At what night time temp do you use heat?

Discussion in 'Heating / Cooling Systems' started by Orchid, Sep 20, 2011.

  1. Travelhoveler

    Travelhoveler New Member

    Messages:
    2,337
    Likes Received:
    6
    Joined:
    Mar 8, 2011
    Absolutely not. Many Southerners have in their head that a cold, drizzly day somehow feels colder than a cold, dry day. In actuality, higher humidity makes you feel warmer. If you put a humidifier in your house in winter, you can set your thermostat lower simply because the humidity makes you feel warmer. Likewise, in summer, running a dehumidifier makes you more comfortable as well.
     
  2. Aladin Sane

    Aladin Sane I'd rather be camping

    Messages:
    1,057
    Likes Received:
    97
    Joined:
    Jul 3, 2008
    Location:
    Iowa
    I totally agree TH. I will be starting my humidifier in the next few weeks.
     
  3. spotfan

    spotfan Virginia

    Messages:
    139
    Likes Received:
    0
    Joined:
    Feb 3, 2006
    Location:
    Madison Virginia
    We camp every year the first weekend in November in North Carolina. It gets pretty cold then. We use an electric heater and turn our a/c on low to circulate the air. Since its a busy noisy campground we want all the noise we can get. I use microfleece sheets on top and bottom plus a couple of fleece blankets on top of our feather bed. No issues with us sleeping like this because we always sleep cuddled up and use body heat. Helps that we like our bedroom cold.
     
  4. Flyfisherman

    Flyfisherman New Member

    Messages:
    3,682
    Likes Received:
    12
    Joined:
    Mar 4, 2003
    Location:
    Shallotte, North Carolina
    Well, actually it does, depending on the temperature, of course. Say you have one of those cold drizzling fall/winter/spring days and the temperature is falling. Obviously when it's raining there's lots of moisture in the air (duh) ... and when that temp hits the magic number of 39 degrees you will feel it most. And that's because as the temp was dropping (water in the air) the water was shrinking, but at 39 degrees F (4 C) it reverses itself and begins to expand ... AND, water is heavier at that point. As we like to say in these parts ... "goes right through ya!"

    As any fisherman knows for the spring time we are waiting for the pond or lake "turnover". That's when the surface water hits 39 degrees and actually rolls to the bottom. And good fishing is soon to begin.
     
  5. mckeapc67

    mckeapc67 New Member

    Messages:
    681
    Likes Received:
    3
    Joined:
    Feb 22, 2011
    Maybe it just is in my head; but "Damp/Wet and Cold" feels colder than just Cold.

    On a visit to Denver, I was more comfortable in single digit temps with just jeans and a jacket than I am here in SouthEast Louisiana when it is in the 20's and 30's.

    I do agree, however, with the humidifier / dehumidifier in the house. But you are talking temps in the 60's and 70's there as opposed to below freezing temps.

    High humidity makes your sweat not evaporate efficiently. So, in the heat you overheat due to an inefficient natural cooling system. In the cold, your sweat doesn't evaporate and just makes you cold and wet/damp.

    Cold and wet is worse than just cold. This is probably where our Southern opinion comes from. :) [:D] [8D]

    To the OP's concern; I wouldn't be likely to run our heat until temps fall into the low 50's.
     
  6. Aladin Sane

    Aladin Sane I'd rather be camping

    Messages:
    1,057
    Likes Received:
    97
    Joined:
    Jul 3, 2008
    Location:
    Iowa
    Sorry Fly, I never wore more than a spring jacket during the two winters I spent in south Arkansas. The locals would be all bundled up in parkas. The humidity did little to make the cold go right through me.

    As per your 39 degree example, are you talking about water vapor in the the air or liquid water droplets in the air. Either way, I don't follow how the changing density of water will affect the heat transfer from your body to the environment. What I do know is that when the humidity is low, liquid water that may be on your skin will evaporate and cool the surface of your skin. This will make you feel colder, and this is why a humidifer in your house used during the winter heating season will allow you to feel more comfortable at a lower temperature.

    Let me ask, are we talking about being physically wet (rained on), or just high humidity?
     
  7. Manper

    Manper New Member

    Messages:
    251
    Likes Received:
    4
    Joined:
    Jul 7, 2010
    As a Colorado native we have a dry climate i agree with you. I will respectfully disagree with some posters reasoning behind humidity and its affects on hot on cold. While in Florida a few years ago it was 98 degrees with almost 100% humidity...needless to say i was miserable and i thought to myself how in the hell do people live like this...willingly [;)] When i flew home it was 95 and dry as long as you didnt exhert yourself it was managable but hot...Now when it comes to cold let me put it to you this way:

    If the air is w/o humidity and the temperature drops to 33degrees its simply 33 degrees but once there is humidity its not just 33 degrees, its 33 degrees with frost and ice which will drop the temperature even further. There is a big difference between 100 degree weather in Colorado and 100 degree weather in California and same goes for the extremes, 33 degrees here does not feel like 33 degrees in a temperate climate but, IMO, here's where i think this may hold some validity:

    If it is warm and humid and it starts to rain the rain is warm but that's all i can say about that.

