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[prsmith]

I live in an old (1906) farm house. It's new to me, so I don't know how well insulated it is. Where I have ripped lathe & plaster out, the insulation has been better than I anticipated, but not 21st century.  When they outfitted the house with forced air heat, they put a furnace in the basement and a furnace in the attic. They did this, I assume, to avoid running ductwork to the second floor through inadequately wide wall spaces. This requires that I run hot water lines from the OWB to both the basement furnace and the attic furnace. I can easily run the foam filled corrugated tile through the rafters of the basement. When it comes to running the pipes up into the attic, though, I am at a loss. I won't be able to fit that big fat pipe up through my walls.

Can you give me your thoughts on the following hair brained scheme?  Pick an interior wall that runs from the basement to the attic. Line the interior of the walls with the shiny styrofoam insulation they put on the outside of houses, wrap the PEX with 1/2" foam pipe insulation, fill the gap between the shiny foam and the wrapped PEX with the nasty pink fiberglass stuff. Any better ideas or suggestions? I am open to nearly anything. Thanks!

[RSI]

Is it a heated area on the inside side of the wall? Is so, I would probably just worry about getting insulation behind the pipes and keep them in as far as possible. The foil covered sheet insulation is probably the best type to use. I would, if possible put spacers between the pex and the foil surface so it doesn't touch. That will keep it from conducting heat into the foil and will reflect the radiant heat much better. Also, I would make sure the insulation board is sealed to the studs all the way around so the warm air in the wall doesn't leak outside.
If you don't want the inside wall surface to be warm where you are running it, I would put pipe insulation on the pex. Otherwise I would skip it.

[prsmith]

Very helpful. Thank you.
prs