# Damn Ice dam -damn!



## Big N8 (Oct 28, 2009)

We have the very same issues here in MN. The refreeze is just a part of life. Some use a heated cord to keep the ice from forming on the eves.

http://www.heatersplus.com/roofcable.htm
That link is good stuff to use.


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## handy man88 (Jan 23, 2007)

As well insulated as an attic can be, it won't be as the outside temperature because a lot of newer homes have furnaces in the attic and gas flues which radiate heat.


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## Grumpy (Dec 12, 2003)

Insulation is only half the equation. Ventilation is also key. When you say you believe it's well insulated, what do you mean? To today's standards you'd need approximately 12" regardless of insulation type to be considered well ventilated IMO. 

As for ventilation, there is a science to the attic ventilation. What kinds of vents do you have and how many? Do you have an intake vent at the overhang? You might possibly need to add more vents.

Ice damning is primarily caused by excessive heat build up within the attic, which melts the snow from the bottom side, and then the snow refreezes, turns into a damn, more melting, more freezing. You've got a problem. The attic space should always be as close to the exterior temprature as possible. While that's somewhat unrealistic, it's still the goal. When it's 15 degrees outside your attic will also be 15 degrees? No, but you'd ideally want the attic also below freezing. Keeping the heat inside the living space is important and is accomplished with insulation. Allowing what heat does collect inside the attic is accomplished with a properly designed and well balanced attic ventilation system. 

If you have a heater or furnace within the attic, then the ventilation must always be increased to allow for this heat to escape as much as possible. I understand why the furnaces are installed inside the attic spaces, to save living space, but it's just a plain bad idea that usually causes alot of problems IMO. It can be dealt with though, like I said when designing the attic ventilation system it must be designed with the furnace in mind. 

I refer you to a link on my website which will explain in a little more detail http://reliableamerican.us/articles/attic-ventilation-ice-daming.htm as well as a manufacturer of attic ventilation which will explain more about how an attic's ventilation system works. http://www.airvent.com


Even with proper insulation and ventilation, ice damning is a fact of life. However with insulation and ventilation the ice damn should be minimized. When your roof is/was replaced it should have an ice and water shield installed no less than at the gutter lines. This should extend from the gutter to at least 24" past the exterior wall. If you have an ice and water shield on the roof, if an ice damn does form it will prevent that ice damn from getting into the attic space. It forms a barrier that the ice can not penetrate.

Gutter and roof heating cables are also an idea which work with mixed results. I install one or two of these jobs per year. What I tell my customers is don't expect there to be no snow or ice on your roof, just expect that yours will melt off sooner than your neighbor's. The heat produced by these cables is very gentle maybe 50 degrees or so. HOWEVER you can sometimes cause more harm than good when installing these cables on the roof if you install them improperly. You can also void the manufacturer and or roofer's warranty so you may want to check with them before installing these heating cables.


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## jpsmith (Jan 29, 2009)

Joe F,

I think your theory holds water. Being a DIYer, I can't offer an answer as thorough as Grumpy the Roofer, but I can say that I, too am having ice dam issues for the first time in the seven years that I've owned my house. In my case, the water is getting into the soffits. My attic space is below freezing. I'm pretty sure this time around it's a perfect combination of 2' of snow on the roof, temps around 30F and sunny during the day, and 10-15F at night. My roof doesn't have any drip-edge or ice shield. I'll be re-shingling this year I think, and I'll definitely fix the problem when I replace the roofing.


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## toeey1 (Feb 10, 2010)

Im having major problems with ice dams as stated in anopther thread. I came from a 60 year old bungalow that had little to no insulation in it and just a bare minimum of roof venting. I got ice dams pretty bad but never had any water seepage into the house. 

I just movbed to a 24 year old home with insulation however because of a poorly insulated and bventilated vaulted ceiling, im getting major ice damming again only this time im getting major water leakage into my garage attic. Insulation companies couldnt help me, they all recommended I hire a roofer.


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## MJW (Feb 7, 2006)

Great post Grumpy. 

