install fiberglass batt insulation between the floor joists. That would go a ways towards eliminating any coldness from the floor. BUT, the floor is most likely not the problem as it is rare that a floor will allow a room to become too cold. Most heat loss is from the walls, ceiling, and especially windows. I will bet that this alcove has windows on three sides, doesn't it?

[The Reverend Natural Light]

Interesting. Any time the topic of basement wall insulation comes up, there are always suggestions to use foam board.

[salty]

Very different application.

[JoeSpareBedroom]

One wall's got the garage on the other side. Viewed from the garage side, the whole wall consists of some sort of masonry. (firebreak?) The other two walls each have a window. In the attic, there's plenty of fiberglass over the ceiling. It's a 1956 house, though, so the socks I'm wearing are probably thicker than what's in the walls.

[dpb]

Didn't follow the whole thread, but particularly if the crawl space is ventilated and the floor is solid, I can see it being a significant heat loss component.

The hADt term doesn't care in which direction dT is... :)

[BobK207]

Joe-

Cut out a couple more cinder blocks to get proper (temporary) access to the space.

I assume that once through the block there's enough room to work?

Install fiber glass roll (cut to fit) with vapor barrier up (if you're in a heating climate, which sounds like you are)

The foam sounds like a quick & easy way to do the job but process control would be tough and having the foam bridging from soil to floor would be asking for trouble (sub type termites)

A 12 x 12 space wouldn't take much time or $'s to fiberglass if you had a helper cutting & supplying material......but filling it completely with foam would be pretty expensive

cheers Bob

[JoeSpareBedroom]

There's only about 18-24" from the beams down to the dirt. That would mean hugging the fiberglass the whole time. No thanks. I'd rather do it from above.

[Buck Turgidson]

Have you priced out the foam vs fiberglass? You'll need a mortgage for the foam. The latter will be pocket change.

[marson]

The spray foam I have seen applied is sprayed from a gun much like an airless paint sprayer sprays paint. You aim the gun at a surface from a fixed distance--about 12" is what I have seen--, be it a rim joist or wall sheathing or whatever, press the trigger, and it adheres to the surface and expands. I have never seen a foam application where you could pump it into a hole with any kind of predictable results.

If you could get in there enough to install some sort of sheet material (plywood, foamboard or the like) or even netting onto the underside of the floor joists, you could blow dense pack cellulose from the top through little holes in the subfloor.

The other alternative would be to figure out a way to insulate the stem walls, and then pump heat in there.

[hallerb]

closed cell foam is more expensive but unaffected by moisture, which is why its used. wet fiberglass or cellouse has near zero insulation value. plus foam fills all the little holes and voids. so it also stops drafts.....

makes for quiet warm area........

[aemeijers]

I'm with you- I crawlspaces, especially shallow ones. Almost didn't buy this place because of the (thankfully deep) crawl under the addition, but talked myself into it because of the low price and basic good condition of everything else. I really need to wall-insulate my crawl down to the footer, but the access hole is borderline for my oversize body. And natch, although the addition is badly designed, the poured-wall foundation is done quite well. Replacing that installed-backwards basement window that is the only access from outside would cost me several hundred for concrete cutting, just like the hole I had to pay for from original basement to extend HVAC out here and get rid of wall furnace.

aem sends...

[marson]

inyl flooring

I agree that closed cell foam is good stuff. But how do you propose he pump it through a little hole in the subfloor?

[hallerb]

vinyl flooring

theres a minimally expanding type that can go in walls floors etc.

i would probably excevate a trench access. eventually something else may come up requiring access under there. such access would help home resale

[Edwin Pawlowski]

Some of it sold in the south has chemical additives to prevent that. I forget the additive right now but I think it is a borate or similar.