Running supply lines in unheated crawl-space that I cannot access

[mike0331]

Hi all,

TLDR at the bottom

DIYer here. I am installing a washer/dryer in the closet in a room that was added on to our house prior to us purchasing it. We have a 1940s colonial in the peoples republic of Massachusetts with a large garage added about 10 years ago. 1/4 of that garage was converted to an insulated room approximately 12X16 in size. I have knocked out half a cinder block in the foundation immediately below the sill plate in the basement of the original house, and have about 8" between the slab in the garage and the underside of the joists in the room built in the garage where the washer dryer is to go, so essentially enough space to pass pipe/utilities.

I had a professional run a gas line for a heater in the room after I nixed the electric heat. I have run a PVC drain pipe for the washing machine about 12 feet to the far end of the room.

The water supply is where I'm looking for ideas. I was planning on drilling into the outside sheathing (balloon framed) from in my basement so that I could pass PEX directly under the sub-floor of the room in the joist bay between the vapor barrier of the insulation and the sub-floor. My other idea was to wrap the PEX supply lines in insulation with a thermostat controlled pipe heater, or possibly pass them through a 1.5" PVC conduit with a heating element that could be replaced if need be. My concern here is avoiding pipe freezing. The second idea would certainly be easier, but I have two concerns. 1st: The heating element burning out over time, although it would be easy enough to remove and replace the PEX/heater if need be. 2nd, my plumber has told me he has now heard stories from a couple inspectors of wiring being run alongside PEX (including network cable) causing the PEX to develop pinhole leaks. Both of us where at a loss as to what could be causing this to occur assuming it's true. Maybe the brain trust here has heard something/nothing of this. While I'm no chemist/physicist, I a do have a STEM degree and I'm scratching my head on this one. Any all/thoughts or ideas would be great.

TLDR: 1. Need a way to run supply piping 12 feet through an inaccessible crawl space that dips below freezing
2. Anyone else heard this craziness about electric fields causing damage to PEX piping (makes zero sense to me and my plumber, but he said he's been told by a couple inspectors they have seen this)

Thanks

Mike

 

[Jadnashua]

I could see where a malfunctioning heat strip could possibly melt a hole, can't come up with a reason it could create a pinhole. Maybe arcing over a long-term?

Adding insulation around the pipe won't help unless you keep a constant flow through the pipe. What you really want is to try to have the pipe up against the heated floor above, with insulation beneath it.

If you don't have access, it gets really tough.

Could you build a box below the subflooring with the subflooring being one side, then run insulation around it? That would help to hold some building heat into the box. Keep in mind, though, that if there's any outside air leaks, that can overwhelm insulation like fiberglass that acts more like a big filter under those circumstances. Foam might be better in that case.

Also, being in MA, technically, you can't do any of this without a license, so beware. They can get nasty if they find unauthorized work later on.

The advantage of using PEX in this circumstance, is that it won't split if it freezes. Just make sure to not have any fittings in that area, and only pipe, otherwise, the fittings can fail.

 

[Sponsor]

 

[mike0331]

As it was communicated to him it sounded like they suspected some type of interference was degrading the PEX. It makes no sense to either of us.

I think I can snake the pipe between the insulation and the subfloor above it, but I'm not 100% certain I can pull that off yet, I'm going to have to drill some exploratory holes above the sill plate.

Here is an idea of what I'm working with:

As you can see, the gas pipe is just about at the bottom of the joists for the room. I need to get the PEX essentially to that corner.

 

[Terry]

Is this a ventilated crawl space? I've almost never seen a frozen pipe in a crawl. They do like you to insulate them, but frozen? Only if there is a cold wind blowing on them. With a heated space over the ground, it's pretty hard to chill it enough to freeze a pipe.

 

[mike0331]

Once the plumbing is done those two openings will be sealed up and it will go back to being entirely sealed. Room is heated between 62-70* with a Jotul gas stove.

Mike

 

[Jadnashua]

I'm not all that further north of you in NH. This past winter, we saw a few periods where the high was barely zero F, and the lows were significantly colder than that and it went on for more than a couple of days in a row. While not typical, it happens.

 

[mike0331]

Would that be likely to drop the temp below freezing in the crawl space? I'd imagine it could, but I've never had that room heated before. On the other hand, given the "crawl space" is only 6-8" high, there isn't much free space.

Mike

 

[Toolaholic]

crawlers should be 18" Min. height .