Just to add to the occuring scenario with this years winter weather........The heat that is present in the attic can possibly be above freezing, either from warming outside temps coming in the soffits or heat loss from the house. This creates a problem especially when we have deep snow and your venting on the roof is covered. The heat will come out the vent and start to melt under the insulation of the snow. This will then run down under the snow and create ice dams and other problems. This makes it possible to have ice dams almost anywhere on your roof. 
When an area gets too muc snow and not enough melt, you must open up the venting. I recommend hiring a professional with proper insurance to do the roof "winter maintenance" for you.


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## Joe F (Jan 27, 2008)

Grumpy, thanks for the great tutorial on ice dams. I guess I'm trying to determine if the current weather conditions are responsible for the ice dams independent of the condition of my attic insulation and ventilation. Using your 12" insulation guideline, I probably fall a little short, but not too bad. On the ventilation side, my 50 year old ranch style house has 2 large gable vents (30" x 40", 1800 sf attic). Is that enough? The thing that has me thinking, is that I only get ice dams on the shady side of the house when we have above freezing days and below freezing nights. 

FYI, I'm due for a new roof either this year or next. What can I do during the re-roof process to help address the problem?


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## concretemasonry (Oct 10, 2006)

To ventilate properly, you need both roof or gable vents AND then enough soffit vents.

The air temp is just an average and some areas are different.

If practical, a snow rake to pull off snow for 2' or more and let Mother Natures sun do the job even on the shady side since ice and snow transpirate. It does a good job even on difficult roof layouts.

Dick


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## drohead (Feb 12, 2010)

*Solve Ice Damm Problems for good*

While I can agree with your observation that many homes are poorly insulated and have areas were heat loss from the home causes problems and should be focused on to remedy, there are many factors as to whether a COLD ROOF will stop ice dams. With so many architectural challenges by poor designs, dormers, gables, cathedral ceilings, getting to a cold roof via ventilation can be difficult and extremely costly. Your article does not address a basic fact of Mother Nature… THE SUN. What do you do about radiant heat from the sun everyday? Most homes will see some sun exposure during the day. That heat melts snow and creates moisture on the roof, typically following the slope to the eaves and valleys. Then the temperature drops and the melt refreeze. If this happens over a couple of days... ICE DAM! Even on a well vented cold roofs like you have described. Keeping valleys, eaves and gutters clear can only be achieved by keeping the refreeze from occurring by keeping the melt liquefied and allowing it to get off the roof and then too the ground. There are products out on the market that can prevent ice dams and keep them from forming.


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## BamBamm5144 (Oct 6, 2009)

Joe - It is hard to know if it is enough without seeing the actual attic or knowing the exact square feet of the attic. There is an actual formula to determine if you have the proper amount of ventilation. You could have 10 of those gable vents, but without any soffit vents, they would be useless. I hear a lot of how important it is to have a balanced attic intake and exhaust although I am not too sure how important is along as they are similar.

In the meantime, I dont suggest taking any snow off of the roof. I think this is more of a sales gimmick than anything else. With a properly vented roof, it should all melt off evenly. I also dont think there is anything you can do until you have the roof properly replaced and when having it replaced, your ice damming issue will only be solved if the intake (soffits) are also done while doing the roof. I believe the best system to know be a ridgevent, however, you must close up the gable vents to make this possible. Closing them could be as easy as putting plastic over them from the inside if secure enough.

As usual, Grumpy gave you the best information and I suggest you follow his advice.


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## handy man88 (Jan 23, 2007)

I'm considering having having my installation topped off. I already have cardboard (I think) baffles in place between the rafters.

One option offered by the installer was for styro vents which would be stapled in place. They cost $3 each, and to me, it sounds very labor intensive and probably worth it, but not sure if I need to replace the existing cardboard baffles. 

A direct benefit is that if the installer is told to install these new vents/baffles, the tech will be able to check and ensure that the soffit is not blocked.

So, what's the benefit of having styrofoam vents?


