Ice Dams And Attic Fan

 
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Old 01-27-2011, 02:28 PM   #1
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Ice Dams And Attic Fan


I have a customer that had his attic blasted with cellulose insulation a couple of years ago. He has soffit, gable and ridge vents.

He has some ice dam issues that he hoped the insulation would rectify. It didn't.

Does anybody feel that running the attic vent fan (normally run in summer) would alleviate the ice damming or is it just a waste of electricity?

Thanks,

Scott
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Old 01-27-2011, 02:38 PM   #2
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Re: Ice Dams And Attic Fan


Actually running the attic fan could cause the problem you're having. It pulls to much moisture through the ceiling and wall cavity from the house into the attic and that could cause a problem especially when you already have a soffit and a ridge vent already...

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Old 01-27-2011, 03:17 PM   #3
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Re: Ice Dams And Attic Fan


Running that fan would do absolutely nothing to benefit this situation.

It's not a good idea to exhaust the attic during the colder months like in winter, and certainly not during coldest days. While some of the exhausted air will come from the soffit and gable vents, some will also come from the living spaces. It's a waste of energy and also likely to cause condensation problems in the attic.
Only running the fan in the summer extended its life, and it will cause more harm even to the fan motor itself in the colder months, and it does not allow the fan to reduce moisture build-up in the attic at all at these times and does not allow the fan to prevent ice dams during the winter.

You'll just be pulling in more moisture that will create more possible problems down the road.
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Old 01-27-2011, 03:20 PM   #4
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Re: Ice Dams And Attic Fan


Also, was the blown-in done properly? He could have drifts in the insulation if it was done wrong or by an inexperience installer.

I know it's asking for much, but could you get a few different snap shots of his attic from the inside?
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Old 01-27-2011, 03:41 PM   #5
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Re: Ice Dams And Attic Fan


How much insulation?? Almost seems like there is a heat loss into the attic--therefor melting the snow and it freezes back up again when it hits the cold soffit area? Just a thought
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Old 01-27-2011, 03:44 PM   #6
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Re: Ice Dams And Attic Fan


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How much insulation?? Almost seems like there is a heat loss into the attic--therefor melting the snow and it freezes back up again when it hits the cold soffit area? Just a thought
( coughs ) Pics
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Old 01-27-2011, 03:45 PM   #7
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Re: Ice Dams And Attic Fan


There will always be heat loss.
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Thanks for that tidbit of information Darcy.
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I don't normally talk to people like I talk to you, however you have the little immature schoolgirl mentality so this is new to me.
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Old 01-27-2011, 03:50 PM   #8
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Re: Ice Dams And Attic Fan


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There will always be heat loss.
Not when I insulate.. I'm superman of insulation..


FSK paper in attics helps a great deal
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Old 01-27-2011, 04:00 PM   #9
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Re: Ice Dams And Attic Fan


What is FSK paper and how is it used??
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Old 01-27-2011, 04:29 PM   #10
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Re: Ice Dams And Attic Fan


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What is FSK paper and how is it used??
I recommend to homeowners to use FSK paper insulation in attics for this reason.. here is how the stuff works, an idea.. but when used it attics, the foil keeps the heat transfer from escaping the living space..

Just reverse the process that's done in this video..

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Old 01-27-2011, 04:37 PM   #11
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Re: Ice Dams And Attic Fan


Understanding ice dams is a tricky thing. Not all ice damning is caused by heat loss from the house.

Ice damns can form after a heavy snow fall, sunny day and freezing temps at night. The shingles warm up and melt the snow, then melt runs down the roof cools off and freezes at the bottom of the roof. The cycle continues for several days and or weeks and you have yourself a nasty little ice damn.
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Old 01-27-2011, 04:42 PM   #12
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Re: Ice Dams And Attic Fan


There will be heat loss. There will be sun that warms the roof and melts the snow. There will be ice at the eaves when that happens.
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Thanks for that tidbit of information Darcy.
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Old 01-27-2011, 05:00 PM   #13
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Re: Ice Dams And Attic Fan


Temporarily - put a regular fan in the attic & let it run if you have condensation or frost in attic

Next the pics would definitely be helpful, including the attic access, and other areas

Are there can lights in the house - the insulation will be thinner there letting heat out

Was the wiring & other penetrations sealed or did they just blow more insulation over the old stuff

If as Crawl-Dog mentions, they have dips, valleys and peaks, you don't have the full r-value that you think you have as this one article brings out (Energy Vanguard site)
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Old 01-27-2011, 05:08 PM   #14
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Re: Ice Dams And Attic Fan


If there is any condensation in the attic, a fan won't resolve anything. Find out where it is coming from and fix it. But since the OP said nothing about moisture in the attic, I will assume that this isn't an actual issue and stick to the original issue described.
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Old 01-27-2011, 05:14 PM   #15
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Re: Ice Dams And Attic Fan


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Originally Posted by TNTSERVICES View Post
Understanding ice dams is a tricky thing. Not all ice damning is caused by heat loss from the house.

Ice damns can form after a heavy snow fall, sunny day and freezing temps at night. The shingles warm up and melt the snow, then melt runs down the roof cools off and freezes at the bottom of the roof. The cycle continues for several days and or weeks and you have yourself a nasty little ice damn.
I half way agree with this. Yes, they are tricky. But a good of example of why I'll disagree with this statement is this.

