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Solar assisted radiant floor heating system - Page 13

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Posted by Rob Dekker on February 14, 2007, 7:56 am
 
Thanks Alan,

Sorry NG members, for top-posting. But it works better for these 'overall'
responses....

Alan : Looks like you had a much bigger project that I have..
I am only changing the interior. Cannot change anything exterior. Long story.
Any way, I have very little space (hight) to work with. Only 1 1/2 inch to be
precise.
I need to fit insulation (I have an uninsulated slab like you), tubing with
radiators, possibly a board (for load) plus the hardwood
in that space.
With that hight constraint, I have now pretty much rules out concrete as a
'radiator'. The 2x4's you installed are at my hight limit
already.

I need to go with alu fins and some lightweight radiation board.
Looked at Warmboard, but it is too thick (1 1/8 inch board leaves me no space
for insulation).
Looked at (5/8) ThermalBoard, but it has a crappy 5/1000 inch alu foil as heat
distributor. Surely I'll get heat stripes in my
hardwood lacker with that. Also it supports only 3/8 PEX, and I would much
prefer 1/2inch tubing.
So, now I'm back to square one. Thinking of a solution with 3/4 inch hard
insulation foam board, cut groves in it for 1/2 PEX, alu
fins to spread the heat upward, and a floating engineered hardwood floor on top.
Should be no more that 1 1/4 inch thick in total.
With R6 underneath, it should be pretty efficient, and ready for my real project
: to drive it with a hot-water tank from solar
panels on the roof.

Still looking for a R6 3/4 inch foam board that I can cut 5/8 inch groves in
(for the PEX) and that also can handle at least 60 PSI
load, so that I do not need plywood over the insulation and under the hardwood.
Let me know if you know something...

It seems to me that you needed the OSB (plus the flooring on top) because you
used tile.
If you would have chosen a floating hardwood floor, would you have floated it
right on top of your sleepers/concrete ? Or did that
not feel good (structurally speaking) ?

Thanks again, I appreciate all your experiences here.

Rob


after 3 weeks of this NG tread being dormant...

(?) plus tile.. That should be close to 3 inch total

so... Was none of that a problem ?

'cement' radiators. 1/2 inch PEX tubing in that space

thin.... Didn't these things break right away if you

heat, up when the concrete expands and contracts

that be a problem (if they are cracked) ? Do you

cement islands were nonexisting...?

distribute the heat) instead of the cement islands ? If

this thing !

(the) water heater.

conservation, but also because I want to make a serious

insulation material down, then a snake pattern of PEX

or using a commercial)floorsystem like that.

to avoid more that 10 or 20% of the heat to

strips ? submerge in a hard thermally conductive compound


Posted by Alan on February 23, 2007, 7:26 am
 
If I had put in hardwood flooring, I wouldn't have needed the OSB.
I'd just cover the concrete with that thin sheeting designed for a
vapor barrier under hardwood, and nailed to the sleepers.  So, that
would be 1-1/2" sleeper depth plus 3/4" hardwood, assuming traditional
non-engineered stuff.  I think that you could use 1/2" tubing (or even
3/8" tubing) and strips of plywood as the sleepers to get the same
effect.  I'm not a fan of engineered oak hardwood, but bamboo and
other hardwoods do come thinner than 3/4".  You will be happier with
radiant floor over baseboard or wall radiator heat for sure.  Also,
you probably do want the foam under the tubing to avoid having the
slab conduct the heat into the soil below.  In fact, there's no sense
putting the foam around the tubing.  So, I'd consider 1/2" foam (the
cheap styrofoam stuff at Home Depot will do) between the sleepers, and
then make the spaces smaller since the 1/2" tubing will also need to
be spaced more closely, say 8 to 12 inch on center, to distribute the
heat.  With smaller tubing and thinner heat sink, you'll need to have
more tubing per square yard, plus there is a need to nail the hardwood
more closely than 16" on center.  Be sure to paint the plywood
sleepers with Jasco wood preservative or similar product and then bolt
and calk the sleepers to the original slab, making the whole floor
more stable for any unforeseen changes during heating or under heavy
loads on the floor.  I'd skip the aluminum heat spreader idea in this
application because of cost and performance.  The packed concrete is a
good cheap heat sink and won't risk any noise or expansion problems
that aluminum might create, but be sure to put a vapor barrier over
the sleepers and concrete before nailing down the hardwood.  I'm
certain that you can do it.  If you use the open loop system, make
sure all the tubes are exactly the same length, so that the pressure
flow will be equal and stagnation can occur in any of the tubes.
Also, make sure that you carefully arrange the radiant tubing manifold
so that you won't get unwanted heat conduction through the water
during summer.  Backflow preventers are important in this regard, but
so is the actual plumbing arrangement in the heater closet.

Alan



Posted by Alan on February 13, 2007, 8:16 am
 I forgot to mention that the aluminum fins are for under raised
foundation subfloor applications only.  You don't want expanding/
contracting metal in the concrete.  That WILL produce cracks.  The
concrete, with the OSB, hardibacker, and tile over it, is quite
adequate for the radiant system really.  You won't be disappointed.  I
think the OSB disperses the heat, so I don't have "heat streaks", but
in any case, the heat is very even and uniform across the floor.  The
once cold sink is now the primary heater for the rest of the house!
We walk barefoot in the deep of winter, and leave second level room
doors open.  It's been cold in some upper level bedrooms, but this
year we went cheap and didn't use the upper house force air system at
all.  The radiant system provides just enough in the most used room in
the house.  I may use the aluminum fins and pex under the hardwood
floors, kitchen, and bathrooms on the raised foundation portion of the
house next year.  Which reminds me.  Make sure you leave open the
possibility for system expansion at the manifold level.


after 3 weeks of this NG tread being dormant...

plus tile.. That should be close to 3 inch total over

so... Was none of that a problem ?

'cement' radiators. 1/2 inch PEX tubing in that space

thin.... Didn't these things break right away if you put

heat, up when the concrete expands and contracts with

that be a problem (if they are cracked) ? Do you feel

islands were nonexisting...?

distribute the heat) instead of the cement islands ? If so,

thing !

(the) water heater.

conservation, but also because I want to make a serious

insulation material down, then a snake pattern of PEX tubing,

using a commercial)floorsystem like that.

to avoid more that 10 or 20% of the heat to disappear

? submerge in a hard thermally conductive compound ?


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