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## Grumpy (Dec 12, 2003)

Styrofoam, cardboard, plastic, it doesn't matter what they are made of so long as they provide no less than 1" preferrably 1 1/2" of positive air flow into the attic. It's very ez to block intake with blown in insulation. By installing the baffles first you can actually be clumsy when blowing in the insulation and be sure you're not blocking intake.


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## handy man88 (Jan 23, 2007)

Grumpy said:


> Styrofoam, cardboard, plastic, it doesn't matter what they are made of so long as they provide no less than 1" preferrably 1 1/2" of positive air flow into the attic. It's very ez to block intake with blown in insulation. By installing the baffles first you can actually be clumsy when blowing in the insulation and be sure you're not blocking intake.


I heard from an installer that the styrovent baffles are installed in addition to the existing baffles if the existing baffles do not offer the requisite height required to achieve the desired R value. They are actually stapled onto the roof's sheathing.

One installer told me they cost $3 each, while another installer said that they are included in the price.


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## Bob Mariani (Dec 1, 2008)

I only scanned the other posts, but I see alot of mentions of insulation and venting. According to all science and what is required by BPI which is the only accredited authority on this subject to get government rebates to fix this problem the real solution is air sealing. When I have more time I will try to post a blog explaining how we fix this. And it is fixable whether your roof is vented or not. We test where the leaks are with a blower door test. But a poor mans test to find air leaks is to look at your roof a few days after a good snow. Houses where all the snow is still there are sealed correctly. houses with no snow have not insulation. But the majority of the houses will have areas of melted snow.... these areas are exactly where the air sealing is not done correctly.


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## handy man88 (Jan 23, 2007)

Bob Mariani said:


> But a poor mans test to find air leaks is to look at your roof a few days after a good snow. Houses where all the snow is still there are sealed correctly. houses with no snow have not insulation. But the majority of the houses will have areas of melted snow.... these areas are exactly where the air sealing is not done correctly.


Areas of melted snow depend greatly on position of house relative to available sunlight.

The south side of the house will most likely see more melting vice the north side.


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## MJW (Feb 7, 2006)

handy man88 said:


> Areas of melted snow depend greatly on position of house relative to available sunlight.
> 
> The south side of the house will most likely see more melting vice the north side.


Ya, but "science" only calculates numbers and theories to make a good assumption, until it is debunked or proven.

Haven't seen many science experiments conducted in the real world. Often it is in a controlled environment. 

I'm interested to read the responses here.


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## Bob Mariani (Dec 1, 2008)

MJW said:


> Ya, but "science" only calculates numbers and theories to make a good assumption, until it is debunked or proven.
> 
> Haven't seen many science experiments conducted in the real world. Often it is in a controlled environment.
> 
> I'm interested to read the responses here.


your response to this is wrong. Actual testing is done and done often now. Almost every government is paying big bucks to find out how to make houses more energy efficient. But because contractors do not understand the science and thus are afraid to change their evil ways even new homes need to be retro-fitted to make them tight enough but still be safe for humans. As such rebates for fixing these problems is only available to owners using accredited building performance analysts. look at the silly response to some of these issues.. These are far less useful then the science you so quickly disregard due to your lack of understanding. Too much is online that gives opinions and not real solutions. But even on the good sites the old articles are still listed and some confusion exists since more testing has refined the best solution. so I will continue to follow the science and do it right. The government offers 18 billion for us to do so. (only if done by BPI auditors) New York and many other states now are adding to this program. And all require the same accreditation. Maybe the too see that understanding how the building interacts with humans, weather and moisture flow has some value in doing things right.


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## MJW (Feb 7, 2006)

Didn't mean any offense Bob.

I purposely watch for your posts for info. Take that however you like. It should be a compliment.

Just stating that many things that are considered "scientific" are debunked or proven every day. Global warming to be one of the big ones.

Codes are often backed up by supposed scientific data, but I have seen the codes change many times in the last 15 years. I even see house codes that totally conflict each other around the country. Walls and moisture is the biggest.

I have seen what the government pushes, and sometimes it really does create more problems for homeowners. Just look at the posts here........


