Interior temp. rise in the evenings. Thoughts?

Summer time in the evenings, an hour or two after sunset my home heats dramatically. What causes this from a building science, thermodynamic perspective? (not asking about adding insulation, more of what is happening)

Here are the details of my home. 1973 build, 4 sides brick in Georgia on a crawlspace with a hip roof. Attic is ventilated with soffit vents and ridge vent. Soffit vents are 8x14 approximately every 10 feet. Crawlspace is ventilated. Attic insulation is pretty poor, R-19 or less in some areas. No floor insulation. I have 14 windows, 7 are double pane replacement windows and the remaining are single pane original.

Can you define this a little more?

I’ll try. It is a comfort issue. Everyone in the home complains about the “hour of heat” in the evenings lol. I’ll have to take some measurements tonight. It’s like a flip…the home is comfortable all day then this happens and then the home slowly cools again. AC just can’t keep up during this period.

Programable thermostat? :man_shrugging:

Good question. But no and the AC is running during the time most people find relief after the sun goes down.

Until @dandersen shows up with his expertise, here’s my simple WAG scenario…

Brick absorbs heat from heat source.
Remove heat source, brick expels heat.



And you think the brick is “releasing” it’s heat to the interior since it is cooler inside than outside?

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Yes, but again, this is Dave’s area of expertise, not mine.

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I will get some thermal images before, during and after the anomaly and tag him. Thanks for the pointer.


Brian me and my wife have been wondering the same thing the last couple of weeks. Our house though is a raised ranch with vinyl siding. My wife likes to sleep in sub-zero temps so usually around bed time I turn off the whole house AC and turn on a window unit in our bedroom. No need to cool the whole house to freezing. If the inside temp of our house was 68 degrees and the outside temp is around 65 within a couple hours the inside temps will easily be in mid 70’s. I also found it odd.

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I would think that would be happing during the day as well.

This would be one of the factors, Do you know what wall insulation you have?
Will wait until you gather more info to share and hear what David has to say.

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Can you list the orientation of the house that are affected by the increase of temps, Sunny side, any shade trees etc.

I do not. I suspect what ever was/is there is not in great shape due to the age of the home.

One would think that, but IMO, heat can only move in one direction without something mechanical driving it, ie. can a brick absorb and expel heat at the same time? I presume there is a limit to what an object can absorn before expelling, but since it takes heat to ‘bake’ a brick, I doubt his home is getting that hot during the day.


What is the humidity situation, as that will/may also be a factor.

Here is the current situation. Humidity is better today than most days.

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It is odd. I obviously need to gather some data which I hope to return with soon.

It feels like the attic just stops venting and is in a state of stasis. Resulting in a blanket of heat on my home. But, it may not be the attic at all.

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Here is some good information that may help.
Heat Transfer Through Buildings | JLC Online


Using thermal mass for heating and cooling | Smarter Homes


Heat energy always flows from the warmer object to the cooler object .