Forced ventilation of the attic creates negative pressure in the attic, which pulls conditioned air from the house. The additional air movement (which you should minimize with air sealing) costs more than the additional loses by the mildly increased temperature differential through the insulation.

If you aren't using A/C and have the windows open, then it only helps, of course.

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scheme271 an hour ago | parent | next [-]

Unless you have really good insulation, in hotter areas, your roof will absorb a lot of heat and that gets transferred to the attic and then to the rest of the house. One of the cheapest and best upgrades in hotter areas is to have an attic fan and vents to send the hot attic air outside.

	▲	WalterBright 26 minutes ago \| parent [-]
		> attic fan The cupola does that using the "stack effect" and the acceleration of the wind as it hits the sloping roof, at zero cost! That said, I do have an attic fan connected to a thermostat. I'd rather have a cupola, though.

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WalterBright 2 hours ago | parent | prev [-]

The idea includes gaps where the roof meets the ceiling, so air is drawn from outside.

> If you aren't using A/C and have the windows open, then it only helps, of course.

I make use of the "stack effect" to cool the house down in the evening. Not even a fan is necessary.

One mistake I made was to not have the A/C pull from the basement, which is always 10 degrees cooler than the rest of the house.