This is an method for insulating underground pipe runs form Don Stephens of Greener Shelter. Basically, the pipes are enclosed in an insulating concrete made from Styrofoam beads and cement. The resulting product is similar to Rastra.
Rastra says that its R value is 1.7 per inch. This is about 1/3 of the R value per inch for extruded polystyrene or polyurethane, so you will need more thickness, but the greater thickness should also provide more mechanical protection, its seems easy and cheap to achieve a nice thick layer using this method.
Thanks to Don for suggesting this!
Here are the full details from Don:
For very inexpensive, durable sub-grade tube/pipe insulation (as well as
poured in "sheets" in-place as perimeter, sub-grade insulation around AGS
structures), I've often called for just pouring a layer of do-it-yourself
"Foam-Bead-crete" in the bottom of a ditch-witched pipe trench, laying the
hot-air/water pipe centered on top of that base-layer (easily pinned in
place to the underlying "FB-crete" with landscape staples...also called
"Robert-pins" by strawbale-building insiders.) Then more BF-crete is poured
in the trench to encapsulate it, after which it's tented with polysheet or
roofing-felt moisture-protection and then rest of the trench-depth is
back-filled in with dirt.
"FB-crete" is just a site-made version of the mix used by Rastra for their
ICF units...about 9 parts of recycled bead-foam "shred" mixed/folded into 1
part of whipping-cream-thick cement slurry. One can buy such shred from a
foam-molder or you can shred your own, with a bucket-full of pre-wetted
beadfoam chunks (from free, salvaged electronics packing, etc.), blasted
apart with one of those drill-driven "swing-wire" wheel-type
paint-strippers, on a long drill-shaft extension down through a hole in the
The mixing can be done in a barrel, a home-style cement-mixer, or (as we do
for big projects) in a commercial cement mixer...we just have them deliver a
half-yard of cement/pea-gravel mix to the job-site in a large pre-mix truck,
and then pour in about 4 1/2 yards of pre-wetted foam bead shred in, when
the truck arrives. (This mix can be just poured, or it pumps nicely with a
stucco pump.) It has an R-value of about 3 per inch... : )
It provide a cheap, durable insulation alternative and keeps some of this
used foam out of the waste-stream, as well. (We also use it to self-fill
Rastra or similar ICF products, greatly boosting their R-values and greatly
reducing costs over the usual cement-fill... : )
- Don Stephens, InA,
Innovating in solar design since 1960,
Don is willing to answer email questions on this technique -- you can find him at his website.
Gary July 28, 2009