Best Floor Insulation?

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When I built my house I insulated the the floor with R19 fiberglass batts. Rodents have - over the years - torn must of it down. I want to insulate once more and never again after that. What would be a better way to go? My floor joists are 2x10's.
Thanks, RO
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Robert Olin
Bob\'s Water & Septic LLC
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Tough job.....solid insulation........cutting and installing....... I used a sawzall mounted on a plywood board.......with blade sticking up to cut rigid insulation. Worked great with less dust...... screw the fence to the plywood for cut measures....push it through.....use a rough blade.....(wood blade) install tightly......... 4" foam foil face is good....... or larger. or 2 layers of 4" depending on R value desired..... jloomis

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Rodents will chew into foam as well. In some cases I think tey like it better, it tunnels easier. At least you will be able to hear them though. Maybe you could wire screen over it? Would be expensive but it would last. By the way, solid foam is quite expensive also. You will need 2" foam to equal R19, and 3" foam would be better, but much more expensive. I don't know how it compares to building up layers of thinner foam (R5 or R10).
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If the space under tha tfloor is not to be finished and used as a room, would it be possible for him to reinstall fiberglass, but then "drop" small-diameter wire mesh by nailing soem sort of "spacers" to every 4th (or so) joist, and then nail the mesh/hardware cloth to the "spacers"? It seems to me that would keep the fiberglass out of the reach of the rats. It'd be expensive, but less so than rat damage (and rat-related stress).
- K.
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wrote:

What kind of solid insulation? Foam? If so cutting is easily done with a hot wire cutter.

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WHY? Heat travels up. Are you trying to prevent ground heat from entering the house?
s

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That is not true. Hot air rises due to convection but heat radiates in all directions.
R
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Yes, but insulating a floor never pays back. It's a waste of time and money.
s
wrote:

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S. Barker wrote:

That's simply a false over-generalization.
hAdT knows no difference between down and up or sideways...
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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
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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.
s
wrote:

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S. Barker wrote:

Except it isn't so...warm, _still_ air rises, not heat.
Heat conduction is independent of anything except h, A, and dT and knows nothing of direction--at a given delta-T, the same amount of heat is conducted out a wall or ceiling of the same area and w/ the same overall effective heat transfer coefficient and temperature differential. And the temperature differential is dominated by the effective k which is insulation value.
--
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Why do you say that it's only still warm air that rises? Any body of warm air rises and induces convection - sailors have been relying on it for millenia. Since convection is a more efficient heat transfer mechanism, it seems a bit misleading to say that heat doesn't rise.
R
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RicodJour wrote:

Because in a circulating system the circulation pattern is generally stronger than the convective force...
But the point is it isn't "the heat" that is rising, it is that warmer air is less dense and hence does tend to rise. But, as the assertion made here again is also misleading at best, it's important to note that it isn't "heat" that's moving somehow magically out the ceiling that leads to the perception that floor heat loss is somehow magically different.
--
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dpb wrote:

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.
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.
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. :)
--

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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).

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.

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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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.

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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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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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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On Thu, 3 Apr 2008 09:10:30 -0500, "S. Barker"

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.

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