# PEX in Trench w/ spray foam advice wanted



## DMX_512 (Apr 8, 2010)

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


----------



## Deere10 (Apr 9, 2010)

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


----------



## trehugr (Apr 9, 2010)

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

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


----------



## coolidge (Apr 9, 2010)

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.


----------



## Chris Hoskin (Apr 9, 2010)

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


----------



## djblech (Apr 9, 2010)

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


----------



## Shelterman (Apr 9, 2010)

BioHeat Sales Guy said:
			
		

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


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?


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


----------



## Tennman (Apr 9, 2010)

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.


----------



## heaterman (Apr 9, 2010)

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.
> ...



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.........


----------



## huffdawg (Apr 9, 2010)

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.
> ...



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.


----------



## huffdawg (Apr 9, 2010)

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



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  .


----------



## Piker (Apr 10, 2010)

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.


----------



## heaterman (Apr 10, 2010)

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.



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.


----------



## RobC (Apr 10, 2010)

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


----------



## woodsmaster (Apr 11, 2010)

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


----------



## foamit up (Apr 11, 2010)

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


----------



## DMX_512 (Apr 11, 2010)

Thanks for all the responses.
I wanted to use 4 - 1 inch lines because the i.d. of the 2 supply and return lines would be closer to a true 1.25" or 1.5" i.d. . Also fittings are much more readily available and much less costly than 1.25" or 1.5". I thought that I read on here that someone else had done the same thing.

I will check that the contractor that I called is going to use closed cell foam.


----------



## shagy (Apr 13, 2010)

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


----------



## goosegunner (Apr 13, 2010)

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


----------



## Tennman (Apr 13, 2010)

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.


----------



## heaterman (Apr 14, 2010)

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.



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.


----------



## ken999 (Apr 15, 2010)

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.



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


----------



## foamit up (Apr 16, 2010)

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.


----------



## goosegunner (Apr 16, 2010)

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.



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

gg


----------



## Shelterman (Apr 16, 2010)

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?


----------



## foamit up (Apr 17, 2010)

GG  and Shelterman  I spaced the 1 1/4" pex lines with 1" sheet (pink) foam pieces about two inches long. One piece between pipes every two feet. Then i put a piece about 1" by4" by 4" on the outsides of the two pex pipes, all four sides. (You will have to experiment with foam size so that it has some space when sliding in the drain pipe.) Then duct taped the sandwich all around. This was done every two ft of pipe as i tried 4 ft but got to many sages.( so i thought) I wanted to make sure the pex was as close to center of the 6" flexible black pipe as possible. I tied the black pipe to a telephone pole and then pulled the pex in with a rope, i had someone at other end feeding it in. It was about 30degrees out when we did it so pipe was a little stiff. Worked a lot better the second time i did it when pipe was warmed up from the sun, 60 degrees. Foamit Up


----------



## Tennman (Apr 18, 2010)

I will post a new thread about our foaming success and I'll figure out how to post pics. The hard part was of course getting out my failed first pex insulation attempt which we did with a Ditch Witch mini-backhoe. Absolutely no damage to the pex tubing. We lined the trench with 4 mil black plastic just to avoid dirt getting blown around and into the foam. We laid the plastic and from the time the foamer started spraying we were done in about 30 minutes to do about 160' of trench. Our goal was to get a minimum of 3" all around with about 2-3" of separation between the lines. Since at least 3" surrounding was my minimum, most of the time it ended up being as much as 5" in some places. We sprayed first under the foam onto the plastic, allowed to expand, then lowered the lines into the still expanding foam. Then the foamer sprayed on top multiple times so i ended up with I'd guess at least 4" on top. By having the trench open he could keep spraying where we saw small cavities. I probably ended up with a monolithic block of foam 10-11" wide x 7-10" deep. It was awesome and very fast. We were walking on the foam 20 minutes after we had completed the entire length. Based on my one-time experience, I would not mess with trying to enclose it in any type of protective pipe for fear of inadvertently creating voids. By spraying in the open trench my foamer was able to see cavities to paint with foam and totally enclose. Also because I was so adamant about minimum coverage, he was conservative and I ended up with much more insulation than planned. He estimated the average cross-section area and multiplied by the length to compute the cubic feet of foam to price the job. I ended up with far more foam around my pex than if I had gone with the stuff you get pre-done. Absolutely awesome process and results. This was the first time doing this for both the foam contractor and me and within 8-10' from when we started we were working as and team and getting better results than I had hoped for. Because we needed to use the mini-backhoe to get the pex out my trench was a good bit wider than necessary which added to my foam expense some. But I spend $800 to have this foamed. I bough the 1 1/4 pex as cheap as it can be bought per foot. Had I not screwed up and did my home brew approach first this would have been very cost effective vs going the prefoamed stuff. Bottomline.... this was easy, fast, way over insulated and Lord willin, done for the rest of my days here. This approach I highly recommend.


----------



## Piker (Apr 18, 2010)

Congratulations!!...  sounds like it was  pretty a smooth operation.  $800 clams for 160' sounds pretty decent too, especially considering the extra volume of foam you have in the ditch.  Can't wait to see the photos.  

cheers.


----------

