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B Colder bedrooms when outside is warmer

  1. Mar 20, 2016 #1
    My house has basement and one floor. When outside is 7 to 10 degrees warmer than the day before, bedrooms, living room always get colder. where did the cold air come from? I am assuming cold comes from basement. I know cold air always is at bottom...heavier than warm air near the ceiling...lighter. When outside becomes warmer, cold air near the floor starts to rise and push warm air even higher. Is that reasonable that it's how I feel colder when it's warmer outside? It must have hidden somewhere unless warm air at the top becomes cold due to air molecules become less vibrant resulting colder. But it should not be cuz I have two windows per room.big enough for sunlight to come through. I think it has to do with ventilation.
  2. jcsd
  3. Mar 20, 2016 #2


    Staff: Mentor

    I think it's a ventilation problem, as you said. However, the cold air from the basement won't start to rise just because the temperature is getting warmer outside. Maybe what's happening is that your attic isn't sealed off well from the living quarters in your house, so as the attic warms up and exits the roof, it draws cooler air up from the basement.
  4. Mar 21, 2016 #3
    Your explanation is logical re: attic. Good answer. I also have another problem. I am aware that the roof ventilator is on roof. At this time, it's off, but I need to understand the basics. It has roof motor fan. Does it always exhaust/blows out warm/hot air out of the attic to outside when switch is on. The switch is right next to thermostat in living room. I know when it's on, I could see the hallway vent draws/sucks air in from the house into attic..I think from attic to its two vents to exhaust air outside while the other part of the house has another vent near kitchen blows out air (exhausts) from attic into living room. It starts air circulation. You may see now see my problem. Where does attic get/draw air into that other part near kitchen. I can see its air blowing into living room from attic. But where? How did new air get into near kitchen?
  5. Mar 21, 2016 #4


    Staff: Mentor

    The fan in the attic will blow air out of the attic whether the air in the attic is warmer than the outside air or not. The idea behind having a fan in the attic is to blow the heated air in your attic out on warm days, with the goal of keeping your house cooler on those days.
    That seems weird to me. You shouldn't be drawing air from the attic to go into the living areas of the house.
    The air that's blown out of the attic should come in through the other vents in the attic, not from the other parts of the house.
  6. Mar 21, 2016 #5


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    Science Advisor

    Are you using a thermostat?
  7. Mar 21, 2016 #6
    You explain. It's clear now how air circulation works in the attic.

    I just doubleckeck air conditioner outside. I thought when I switch on next to thermostat, the outside air conditioner fan starts. Air conditioner may work two ways.. Circulating air and a.c with freon. But it didn't happen. It did not turn on the fan at all.

    I always thought the motor fan on the roof is wired to the switch next to thermostat. It appears that the roof fan has nothing to do with the switch.
    The roof motor fan has to run on power wired somehow. Also it may run automatically by itself.

    To make it clear, the thermostat in the hallway has its two switches.. One for cool. That's ac. I know. When on, the ac fan starts on. And the other switch is fan on.

    It looks like the switch (fan on) had nothing to do with the roof fan, but when turned on, I could see air sucks air out the living room and the other Vent blows out into other part of the living room. Where is the motor fan? I now believe the small ceiling vents 1x1 foot square has ducts on top . Of them.
    The air that has sucked out of living room has 24inch x 30 inch air filter, but it has no duct. mystery up in the attic?

    Thank for the replies.
  8. Mar 21, 2016 #7
    I have two thermostats. It's set to 62. Both. But they don't have motor fan! It bring up heat from oil furnace.

    Mark, I had said about hallway thermostat. But it is not. I don't know what it is. But when house gets too warm in summer, I set to to lower temperature and ac kicks in to cool the house. what's that gadget?
  9. Mar 21, 2016 #8


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    If your thermostat is on, then it changes things a lot. If your thermostat is in a less insulated part of your house, then when it is warmer outside, it will feel a warmer temperature before the rest of your house, and will adjust the heater accordingly.
  10. Mar 21, 2016 #9
    I agree with you. You are referring to air temperature. I beg apology for bringing up two different issues at the same time on same topic.
    The first question is about room temperature that gets colder when outside gets warmer. Mark explains. And yours,too.

    The second question is about motor fan that triggers suction and exhaustion through vents. Where is it? I may find out later.
    Thank you.
  11. Mar 21, 2016 #10


    Staff: Mentor

    Without knowing exactly what the thermostat looks like, it's hard to say for sure. Possibly your control has one switch for heat/AC and another for fan on/off. The fan on/off switch could be used when neither the heat nor AC is on, and would just blow unheated/uncooled air.
    I have a fan in my attic. It's set to come on when the temp in the attic gets above 95 deg or when the humidity gets above about 90%. The fan's controls are in the unit itself -- there's no separate switch.
    The fan for the AC is almost certainly in the AC unit itself, which might be on the roof. I doubt that the installers would put it in the attic.

    62 degrees? That's a very low setting. Usually people set their thermostat so the heat comes on when the temperature in the house gets below 68 to 70 degrees. People usually have their AC set to come on when the temp gets above anywhere between 70 and 75 degrees, sometimes warmer if they don't want the house to get too cool (or their electric bills too high).
    Sounds like a thermostat.

