Basement insulation question

I'm building a new house with a full basement. The basement is not heated. The rest of the house will be heated with forced hot air. Should I insulate the basement ceiling? Should it have a vapor barrier on the basement side? It may not be practical to install with a vapor barrier on the living area side at this point.

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On 11/29/2004 11:46 AM US(ET), SteveC1280 took fingers to keys, and typed the following:

The vapor barrier should always go to the heated area side. There are exceptions in hot, humid areas of the planet when it should be reversed. I installed fiberglass insulation in my basement ceiling joists 20 years ago with the barrier down, but it was mainly for noise insulation (kids, then teens played in the basement). My unheated (except for the ambient heat of the boiler and water heater) basement is dry and insulated around the outside walls with studded, insulated, and sheetrocked walls. I have had no problem with wet insulation up there, and I just removed some last week to run a 220v wire up through the floor. Just curious, but why is it impractical to install it with the vapor barrier up?

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I guess it's not that difficult to install the insulation with the vapor barrier up. I just won't be able to staple the paper to the joists. I've seen people insulate this space with inslation that does not have a crafted side. I was wondering if i't OK to use that type of insulation.

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On 11/29/2004 3:42 PM US(ET), SteveC1280 took fingers to keys, and typed the following:

OK. They use short pieces of stiff wire rods (16" or 24" long, depending upon joist spacing) called 'insulation supports' that are pressed in between joists about every foot or so, to hold up instapled bats when there won't be sheetrock or other panels secured to the ceiling, like under dropped ceilings. They may have them in HD or Lowes.
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Insulation can be purchased with built in vapor barrier so it should be possible to have it installed with the barrier face up. By the way, if you live in most states of the US, code will require insulation of the finished floor above an unfinished basement.

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Speaking of which, when you're trying to figure out how much heat is getting sucked out of your house, is there some standard multiplier or other adjustment for floors and ceilings, or do you just figure the nominal R value and multiply by area?
Conventional wisdom seems to be that most heat loss is through the ceiling. Is this because ceilings leak, because in a reasonably sized house, ceilings are big, or because it's easier to get insulation there, and people translate "best place to add insulation" to "biggest source of heat-loss".?
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Perhaps I am missing something here, but isn't it at least in part because heat rises?
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Except that that's not really true. hot fluids (air, water, etc) generally rise in the presence of colder fluids, but heat itself doesn't care about gravity. That means that an actual HOLE in the ceiling does more damage than a hole in a floor, but once you've sealed all the air leaks, I can't figure out what, if any, difference there is between walls and ceilings.
I guess what I really wanted to know was, do you calculate heat loss through a ceiling and floor the same way as through a wall, or is there a correction factor, and if there's a correction, what's it based on?
--Goedjn
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-snip-

It's been 30 years since I did any, but I think there was a factor for ceilings and floors.
You are correct that 'heat' doesn't rise, but hot air does. Hopefully your house is full of air. That air rises & causes the ambient temp to be greater near the ceiling than at the floor. So the temp differential & therefore the heat loss, is different.
There is also something called the 'chimney effect' that magnifies the problem of a poorly insulated ceiling. [I'm not trying to be vague here-- I'm pretty sure that is the term but I can't think of an easy way to describe it.]
To the OP-- I'd insulate the floor. The actual heat loss won't be that great, but because it should keep the floor a couple degrees warmer, the house will feel more comfortable at a lower temp. If you are one who keeps the thermostat at the lowest comfortable temp instead of some arbitrary number, then you might save money in the long run, too.
Jim
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Speaking of which, when you're trying to figure out how much heat is getting sucked out of your house, is there some standard multiplier or other adjustment for floors and ceilings, or do you just figure the nominal R value and multiply by area?
Conventional wisdom seems to be that most heat loss is through the ceiling. Is this because ceilings leak, because in a reasonably sized house, ceilings are big, or because it's easier to get insulation there, and people translate "best place to add insulation" to "biggest source of heat-loss".?
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If your furnace is going to be in the basement, chances are it will end up being almost as warm as the rest of the house anyway. I suggest you save your insulation money for the attic area where the temperature difference will be much greater and will give you a better payback.
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On 11/29/2004 2:01 PM US(ET), Joseph Meehan took fingers to keys, and typed the following:

My basement averages about 70 year round (NY). The entire basement is 6' to 7' below ground. As mentioned in another thread, I only have the ambient heat from the boiler (winter) and water heater, which are in a small utility room, part of which is below the basement stairs. On the coldest days, it may drop to 65, and on the hottest days, 75. All my poured concrete exterior walls are 2x4 studded, fiberglass insulated, and sheetrocked. In the winter, I place a small desk fan high in the utility room to blow the warm air through the doorway and into the basement.
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I have 2 furnaces in the unfinished portion of my basement. No way do they warm it up to the point that I would not want insulation in the floor of the room above it.

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