Electric bills this month (pool, crawlspace, money)

[harry chickpea]

"So if I understand correctly, your statement is that it takes less energy to remove stored heat from the insulation in the house if you change the temperatures during the day than it would require to keep the heat from ever soaking into the house?"

Without getting too deep, the concept relates thermal mass and change in temperatures (Delta T) and insulation.

If a house is shaded and uninsulated, the thermal mass of the furniture, walls, and such will cool overnight and heat up during the day. For simplicity, call it a big covered pot of water under a tree. The average temperature of the water will be very close to the average temperature of the air. The change in temperature of the water will lag because of the thermal mass - it'll remain cooler longer than the air in the early part of the day, and once heated up will take longer to cool down than the air at night.

Add insulation around the pot of water and the average temperature will STILL be similar to the average temperature of the air, but the lag in temperature change of water in the pot will be even longer.

Pots of water and houses don't always sit in shade. When they are hit by the sun, and especially if there is glass or metal that allow radiant heating but not airflow, there is the dog dying in the car greenhouse effect that can get the air in the house hotter than the air outside. Once that happens, the insulation keep the hot in the house.

The greater the difference in cool air temperature inside and the hot air outside, the more energy is required to keep that balance.

This all gets around to saying that if, when you leave in the AM, you set the tstat about 2 to 4 degrees lower than the average high for the day, your energy use should be less than if you keep the tstat cranked down to low 70s. If you allow the place to heat up like an oven by cutting it off entirely, you could use more energy cooling it down.

Exact temps and figures would vary, but that is the general idea - keep the delta-T minimal but under control, then cool the few degrees down to comfort level as needed.

[Nlambert]

Originally Posted by r x f

What was the overnight set temp? 73?


Did you start at 73 degrees for test 1 and 77 for test 2? If so, your run times don't take into account the energy required to lower the house from 77 to 73.

The overnight temp is 73 (my normal and constant temp)




Yes, on the first test I started at 73 and allowed it to maintain 73 degrees all day until 8pm.
On the second test, I started at 73 and at 7am I raised it to 78 degrees. At 4pm, I lowered the temp back to 73 degrees.


The run time required to lower the house temp is what was indicated in test #2 (Sunday).

[Nlambert]

Originally Posted by harry chickpea

"So if I understand correctly, your statement is that it takes less energy to remove stored heat from the insulation in the house if you change the temperatures during the day than it would require to keep the heat from ever soaking into the house?"

Without getting too deep, the concept relates thermal mass and change in temperatures (Delta T) and insulation.

If a house is shaded and uninsulated, the thermal mass of the furniture, walls, and such will cool overnight and heat up during the day. For simplicity, call it a big covered pot of water under a tree. The average temperature of the water will be very close to the average temperature of the air. The change in temperature of the water will lag because of the thermal mass - it'll remain cooler longer than the air in the early part of the day, and once heated up will take longer to cool down than the air at night.

Add insulation around the pot of water and the average temperature will STILL be similar to the average temperature of the air, but the lag in temperature change of water in the pot will be even longer.

Pots of water and houses don't always sit in shade. When they are hit by the sun, and especially if there is glass or metal that allow radiant heating but not airflow, there is the dog dying in the car greenhouse effect that can get the air in the house hotter than the air outside. Once that happens, the insulation keep the hot in the house.

The greater the difference in cool air temperature inside and the hot air outside, the more energy is required to keep that balance.

This all gets around to saying that if, when you leave in the AM, you set the tstat about 2 to 4 degrees lower than the average high for the day, your energy use should be less than if you keep the tstat cranked down to low 70s. If you allow the place to heat up like an oven by cutting it off entirely, you could use more energy cooling it down.

Exact temps and figures would vary, but that is the general idea - keep the delta-T minimal but under control, then cool the few degrees down to comfort level as needed.

My house isn't shaded at any point during the day (sad considering my back yard is covered in oak trees).


It seems like we're saying similar things but in different ways.


You said:

Originally Posted by harry chickpea

it'll remain cooler longer than the air in the early part of the day, and once heated up will take longer to cool down than the air at night.

Add insulation around the pot of water and the average temperature will STILL be similar to the average temperature of the air, but the lag in temperature change of water in the pot will be even longer.

