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Just call me Andrew
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Discussion Starter · #1 ·
I live in a 2-story cape (second floor is the attic). First floor is brick, second floor is siding. I use window a/c units. I will have my house around 74 when I go to bed, and the temp falls well below that overnight (last night in the low 60s). I shut off the downstairs a/c at night.

When I come down in the morning, the house is hotter than it was the night before, sometimes around 80 degrees F. The only things generating heat downstairs are the fridge & computer, and a dehumidifier in the basement.

Any ideas what might be going on?
 

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If there is a temperature difference, heat will always move from higher to lower temperatures. so if your house is not insulated properly all the heat coming from outside will get inside.
 

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Hvac Pro
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Fridges give off quite a bit of heat and so does a dehumidifier. A dehumidifier is a small refrigeration system/unit. It has a cooling coil and condensor which has to get rid of the heat of compression from the compressor. In a window shaker that heat exhausts outside but with a dehumidiifer it goes into the house. I have one in my basement and it keeps it reasonably warm in the summer.
 

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If you open the windows yes, check for conduction, convection and radiation:thumbsup:
 

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KemoSabe
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The brick veneer will absorb heat all day and slowly release it throughout the night. When you shut the air off, you're realizing the load that is present all day, but is being cooled by the AC unit.
 
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Learning by Doing
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Lots of things happen at night that 'build' heat: lights on, TVs and audio equipment (my tv room can be heated nearly exclusively by our big tv and the amp for the stereo), people in the room.... Etc.

I'm in a similar situation (window units) but my house cools off at night when the outside temp is lower than inside.... Because when the sun goes down (or when it is cooler outside than inside) I open up the windows on the first floor, open the door to my attic, and vent all that warm air out an attic window with a fan.

My stairwell is like a wind tunnel. :wink:

For example: it was around 98f outside yesterday. Inside temp in an unairconditioned area was 82. When I went to sleep last night the outside temp was down to 78 (dropped to 74 overnight). 82>78 so I implemented my plan. This morning the temp in the same area was down to 76 :)

Materials mass and densities matter as mentioned above. My house is made of solid 16 inch thick brick walls (takes a long time to heat them up to the warmer air temp. All spring they are colder than air temp, chilling the house. It takes several months of heat to get them up to air temp ) whitewashed (helps reflect away heat from the sun) with few windows on the SW side of the house (reduced radiant exposure). All of this helps keep it passively cool. 206 years ago this was state of the art.

We borrow their philosophy:
- closing curtains when they are getting direct light - or when they are in an unused room

- isolating space for climate control- we only run our window units for discrete parts of the house
 

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A variety of factors, but, in my opinion, Loneframer probably hit on the largest one. We have a brick ranch, and I decided a long time ago that the brick was absorbing all of that heat during the day, so even though we would open the windows in the evenings, and let the cool air in, the heat stored in the bricks was moving in, causing the temperature to actually rise.
 

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Just call me Andrew
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Discussion Starter · #10 · (Edited)
That's interesting....so my house is a brick oven? I guess it helps out in the winter...which is about 60% of the year in upstate ny!

So I guess the best way to address it would be to air out the house with intake downstairs and exhaust upstairs, like Leah suggested. I just don't like leaving my windows open at night downstairs...oh well. Or I can just wrap my house in foil to reflect the heat? :)

Thanks for all the input.
 

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Learning by Doing
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That's interesting....so my house is a brick oven? I guess it helps out in the winter...which is about 60% of the year in upstate ny!

So I guess the best way to address it would be to air out the house with intake downstairs and exhaust upstairs, like Leah suggested. I just don't like leaving my windows open at night downstairs...oh well. Or I can just wrap my house in foil to reflect the heat? :)

Thanks for all the input.
This IS the primary purpose of whitewashing brick homes in the South. It keeps the brick from heating up as much. My house stays cooler than ambient day time air temp for the entire day/night cycle (this is a distinct advantage when the daytime temp is 98+ degrees and my masonry walls are 79-80 degrees). Because of our location, nighttime temps do not have as wide swing as in the north (we usually see a 10-15 degree decrease at night). This small swing does not allow for the brick to cool off sufficiently before it's day again.

When the day/night temp differential gets more substantial 20-35 degrees, in the fall. The house starts cooling off, but due to low thermal inertia, for several months the temp of the brick is HIGHER than daytime ambient keeping the home warm.
 

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Hvac Pro
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That's interesting....so my house is a brick oven? I guess it helps out in the winter...which is about 60% of the year in upstate ny!

So I guess the best way to address it would be to air out the house with intake downstairs and exhaust upstairs, like Leah suggested. I just don't like leaving my windows open at night downstairs Beware of burglars:ninja::shaun::shuriken:...oh well. Or I can just wrap my house in foil to reflect the heat? :)

Thanks for all the input.
.......
 
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