PEX in Trench w/ spray foam advice wanted

No expert here but MHO foam the trench,insert pex,foam over pex..

Read my thread... and make sure you do everything right the first time.

https://www.hearth.com/econtent/index.php/forums/viewthread/54514/

There are multiple ways too do this. Lift the lines ahead of the sprayfoamer. Install 2" insulation baord under the lines first(no foil faced). Use the insulation board between the two lines, tape in place to ensure the foam gets all the way around and to seperate the lines of course. We usually install no less than 4" closed cell foam when doing these lines.

curious, why four 1" instead of two 1 1/4" or 1 1/2"?

Also, it is my experience that blue board insulation will eventually absorb water, was I using the wrong stuff?

Chris

If the entry into your house is the lowest point you need to dig a diverision trench away from the house to give the water another path to follow. Just slope it away and put some gravel in the bottom. Daylight it down slope if you can. Cover with a silt membrane and cover. If you give the water an easier path to follow you won't end up with it in your basement. If you have a backhoe digging the trench it shouldn't cost much to dig this at the same time.

Doug

BioHeat Sales Guy said:

curious, why four 1" instead of two 1 1/4" or 1 1/2"?

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I may or may not be speaking for DMX here, but the reason I have decided to go with four 1" lines is the fact that 1.25" PEX is almost 3X the price of 1" PEX....1.50" was well over 3X.

BioHeat Sales Guy said:

Also, it is my experience that blue board insulation will eventually absorb water, was I using the wrong stuff?

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Since I've been unable to locate a spray foam contractor within a reasonable distance in my area, I'm considering the rigid insulation board + DIY spray foam in a well drained trench method. After researching the different types of rigid insulation board, I've found that it makes a great deal of difference in the type of board you use. This product from Owens-Corning is designed for contact with water and should be fine for the below grade application that we need, especially if it is well drained.

http://insulation.owenscorning.com/homeowners/insulation-products/foamular-250.aspx

Easter and weather prevented me from digging up my pex and foaming this week. I've been in contact with Heaterman who's done quite a few lines using the polyurethane foam. If you look at his heat loss data from several years ago it's amazing. My goal is to get 3" minimum around my 1 1/4 pex lines and I will be using some tiewraps to try to keep a fairly consistent spacing between the lines as my contractor blows the foam. I do not plan on using any blue board just blow under pex for 3'-4' allow to expand for 10-15 seconds, lay the pex, and blow on top. We'll be doing the 3'-4' increments and adjusting that length as we get experienced with the rate of foam expansion/curing. I intend to drop the pex into the foam while it is still somewhat soft, but that margin of time is very short. With the superior insulating properties of the foam itself, I've not understood the purpose of the blue foam board some folks have talked about. Heaterman never uses it and he installs commercially. So that's about it. I'll probably be out of the trench holding/lowering the pex with my foam contractor in the trench blowing foam. I'll post what I learn in the next week or so after I redo. If there is ANYTHING you don't want to do is to go cheap or shortcut the underground element, it is this most miserable and energy sapping part of your project. This job really sucks and if you go cheap like I did on my first attempt you'll be haunted by your poor decision or will kill your boilers efficiency OR BOTH. I did mine in a hurry in Oct/Nov last fall so I could move on to the boiler installation. If you're on the borderline for pex sizing go 1 1/4 not four lines. I can't emphasize enough the underground part is not where you want to go cheap or cut corners.

DMX_512 said:

I did a little searching on the forums and found that putting PEX directly in the trench and then using spray foam is a fairly popular method.
I am getting ready to get started on a Pole barn and then trench to the house. I know, I know, I have had my boiler sitting in my basement for over a year (not hooked up...just sitting there) but time and money.......well y'all understand I am sure.
Anyway, I am thinking about using (4) 1 inch PEX lines running into the house and bringing in a contractor to spray the trench.
1) The boiler/storage will be approx. 6 1/2 to 7 feet higher than the current grade at the house. I would be interested in hearing feedback regarding this height differential. The point of entry to the house WILL be the lowest point of the entire trench run.
2) I am thinking about having 2 inches of foam surrounding PEX lines. The spray foam guy has a $600 minimum and my trench will be approx 75'. I believe that I can get him to do the run w/ 4 inches of foam and still be within the minimum. I am wondering if I need to or should lift the PEX off of the bottom of the trench prior to spraying. Any other thought suggestions?
I know that I have very expansive soil but I dont know if that really matters in relation to the project.

As usual....any input, thoughts, suggestions are appreciated

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I'd probably start by asking your insulation guy how he does it and what he suggests and how he approaches the foam under the tube. If it sounds like a bunch of smoke and mirrors it probably is. Ask him how much of this work he has done and ask him for references.

AFA the slope goes, if you have heavy soil I would sure recommend a "drain trench" extending off the pex trench to a lower location if possible. If not, I would advise elevating out of the trench prior to entering the basement wall. Water following the trench into your basement can be a real headache. I typically have our spray guys build a good size mound where the tube enters the basement wall and bring it back into the trench at least a foot or more. That helps to keep moisture away from the entry point and the foam they use will actually bond to the basement wall if brushed free of dirt.