    Can you take a picture of both controls and post them here?
  12. Mar 21, 2016 #11
    I tried to upload all 4 pics. Actually three controls.
    The first two picture is ac thermostat pictured from left and right. It's wired to ac unit outside. The left side is for ac and heat...but I never use heat cuz it's not wired at all. The right side is fan on/off. That right causes air suction into 24 x30 air filter when on. The switches are of dial mode.

    The third picture is thermostat is near the kitchen.

    The 4th picture is another identical thermostat in den room.

    I tried to upload them all four pictures.hope it works.


    Attached Files:

  13. Mar 21, 2016 #12


    Staff: Mentor

    This one is pretty much as I described, with a switch on one side for heat/cool and a switch on the other side for fan on/off.
    Since the thermostat in the first two pictures isn't wired to the furnace, probably the one in the third picture is wired to the furnace. The thermostat in your den might be to an electric baseboard heater or a wall heater of something. I don't think you can have two thermostats controlling one furnace.

    Have you ever been up on your roof? I'm betting that's where the AC unit is. And if you notice air coming out of the ductwork, it doesn't seem likely to me that it's coming from the attic. Instead, I'm guessing that it flows through ducts in your attic. Did you just recently move into this house? It doesn't sound like you're very familiar with it or its workings.
  14. Mar 21, 2016 #13

    After some exchanges, I began to realize that you are correct about the ductwork. It's flowing through ducts in my attic; not from the attic. No, it's old house.
    I am not familiar with its workings cuz I am deaf and dumb.

    No, I have never been up on the roof. You think it's where AC unit is...but I always thought the unit is outside in front of the kitchen cuz it has big fan... Looks like horizontal propeller. What is that housing with fan outside doing in front of the kitchen if you think AC unit is on the roof? Can it be possible to have both? I will identify that housing tomorrow. It's already dark. And let you know.
  15. Mar 21, 2016 #14


    Staff: Mentor

    That sounds like the AC unit. I don't think you mentioned it before, so I thought it might be on the roof. I doubt that there are two AC units.
  16. Mar 21, 2016 #15
    Right, I never mentioned ac unit on the roof. I had said ventalitor.. Anyway the ac unit on the roof you suggested may be attached via ductwork to housing outside to exhaust hot air. I will take another look at the housing tomorrow morning. I think you solved it.

    The surrounding air in the attic not inside ducts has to be ventalited, too but this is another thing. I thought it was already solved, I will let you know tomorrow.
  17. Mar 22, 2016 #16
    image.jpeg image.jpeg

    Two pics.. The first one is AC cuz no ducts are attached to it. When AC is turned on, I could feel hot air coming out from the top of the AC.
    The second one is the label for AC.

    I will take another pic later of the roof. The sun glare right now is too strong.

    I have an appt for AC annual maintenance on April 4th. I will ask him what it is on the roof and update for those who are interested.
    Also, I will ask him if it's AC and also attached to ductwork underneath.
  18. Mar 22, 2016 #17
    image.jpeg Added comment:

    After reviewing AC (refrigerator) basics, the AC has condenser coils inside throws out hot compressed air from coolant i.e. freon. on the condenser fins. It has to go compressor first before that happens. The coolant now gets little cooler after throw it out then go through expansion device to expand coolant further to make the coolant cold further at low temperature then through evaporator coils in the attic with cold coolant inside. The hot air linside the attic are absorbed to the evaporator coils make air in attic cooler. The absorbed hot air inside the coolant now warm. It then goes to compressor to get very hot on way to condenser coils. And the cycle repeats.

    The basics help me get general understanding.

    I am uploading a picture of the roof. It's not close up, but you may see like a small black hat on the top roof. The others on right belongs to chimney. not related to this topic. By now I think it (black hat) has nothing to do with AC. It's separate by itself.i believe there is a "evaporator" unit somewhere in the attic that couples with AC outside.

    I will find out on April 4th. Thank you guys for the help.
  19. Mar 22, 2016 #18


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    Staff: Mentor

    So, are there supply and return air vents in your bedrooms? You should feel the cold air coming out...

    The evaporator (and fan) aren't there to cool the attic, they are there to send cold air into the house through ductwork. It is not uncommon though for there to be a single large return (not an exhaust) in a central hallway.

    It sounds like you have been air conditioning your house (really cold!) without realizing it. Your electric company must be thrilled.
  20. Mar 22, 2016 #19


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    It's totally reasonable if you are tough and want to save energy during the winter. I don't even bother with heating unless it's near freezing.
  21. Mar 22, 2016 #20
    Yes, you are correct that evaporator has to send cold air through ductwork in the attic. Not to cool the attic or the house will be drowned with bills. I thought it's obvious.....not necessary to mention it. Thank for the reminder. I have to be more careful next time.

    Yes, the supply vent is in the living room, all bedrooms just have return vents. Looks like 6 return vents and 1 supply vent. Maybe 2. Another one is in family room. I will check f.r. Later. You ask an excellent question. Oh I forget about the 24x30 " filter. I guess it's another return vent, but bigger than the register sized vents. That 24x30 does not have duct. Can I call it return vent?

    Re: billing.. I use AC very seldom during the summer. Maybe twice. 2 days in total. Very little, but annual contract is lots more expensive. Nothing I can do.

    Nevertheless, I just learned that AC can be used as heater in the winter from YouTube videos. But mine is not. Just AC for the summer.
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