[VAC] Re: Balsa core flooring

["Dr. Gerald N. Johnson, electrical engineer" <geraldj@xxxxxxxx>]

The manifold based radiant heater requires far smaller diameter lines to
have enough pressure drop in each to split the flow between them well.
Small diameter lines present some problems: they clog easier and they
have far less surface area so don't transfer water heat as well. Plastic
lines depend on having a fairly large surface area to overcome the
insulation inherent in the plastic.

Copper lines transfer heat well, but make noise as their temperature
changes because they have to grow and shrink independent of their
surroundings.

The wall mounted radiant heater band would tend to not warm the feet,
and other than my hands, I find warm toes are more important than the
rest of me (probably because the rest of me has more padding). A problem
with running lines the length of the sides (or even a significant
fraction) is in getting past the skin spacer spars inside the walls
(e.g. aluminum wall studs.) And tends to require pulling the entire
interior skin to install in the wall. So long as the temperature is low
like the modern in-floor radiant heating, finger contact shouldn't be a
problem. When you raise the water temperature significantly, then you
begin to work on heating and moving air and you need fins to be
effective. Which makes the heater gain in thickness.

There are low temperature heaters sold for bathrooms that are a manifold
of flat tubing, good for use as a towel warmer too. Look for it in Fine
Homebuilding magazine.

I think the chemical version of the surflo RV water pumps would do fine
and would run on 12 volts when away from utility power. While I'm also
no fan of gas, it has a portability not available with a power cord. It
allows being independent of special camping places, to park most
anywhere and to be self sufficient. Many prefer that mode to being
parked cheek by jowl even if the close parking includes lots of electric
power capability.

I disagree with some fundamentals of the Icynene applicators. I believe
that walls insulated with it will be found supported only by the foam
because it appears to trap moisture in the wood studs and sheathing. I
believe that roofs insulated with no airspace above the insulation will
require roof shingles far more often than a well ventilated attic
because the roof will heat up a lot more from sunshine without that
ventilation. The applicators (at least the local one who can't be
reasoned with) believe that the sealing factor makes the product so much
more effective than fiberglass that rated r-factors can be neglected
that show fiberglass to be more price effective. I see that as a problem
when some state laws base minimum insulation qualities on r values of
the insulation material, neglecting leaks and studs that bridge the
insulation. My house plans include a double wall made of 6" studs inside
and 4" outside, but no extra space in between. Fiberglass insulation.
The studs on the interior wall will be on 24" centers and those on the
outside wall will be on 16" centers (because sidings require that to be
installed without sheathing). That way not all studs will be aligned
(except at corners and openings).

Anyway there is a version of Icynene suited for filling mostly closed
walls that might fit into an Airstream's walls. I know that I don't
appreciate cellulose blown into walls. In this old house the leaks let
the stuff contribute a gray color to all dust bunnies and to creating
large dust bunnies even out in the open.

There is an ASME formula for figuring the volume required for an
expansion tank. Its on page 12-70 of the Eighth Edition of Marks'
Standard Handbook for Mechanical Engineers. Too complex to type, easier
to scan. No doubt the ASHRAE handbooks would lend much information to
the design of a modern radiant heating system. This discussion has grown
wildly out thoughts of a lighter weight composite floor when replacing
an Airstream rotted floor.

Gerald J.