Why is my house so hot?

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Like JHZR2 mentioned, it's gotta be the thermal mass of your structure. Up here, a lot of stuff is brick and stone. It's pretty amazing how strongly you can feel the heat coming off a building after the sun goes down.

I hear that a whole house fan could be a good option for this kind of environment.
 
Late to the game, but my first thought:

"I turned my gas burner off 30 seconds ago; why did I just burn my hand on the iron skillet, trying to pick it up bare-handed!?"
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All in jest, and the technicals seem to have been covered by other above.
 
Our indoor radiated heat dropped a lot when we went from asphalt shingles to a lightweight concrete tile.

We should have gone for a lot more insulation though; maybe there's at best an inch of old cotton-looking stuff up there.
Would be nice to have an IR-reflective barrier (similar to Reflectix) stapled to the underside of the roof, and a foot or two of insulation above the ceiling.

Anyway, to maybe answer your question, longwave IR is what I guess is heating your house.
Shortwave IR from the sun heats the roof; its materials then radiate that heat away via longwave IR.
If you could block the longwave IR from going through the ceiling and onto you, then you'd feel cooler.

From: http://homeenergy.org/show/article/id/1933/viewFull/
A radiant-barrier system is most commonly used for attics in warm climates, because it effectively works like a shade tree, protecting the ceiling insulation from heat that would otherwise radiate downward from the hot roof heated by the sun. Because it’s impossible to measure an R-value where there is no defined closed air space, a radiant- barrier system technically doesn’t have an R-value. By effectively eliminating the radiant-heat transfer from the hot roof, the temperature of the attic space may be reduced by 20 0F or more on very sunny hot days.
 
Originally Posted By: Chris142
My house is not well insulated. I get that. It was 106 today and we had the coolers on which kept the house bearable. The sun set and its now 85 degrees outside. I turned off the cooler and now its 96 in the house! Why did the temp go up and above the outside temp? My wife thinks it's built on lava.


Latent heat radiating from objects is my guess.
 
It's heat-sink. Once you stop the cooling, the heat from the outside of the structure warms it up pretty quick.

Think of what the Indians used to do with mud-brick buildings. It would warm up during the day and keep them warm at night, then it would cool the mud-brick at night to keep cool during the day.
 
The house heat soaks. When we lived Palo Cedro Calif. at 10:00 pm the inside of the house would be 25* hotter that out side with out the swamp cooler on.
 
You ABSOLUTELY need gable end vents with forced expulsion on one gable. That be a thermostat controlled fan Hopefully you have UNBLOCKED soffit vents also.

Very basic.

Now do you have gable ends ??
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That is a prerequisite
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I had the heat sink problem with our previous 1985 stick built ranch here in the high desert. 2x6 insulated walls but not enough in the attic, you could feel the heat radiating from the ceilings. I blew in 10 additional inches and put an attic fan in one of the gable ends and additional vents in the other gable end. Absolutely made a difference although I didn't quantify it. We turned the cooler (no water) on early morning to pull in cool air until wife went to work,then shut the house up until we came home and it would be in the high 70s. A couple of window ACs got us through the evening.

I think Chris posted a pic of his house once, white 2 story out in the desert brush with some trees about?


Now we have AC and live at a higher elevation and I'm considering a whole house fan to get that cool night air in.
 
Your house is a heat sink and heat flows downhill, which in your case, is the interior of your abode and all occupants. I take it by "coolers" you mean swamp coolers. Get an A/C system and enjoy life.No matter what electric rates are in your area.
 
Not sure. Need more info + photos.

However you can quickly cool your house with water: Spray your roof! Direct a stream at the highest point and let it run all the way down. Thoroughly wet the whole roof. Ditto for the side shingles. At your low humidity, it will quickly evaporate absorbing a lot of heat. Repeat if necessary an hour later.

Works even here in humid Tx. I can drop my attic temp about 15F by watering down the asphalt shingles. My attic is well ventilated + radiant barrier + light shingles + lots of fiberglass on attic floor.
 
Originally Posted By: ARCOgraphite
You ABSOLUTELY need gable end vents with forced expulsion on one gable. That be a thermostat controlled fan Hopefully you have UNBLOCKED soffit vents also.


I'm looking at putting in a thermostat controlled fan in one (or more) of my gable vents. I've blown in more insulation and added some reflective barriers.....both of which have helped.....but, I think more can be done. I'm curious, does it matter which gable vent you use (I have them on every side of the house except the south facing)? If it matters, how do you determine the best gable vent to put one in?
 
Have looked at your swamp coolers. Have the pads been replaced, water level, pump, blower wheels clean, did they ever work. If they take all their air from outsider any windows open to relieve the air.
 
Originally Posted By: Chris142
My house is not well insulated. I get that. It was 106 today and we had the coolers on which kept the house bearable. The sun set and its now 85 degrees outside. I turned off the cooler and now its 96 in the house! Why did the temp go up and above the outside temp? My wife thinks it's built on lava.


The simple answer is to have a white roof. Here in South Florida, we've learned that radiant heat from a dark roof permeates the house. It matters very little if the attic is vented. The heat is radiant, and comes right through fiberglass insulation and drywall.

Not unlike a portable radiant heater that does not heat the air, but instead heats anything in it's path.

EDIT: Guess what color my roof is? White, barrel tile. I have a very efficient Florida house and my utility bills are very reasonable. The builder thought I was crazy when I declined the expensive attic insulation package, and instead went for insulated low-e windows. Unlike my old home, I can't feel any radiant heat from above.
 
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I had a poorly insulated house in the 1980's and once it cooled off at night I placed two fans at opposite windows of the house. One fan blowing the hot inside air out and the other sucking the cooler outside air in.

At 6am before I left for work I turned off the fans, closed all windows and drapes and sealed off the house best I could.
 
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