Reuben's Home Inspection Blog

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Attic Fans Won't Fix Ice Dams... or Anything Else

Icicles hanging over the edges of roofs might look pretty, but once enough melted water gets trapped behind that ice, water can leak in to the house.  Minnesota saw a ridiculous amount of ice dams two and three winters ago, which prompted many homeowners to start looking for ways to prevent ice dams.

The two main driving factors behind ice dams are attic air leaks and insufficient insulation.  If those two are fixed, the potential for ice dams is quite minimal.  A third component to ice dams is attic ventilation.  Attic ventilation is required by code, but it's not an ice dam elixir.  As long as attic air leaks are sealed and insulation is sufficient, only small amount of ventilation are needed to keep the attic space cold.

Unfortunately, lots of people claim that inadequate attic ventilation causes ice dams, which leads people to do all kinds of crazy stuff to get more air flowing in to their attic.

Attic Fan

While the photo above of a desk fan installed in someone's attic is a little silly, the person who installed it obviously thought it was a good idea.  There are actually fans made specifically for attics.  Most need to be connected to a 120 volt power source, but there are also solar powered fans available, such as the one pictured below.  This one was sold at Costco for a while.

Solar Powered Attic Fan

My advice is to skip these fans entirely.  While attic fans will certainly suck air out of your attic, the problem is that this air needs to be replaced.  Where does the air come from?  Some of it will come from the soffit vents, and some will come from attic air leaks.  If you have problems with ice dams, a LOT of air will come from attic air leaks.  This means you'll actually be sucking warm air IN to your attic.

If you have problems with ice dams, focus on fixing your air leaks and insufficient insulation.  Once your attic lid is perfectly air sealed and you have enough insulation, the main causes of ice dams will have already been corrected.  Don't waste your money on an attic fan.  If you already have an attic fan installed, your best option would be to have it removed and have proper passive ventilation added if not already present.

What about using these fans during the summer?  Nope.  Check out any of the links below for more info on why you're better off not using attic fans... ever.

Related links, mostly pertaining to attic fans running during the summer:

Reuben Saltzman, Structure Tech Home Inspections

        

Comment balloon 9 commentsReuben Saltzman • January 16 2013 06:13AM

Comments

This is very interesting information. I live in Virginia, so extreme weather is not common to us, but I have seen a desk fan in an attic before! I guess that's universal regardless of where you live.

 

 

Posted by Rebecca Lee McAnallen, Big city experience, small town service (MBH Settlement Group, LC) over 4 years ago

Both of those excellent ideas should be working well Reubs. I am sure there are no ice dams there now.

So moving air works?  A couple of geisha girls with fans should do the trick, right?

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 4 years ago

Seems like a popular subject right now; ice dam, attic fans and ventilation. 

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 4 years ago

Reuben, it seems like you me and Jim are all on the same page this week :)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 4 years ago

Reuben, I like the creativity, The plenum stand and extension cord was a nice touch.

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) over 4 years ago

Rebecca - if there is a ton of frost in the attic and someone wants to get rid of it before it melts, I suppose the desk fan wouldn't be that bad of an idea.

Jay - sure, either that or you get a bunch of people in the attic to blow really hard ;)

James - it's the right time of year.  We haven't seen much in the way of ice dams here in Minnesota this year, but I know they're happening in other parts of the country because my old post on how to remove ice dams has seen a ton of traffic recently.

Charles - I have half a mind to start giving you a schedule of my upcoming posts so we can post them on the same day ;)

Donald - the funny thing about that house was that it was a bank owned property.  I guess they forgot all about the fan.

Posted by Reuben Saltzman, Minneapolis Home Inspections (Structure Tech Home Inspections) over 4 years ago

People using fans in the attic: Conceptually challenged, not clear on the subject and blindly optomistic.

Posted by Robert Butler, Montreal Home Inspector | Aspect Inspection (Aspect Inspection) over 4 years ago

People are always trying to get by without spending a few bucks to do it right.

Posted by William Feela, Realtor, Whispering Pines Realty 651-674-5999 No. (WHISPERING PINES REALTY) over 4 years ago

Hi Reuben,

If you stop the heat loss in the attic, then you will stop the ice buildup on the eaves.

The attic temps need to be the same as the exterior temps. In a perfect world if course.

Have a good day my friend in Minneapolis.

Best, Clint McKie

Posted by Clint Mckie, Desert Sun Home, Comm. Inspection 1-575-706-5586 (Desert Sun Home, commercial Inspections) over 4 years ago

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