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## Bob Mariani (Dec 1, 2008)

all of what you say is correct. But we need the tests and the science to make things better. The code changes when they feel that things are proven to be so and then accept the changes. These changes take longer than we want them too. A good example.... we always had to cross vent crawlspaces. No with new rules backed by science and testing we have to seal crawlspaces. And poly as you mentioned... best to never use it unless you are in the very cold climate areas or under slabs. Another issue we have to deal with is codes that are not updated. But I have submitted info to building departments showing them why I need it the way I do it and have had much success in changing their minds with few exceptions.

And thanks for the compliment. Did not take your comments personally, just trying to explain that much in the industry still needs to be fixed and all contractors and DIYer need to be educated more.


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## MJW (Feb 7, 2006)

Bob Mariani said:


> just trying to explain that much in the industry still needs to be fixed and all contractors and DIYer need to be educated more.


I can't agree more. :thumbsup:

It's funny, I remember the energy audits in the early 80's. The "government" had people running around adding styrofoam inserts behind the plates of our light switches and outlets. Money, time, and research well spent. :whistling2:


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## Bob Mariani (Dec 1, 2008)

yeah... I was an energy auditor then. But now the science has shown new things that are more valuable to fix. And things like windows and plate insulation is not longer on the list.


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## Gary in WA (Mar 11, 2009)

Foam baffles are an inferior product- they burn toxic smoke, vent *only 18.7sq.in.* per -24” bay, snag and rip on the nail points in the roof deck., need an additional Windblocker to protect the insulation edge from wind washing: http://www.adoproducts.com/duro.html http://www.adoproducts.com/wind.html 
Even the O.C raft-R-mate vents *22.3sq.in. (17% more)*: http://www.owenscorning.com/around/ventilation/pdfs/VentSure.pdf
I’d use the H.D’s plastic one that self-extinguishes in -5 seconds, with *25.3sq.in. (35% more)*: http://www.bergerbuildingproducts.com/productsAccuvent.html

The basics: http://bct.nrc.umass.edu/index.php/publications/by-title/preventing-ice-dams/

Start with your own visual diagnosis: http://www.homeenergy.org/consumerinfo/roofs.php

Be safe, Gary


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## Wildie (Jul 23, 2008)

Central Mortgage and Housing in Canada has researched this problem thoroughly! Here's a link to a good article about this problem.

http://www.cmhc-schl.gc.ca/en/co/maho/gemare/gemare_001.cfm

A quote from this article! "If you have properly sealed the attic you should not need more attic ventilation. Attic ventilation is overrated. In winter, the cold outside air cannot hold much humidity or carry moisture away from the attic. In summer, attic temperatures are more affected by the sun and shingle colour than by the amount of ventilation"


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## Grumpy (Dec 12, 2003)

Wilde, That quote you entered pretty much goes against everything any other orginizational body is saying including HUD and the FHA in addition to ASHRE, IBC, as well as the University of IL and most shingle manufacturers. 

With proper ventilation, the color of the shingles doesn't matter much to the interior temprature of the attic. A properly ventilated attic will evacuate that difference. However yes the surface temprature from a white to black shingle could easily be 40 degrees F. But surface temprature doesn't necessarily equal interior temprature.



GBR, In regards to "burning toxic gas", if you are worrying about that, you have bigger problems than your attic ventilation.


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## handy man88 (Jan 23, 2007)

Grumpy said:


> Wilde, That quote you entered pretty much goes against everything any other orginizational body is saying including HUD and the FHA in addition to ASHRE, IBC, as well as the University of IL and most shingle manufacturers.
> 
> With proper ventilation, the color of the shingles doesn't matter much to the interior temprature of the attic. A properly ventilated attic will evacuate that difference. However yes the surface temprature from a white to black shingle could easily be 40 degrees F. But surface temprature doesn't necessarily equal interior temprature.
> 
> ...


What was your main reason for going with blown fiberglass vice cellulose?

Do you buy into the claim that the R value of fiberglass drops by 50% as temps drop below freezing?

What R value do you have in your attic?


