David,
I think your observations about radiant floors are mostly correct---if you
consider them as a discrete entity. You said that the heat goes where it isn't
needed most---which I take to mean the inside of the envelope. Well, sure the
interior floor is heated, but a properly installed radiant floor system has a
greater concentration of tubing _at the perimeter_. This performs the same
function as the trusty fintube radiation under the windows---knocking down the
heat lost through the shell (mostly the windows).
Granted, there is some convective transfer, but I'm sure that's a secondary
effect. The bulk of the heating is done by radiant warming of people and
surfaces, which is EXACTLY where the heat is needed. That's one reason radiant
floors are so "green"---they are easy to integrate into a passive solar design,
require little additional machinery, and little wasted energy.
David, you are absolutely correct---space heating IS all about human comfort
andnot just a matter of dumping BTUs into a room. Isn't that what a forced air
system does---just "dump BTUs into a room?" Even with the best diffusers you
could buy, control isn't that great; also, where does the heat enter the space?
Typically the ceiling, where there are no people and the air is already warm.
Put the registers in the floor---that's better as the warm air will rise, but
look at where we place the registers. Under the window at the outside wall,
usually. How often do we occupy that 2 feet right by the window? What about the
center of the room?
And yeah, radiant ceilings just suck. The top of your head gets baked and your
feet still freeze (though the desk tops are nice and toasty). Here's a
misapplication if there ever was one---it meets every theoretical need but just
denies that humans are typically vertical. Look at a person in plan view
(as the radiant panel sees it). Not much surface area to radiate onto. Of
course, this is where y'all will say, "OK, smartass, look at the radiant floor-
how much surface area does a person present to THAT?" Well, you're right, but
that's what's cool about radiant floors---they also incorporate a
_psychological_
effect, mentioned before.
I suppose radiant WALLS would be a good compromise, but then you've got the
practical problems of installation and the inverse-square law to deal with,
thus making the surfaces in the interior of larger rooms harder to heat through
radiation.
Well, I sure beat THAT one to death! Sorry to ramble, but I hope this helps
clear up any misunderstandings.
Mark
I think your observations about radiant floors are mostly correct---if you
consider them as a discrete entity. You said that the heat goes where it isn't
needed most---which I take to mean the inside of the envelope. Well, sure the
interior floor is heated, but a properly installed radiant floor system has a
greater concentration of tubing _at the perimeter_. This performs the same
function as the trusty fintube radiation under the windows---knocking down the
heat lost through the shell (mostly the windows).
Granted, there is some convective transfer, but I'm sure that's a secondary
effect. The bulk of the heating is done by radiant warming of people and
surfaces, which is EXACTLY where the heat is needed. That's one reason radiant
floors are so "green"---they are easy to integrate into a passive solar design,
require little additional machinery, and little wasted energy.
David, you are absolutely correct---space heating IS all about human comfort
andnot just a matter of dumping BTUs into a room. Isn't that what a forced air
system does---just "dump BTUs into a room?" Even with the best diffusers you
could buy, control isn't that great; also, where does the heat enter the space?
Typically the ceiling, where there are no people and the air is already warm.
Put the registers in the floor---that's better as the warm air will rise, but
look at where we place the registers. Under the window at the outside wall,
usually. How often do we occupy that 2 feet right by the window? What about the
center of the room?
And yeah, radiant ceilings just suck. The top of your head gets baked and your
feet still freeze (though the desk tops are nice and toasty). Here's a
misapplication if there ever was one---it meets every theoretical need but just
denies that humans are typically vertical. Look at a person in plan view
(as the radiant panel sees it). Not much surface area to radiate onto. Of
course, this is where y'all will say, "OK, smartass, look at the radiant floor-
how much surface area does a person present to THAT?" Well, you're right, but
that's what's cool about radiant floors---they also incorporate a
_psychological_
effect, mentioned before.
I suppose radiant WALLS would be a good compromise, but then you've got the
practical problems of installation and the inverse-square law to deal with,
thus making the surfaces in the interior of larger rooms harder to heat through
radiation.
Well, I sure beat THAT one to death! Sorry to ramble, but I hope this helps
clear up any misunderstandings.
Mark