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
If you have a cold room above the garage the solution to the problem
is obvious: pull down the garage ceiling drywall, pack it solid with
insulation, spray foam or whatever, then see what other steps might
help move warm air to the room. Remember, for warm air in you need to
move cold air out.
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
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.
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
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
heat, which could be easily installed exactly where needed. Given
supplemental heat for one room, the operating cost shouldn't be very
You;d have a control, timer, etc in the bathroom.
yeah my suggested solution too, easy to install, just run when needed.
if the OP were putting in a new ceramic floor they could imbeed
electric floor heat grid, but its probably not worth the effort.
or a combo fan heater for the cieling. they really warm things up:)
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.
years ago I was single and lived alone, would leave furnace set at 50
but i could come home shower and still leave furnace set at 50.
come home leave house cold, turn on shower, close door warm up
bathroom, then shower, nice warm and comfy.
cost? just some extra hot water... which also adds huidity to home.
i would turn heat up at night to 62 since i spent so little time
later i got a electric blanket and often let home cold at night
The op referred to "insult" ing the sides of the space, he meant
"insulat"ing the sides. Since we are former co-workers from many
years ago, the OP knew I was trying to be humerous. I'll try to do
better next time.
On 2/24/2011 10:48 PM, hr(bob) email@example.com wrote:
Huh, huh, I don't understand, spell check didn't catch anything??
But it did catch humerous! I'm insulated that you would publicly be
humorous at my expense. :)
BTW, to not make this a private communication between 2 people, I do
like the idea of putting "warming panels" under the subfloor, as
someone suggested. I did a little investigation but will have to do
more. But, if I do that, I still have to take down the garage
ceiling and insulation. I also still have to spend $$$ on
electricity to warm the thing. That's why I originally like the
idea of a warm plenum under the floor. The rug is looking better
You are considering a very complicated solution when there is a much
simpler one. You say that the room temperature is comfortable; your
only complaint is that the tile floor is cold. Get a mildew resistant
area rug and if necessary, cut away the part of the rug that otherwise
would cover the floor register. Problem solved.
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