Author Topic: Summertime and "the heat within."  (Read 263 times)


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Summertime and "the heat within."
« on: August 23, 2018, 11:06:09 PM »
Dear WeatherCat building climate managers,

Yesterday, our local electrical utility had to replace a pole and transformer.  That left us without power from 8:30 am to about 12:30 pm.  I powered down all computers, but my Davis station of course continues collecting data on battery power.  It even kept track of the internal temperature.  That led to this interesting graph later that day:

When I got up at 6am, I ran a fan to cool the room that has the Davis Weather Envoy.  There are 3-4 computers running 24/7 in that room.  One had already been shut down so only two were heating things up.  Even so those computers (and body heat) contribute to keeping the room over 10 degrees warmer than the outside temperature.  This can be easily seen on the graph of "exterior cooling potential" (the difference between the outside temperature and inside temperature) :

By 8:30 am all computers were shut down and there was no reason to spend time in this room any more.  As you can see on the first graph the room temperature actually drops at first and then only slowly climbs.  By the time the power was put back on, the inside was only 2 degrees warmer than the outside which had warmed up into mid to upper 60s.  After the computers were put back on, the room started once more to warm up significantly.  So much so that it was almost 13 degrees warmer than the outside air temperature by 7:30 pm.  By then the exterior temperature was back down in the lower 60s.  After 7:30, I once more ran a fan to cool the room.

There is an important lesson for all of us who need to run air conditioners to remain comfortable.  In the winter, insulation will always improve your heating situation.  Heat is being removed from your dwelling and the more insulation you have the slower that process will be.  However in the heat of summer the situation is more complicated.  Insulation does prevent that outside heat from getting in as much.  However, that very same insulation traps the heat you generate inside.  So the heat of things like computers, appliances, and you will make your living space uncomfortable even if your insulation was perfect.  Ironically, the better your insulation the more the interior heat will be trapped and need removal.

These past few years, I've noticed that our air conditioner often starts up relatively late in the afternoon.  The reason seems clear from these graphs.  Even if the exterior temperature isn't too extreme, the interior heat has no place to go.  Eventually we need air conditioning to remain comfortable.  It is a point that has important ramifications for public policy in the face of global warming.  Areas were people could live without air conditioning are changing so that people are needing air conditioning to be comfortable or in extreme cases simply to survive.  Heat is the number 1 weather related killer and heat related deaths are on the rise.  Like it or not, the use of air conditioning will have to increase in order to save lives.  The energy needed to power those additional air conditioners needs to be included in the evolution of our society's energy needs.

Cheers, Edouard


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Re: Summertime and "the heat within."
« Reply #1 on: August 24, 2018, 11:15:14 PM »
Interesting read and data, Edouard. Thanks for sharing. Where I live we do not have air conditioning and depend on windows to control the internal temp in the summer. My handy WeatherCat alert emails me when it is time to consider opening them and I get a similar email when it's time to close them. Love it.