how to heat shallow crawl space

[hnash53]

I'm rehabilitating a small house, 16x30.  It has a small crawl space under the floor.  The ground is only about 12" below the floor joists.  We are going to have to run new plumbing either through the joists or just below them.

Can I just use heat tape to keep the water lines from freezing, or am I going to have to heat the entire crawl space?

If I have to heat it, can you make some suggestions as to how I can do this?

This is in Wyoming.

Thanks.

Hal Nash

[bil2054]

Hi, Hal.
A combination of heat tape and and fiberglass pipe insulation works well here in the North East.

It is a common solution to plumbing issues  in mobile homes, which often have concrete block piers and no more than vinyl skirting to enclose their nether regions.

The "cut to length" type heater seems to work best, combined with a thermostatic switch.  Note that the systems I have used to date were NOT reccomended for PVC pipe, nor the closed cell type insulation I have encountered.  Also, make sure to check the heat tape at the beginning of each season.  Nothing like a below zero night and a heat tape that ceased heating. [smiley=tongue.gif]

Good luck with the project.

[Amanda_931]

Sounds like my Nashville house.

The people who had owned it before me had put their washing machine in the detached garage, heat-taped and fiberglass taped the water lines.  The whole mess had  been turned on that fall.  It was protected to almost 27 degrees F.  Sigh.  I ended up with a washing machine in the kitchen, and the dryer on the porch.  Much better, thank you.

I also had troubles with the wrapped but not heat taped pvc (or whatever--CPVC?) pipes to the kitchen sink that were in the outside wall--especially if I forgot to open the cabinets on really cold nights.  I could have stuck probably even a moderate, e.g., 100 watt standard incandescent trouble light in there instead.

Since there was no insulation under the house, only the opening to the crawl space (through the foundation) was really in danger, but that was under the bathroom, and the pipe to the meter.  So I got quite good at fixing those pipes.  A little heater, or something like a 250-500 watt halogen light kept them pretty warm.

When I remembered it.

Pex is reputed to be harder to break by freezing.

Galvanized iron often doesn't break.

[glenn-k]

Sorry I can't help, Hal.  That environment is too harsh to support life as I know it. :-/

[bartholomew]

Shower traps should be protected too. I once had a shower drain freeze up in a rental house. Tried the switch for the heat tape but there was no light or marking to indicate which position was on. After trying both for a while, I concluded that either it wasn't working at all or it was just too cold for it to keep up. Had to resort to several kettles of boiling water and a wet vac.

[glenn-k]

Frozen metal pipes can be thawed with a welder - watch for sparks - maybe hook up with a set of jumper cables or some other way - usually a portable was used.  It was information that came out with the old Lincoln welders.  Hot lead on one end -ground on the other - turn it on and the pipe heats up.  Won't work with plastic though.  Don't get a loose connection and burn a hole in your pipe.  I assume if you are willing to try something like this, you are able to fix your own pipe. :-/

The resistance in the pipe causes it to heat as current flows through it.

By all means be sure which pipe you have ----like ---don't get the gas line ---- see-----[size=20]DANGER[/size].

[Amanda_931]

Bear in mind that I lived in the Nashville TN area.

Although the worst of those experiences--except the washing machine pipes--was when it was right chilly--lows in the -10 F range, not above +15 for a day or two.

Had a roommate from Cheyenne WY once, though, she talked about the tires on the cars freezing in a square pattern, driving down the street going [highlight]bonkety-bonkety [/highlight]until they thawed.  I could cheerfully never experience that.  But since my AC is out right now, I've got my own problems the other way here.

[jraabe]

More and more data points to sealing up the crawlspace and insulating it.

I have 48" wide metal building insulation (R-19) stapled to the floor joists and then draped down the inside of the CS and taped to the heavy poly moisture barrier over the soil.

Then I use the space as a return air plenum so it is close to house temp.

Solves the plumbing issues and keeps the floors comfy. I've never had any mice or bugs down there either.

[CREATIVE1]

So, how much heat do you lose through the floor and ceiling?  If you had R-30 walls and no insulation otherwise, how would that stack up to R-19 walls and insulated floor/crawl space and ceiling? Seems that the house is an envelope, and there are big holes in it if everything isn't insulated?

[Amanda_931]

Less loss through the floor than the ceiling?

There is a form of building in which you insulate the ground down and out from the house, try to keep the dirt under the house as a heat/cool sink, depending on the season.  An old internet acquaintance did mention the other day that there seems to be not much experience or engineering to help anyone who wants to try this.  (not PAHS but AGS)

[bil2054]

What Glenn said about thawing pipes with a welder: DANGER!  It does work, I have done it, and I promise to not do it again.  If the pipe heats too quickly you get steam under pressure; if there is a poor connection either at the clamp, or a poor joint between the clamps, you can get arcing/ hot spots.  Did somebody sneak an electrical ground to the plumbing system?  Imagine what stray currents of who knows what amperage/voltage roaming through your electrical service can do to your new plasma TV, etc.
There are approved electrical thawing systems designed to avoid these problems, but I bet you don't know anyone who has one! [smiley=sad.gif]
Prevention is the best thing; open cabinet doors/leave a faucet dripping if there's a cold snap and you suspect it's likely.  Heat tapes and insulation can be a cure as well as prevention, though it's slow.  Torches work, but pipes are so often near flammable stuff!  Blow driers work, too.  And finally, if all else fails, and as expensive as they are, your plumber will be the first to tell ya, "You can pay me now, or you can pay me later".
The voice of experience?  You bet!  My mom lives in a senior "manufactured housing" community, (used to be a trailer park [smiley=wink.gif]), and she can't help bragging about how handy her son is.  When it's sub zebra at 3 ack emma, and the terlet don't flush, who ya gonna call?  You guessed.  And could it have something to do with building MY retirement home in AZ?  Hmmmm. [smiley=happy.gif]

[jraabe]

Yes. Of course you insulate the ceiling. All surfaces of the house should be insulated.

The options discussed were:
1-  insulate the floor joists and vent the crawlspace to the outside, or
2 - insulate the walls of a sealed crawlspace and eliminate the floor insulation. This was the option I was discussing.

[hnash53]

John,

You said in your last post on this thread that one could insulate the walls of the crawl space and not insulate the floor, right?

This crawl space is only about a foot deep below the joists.  If I were to insulate the inside and the outside of the the crawl space would that be sufficient to keep pipes from freezing if I don't insulate the floor?

And if so, do I insulate the concrete walls inside and out with foam?  And if so, how thick and how deep do I dig?

If so, if so, if so...ad infinitum.

Thanks, man.

Hal

[jraabe]

I have a number of details for the crawlspace insulation and there are others on the web.

One way is to use 2" blueboard on the outside of the concrete and for 24" wide inside the crawlspace over the floor. This forces heat to go downward - which it doesn't like to do. Seal the CS airtight and cover the soil with a 6 mil poly VB. Don't insulate the floor but do have some way of occasional air exchange between the CS and the heated area above (I have several 4" floor registers).