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## Gary in WA (Mar 11, 2009)

Simpson and McPherson25 found
that white roofs were up to 36°F (20°C)
cooler than gray roofs, and up to 54°F
(30°C) cooler than brown roofs. Cash and
Lyon26 have recently shown through
computer modeling that *shingle temperature*
is more strongly a function of geographic
location, the direction a roof
faces, and surface color than ventilation.
Venting cools shingles, but the cooling
effect is not strong.


 By 1967, the “cold roof ” concept had been introduced, but it was based on a combination
of measures. cathedral ceilings are presented in Tobiasson et al.22 for various roof slopes, airway heights and insulation levels. These calculations do not consider the effect of wind, air leakage up through
the ceiling or heat lost up through the snow. They concluded that the need for ventilation is related to the
amount of snow to be expected in the area and the amount of insulation in the ceiling. In Philadelphia,
Washington, D.C. and Chicago, roofs with at least R20 (3.5 m2kW) need not be ventilated. In Madison,
*Heat loss into attics from air leaks, ducts or flues can lead to ice*
*dams, even when the attic is vented.*
Baker15 stated that for a permanent solution to ice dams, “consideration must be given to more adequate roof or ceiling insulation, ventilation of air spaces above the insulation, and moderation of inside temperatures.” He observed that on insulated buildings, ice dams form at outdoor temperatures above 15°F (–9°C). Latta16 recognized the importance of air leaks and recommended attic ventilation, but only after “blocking all passages by which warm air can leak into the space below the roof.” Wolfert and Hinrichs17 only briefly mentioned ice dam minimization in their manual on attic ventilation.
Grange and Hendricks18 authored the first publication that fully focused on ice dams. They emphasized a combination of attic vents at the eaves and ridge and minimization of all attic heat sources. The importance of attic heat sources strongly emerged in a recent study of 33 houses in Ottawa, ON, Canada.19
All 16 houses with ice dams had interior chimneys and their Wis., Boston, and Sioux Falls, Idaho, the minimum amount of insulation increases to R-30 (5.3 m2kW), and in Minneapolis and Portland, Maine, it increases to R-40 (7.0 m2kW). In Marquette, Mich., and Bangor, Maine, all roofs, no matter how
well insulated, need ventilation to avoid ice dam problems. From: http://www.fpl.fs.fed.us/documnts/pdf2002/rose02a.pdf 

"GBR, In regards to "burning toxic gas", if you are worrying about that, you have bigger problems than your attic ventilation."----- missed you completely... 



30-50% at 60-70* under certain conditions: http://www.osti.gov/bridge/purl.cov...333C48298EB4?purl=/390620-AFowQ8/webviewable/



Be safe, Gary


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## Wildie (Jul 23, 2008)

Grumpy said:


> Wilde, That quote you entered pretty much goes against everything any other orginizational body is saying including HUD and the FHA in addition to ASHRE, IBC, as well as the University of IL and most shingle manufacturers.


 I wouldn't dispute that it goes against what has been the standard methods! 
Makes one wonder how this will end up after the dust has settled!
CMHA is staffed by very crdible scientists and of course financed by the Canadian government.
These guys aren't a bunch of rabble rousin' yahoo's. They are the guy's that are setting Canadian standards for construction!


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## MJW (Feb 7, 2006)

Imagine that......scientific data that contradicts itself from one study to another.......

GBR, your quote is for "cold roof" or "hot roof", which is not ventilated. It's parallel board construction with no venting.


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## Grumpy (Dec 12, 2003)

GBR it didn't miss me. Your house is on fire. Get out. Everything's going to burn, stop worrying about your attic ventilation and get out quick. LOL it's not like those baffles would be the ONLY foam in the house, couches, chairs, mattresses... any of which have tons more foam and toxuc gas than foam baffles. I am not disputing your comment, it is totally true, however not worth further discussion so it's sooo far out there. I'd not make a decision on a foam baffle based on my house burning down, if that were the case I'd have them made out of some kind of class A material.


