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Old 05-20-2012, 02:13 PM   #1
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House gets too Hot at night

Hello there,
I moved into my house 2 years ago, it's a 2 story house built in 1921. It was freshly insulated and had new windows put in about 2 years before I bought it. I've gone through the house, we checked the insulation, the attic vents, the basement everything. It sits on a flagstone foundation, it has wooden siding downstairs and the old asbestos siding upstairs. It's a smaller house.
My problem is in the spring, my house stays comfortable most of the day, but in the afternoon/ early evening it starts really getting warm in here. It will be between 70 - 75 outside and be 70 - 71 inside until about 5 or so when it starts heating up, and it just keeps getting warmer and warmer. I don't have any AC going, but some nights i have to turn it on because it gets so hot in here.
Last night it got up to about 75 outside during the day, but last night it was 55 outside at around 10, and it had climbed to 77 inside. At midnight it was 52 outside and 83 inside, it was too cold if I opened the windows, but as soon as I shut them it warmed right up again. I don't really know what to do, it's even worse upstairs, I don't have an AC unit for up there, it was over 88 up there last night. I'm at a loss as to why it gets so hot inside when it's getting chilly outside. In the summer it's not so bad, when it stays warm all day long, it still gets really warm upstairs then, but downstairs stays around 75 ish without the AC on.
In the winter my house is pretty good, I use less then half the heating oil my parents do, and their house is a little bigger then mine even, they live next door.
If anyone has any suggestions I'd love to hear them. The design of the house does not promote very good airflow at all though, the stairs run right through the middle of the house with just a small entrance-way at one end, so there is effectively 0 airflow from one half of the house to the other.


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Old 05-20-2012, 02:34 PM   #2
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House gets too Hot at night

How well is the attic vented? Are the windows, doors & electrical outlets well sealed, to not allow air movement? How old are the windows & doors? How old is the hvac system. As for the attic, even if it is vented, it can still get up to 130 if there is no proper air movement.

We run our a/c down to 68 at night during cool but humid nights, otherwise it is at 70 during the Summer months from late June to Late august. If your a/c or fan is not running, air will get stale, and the house will feel warm. Especially if there is not enough air return back to the furnace. BTW, our house stays around the set temp of the thermostat all of the time. Right now it is 102 up in our attic, with a powered attic vent fan running. Without it, the attic would be at around 120-130 right now, and yes our house would feel warm, along with if I did not seal up around the windows, and put in good weatherstripping around the doors, and air seal outlets and receptacles.


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Old 05-20-2012, 11:25 PM   #3
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House gets too Hot at night

My windows are about 4 years old they were put in by the previous owner, when the house was "winterized" through some government program. I don't have central air, I have 1 wall unit AC downstairs. The Attic vents are good, no fan is up there but I store wood up there and it really doesn't get all that hot in there. I use my one upstairs room as my workshop and I go into the attic frequently to get more wood, or take a piece I don't need back up. While I don't have a temperature gauge up there, it's definitely better then my parents house.

My problem is only during the night though. All day long I can get away with just my ceiling fan in my living room. Then as soon as the sun starts setting the house heats up. I really don't understand it. My living room will be between 70 - 75 degrees F all day, then the sun goes down and the temperature shoots up. It's midnight here, 65 outside, and even with the windows open it was 88 degrees in here, 87 upstairs in my bedroom. At 4 pm today when it was 80 degrees outside and the sun was out it was only 75 in the same room with just a ceiling fan on at the lowest speed. I don't understand why the house heats up so much when the sun goes down.

That's really my only problem, it just gets very hot at night in here. It doesn't just feel hot, the thermostat shows the actual temperature rises at night. The temperatures I wrote previously are from the thermostat display, and my digital clock/weather station thing, not subjective temperatures. I guess when i think about it, it does it in winter too, just I never really complained about the house getting warmer on a cold winter But if there is something I can do so I don't have to run the AC all night it'd be great.
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Old 05-22-2012, 09:24 AM   #4
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House gets too Hot at night

Are sure your heat is not running? Do you have any electric heat, either baseboard or ceiling/floor type that might be on?
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Old 05-22-2012, 11:27 AM   #5
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House gets too Hot at night

We have a brick house (see avatar). Between the brick and the dark shingles it will absorb heat. Then like you, the temp often rises in the evening when you think things should be cooling off. Nice in the winter, not so nice in the summer. The original owner installed a full house attic fan. When we use it, it works well since we have an open floor plan, but we do run our A/C a lot.

Your fluctuations seem a bit extreme though.
Our heat uses propane, and even if the heat is not on, just the pilot will raise the temp in the house.

Trees can also help. You might also consider a lighter color shingle when it comes time.

Not an expert, but I would look into an attic fan of some sort.
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Old 05-22-2012, 02:44 PM   #6
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House gets too Hot at night

I think an attic fan system would make a big difference for you. It will make things more comfortable for you and reduce the load on your AC unit. Part of what is happening has to do with basic laws of physics. During the day the temperature and weight/pressure of the air in the house are somewhat close to equal or that outside. Or outside is warmer and the air lighter. When evening settles in the colder and heavier air outside tries to sink and in essence forms sort of a barrier for the hotter air in the house trying to rise and escape. It gets trapped.

A thermostat control attic venting system (super important it have a shut off in case you ever had a fire) provides a forced air path for the hot air to exit.

Everybody thought my Northern California/Bay Area home had air conditioning but it never needed it since most evenings in the summer could be as much as 40 degrees cooler than daytime. Same thing happened as with your home though and as the temps fell outside the heat in the house built up. Insulation and good glass did its job but it was uncomfortable at night. I added a nice attic ventilation system and the problem went away instantly.

Do make sure you line up a good HVAC person and roofer if need be to do the system for you. Last thing you want or need is a rooftop hack job. You want someone that can flash the units so they do not leak.


Last edited by user1007; 05-22-2012 at 02:55 PM.
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