Good Grief! 85* degrees here last week and it's snowing like crazy right now. April in Michigan.........

DMX_512 said:

I did a little searching on the forums and found that putting PEX directly in the trench and then using spray foam is a fairly popular method.
I am getting ready to get started on a Pole barn and then trench to the house. I know, I know, I have had my boiler sitting in my basement for over a year (not hooked up...just sitting there) but time and money.......well y'all understand I am sure.
Anyway, I am thinking about using (4) 1 inch PEX lines running into the house and bringing in a contractor to spray the trench.
1) The boiler/storage will be approx. 6 1/2 to 7 feet higher than the current grade at the house. I would be interested in hearing feedback regarding this height differential. The point of entry to the house WILL be the lowest point of the entire trench run.
2) I am thinking about having 2 inches of foam surrounding PEX lines. The spray foam guy has a $600 minimum and my trench will be approx 75'. I believe that I can get him to do the run w/ 4 inches of foam and still be within the minimum. I am wondering if I need to or should lift the PEX off of the bottom of the trench prior to spraying. Any other thought suggestions?
I know that I have very expansive soil but I dont know if that really matters in relation to the project.

As usual....any input, thoughts, suggestions are appreciated

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That seems like a fairly high price . I just had 50' done around two 1-1/4 pex lines done for $200 . He sprayed 3 to 4 " around their circumference. I held up the lines and he sprayed under them we layed down some typar house wrap underneath it. The foam sets up almost instantly, then we sprayed the top. I guess I will find out how good the job is when I monitor temps after I get it all fired up.

djblech said:

If the entry into your house is the lowest point you need to dig a diverision trench away from the house to give the water another path to follow. Just slope it away and put some gravel in the bottom. Daylight it down slope if you can. Cover with a silt membrane and cover. If you give the water an easier path to follow you won't end up with it in your basement. If you have a backhoe digging the trench it shouldn't cost much to dig this at the same time.

Doug

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I had the guy spray foam into the 8" by 8" hole through the concrete it kept he water out just fine . I was quite worried about this as I live in a very wet climate Ive had loads of rain in the last 2 months and no ingress .

My $.02... make for certain the contractor uses closed cell foam. Ran across a story where a contractor foamed a guy's underground line with open cell... which is like not foaming the line at all.

cheers.

Piker said:

My $.02... make for certain the contractor uses closed cell foam. Ran across a story where a contractor foamed a guy's underground line with open cell... which is like not foaming the line at all.

cheers.

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The actual product used must be certified for ground contact and underground use. There are a LOT of different foams out there and you have to find a contractor that knows what to use in a given application.

before closing up the trench consider adding a couple of extra pipes for the future. Black poly pipe works for this, irrigation or well pipe.
It was pointed out by another not to use a-lot of foam board under ground. It's a insect home, area to tunnel. Good for blocking. This came up when discussing burying propane tanks I think.
Chris you are right, blue and pink board are not the board of choice. It's the foil board that's closed cell. Like the spray foams it's more $.
Rob

I recently looked into running undeground 1-1/4 pipe and found that on my run of 115' it would only cost about $300 - $400 more to run logstor or thermopex. I think It would be hard to beat those products quality and
heat loss numbers on a d.I.Y. job

I am a foamer in Maine, so this is what i did. I put 2 - 1 1/4' PEX IN A 6" Black pipe spaced with foam spacers. Then drill 1/4' hole in top of pipe every foot and filled with foam. Then silcone the holes. I have very wet soil so lined trench with 6 mil plastic, foamed 2" on top of that, install drain pipe, and covered with 2" foam. Then covered with the plastic. This system work great as line is 100ft. I do not loose a degree getting to house. Where it goes through the wall i patches with Hydraulic cement and the foamed it good. Foamit up

Foamit up has the best idea posted. kinda a pain to do but better. A outdoor furnace dealer in Northern NY I know did as most are referring to by spraying the lines with the most dense foam. It worked for about 2 yrs. As time went by it soaked up water like a sponge in heavy soil and ones that put it deep. Installs in sandy soil had better results. Aqua Therm used dense foam board in the early 90s , this also soaked up water. You would be better off biting the bullet and getting the Thermo Pex style insulation. Do it once .... Do it right

I am trying to decide what to do for my final install of my underground pipe. I called a foam company in my area and asked then about it. They said they can't foam the pex itself due to temperature and expansion.

I asked if they could foam the outside of a 4 inch sleve, either drain tile of PVC. He said yes, $700 for 125' 2 inches, r14 and no wrap needed on the outside of foam.

What do you think about that method?

