[Strawbale] PEX tubing in floors

[Chris Green]

Raftercat5 at aol.com wrote:
> 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? 
It sure can.
>  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?  
>   
You might find some moisture condensing out of the air in the room if 
the flooring gets cold enough and you live in a hot, humid environment 
where the RH is around 100%, but this is a minor possibility if you're 
keeping things in the 69 degree range and live in a milder location.
> 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? 
Use tie wire to bind the tubing to the rebar every 4' or so. That way it 
doesn't float. You don't have to twist the tie wire really tight, just 
'good enough.'
>  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. 
That will work, but the string could get in your way. Get some orange 
spray paint and mark the rebar where the walls will go. Double check 
your measurements. Keep the tubing about 2' away from the walls. Then 
pour the concrete.
>  I just hope we don't screw it up.  One mistake is all that's  needed.....
> - Kathy
>   
If possible, take some digital photos of the lay-out before you pour the 
concrete. Use a 4' level or extended measuring tape as a reference 
guide. Or you could use bright  spray paint and mark out 1' or 2' marks 
on the rebar if you want. Save the photos on a cd, if possible (and 
don't forget to label it and save the cd somewhere where it won't get 
lost (safety deposit box at the bank?)). You could even draw up a floor 
plan showing where things are, and photograph that and save it. 
Somewhere down the road when you need it, you should be able to have the 
photo of the drawn plans printed out as a 2'x3' photo.

If you want to put up a wall later on, you can use the photos for 
reference purposes. If you're still not comfortable about drilling holes 
in the floor, you can actually use beads of construction glue (Bulldog 
PL 600 or an equivalent) along the edges of the new wall plates (don't 
forget to have foam underneath the plates) to hold them in place. Treat 
the glue like a silicone bathtub caulking, and run a (gloved) finger 
along as you go to make a smooth cove.
I have used glue like this to hold down walls, then had to remove the 
walls because of changes in room lay-out: it was a really big chore to 
remove the wood from the floor. The glue has a binding force of 
something like 3500 psi, so the wood will tear apart long before the 
glue lets go.

Cheers,

Chris Green.