DIYbanter - View Single Post - does radiant heat work under carpet in basement?

Matt Whiting

wrote:
On Mar 12, 5:01 pm, Matt Whiting wrote:
wrote:
On Mar 12, 6:31 am, Matt Whiting wrote:
Doug Miller wrote:
In article . com, wrote:
I am not sure that the foundation was insulated underneath...is there
a way to verify? The house was built in 2000 and I don't know the
builder. The original owner wouldn't know either. Is there a way to
check/verify (without digging under the foundation of course).
Stand on it barefoot for ten minutes. If it feels pleasantly cool, it's
probably insulated. If it feels cold, it's probably not.
That is funny. It would take a pretty well calibrated set of feet to
tell the difference in ten minutes for a standard 4" thick slab.
Or you could try measuring the temperature of the slab with an IR thermometer.
I'd expect it to be noticeably above 60 deg F if it's insulated, but that's
just a guess.
This won't work either as there are too many uncontrolled variables.
You are looking for a rate of heat transfer, not an absolute
temperature. Depending on the ambience temps in the basement, a slab
could be at 60 F whether it is insulated or uninsulated. If you knew of
a slab nearby that was insulated and one that wasn't, you might be able
to heat a spot on both and watch the cool down rate with an IR camera
and compare them to your slab. But that is a lot more work than finding
the original building or drilling a 1/2" hole and seeing if you hit
foam. A core bore would give you a more accurate sample, but a simple
drilled hole would tell you if foam was there, but it would be harder to
get the exact thickness.
Matt
I just realized that there is an open 1ftx1ft hole in the floor for
the roughed in shower drain. There is crushed stone in the bottom . I
can probably scoop some of it out looking for insulation. How far
down is the foam board insulation usually in a foundation? If there
is none, should I not conisder radiant floors there? A friend of mine
said he had routed out plywood to run pex tubing and that was it for
his radiant floor...he hasn't hooked it up yet and it was on his
second floor. Is that an option for a basement floor (need to lay
plywood).
It should immediately under the concrete and above the gravel. If you
have to dig through much gravel to find it, then it probably isn't there.

Running the pex within plywood or furring strips covered by plywood is
your only option. It is probably still worth it, but certainly won't be
as effective as it would be with an insulated slab. If you have enough
head room you could always lay insulation on top of the slab and then
lay the pex on top of that and over with plywood. However, you are now
adding close to 3" to your floor which may be an issue.

Matt- Hide quoted text -

- Show quoted text -

Just verified that there is no insulation. Would laying 3/4" of foam
on top of slab (R4 I think), then plywood with pex be a good
approach? Do I need the aluminum in the plywood to make it work? It
seems it would be cheaper to route my own plywood and snap the pex
in. My other option is to use hydronic baseboard heaters...

It would probably work, but I would contact one of the many makers of
this equipment and get their advice. They have worked with a lot of
different situations and know their systems best. If you are at the
design stage, it is time to get help from the folks that know best.

Matt