My garage roof is completely cold with no heat source. Yet the snow stays on this roof almost all of the time. On the other hand, on my house it does not. A few days after a snow fall the least insulated portions are down to the shingles and my gutters are full and I have icicles.

Now it got much better this year. I had the portion of my roof that I could access behind the knee wall sprayed with open cell insulation. That portion of the roof is now like my garage (snow doesn't melt), while the upper portion with only fiberglass melts.

So let's hear from a Spray Foam guy. To me, that's the way to go. Insulate your cold roof, condition it to the rest of the house and now you have heated storage. Totally isolated from the heat, no more damming.

Just my own personal experience.
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Old 01-27-2011, 05:21 PM   #16
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Re: Ice Dams And Attic Fan


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If there is any condensation in the attic, a fan won't resolve anything. Find out where it is coming from and fix it. But since the OP said nothing about moisture in the attic, I will assume that this isn't an actual issue and stick to the original issue described.
If there are ice dams, sometimes one will have condensation inside on the roof sheathing (generally where the problem area is / are) - most times in the early morning, it will be frozen and the fan will help keep it from thawing, dripping, soaking the insulation, and starting the cycle all over again. When it does start warming up hopefully towards spring, it will help dissipate the moisture before it starts raining down.

Next a fan in the attic can help keep the cool air found in other area's of the attic circulating around to help counteract the heat (and moisture) coming up from below & heating up the sheathing which is one of the main causes of ice dams.

Next...
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Old 01-27-2011, 05:27 PM   #17
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Re: Ice Dams And Attic Fan


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Originally Posted by SLSTech View Post
Next the pics would definitely be helpful, including the attic access, and other areas

Are there can lights in the house - the insulation will be thinner there letting heat out

Was the wiring & other penetrations sealed or did they just blow more insulation over the old stuff

If as Crawl-Dog mentions, they have dips, valleys and peaks, you don't have the full r-value that you think you have as this one article brings out (Energy Vanguard site)
Bingo, high-hats ( can lights ) will contribute to this as well.. I cover them with an UF then blow on top, they say not to, but I damn it high enough so there is no issue.

Like you said about the vallys and dips, thats exactly what I was referring too, glad you worded it better.

Good like too

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If there is any condensation in the attic, a fan won't resolve anything. Find out where it is coming from and fix it. But since the OP said nothing about moisture in the attic, I will assume that this isn't an actual issue and stick to the original issue described.
When I spoke in regards to the fan, I was referring to it pulling more moisture in the attic, not in-regards to removing it. Fans will pull from the eves and living space in the winter if ran and create an issue.

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I half way agree with this. Yes, they are tricky. But a good of example of why I'll disagree with this statement is this.

My garage roof is completely cold with no heat source. Yet the snow stays on this roof almost all of the time. On the other hand, on my house it does not. A few days after a snow fall the least insulated portions are down to the shingles and my gutters are full and I have icicles.

Now it got much better this year. I had the portion of my roof that I could access behind the knee wall sprayed with open cell insulation. That portion of the roof is now like my garage (snow doesn't melt), while the upper portion with only fiberglass melts.

So let's hear from a Spray Foam guy. To me, that's the way to go. Insulate your cold roof, condition it to the rest of the house and now you have heated storage. Totally isolated from the heat, no more damming.

Just my own personal experience.
This was explained great, with a good exp. The fluctuation of the heat off and on, and the sun off and on all day will do this, compared to the cold dead space that you spoke about. Glad you brought this up.

Heating it and treatingit as a living space is not a bad idea if one cares to spend the money. if that is the case.. use FSK foil face with everything up there, and I mean EVERYTHING, pipes, ducts, insulation, the works..
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Old 01-27-2011, 05:38 PM   #18
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Re: Ice Dams And Attic Fan


Quote:
Originally Posted by Teoli View Post
I half way agree with this. Yes, they are tricky. But a good of example of why I'll disagree with this statement is this.

My garage roof is completely cold with no heat source. Yet the snow stays on this roof almost all of the time. On the other hand, on my house it does not. A few days after a snow fall the least insulated portions are down to the shingles and my gutters are full and I have icicles.

Now it got much better this year. I had the portion of my roof that I could access behind the knee wall sprayed with open cell insulation. That portion of the roof is now like my garage (snow doesn't melt), while the upper portion with only fiberglass melts.

So let's hear from a Spray Foam guy. To me, that's the way to go. Insulate your cold roof, condition it to the rest of the house and now you have heated storage. Totally isolated from the heat, no more damming.

Just my own personal experience.
I am just saying that it is not as simple as just blowing in insulation or spraying foam. There may have to be some serious detective work to see what is causing the damning. I was just giving an example. I have seen it happen on well insulated roofs. The damns were not serious, and they were mostly at the gutters. This is why I agree that pics of the attic and of the roof would be helpful.
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Old 01-27-2011, 05:41 PM   #19
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Re: Ice Dams And Attic Fan


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Next a fan in the attic can help keep the cool air found in other area's of the attic circulating around to help counteract the heat (and moisture) coming up from below & heating up the sheathing which is one of the main causes of ice dams.

Next...
SLS, do some research on why NOT to use fans in the winter..

People, contrary to popular belief, at times common sense can be very wrong.

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Old 01-27-2011, 05:42 PM   #20
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Re: Ice Dams And Attic Fan


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I agree that pics of the attic and of the roof would be helpful.

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