Pots of water and houses don't always sit in shade. When they are hit by the sun, and especially if there is glass or metal that allow radiant heating but not airflow, [/b]there is the dog dying in the car greenhouse effect that can get the air in the house hotter than the air outside. Once that happens, the insulation keep the hot in the house.[/b]

I said:


Insulation absorbs heat, and radiates it through the walls and into the house. By keeping the temperature constant I am combating the heat build up in the house with the AC by maintaining a constant. Since it isn't trying to remove the excess heat buildup from the afternoon sun (because it's been working to keep the excess heat out of the house all day) it doesn't require a long run time to remove it. It's already manageable.




So going back to my bonus room that I've been working on.


Initially, it had a 26" x 44" skylight in the ceiling (aka wall in this room) that was open to the sun. Even with a return and a large register in the room it could not cool the room down to even manageable levels despite the air being very cold coming from the vent. There was too much heat transfer from the skylight.


Las week, I stapled a couple of the car windshield solar reflectors over the opening to see what would happen. The next evening, the temp was considerably lower. There wasn't as much heat soak, so less for the HVAC to try to remove.


Early Saturday morning I installed fiberglass batt insulation in the hole, framed it out, and screwed in a piece of 3/4" birch plywood into the hole, sealing it off.


Thursday night at 7:30 pm the room temp was in the mid 80's. By 10pm it was down into the mid 70's.


Saturday at 1pm the room was 77 degrees. By 7:30 pm it was 74 degrees (where it consistently runs now). The point with this was that once I removed the access point in which heat was transferred into the room and soaked up by the walls/insulation/carpet/etc... the AC could more efficiently keep the heat out of the room.


Sunday, at about 3pm the bonus room (remember the HVAC was set to 78) was 84 degrees WITH the skylight blocked off. I attribute that to a "heat soak" of sorts whereas the unit wasn't running and pulling heat from the room. It was after 9pm last night before that room was back to 74 degrees.

[Melodica]

Originally Posted by steveklein

I am sorry that the laws of physics aren't enough evidence for you.

The laws of my power bill are enough evidence for me.

Originally Posted by steveklein

If you are waiting 6-8 hours for your AC to catch up and cool the place down, then your system is not working as intended for the size of your home. My home cools from 88 to 76 in just over an hour, even when the sun still out and temps in the upper 80s to low 90s.

And? Not everyone owns a home and thus has control over the size or type of cooling they have.

Originally Posted by steveklein

I am sorry to tell you, but you will need to rely on science. You don't have to jump off two differemt buildings to determine how fast you will be going when you hit the ground on each one. It is simple physics. Heat transfer is a little more complicated, but when you work everything out... you will find my statements hold water.

Blah blah blah. No, I won't find anything because I will continue to use the method that has PROVEN better results for me.

So you can keep responding with the same crap, just like you've done with many of the other posters who have proven that their method works better for them, but you're just blowing smoke.

Have a great day!

[Reactionary]

"In theory there is no difference between theory and practice. In practice there is." - Yogi Berra

[steveklein]

Originally Posted by Melodica

The laws of my power bill are enough evidence for me.



And? Not everyone owns a home and thus has control over the size or type of cooling they have.



Blah blah blah. No, I won't find anything because I will continue to use the method that has PROVEN better results for me.

So you can keep responding with the same crap, just like you've done with many of the other posters who have proven that their method works better for them, but you're just blowing smoke.

Have a great day!

Their method works "better for them" lol... great anecdotal evidence. But proves nothing. That's what science is for, and science proves that my method uses the least amount of energy.

Keep throwing money away if you wish. I am telling you turning your air conditioning off or at the very least increasing the temperature 10 degrees is much more effective.

It really is comical that people can be given actual science and still refuse to believe it and instead just go with their "real world" experiment where they have literally dozens of variables they aren't accounting for.

Sheer hilarity.

Keep your house at 73 when you go out of town for 2 weeks and then keep it at 87 for 2 weeks when you go out of town and let me know which power bill is higher. LOL. Just hilarious that you think keeping it at 73 uses less energy.

[NoleFanHSV]

I don't think my AC could do a 10 degree difference in a reasonable amount of time.

[Weichert]

Originally Posted by steveklein

Keep your house at 73 when you go out of town for 2 weeks and then keep it at 87 for 2 weeks when you go out of town and let me know which power bill is higher. LOL. Just hilarious that you think keeping it at 73 uses less energy.

A not so subtle change of parameters.

[brownbagg]

Insulation absorbs heat, and radiates it through the walls and into the house.

No it doesnt, insulation blocks the heat from migration through the walls

[Dirt Grinder]

I did learn one thing from this thread: there's at least one individual with whom I'll never sit and share some of my BBQ and a beer.