    As to the topic of when to turn the heater on? Because you have a limited amount of gas i usually keep 5 degrees colder than what i would at home if you do it to low you will have a condensation issue which may, or may not, cause problems.
     
  8. Travelhoveler

    Travelhoveler New Member

    Messages:
    2,337
    Likes Received:
    6
    Joined:
    Mar 8, 2011
    As I noted, that's a popular perception in the South.

    A humidifier is especially effective when temps drop below freezing. You don't want to run one when temps are in the 60s or 70s.
    Actually, when it's cold, it's usually low humidity. So your sweat evaporates even more rapidly, which is why you feel even colder in dry air.

    As I noted, it's a popular opinion here in the South. But read about the dew points and evaporative cooling and you'll see it's just an opinion, and a wrong one.
     
  9. Unstable_Tripod

    Unstable_Tripod Well, there's your problem!

    Messages:
    14,279
    Likes Received:
    29
    Joined:
    May 20, 2008
    Location:
    Seattle, Washington
    I grew up in Minnesota and the primary reason we ran a humidifier in the winter was to replace moisture that the furnace evaporated. When a forced air furnace runs a lot it dries the internal air out so much that wood furniture can crack, static charge builds up (you get zapped touching door knobs) and nasal membranes dry out. In the old days the humidifier was separate but now it's pretty much a universal practice to have it built into the furnace and plumbed to the house's water system. Humidifiers can be set much more accurately now, too. In the old days if we saw condensation starting on the windows we knew we had to set the humidifier back a bit.
     
  10. Travelhoveler

    Travelhoveler New Member

    Messages:
    2,337
    Likes Received:
    6
    Joined:
    Mar 8, 2011
    That's not unique to Lime Jello land. We run them here for the same reasons. They do make you feel more comfortable in cold weather as well, and your socks don't stick together.
     
  11. mckeapc67

    mckeapc67 New Member

    Messages:
    681
    Likes Received:
    3
    Joined:
    Feb 22, 2011
    I was talking indoor temps. I hope your temps don't drop below freezing indoors where the humidifier is running. [;)]

    [quote author=Travelhoveler]
    Actually, when it's cold, it's usually low humidity. So your sweat evaporates even more rapidly, which is why you feel even colder in dry air.
    [/quote]

    Your point about lower humitity in cold weather is only partially correct. There is less moisture in the air at lower temperatures due to the dew points where water starts falling out of the air as frost / dew. However, we're talking "relative humidity" in the weather. Relative Humidity refers to the amount of humidity that the air (at it's current temp) can hold. When it is at 90% relative humidity, water & sweat can't evaporate as easilly as when at 25% relative humidity.

    [quote author=Travelhoveler]
    As I noted, it's a popular opinion here in the South. But read about the dew points and evaporative cooling and you'll see it's just an opinion, and a wrong one.
    [/quote]

    If you study HVAC refrigeration you'll see that heat exchange systems are inefficient at lower temps. It takes heat (calories) to make things like water or refrigerant evaporate. This heat has to come from somewhere. That is why heat pumps don't work in cold temperature.

    Also, evaporative coolers (swamp coolers) don't work well in high humidity environments. They are only recommended for climates where the air is hot and relative humidity is low.

    Plus, like I said earlier in this post. If the high humidity (relative humidity) is present, then the water has nowhere to go and thus stays on your body. The sweat cools down below 98.6 and then starts pulling heat from your body.

    Dew points just add to this. When the dew point is reached, water starts falling out of the air in the form of dew @ ambient temp. If it's near or below freezing, then this dew will then start freezing. This frost and dew at 32 F or below will try to absorb heat from your body in order to melt and raise the temp.

    Another reason for the perceived colder feel to high humidity is that air with high humidity transfers/conducts heat more efficiently than dry air. Thus, your body heat is transferred away from your body into the cold environment at a higher rate.

    Therefore, based on this basic physics on heat and equilibrium, I respectfully disagree with your disagreement. :) [:D] [8D]
     
  12. Travelhoveler

    Travelhoveler New Member

    Messages:
    2,337
    Likes Received:
    6
    Joined:
    Mar 8, 2011
    No, it doesn't. We can keep our house in the upper fifties or around 60 in the winter with the humidifier maintaining humidity in the 40ish percent range. If we let the humidity level drop, we have to boost the thermostat to stay warm enough.

    Such high level humidity is rarely present at quite low temperatures. But yes, it's harder to get rid of sweat in humid Southern weather. I know, as I live in the South as well. Usually, relative humidity is pretty low in winter, hence our use of a humidifier to make things more comfortable. We don't run it when its rainy though, or those brief periods of elevated humidity that do occur in winter. There's enough moisture in the air to make things more comfortable then.

    True, but high humidity rarely accompanies very cold weather, and it does get colder here in the Upper South than say, Florida or Louisiana. We increase the humidity here to make ourselves feel less cold.
     
  13. rabird

    rabird Howdy!

