I am looking at my attic insulation and ventilation and came across things I have hard time understanding.
I have a fan in the roof in the attic to exhaust hot air to prevent attic from overheating. Pretty standard feature, 14" diameter fan operated by thermostat - I am sure many people here have something similar. Current fashion recommends using solar powered fan in such situation and without thermostat. The topic of fan in the attic lately became quite controversial. If you google "attic ventilation" you will find plenty of articles saying that attic fan is useless and unnecessary and should not exist at all - regardless what powers it. Some places (like State of Georgia) outlawed use of attic fans except solar powered. I looked at technical characteristics and got puzzled. Most common traditional attic fans are designed to operate on 115Volts, using 3.5 - 4 Amps, so it consumes 400 - 450 Watts. Such fans are rated for about 1000 - 1600 CFM. But then you look at solar powered fans and those claim to have 500 - 2500 CFM even though they are connected to solar panels rated for 20 - 60 watts and equipped with motors rated at 10 - 40 Watts. Leaving aside loaded discussions about advantages of solar power or fan in the attic - I am just wondering - how is it possible that a fan with 10 watt motor have similar air-moving capacity as another fan with similar dimensions but with 350 watt motor?
I have a fan in the roof in the attic to exhaust hot air to prevent attic from overheating. Pretty standard feature, 14" diameter fan operated by thermostat - I am sure many people here have something similar. Current fashion recommends using solar powered fan in such situation and without thermostat. The topic of fan in the attic lately became quite controversial. If you google "attic ventilation" you will find plenty of articles saying that attic fan is useless and unnecessary and should not exist at all - regardless what powers it. Some places (like State of Georgia) outlawed use of attic fans except solar powered. I looked at technical characteristics and got puzzled. Most common traditional attic fans are designed to operate on 115Volts, using 3.5 - 4 Amps, so it consumes 400 - 450 Watts. Such fans are rated for about 1000 - 1600 CFM. But then you look at solar powered fans and those claim to have 500 - 2500 CFM even though they are connected to solar panels rated for 20 - 60 watts and equipped with motors rated at 10 - 40 Watts. Leaving aside loaded discussions about advantages of solar power or fan in the attic - I am just wondering - how is it possible that a fan with 10 watt motor have similar air-moving capacity as another fan with similar dimensions but with 350 watt motor?
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