 

[Dana]

Is this a ventilated crawl space? I've almost never seen a frozen pipe in a crawl. They do like you to insulate them, but frozen? Only if there is a cold wind blowing on them. With a heated space over the ground, it's pretty hard to chill it enough to freeze a pipe.

Frozen pipes in crawl spaces that have an insulated subfloor above is pretty common in New England except perhaps along the southern New England. Even as close as 40 miles from the coast in MA there will a few cold snaps every decade where the daily high is in single digits F for a few days, with lows at negative double-digits. During those cold snaps even pipes in uninsulated basements running near the band joists can freeze, unless actively heating the basement. It may still be ~40F in the middle of the basement, but not along the foundation & band joists.

Punching a hole from the foundation of the main house into the crawlspace wasn't the greatest approach either, since that's just another air leak in the bottom of the house for stack effect infiltration to suck cold air in via the crawlspace, increasing the freeze up risk.

A ground vapor barrier and insulating the WALLS of the crawl space with rigid foam to a code-minimum R15, caulking & insulating the band joists & foundation sill of the crawlspace, then removing the subfloor batts between the joist is really the right way to go, but if there's no hatch big enough to get sheets of foam-board in there it may have to be a couple inches of closed cell polyurethane instead. (In my own house I ended up cutting a hatch in the common foundation wall from the basement big enough to slip in 2' wide sheets of foam board in order to insulate a crawlspace wall.)

 

[Dana]

Would that be likely to drop the temp below freezing in the crawl space? I'd imagine it could, but I've never had that room heated before. On the other hand, given the "crawl space" is only 6-8" high, there isn't much free space.

Mike

Is it possible to dig down 2' below grade along the full perimeter of the crawlspace foundation?

If yes, 2.5-3" of exterior EPS foam board would keep the pipes from freezing even during a Polar Vortex event, as long as it's reasonably air tight. There would need to be Z-flashing behind the siding & housewrap to kick bulk-water coming down the housewrap out to the exterior side of the top of the foam board. The exterior side of the EPS can be protected with a 1/2" or thicker stucco scratch coat on chicken wire fencing or purpose made metal lath.

Air tightness matters too. If you can get visual access to the bottom plate of the walls from the exterior, if there isn't an obvious sill gasket see if you can't caulk the seams between the foundation & sill plate, and between the sheathing & sill plate with polyurethane caulk. Those long skinny holes are bigger than they look, and the hole that got punched between the basement & crawlspace are going to create a stack effect suction pulling cold air into the crawlspace in winter.

 

[mike0331]

As I mentioned, the "craw-space" is about 8" tall.

Mike

 

[Dana]

As I mentioned, the "craw-space" is about 8" tall.

Mike

And...??

An air leak in a 8" tall crawlspace is as risky as in a 48" crawlspace, and creates just as much of a stack effect infiltration problem- a problem that increases as temps drop into negative digits.

Digging down 2' to insulate & air seal from the exterior with EPS all the way up to the sill-plate will pretty much eliminate the risk, even with the increased risk of having insulation at the subfloor blocking heat flow into that crawlspace from the house.

 

[mike0331]

I understand that, but braking the slab, and digging down is not worth the effort here, especially as it's our plan to sell the house in 3-5 years.

Mike

 

[Dana]

I understand that, but braking the slab, and digging down is not worth the effort here, especially as it's our plan to sell the house in 3-5 years.

Mike

Is it ALL along a slab?

If you can air seal the foundation sill from the exterior and put even 1- 1.5" of EPS insulation down to slab level it will mitigate the risk, even if it's nowhere near current code for foundation insulation. Z-flash the top of the EPS, and put an L-flashing for kickout to direct any moisture that finds it's way between the foundation & EPS out toward the slab. For foam that thin and short in height 1/4" of mortar mix with a bit of concrete bonding agent troweled onto the EPS is probably enough protection. Even if it cracks it probably won't fall off, and would be easy enough to repair if it did.

 

[mike0331]

Yes. The room was built in 1/4 of a 2X2 car garage that was put on before we bought the house, right on top of the slab. Given the foundation height, I could only access part of the underside of the room from within the garage, and would not be able to get anything outside of arms length, and the interior dimensions are 12X16. I can probably, at the very least, air-seal the tiny space.

 

[Dana]

Air sealing the space is always more important than insulation, so that would be a good start.