Weird OT mystery...

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I'm sitting here in my skivvies, sweating. I turned the air conditioner off an hour ago because it was getting cold in here.
This is November mind you. In the mountains of Virginia.
It got up reasonably warm today, maybe 70-something. It rained a lot, and was generally overcast. Not very much solar radiation getting in to warm the place up. Around 10:00 PM the heat became so intolerable that we actually turned the A/C on and let it go for around half an hour.
So now it's about 1:00 AM. Somewhen between then and now the air has picked heat back up from somewhere, and I'm scratching my head trying to figure it out. It's back up to 81 degrees in here, and it was down to 71 at 10:00 PM. No sun in that time. No electric heat, no propane heat...
Could be waste heat from the big dehumidifier that has been chugging 24/7 in the crawlspace for the last six months maybe.
Residual from the hot water heater that really needs replacing very soon now.
Halogen lights...
Still, adding all of this up, it's about 1500 sq. ft. of open space in here, and it would take a lot of BTUs of heat to raise that much air by 10 degrees.
Could it be a simple matter of body count? House empty all day, then four big'uns, two little'uns and three furry'uns? (Three medium sized dogs.)
I won't be complaining about free heat in a few more weeks, mind you, but it's a real mystery. I'm wondering if I have some problem developing.
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Michael McIntyre ---- Silvan < snipped-for-privacy@users.sourceforge.net>
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*Everything* contributes.
I forget how many BTU/hr a person puts out, at rest, but _occupied_ school buildings almost -never- run the heat plant at temperatures above *MINUS* *TWENTY*FIVE* Farenheight. The warm-body factor is enough that they're dumping heat to the outside.
Other things, like the _refrigerator_, the dehumidifier, lights, the TV, computers, etc. -- they all add up. non-trivially.
Betcha you've got several kilowatts of electric load that you don't even -realize- are running.
Plus all those "warm bodies".
An additional point -- *rain* releases _tremendous_ amounts of heat into the atmosphere. 1" of rain, over a medium-sized city, say one the size of Omaha, NE, releases more total energy than a mid-size atomic bomb. Not from lightning, etc. -- just from the reverse 'heat of vaporization' released by the water-vapor condensing out.
Now, +most+ of that heat is released at higher levels in the atmosphere, and you'll freqently get some 'evaporative' cooling at/near ground level. but, it's not uncommon for ground-level temperatures to climb by several degrees, several hours after the rain.
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On Thu, 06 Nov 2003 14:10:06 GMT, snipped-for-privacy@horatio.agresource.com ()

Just for kicks, do a rough estimate of the volume of the space David Blaine occupied in that block of ice. Then using 2500Cal/day as a rough first-pass, figure out what the temperature of the air in that small space was. Heck, be generous and say he only put out 2000Cal/day.
Plus, he was given hot soup to eat.
Nice work if you can get it, assuming one isn't claustrophobic.
n.b. that keeping himself dry and keeping bare skin away from wet ice were nontrivial concerns.
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snipped-for-privacy@horatio.agresource.com () wrote in message news:<2Dsqb.12846 SNIP

Huh?! I am the Business Manager for a school district near Pittsburgh, PA. It NEVER gets to -25 F here. I don't think it even went below 0 last winter. We seem to run the heating systems all winter though and spent a total of $350,000 for natural gas last year for 9 buildings. I doubt that body heat can do much for heating significant spaces and if there were enough bodies in the space to heat it when it is -25 outside then the CO2 being given off would kill everyone if there wasn't a MAJOR fresh air exchange going on...not to mention the smell ;)
Dave Hall
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Dave,
The old science building at the University of Pittsburgh at Johnstown (built in the early 70's?) was so energy stingy, they only had to run the heat during the Christmas break ... because there weren't any bodies to keep it warm. Rest of the time they had a heat surplus without the stale air syndrome.
Also ... http://www4.ncdc.noaa.gov/cgi-win/wwcgi.dll?wwevent~ShowEvent~206153 shows record low temperature for Pittsburgh area ... pretty close to -25!
Rick
() wrote in message news:<2Dsqb.12846

