Foam in trench success !

[Adirondack Handy Man]

I just wanted to forward a success story on foam in trench piping method. I started my install nearly two seasons ago. My boiler building is 250ft from my house with approx 240ft underground. I used 1 1/4 OD pex tubing for the install. I ripped 2" blue foam board down to 2 x 2 and zip tied 6" pieces between the pipes every 2 ft for all 240 ft under ground. It took less than half a sheet of blue board. I then zip tied a 3/4 poly feed pipe to the return to service the out building with water all year. My foam contractor sprayed 8" of closed cell foam onto the ground, i set the pipes onto that and he filled the ditch side to side until 8" built up on top of the pipes. I filled the pipes with water before spraying to be sure they wouldn't melt. Closed cell foam creates unbelievable amounts of heat. After back filling, setting up the boiler and firing I am proud to say that for two seasons now I experience less than 2 degrees of loss from building to building. I use digital thermometers at both locations so there may be some variance however it's small. I have learned one lesson that I'd like to pass onto other DIY ers , piping is everything. Both in the ground and in the home. Do your research on primary secondary methods. You'll be glad you did. I'm using a cast iron Weil McClain wood boiler that's 300btu and was built in 1960. I heat a 3000sqft home we built in 2006. Last season I burnt 16 face cord of 16" wood. This season to date I've burnt 19 face cord of 16" wood. I could not be happier with the way it has worked out. The boiler is a " BLDMS" but it's cheap to run. For those whose did not follow the initials that stand for : Breakfast, Lunch, Dinner, and a Midnight snack... I hope others can find the confidence to try new ways to save some money.

 

[velvetfoot]

Closed cell foam creates unbelievable amounts of heat.

That's good to know.

 

[Tennman]

Congrats. As far as I can tell all the pre-foamed products use the same closed cell polyurethane so insulation performance boils down to thickness. No other method can give the water to dirt foam thickness as "in trench". Be good to post your experience in the Underground Sticky for the next guy that comes along. Not a bad idea to fill with water, but never heard of the curing temp affecting the Pex. Yeah that's a pretty remarkable return temp. During long periods of idling and pump running (I know... wasted energy) I've also seen a 2 deg F difference between boiler barn exit and return for our ~340 ft loop. I'm sure at least 1 deg of our loss is HX, manifold, in-house plumbing loss. So the underground is really amazing which ultimately results in me fetching/handling less wood. Share you story in the Sticky, over 31,000 folks have gone there to see how it's done and if it works. Again, big congrats from a guy who spent a long season heating a lot of dirt.

 

[Buzz Saw]

foam contractor sprayed 8" of closed cell foam onto the ground

Did you put down plastic first or spray directly on the dirt?

 

[Fred61]

Closed cell foam creates unbelievable amounts of heat.

Exothermic. = creates heat in the curing process. Like concrete and most epoxies.
If your foam installer is experienced he will first apply a thin coat and allow it to cure and cool before applying the full thickness. This will insulate the pipe from the intense heat generated from the curing process.

 

[mech644]

General rule of thumb with closed cell spray foam is applying it in 1" to 2" lifts, though installer has to asses what kind of heat retention is provided by immediate surroundings.
I've seen pieces that were removed from 2x6 walls for rework, foam was applied in 2 passes of approx 3", the pieces removed had large voids inside caused by excess heat retention.

 

[Leonard]

I wondered why nobody had poured two part closed cell foam in a form with tubing versus buying the stuff off the shelf.

 

[Adirondack Handy Man]

Did you put down plastic first or spray directly on the dirt?

Directly on the dirt

 

[crankshaftdan II]

Directly on the dirt

As a newbie here trying to gather helpful information--Q? How much allowance in inches/feet did you allow for expansion of your line set inside your basement? Do you notice any deflection in the Pex at the OWB or in the basement and what specific type of Pex was used? Thanks! Cranky

 

[Adirondack Handy Man]

I allowed for no expansion of pex in basement . 4 in inside to wall they go directly into a manifold. I used standard oxygen barrier 1 1/4 od pex tubing. The lines have room in my outbuilding to expand but I haven't experienced any.

 

[flyingcow]

OK, sounds good. Congrats. Exclude the ditch digging, how much did this cost per foot? Pex plus foam, etc