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The house we have in the US south seems to function in this way in summer:

enter image description here

I know nothing about AC/insulation systems but it seems that:

If there was simply airflow through the attic, it would stop the attic being actually warmer than outdoors?

Am I totally wrong?

So I propose this:

enter image description here

Do I have head up ass?

Is this something every other house has and I'm just behind the times? Have I "reinvented the wheel" or ...?

I've noticed anyway, from the attic, the gaps to the outisde walls are just really poor (ie, you can generally "look out" the gaps and see the grass) ... should I perhaps just install massive fans that pump the hot air out those gaps?

(I realize that would be the wrong direction - but my guess is it would be a huge improvement.)

Maybe I'm wrong and it's not actually that hot out there - I'm running out to buy many thermometer devices!

What's the deal on this?

  • BTW I searched but could not find a dupe on this. It's probably "really obvious" to folks who know about houses, so it may never have been asked? – Fattie May 26 '18 at 19:47
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    Yes, you're reinventing the wheel. :-) Attics do have cross ventilation, sometimes augmented by a fan, for exactly the reasons you've stated. – fixer1234 May 26 '18 at 19:53
  • @fixer1234 - fantastic information. thanks! maybe, in a word, in this house I should "beef up the cross ventilation" one way or another? (Apparently at the moment it has either none or garbage X-ventilation.) – Fattie May 26 '18 at 19:56
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    BTW, there are whole house ventilator fans that mount in the attic (much more common before AC became popular). You open windows on the ground floor where the air is coolest, and the warmest air in the house is pulled out into the attic, which pushes out the even hotter air there. – fixer1234 May 26 '18 at 19:57
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    Our house in Dallas TX has a straight gable roof with a 3 in 12 pitch. It is one story 2500 sq ft including the integral garage. A combination of a full length ridge vent on the ridge (to let air out) and soffit vents (to let air in) exchanges air in our attic. Without air exchange the air in the attic would get extremely hot, perhaps >140 F. – Jim Stewart May 26 '18 at 22:11
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Great drawings...even I understood what you’re saying.

Yes, additional ventilation will help. However, no matter how much outside air you circulate through the attic, the temperature will never be less than the outside air temperature. By increasing air circulation you lower the Air temperature in the attic and thus the “load” on your air conditioning system.

In the tropics and Hawaii (about the same latitude as you) you’ll notice they don’t use air conditioning in lobbies , etc., because it’s too expensive. In stead, they leave whole walls off and let the “trade winds” blow. The temperature of the trade winds is still 90 degrees or so, but increased air movement helps the body “feel” cooler. (That’s why sitting in front of a fan feels good. It’s a matter of having air blowing across the skin...it lowers the “apparent” temperature of the body.)

You can’t rely on trade winds, so you need fans to increase air circulation or pay for air conditioning. (There are other means too. You can google ground air circulation, or geothermal ventilation, etc., They work on the basis that the ground is always about 55 degrees and you can “draw” that air into your house through fans by burying ducts in the ground. Actually, you don’t want that air because it’s musty, but you can use a heat exchanger. It gets complicated and expensive, so most people just pay the local utility.)

Reducing your air conditioning load, you can 1) insure the walls are in shade (that’s why people have large overhangs and they plant shade trees on the south side of there house), 2) increase wall and ceiling insulation, 3) provide thermal pane windows, 4) provide weatherstripping to keep unconditioned air out from heating up conditioned air, and 5) increase ventilation...including the attic, which is your idea.

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We paid for a solar powered attic fan. It installs near the top of the roof peak and ideally points south (ours is east) and when the attic temperature exceeds 85°F, the fan starts. This presumes that there is sufficient sunshine to power the motor.

Our air conditioning use dropped substantially after the installation. It is still quite hot in the summer in the attic, but not body-killing hot as it usually is.

Because heat rises, you'd want a fan that blows out at the top and pulls cooler air in from below.

  • fantastic information ..... – Fattie May 26 '18 at 19:55

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