[Strawbale] PEX tubing in floors

[Alan Mason]

Kathy,

I see you've already gotten lots of good feedback here, but having had the
"pleasure" of personally installing a radiant floor for a client, thought
I'd throw my two cents in.

First, and someone correct me here if I'm wrong, I think that any time you
have a temperature differential between the concrete and the pex tubing, you
are going to get condensation. Since the concrete will tend to want to cool
towards the temperature of the earth underneath in summer or winter (approx
55 F)  you may actually get less condensation running cool water through it
than hot.

Second, yes the tubing will want to float when you pour. We did not charge
the system before pouring, as Shody suggests, but I'm not sure it would have
helped, as the concrete is still a much denser material. Be sure to secure
the heck out of it. We used zip ties (NOT tie wire) to tie it to the top of
the rebar per the manufacturers instructions, especially in areas where
there were walls and at all the bends which will want to float more than
straight runs. .We still got a couple floaters, and had to repair a couple
of leaks. Fortunately they were under walls or in other places where the
patch in the concrete didn't show. Charge the system as soon as the concrete
is reasonably cured to see if you have any leaks due to damage during the
pour as well as when you are putting the walls up to find out if you have
hit a tube. Its a pain to have to rip the concrete up to repair a leak, but
its not the end of the world. Be sure to order some tubing repair kits when
you order your pex.

We marked the location of the pex by laying a long 1 x 4 down in the
different rooms and marking where the tubing was. The dealer who sold us our
system provided a drawing showing where the tubes should be laid. If your
dealer does this, I recommend you mark up a copy of that with exact
measurements of where the pex is - it will take longer but be much more
accurate than a stick. Still no guarantee of not hitting a tube, but it will
help. The problem with photos is that its hard to pull an accurate
measurement off of them, but they are probably not a bad idea as in addition
to a drawing with measurements on it.

As others have said, avoid running tubing under cabinets, refrigerators and
other appliances, near toilets (the wax sealing ring  will melt) or any
other place you can conveniently avoid that doesn't require heat. This will
also reduce the size of your system.

Finally, I don't know where you live, but you might ask yourself if you
really need a radiant floor. I just talked with the client I installed the
radiant floor for, and he has used his system a total of 3 times since Feb,
2006. We are in southern California, but his house is at the same elevation
as mine, about 3700 feet, and it got well below freezing here on at least 8
days. . During the same period I have had at least 60 heating days here in
my stick built non-strawbale.See
http://www.oregon.gov/ENERGY/CONS/RES/tax/Radiant.shtml for more thoughts in
this subject.

Good luck.

@


----- Original Message ----- 
From: <Raftercat5 at aol.com>
To: <strawbale at listserv.repp.org>
Sent: Saturday, April 28, 2007 9:15 PM
Subject: Re: [Strawbale] PEX tubing in floors


> I'm hoping to get some good feedback from all you guys (and girls) that
are
> knowledgeable in this department.  When we get ready to pour our concrete
> flooring for the SB house, we'll be putting in PEX tubing.  We plan to use
solar
> hot water, run by a solar pump, to heat the floors in the winter.   When
the
> sun is not shining, it will automatically kick over to propane heating
the
> water.  My question is:  Can it work to cool the floors in  the summer by
> pumping cold well water thru the PEX tubing too?  I'm  wondering if there
would be
> any kind of moisture problem from  condensation.  I think not, as where
would
> the moisture come from, if it's  not in the ground where the PEX will be,
which
> is on top of plastic sheeting,  and under concrete?
> Also, I'm concerned about the depth of the tubing into the concrete.
Would
> there be a chance it could work its way toward the surface of the concrete
> right after it's poured, thus leaving it vulnerable to nails when the
interior
> walls are built?  My husband said we would mark with string where the
> interior walls will be put before we lay the tubing down, so that won't be
a
> problem.  I just hope we don't screw it up.  One mistake is all that's
needed.....
> - Kathy
>
>
>
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