    Messages:
    6,696
    Likes Received:
    299
    Joined:
    Mar 3, 2006
    Location:
    TX
    y'all ever heard of fog or dew? High humidity.

    I'm aware how 'air conditioning' removes water from the air, changing the air make up, but in the winter when cold air is heated the RH goes down without removing any water vapor from the air. Same thing happens outside at the temp go up during the day. New air with different water vapor content can come blowing in at any time.
     
  14. Aladin Sane

    Aladin Sane I'd rather be camping

    Messages:
    1,057
    Likes Received:
    97
    Joined:
    Jul 3, 2008
    Location:
    Iowa
    There is a flaw in this reasoning. Dew only condenses on objects that are cooler than the dew point of the air around them (this is why dew collects on a cold soda can on a hot humid day, but not the table the can is sitting on). Since your skin surface temperature will always be above 90 degrees (yes I know your core temp is 98.6, but your surface temp is often lower), you will never have dew condensing directly on your skin on a cold day.

    Increased evaporation caused by low humidity will have much more of a cooling effect than the small increase in heat transfer found with moister air. The physics of phase change heat transfer is the winner in this argument.
     
  15. mckeapc67

    mckeapc67 New Member

    Messages:
    681
    Likes Received:
    3
    Joined:
    Feb 22, 2011
    Agreed, this is true for a cold object on a hot humid day. However, if the dew point is reached in the ambient temperature, the relative humidity of the air is now 100% and the water starts to come out of the air on all objects (e.g, the grass, table, car, tent, etc.).

    Dew point is directly related to relative humidity and temperature. If the relative humidity is higher, then the dew point is closer to the ambient temperature.

    The higher the relative humidity, the less water (sweat) can evaporate to cool the body.

    The reason a cold object sweats on a hot day is because of the heat transfer from the air to the cold object making the temperature of the air in contact with the cold object reach the dew point; but, the rest of the air in the area remains above the dew point at some relative humidity below 100%.

    I agree with the argument that if you are exerting yourself (sweating) on a cold day, you would feel colder in a low humidity environment than a high humidity environment due to the heat (calories) that it takes to make water change to a gas being more than the amount of heat (calories) that is needed to raise the air temp through heat transfer to the air.

    But, in the same respect, when you aren't sweating it would be just the opposite. The heat transfer to the moist humid air would be more than to dry air thus cooling the body more.

    So, I will compromise and say that if I'm out running, chopping wood, or otherwise breaking a sweat on a cold day I would feel hotter here in the humid south than I would other less humid areas. But when I am not working up a sweat sleeping, relaxing, ambling around a campground, etc. I'll feel colder in the humid south. :) [:D] [8D]

    I think we've hijacked this thread enough on this so I'll leave with my previous statement that I'll start using my heater down here in the humid south when the temps fall into the low 50's and below. If I go camping somewhere less humid, that may change accordingly. [:D] [:D]
     
  16. Travelhoveler

    Travelhoveler New Member

    Messages:
    2,337
    Likes Received:
    6
    Joined:
    Mar 8, 2011
    I'll agree with you on that point. We too usually don't use our camper heater until it drops into the 50s as well. If it's particularly dry, we'll need it at a higher temp.
     
  17. Aladin Sane

    Aladin Sane I'd rather be camping

    Messages:
    1,057
    Likes Received:
    97
    Joined:
    Jul 3, 2008
    Location:
    Iowa
    CD, it is not physically possible to have dew condense on an object that is at a temperature higher than the dew point of the air surrounding the object.

    When I lived down south, and one of the locals would tell me that because of the humidity, 30 degrees in sourth Arkansas really felt like -30 in North Dakota, I would reply BS, I had just left -30, and it would have killed anyone from south Arkansas that set foot outside in it. That usually ended the discusion. [:D]

    Suffice it to say, in my experience, the cold moist air claim is a myth.
     
  18. Unstable_Tripod

    Unstable_Tripod Well, there's your problem!

    Messages:
    14,279
    Likes Received:
    29
    Joined:
    May 20, 2008
    Location:
    Seattle, Washington
    When I lived in San Antonio one of the secretaries in the office, who had never been out of Texas, started asking about the experience of being cold in Minnesota. She just couldn't imagine what zero or below felt like. I said, Well Virginia, go home, open your freezer and stick your head in there. Now imagine that the whole world is like that." The look on her face was absolutely priceless.

    This 30 in Arkansas is like -30 up north is absolute nonsense and could only be uttered by someone who had never experienced an actual -30 temperature.
     
  19. Aladin Sane

    Aladin Sane I'd rather be camping

    Messages:
    1,057
    Likes Received:
    97
    Joined:
    Jul 3, 2008
    Location:
    Iowa
    My point exactly UT.
     
  20. aeisbren

    aeisbren New Member

    Messages:
    80
    Likes Received:
    0
    Joined:
    Apr 8, 2010
    As a Canadian We tend to turn on the heat when we can "See our breath" i.e. when you breath out and it's cold enough to condense the watervapor to steam, say 10-12 degrees Celsius (say 50 degrees Fahrenheit), otherwise it's just hooded sweatshirts and long pants!
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.