Right now I have Rehau in a draintile that is wrapped with Micro foil. It laid on the ground through the winter. Stove temp gauge and manifold temp gauge showed 5 degree difference. I really need to put one on the supply at the stove to see true difference.

gg

I called my foam contractor based on the most recent comments here about water getting thru the foam and saturating the insulation. My foam contractor can and does spray TWO types of polyurethane foams. There is an open cell foam used in the insulation business because sometimes you want to see if you have a leak or let the surface breathe! His example was foaming the underside of a metal roof. If the closed cell was used you could get a leak and never know until the roof rusted thru. I was presuming my contractor was planning to use CLOSED CELL foam in the trench. I didn't know they also blew OPEN. SO, those of you who have had saturated foam problems I'll bet your contractor used the OPEN CELL foam (or maybe you had another problem) which acts as a sponge. BOTTOMLINE, there is OPEN and CLOSED CELL foams. We want closed cell for our underground insulation installations. He also suggested we lay some plastic down in the trench to prevent blowing pieces of dirt into the mix as he blows. Sounded good to me. Starting the digging Thursday and hopefully foaming Friday afternoon. I'll keep ya'll informed. WHATEVER happens it's staying put, even if I need to put in a 400Kbtu boiler I'm done with dirt work!

Unfortunately I won't be able to report until November what the deltaT results are. But based on the measurements Heaterman posted back in 2008 on a system similar to ours, I expect it to be remarkable. I have two AZEL temp measurement systems; one in the boiler barn and another in the root cellar attached to the HX so we can measure precisely temp drop in the whole loop. I think we were throwing away 20-30Kbtu/hr with my first pex insulation attempt.

Tennman said:

I called my foam contractor based on the most recent comments here about water getting thru the foam and saturating the insulation. My foam contractor can and does spray TWO types of polyurethane foams. There is an open cell foam used in the insulation business because sometimes you want to see if you have a leak or let the surface breathe! His example was foaming the underside of a metal roof. If the closed cell was used you could get a leak and never know until the roof rusted thru. I was presuming my contractor was planning to use CLOSED CELL foam in the trench. I didn't know they also blew OPEN. SO, those of you who have had saturated foam problems I'll bet your contractor used the OPEN CELL foam (or maybe you had another problem) which acts as a sponge. BOTTOMLINE, there is OPEN and CLOSED CELL foams. We want closed cell for our underground insulation installations. He also suggested we lay some plastic down in the trench to prevent blowing pieces of dirt into the mix as he blows. Sounded good to me. Starting the digging Thursday and hopefully foaming Friday afternoon. I'll keep ya'll informed. WHATEVER happens it's staying put, even if I need to put in a 400Kbtu boiler I'm done with dirt work!

Unfortunately I won't be able to report until November what the deltaT results are. But based on the measurements Heaterman posted back in 2008 on a system similar to ours, I expect it to be remarkable. I have two AZEL temp measurement systems; one in the boiler barn and another in the root cellar attached to the HX so we can measure precisely temp drop in the whole loop. I think we were throwing away 20-30Kbtu/hr with my first pex insulation attempt.

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You know, I was at the particular install I referred to the first part of this winter. It is still rocking along as new. About a degree-degree and a half loss circulating the loop with no load on it. Pretty darn impressed with that stuff.

Tennman said:

I called my foam contractor based on the most recent comments here about water getting thru the foam and saturating the insulation. My foam contractor can and does spray TWO types of polyurethane foams. There is an open cell foam used in the insulation business because sometimes you want to see if you have a leak or let the surface breathe! His example was foaming the underside of a metal roof. If the closed cell was used you could get a leak and never know until the roof rusted thru. I was presuming my contractor was planning to use CLOSED CELL foam in the trench. I didn't know they also blew OPEN. SO, those of you who have had saturated foam problems I'll bet your contractor used the OPEN CELL foam (or maybe you had another problem) which acts as a sponge. BOTTOMLINE, there is OPEN and CLOSED CELL foams. We want closed cell for our underground insulation installations. He also suggested we lay some plastic down in the trench to prevent blowing pieces of dirt into the mix as he blows. Sounded good to me. Starting the digging Thursday and hopefully foaming Friday afternoon. I'll keep ya'll informed. WHATEVER happens it's staying put, even if I need to put in a 400Kbtu boiler I'm done with dirt work!

Unfortunately I won't be able to report until November what the deltaT results are. But based on the measurements Heaterman posted back in 2008 on a system similar to ours, I expect it to be remarkable. I have two AZEL temp measurement systems; one in the boiler barn and another in the root cellar attached to the HX so we can measure precisely temp drop in the whole loop. I think we were throwing away 20-30Kbtu/hr with my first pex insulation attempt.

Click to expand...

Open cell spray foam is also used in interior walls and ceilings for sound proofing.

Open cell foam takes on water like a sponge. Closed cell of 2 pound or better will not take on water. 2 pound CC is R6.9 per inch. The foam when sprayed can reach up to 200 degrees before curing. Heat pex is rated at more than that, so applying foam directly to pipe will not hurt it. If you do not use the plastic in trench and blow dirt in to the foam then you could possibly take on some water where the dirt is in the foam.

foamit up said:

I am a foamer in Maine, so this is what i did. I put 2 - 1 1/4' PEX IN A 6" Black pipe spaced with foam spacers.

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Could you explain what or how you spaced the pipe in the 6" sleeve?

gg

Yes, I'm interested in hearing how you did that also Foamit up. And when you refer to black pipe, do you mean black ABS pipe or steel pipe?