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## piste (Oct 7, 2009)

Joe F said:


> It seems that once every 5 years or so, we have an ice dam issue. My attic is pretty well insulated, so I believe that my ice dams are caused by a combination of temp (30-35) and sun warming near the peak of the roof. Melting starts, and the water runs. The north side of my house gets little to no direct sun in the winter which causes refreezing down near the gutter. Does this theory make sense? What can I do? Gutters are full of ice.


Hunh...running at two pages in this thread now. I've read every post and conclude (incorrectly??) that actually there is virtually NOTHING that one can do to deal with the large volume of ice frozen in gutters and downspouts in virtually every home in the mid-Atlantic right now??? Is there ANYTHING that folks can do right now or no?

All the info about ventilation and insulation is useful..and indeed more of both is better. However, as was stated in the OP regarding sun warming I think there are very few and far between any houses in the mid-Atlantic that are NOT dealing with this issue right now...insulation and ventilation ...or not. 

I've been knocking down the icicles while reaching out second story windows...goal there is to reduce weight pulling on gutters. But one needs to be careful with that so as not to rip off gutters or downspouts. Also been thinking of trying the "reach out the window with the blow torch" to reduce some additional volume of ice/weight but I carry no delusions that will "fix" the overall issue. And the cautions with that method go without saying. There's no miracle cure. I think something that would slowly warm gutters and downspouts would be great...but know of no such product.

ETA: Sorry...correction...now 3 pages to the thread with this post!!


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## Big N8 (Oct 28, 2009)

piste said:


> I think something that would slowly warm gutters and downspouts would be great...but know of no such product.



What about this second post??????



Big N8 said:


> We have the very same issues here in MN. The refreeze is just a part of life. Some use a heated cord to keep the ice from forming on the eves.
> 
> http://www.heatersplus.com/roofcable.htm
> That link is good stuff to use.


Looks like that product right there will warm your gutters just fine.


The issue all the people in the Atlantic may be having could be from not venting the roof enough. It should be the same temp in your attic as it is out side bottom line. If that is not the case you may have an issue.


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## longshanks (Jul 23, 2009)

I'm dealing with the same problem. What can YOU do? Based on what I've learned so far I'd say:

- seal any air leaks between the indoors and your attic
- ensure you have adequate insulation between ceiling and attic
- ensure that there is adequate soffit and gable or ridge ventilation to carry away any heat that is escaping.

Depending on your level of ability, you can do most of this stuff yourself, if you can get to it. It's easier once the ice melts.

The ice in your gutters and downspouts is mostly a symptom of a hot roof, although some of it is caused by the natural freeze/thaw cycle. The only surefire way I'm aware of to keep gutters/downspouts clear would be to lay some electrical heat cables in them and turn them on occasionally.

On my house, I've sealed the air leaks and insulated like crazy, but still getting some ice damming. I'm hoping that adding a ridge vent this year will cool the roof down a bit more and reduce ice dams even more.

good luck


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## piste (Oct 7, 2009)

Big N8 said:


> What about this second post??????
> 
> 
> 
> ...


I did see that....I'll have to look into that product a bit more. From the picture it looks like it's primary design is on the roof as pictured though it IS called "roof AND *gutter*". Just don't know how I'd attach that securely along a gutter and/or downspout. Personally I would NOT want to just lay it in the gutter as I don't want to contribute to gutter debris clogging. Also...that is a preventative measure...and possibly a very good one...but right now I (and millions of others) need a CURATIVE solution. ETA: Actually...maybe I could get some of that...and wrap it up the gutter now..might begin to help. Also..I should read a bit more before typing..further down the page for that product they give a nice diagram of how to attach.

Admittedly the currrent conditions in mid-Atlantic are unusual....but I reiterate my contention that NO amount of insulation and venting would eliminate them. Throughout the wide region I travel in ...EVERY house is visibly afflicted...just some more than others. With all the snow we've had...dark roofs...moderate daylight or even full sun...daytime temps anywhere from high 20's and up....and you got ice buildup along the periphery of your roof...irrespective of how insulated and vented your attic is. Only difference from one house to the next is whether your roof is adequately designed and built to avoid internal water leakage under these conditions...or not.

