Attic ventilation fan question


  #1  
Old 03-13-23, 01:58 PM
JohnQFlorida's Avatar
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Attic ventilation fan question

I'm in hot sunny Florida.

I do feel as if my roof is almost definitely under-vented according to code, so I'm curious if an attic vent fan would help, in my case, with extreme electric bills in the summer.

The solar industry has peppered the internet with articles (many by the same lady) talking down attic fans, saying they do no good, so buy solar panels instead. At the same time, people who sell attic fans pepper the other half of the internet with stories about how great attic vent fans are, so buy attic fans instead. And the people who sell insulation say fans make no difference, buy more insulation instead. As you can see, I'm a bit cynical, but there's no doubt my attic gets extremely hot, so I'm curious if an attic vent fan would help.)

My situation:
  • Almost the whole house is covered by a hip style roof, coming up to a single peak in the middle, with a shortish ridge (maybe 20 feet) with a shortish ridge vent, maybe 15 feet long, and that's the only vent. All this on a pretty large roof, roughly a 3000 square foot house. (That's why I say it seems under-vented to me)
  • There's a pretty decent layer of insulation in the attic
  • All the ductwork is up in the attic, all the longer expanses mostly up above the insulation line.
  • One of the two air-handlers are also in the attic.
  • Attic temps in the summer hit 130 to 140 easily. Outside temps here are very regularly about 90 to 95 degrees F in the summer, occasionally all the way up to 100 or so.
  • So, if I invested in an appropriately sized attic vent fan, would I expect a little energy savings? I like the knowledgeable community here, and the variety of advice that people share.
  • Wintertime I'm far less worried about; I have natural gas for heat, and the wintertime electric bills are like a day at the beach, compared to summer.
Thanks in advance.
 

Last edited by JohnQFlorida; 03-13-23 at 02:13 PM.
  #2  
Old 03-13-23, 03:43 PM
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Those attic temps are not unexpected but just installing an exhaust fan without proper inlet vents may not do much. For all the air you want to push out you need to have sufficient soffit vents allowing the cooler air to enter the attic!

Here is link for some reading and ways to calculate the amounts ventilation needed!

https://www.gaf.com/en-us/for-profes...ion-calculator

 
  #3  
Old 03-13-23, 10:52 PM
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Attic ventilation is largely for prevention of ice dams in the winter though it can prolong the lifespan of the roofing materials in warmer climates. If adequate ventilation exists, which it sounds like it does, the warm attic does little to affect the temperature inside the home.
 
 

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