David asks...
> I realise hydronic radiant systems are better in this regard, but how
>much less energy can a radiant system really require to obtain the same
>feel?
Ok, this is my take over many years and lot of different experiences
heating areas. I may be way wrong, but it's based on my human or
human*like* if you ask my ex's!) feeling of heat.
There are 2 types of heat that you feel. 1 is warm air, and the other is
radiant.
Warm air is like your car's defroster blowing on you. It's warm and you
can feel it working as it warms you from the outside.
Radiant is from a hot mass. Such as a fireplace. Stand in front of one
and you will feel the warmth inside you.
Now place a small piece of plywood between you and a fireplace. The warmth
is gone. Radiant seems to work in LOS and increases in heat
logarithmically as you move closer.
Now, with that said. Central air units that warm up a space do so by
warming the air. The items in the room will only heat up if left in there
over time. Once the warm air stops blowing, the room is cooling off.
With radiant, (either floor or baseboard. (Note, the larger the radiant
mass, the better the effect. That is why a floor is better than cast iron
baseboard, which is better than copper pipes.)) You get items in the room
heated from the inside and that in turn heats the air. When you are not
pumping heat to a radiant system, the objects in the room will continue to
heat it for a while.
So, say you have a big shop and you heat it with forced hot air. You get
it to 80 Degrees in there. Now, you open the garage door to drive your
truck in. You just lost all that warm air. The heater will now have to
reheat that room to the temp. With Radiant, when the door is opened, the
air is lost, BUT the heat is in the items. So once the door is closed, the
air will be reheated quickly. (a very nice feature for a shop!)
There are lots of perks to a radiant system. I will never build a building
for myself that doesn't use it.And when I redo my 200 year old house, I'm
putting radiant throughtout.
Now, the problem for efficiency sake is what are the breaking points.
Is is cheaper to heat the air for the few hours you are in the shop or is
it better to have it maintain a constant temp? This depends on a ton of
factors, but it's the choice you have to make.
Your original question was when you would recoup the money spent on the
system. My answer is, the first cold day that you walk on that floor.
Radiant systems make you feel like you are sitting in front of a fireplace.
To me, that feeling is worth alot of money! YMMV 8>)
Inch
http://megageek.com
"Did you exchange, a walk-on part in the war,
for a lead role in a cage?" R Waters.
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