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Body heat sure adds up. I used to work for a company that built heating and AC units for commercial and industrial applications. Schools were one of their largest markets.
Body count is very seriously taken into consideration when calculating heat loads. IIRC, it is 485 Btu per person. or enough heat from 100 people to heat a small home.
Ever go to a concert or sports game in an arena? Notice how cool it is when you first arrive and how much warmer it is when the crowd fills the place? And yes, air exchange is also considered. Often the heat is off and the ventilation is bringing in the cold outside air to cool the place down. Ed snipped-for-privacy@snet.net http://pages.cthome.net/edhome
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I've got numbers ranging from 450 (sleeping), to 570 (hard work). I know that that second number is somewhat _conservative_. For rough calculations, and 'average conditions', 500 BTU/hr/person is a reasonable approximation.
Guess it depends on what you consider a 'small home'. The house I grew up in was about 1200 sq ft on the main floor, 2 stories over 25% of the space, and unfinished basement under about half the main floor. Due to 'accident' of incremental construction, the place had _two_ smaller furnaces. one rated at 48KBtu/hr 'net', the other at 64k net.
One winter, one of the furnaces *died*. We don't know just when, we -noticed- "something unusual" during a viscious cold spell (daily highs circa -20F, lows below -35 F brrr!). The "big" furnace was running nearly continuously. about 50 minutes out of each hour. Vs. a normal 12-15 -- maybe 20 in really cold weather. Went looking, and discovered the other furnace wasn't running _at_all_. So we've got the _one_ furnace, 64kBTU/hr, running at about an 85% duty cycle, keeping the _entire_ house comfortably warm. In *sustained* -25 F weather.
Call it about 55k BTU/hr effective, from the furnace. For somewhere between 1600 and 2200 sq ft of 'livable space', depending on how you count things.
Four 20'x20' classrooms (1600 sq ft total), with 30 people/room, produces around 60K BTU/hr of 'people power'. The 'energy' _is_ there to keep the place warm at -25F, without requiring supplemental heat. <grin>

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snipped-for-privacy@horatio.agresource.com wrote:

In the HVAC ( heating venilating & Air Conditioning ) racket we use to figure 500 Watts per person (warm body) :-) ...lew...
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I got out my reference books. I think you mean 500 BTU/hr. 500 watts is about 3x higher.
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snipped-for-privacy@horatio.agresource.com says...

I seem to recall from my college days (engineering school), the rule of thumb was 100 Watts / person.
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On Thu, 06 Nov 2003 20:37:11 GMT, Lewis Hartswick

European practice is more like 150W -- Die Gotterspammerung - Junkmail of the Gods
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That's more in line with the number I remember from one of my engineering courses many decades ago. The human body at rest generates ~100W of heat. An active body generates more but I don't remember how much more.
Art
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Possibly. I seem to recall reading that the heat output of an adult human is around 500 watts asleep, and 750 watts awake, but I could be imagining that. Dogs have a higher body temperature than humans, too.

Well, you might. Does anyone *else* think it's too hot? 81F isn't hot IMO. That's a comfortable-in-tee-shirt-and-shorts kind of temperature, not a sweating-in-your-skivvies kind of temperature. If you're the only one sweating, it might be time to call a doc (or at least get out a fever thermometer). Have you been drinking enough water?
-- Doug Miller (alphageek at milmac dot com)
How come we choose from just two people to run for president and 50 for Miss America?
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Doug Miller wrote:

SWMBO stripped down to her skivvies too.
No, unfortunately, that didn't lead anywhere interesting. :(
The kids both kicked off their covers. It wasn't just me.
Maybe we got microwaved by aliens from another galaxy. :)
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Michael McIntyre ---- Silvan < snipped-for-privacy@users.sourceforge.net>
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It is also humid under the conditions we've had the past few days adding to the dis-comfort level. All of a sudden it feels very close, very stuffy.
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snipped-for-privacy@snet.net says...

I suspect that may be your real problem. If the humidity is high, water isn't evaporating from your skin, thus you aren't benefiting from natural cooling. 81 and dry is pretty comfortable, 81 and humid might be pretty uncomfortable. Did you say you have a de-humidifier? Is it running?
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I think your numbers are correct but it is BTU per hour. Not trivial but not a huge source. my house here in NC gets much warmer after sunset. the heat trapped in the attic tends to start leaking into the living space after about 10 hours. Insulation only works so long. It is a cathedral ceiling so no way to exhaust the waste heat.
BRuce
Doug Miller wrote:

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Brick house? They can retain quite a bit of heat within the bricks for a few days. That or a very-well-insulated house and all them bodies....
Did you turn the oven off? ;-)
I have my computer in a bedroom converted to an office. That rooms stays pretty much five degrees warmer than the rest of the house just from heat generated by the computer. If you have a computer over 1Ghz, particularly an AMD system, it doubles as a room heater. Ditto for an inefficient computer monitor.
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mrdancer wrote:

Half brick. Weird construction. Bricks are mostly on the north side though. Not terribly well-insulated.

Used the microwave.

I do have a 1 GHz AMD box that runs 24/7 and makes this room toasty, but the rest of the house was pretty toasty too. Same thing again this evening, actually.
Must be body heat.
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Cold fusion?
Come winter we're so desperate for heat and humidity that we filter the dryer outlet and dump it indoors. Makes the choice of fabric softener scent more important than in the summer when we hang out....

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