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Bud--

wrote:
On Feb 24, 12:53 pm, jamesgangnc wrote:
On Feb 24, 12:23 pm, Art Todesco wrote:

I have a small room with a shower stall, toilet and pedestal sink.
The floor space is about 48" x 56". It is located in the corner of
the house, so 2 walls are outside walls. The house is in western
NC. While the room is comfortable as far as air temperature, the
tile floor is cold. There is one register in the floor on one of
the outside walls. The area below is garage, so it could be
accessed from below by removing a piece of garage ceiling drywall
and insulation. I would like to use the area below the the small
bathroom as a heat plenum, hopefully warming up the floor. I know
people (including me) will say, "you can't do that ....." But in
my house and in many other houses in this area, they put the heat
registers for the kitchen and bathrooms (not this bathroom, but the
other one) in the cabinet kick plate. The duct just comes through
the floor and dies there. The air just pressurizes the "kickplate"
area and it eventually comes out of the register mounted up front.
So if I were to wall off the area directly below the floor, insult
the sides and against the garage drywall, and just like the kitchen
cabinets, let the air find its way to the register. I would have to
put a shut off on the duct for summer use or suffer an even colder
floor in the summertime. BTW, the heat comes from a heat pump with
a propane furnace for backup heat. Any comments pro or con or other
ideas?
Using the space between framing as hvac duct work is done sometimes.
Normally it is interior wall spaces. You need to make sure the ends
are sealed or add blocking yourself. I would try to put some minimal
insulation on the garage ceiling side like maybe foam sheet or
something.

One of the problems created by doing this is wider temp changes where
the framing is located. This could result in more shrink and
expanding depending on temp and humidity.- Hide quoted text -

- Show quoted text -

Here's the problems I see with this approach:

Normally there aren't heating ducts in unheated garage space, so where
is the hot air coming from?

The joists have to run in the right direction

You only get one bay's worth of heating area between joists. To do
the
whole bathroom would require several bays.

The air has to come from and go somewhere as it flows through the
bay. Where does it go?

Given the above, I would think a better solution would be electric
radiant
heat, which could be easily installed exactly where needed. Given
it's only
supplemental heat for one room, the operating cost shouldn't be very
high.
You;d have a control, timer, etc in the bathroom.

I agree that using the hot air system is not likely practical, and that
electric might be the best fix (other than a rug). I think there are
electric panels that mount to the bottom of a subfloor to heat the
floor. Like trader suggested this probably has to be installed in
multiple joist spaces.

Maybe a plug-in (GFCIed) electric heater blowing across the floor when
(before) you use the bathroom?

If you walk on the floor with bare feet the floor has to be warmer than
the walls or air because you get real good heat transfer.

--
bud--