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Posted by RicodJour on April 3, 2008, 3:25 pm
> dpb wrote:
> > RicodJour wrote:
>
> >>> Except it isn't so...warm, _still_ air rises, not heat.
>
> >> Why do you say that it's only still warm air that rises? ...
>
> And, I didn't say "only", I simply emphasized "still" owing to the
> effect as noted earlier being most significant when forced convection
> isn't in play.
I'm not a big fan of forced hot air heating, and at least in my area
the predominant heating systems are hydronic and steam radiators
(which, of course, are really convectors).
> And, of course, while convection is effective in heat transport within
> the room, once it gets to the wall/ceiling/floor surface, except for
> undesirable leakage paths it becomes a conduction problem for the most part.
>
> Hence, except for the probably relatively small (in general) temperature
> difference in a well-regulated room between the ceiling and floor the
> heat loss is pretty much dependent on how cold the other side is and the
> effectiveness of the insulation.
All you have to do is calculate the location of the dew point
temperature to graphically determine that an insulated floor is
warmer. The only time it wouldn't be warmer is if there's no heat in
the house and there's no sun. Luckily that excludes most of our
planet.
> Of course, there's the sensitivity of bare skin to hard floorings issue,
> too, that is a localized heat transfer effect, particularly to bare feet. :)
I love my radiant bathroom floor. I have to fight the urge to lie
down on the warm tile...sometimes I even win. ;)
R
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Posted by Wayne Whitney on April 3, 2008, 1:33 pm
> Insulating the floor will not make it warmer, 'cause the 'cold' does
> not come from below.
For a floor separating a conditioned area above from an unconditioned
area below, the floor temperature will be determined by equilibrium.
That is, in the steady state, the rate of heat loss to the cold space
below will equal to the rate of heat gain from the warm space above.
If at some point, the heat loss to the cold space below is higher, the
floor temperature will fall, which reduces the heat loss to below
(smaller temperature difference) and increases the heat gain from
above (larger temperature difference). Eventually the two rates
balance and you have equilibrium.
Conversely, if the heat loss to the cold space below is lower, the
floor temperature will rise, as the floor absorbs more heat from the
heated space, until again the two rates balance. So if you reduce the
rate of heat loss to the space below, by insulating the floor, you
raise the floor temperature.
> Heat rises, cold falls. can't change that.
That's simply false. Heat can be transferred by 3 mechanisms:
convection (movement of air), conduction (touching objects) and
radiation (infrared radiation all things emit). For convection, yes,
hot air rises and cold air falls. But conduction and radiation don't
care about gravity at all.
Cheers, Wayne
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Posted by RicodJour on April 3, 2008, 1:39 pm
> BUT, only one thing wrong with this statement about the cold floor.
> Insulating the floor will not make it warmer, 'cause the 'cold' does not
> come from below. The only way to make a floor warmer is to put heat UNDER
> it. Heat rises, cold falls. can't change that.
Besides the fact that you're completely wrong, you shouldn't argue
points you don't really understand. It's even worse to give advice
based on those errors in comprehension. Maybe this will help you
understand heat transfer a bit better:
http://www.diynetwork.com/diy/cda/article_print/0,1983,DIY_16803_2644049_ARTICLE-DETAIL-PRINT,00.html
R
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Posted by Andy Energy on April 5, 2008, 12:36 am
>
> > Yes, but insulating a floor never pays back. It's a waste of time and
> > money.
>
> Based on what time and energy cost assumptions are you basing that
> particular gross generalization? I'd imagine that floor insulation
> life would be on the order of several decades, and unless you've got a
> Mr. Fusion cranking away to keep you warm, I doubt that energy costs
> are going to go down in the foreseeable future. There's also the
> issue of comfort. A warmer floor is more pleasant to walk, keeps your
> whole body warmer, regardless of time and money invested, and cuts
> down on drafts - a major source of heat loss and discomfort.
>
> R
I agree with all of the above except cutting down on drafts unless a
spray foam or ridged sealed in place. Loose fill, glass or mineral
wool do not stop air flow and normally will not even slow it down.
I have a thing about payback. What is the pay back on the boat,
plasma TV, SUV, 6,000 sq ft house for one person, vacation, going out
to dinner, remodeling the kitchen and the list goes on.
We are brain washed by marketing that we can spend thousands on a SUV
but when it comes to making our homes comfortable and energy efficient
we will not do it unless it has a payback better than we can get in
out investments. I'm not saying we should give up all those other
things just put the energy efficiency of our homes on the top of the
list, not the bottom.
If I was into betting man I bet on much higher prices of energy.
AndyEnergy
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Posted by PeterD on April 3, 2008, 1:02 pm
On Thu, 3 Apr 2008 09:10:30 -0500, "S. Barker"
>Yes, but insulating a floor never pays back. It's a waste of time and
>money.
>
>s
>
You clearly don't live in a cold climate, do you? 'Pays back' is
meaningless, an ice-cold floor in winter is not. But, even still it
will pay back, just as any reasonable insulation job will do.
>>
>> That is not true. Hot air rises due to convection but heat radiates
>> in all directions.
>>
>> R
>
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