On the other hand....there are parts of the world that regularly see what mid-Atlantic has seen in the last few months....wonder what they do...lemme guess...insulation and ventilation!!:thumbsup:


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## MJW (Feb 7, 2006)

piste said:


> On the other hand....there are parts of the world that regularly see what mid-Atlantic has seen in the last few months....wonder what they do...lemme guess...insulation and ventilation!!:thumbsup:



And maintenance. We do a few buildings and houses every year. With the freeze-thaw cycles we have, there is no "permanent fix" for every building or home.

Some people prefer to not go on their roof in winter. Some prefer not to cut their own grass. They have to hire someone to do it for them. Hopefully they hire a professional.


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## handy man88 (Jan 23, 2007)

longshanks said:


> I'm dealing with the same problem. What can YOU do? Based on what I've learned so far I'd say:
> 
> - seal any air leaks between the indoors and your attic
> - ensure you have adequate insulation between ceiling and attic
> ...


If you don't have a ridge vent now, what do you have?


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## piste (Oct 7, 2009)

*Retraction*

I have to admit that I now think I was incorrect above when I stated NO amount of insulation and ventilation would eliminate the problem. The problem may not be possible to eliminate...but I now agree that insulation and ventilation can significantly reduce the issue. My reason for this change of heart is as follows. I live in a fairly new housing development. There are two houses that were recently completed but are not occupied...and guess what....they have pretty much NO icicles on them.


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## handy man88 (Jan 23, 2007)

piste said:


> There are two houses that were recently completed but are not occupied...and guess what....they have pretty much NO icicles on them.


Which probably means their heat was probably not turned on but in newer homes, which typically have at least 2 zones, you're going to see a gas furnace in the attic along with warm flues.


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## piste (Oct 7, 2009)

handy man88 said:


> Which probably means their heat was probably not turned on but in newer homes, which typically have at least 2 zones, you're going to see a gas furnace in the attic along with warm flues.


Exactly. I have a furnace in my attic as well....so it's tough to get enough ventilation to dissipate that heat. Will have to work on it though.

On my way to work today I saw a house with a very large open front porch with fairly large roof...with many icicles hanging down...so I think I'm back to the position that in some circumstances no amount of insulation and ventilation will eliminate the problem...just improve/reduce it.


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## Wildie (Jul 23, 2008)

piste said:


> Exactly. I have a furnace in my attic as well....so it's tough to get enough ventilation to dissipate that heat. Will have to work on it though.
> 
> On my way to work today I saw a house with a very large open front porch with fairly large roof...with many icicles hanging down...so I think I'm back to the position that in some circumstances no amount of insulation and ventilation will eliminate the problem...just improve/reduce it.


 This is exactly what the scientists at CMHC have said! ( see my post #24 )
Ventilation is questionable! Because the cold air cannot absorb any moisture!
To keep ice from forming on the underside of the roof, infiltration of warm, moist air from the interior of the house must be prevented at all costs!
Ice dams form when snow on the roof melts from heat from the sun and from the building. The water runs down the roof until it encounters a cold section above the soffits where it freezes. It then builds up and traps the water.
To my mind, in our climate, we should quit building eaves and soffits, or plan on allowing heat into the soffits to keep the ice melted!


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## MJW (Feb 7, 2006)

You will never eliminate heat being transferred from the living space to the attic. That is why we MUST have eaves and soffits to ventilate the attic.


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## Wildie (Jul 23, 2008)

MJW said:


> You will never eliminate heat being transferred from the living space to the attic. That is why we MUST have eaves and soffits to ventilate the attic.


 From what I have read in this discussion, ventilation is a waste of effort!
We cannot stop heat loss into the attic, all we can do is minimize it! So, if eaves and soffits are problem, why not quit using them!


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## Shamus (Apr 27, 2008)

Good thread.

I do have some firsthand experience with ice damming. I have an 1898, 2 story with a hip roof and 28" soffit all around. Last year I had icicles 5' long all along the gutter on most of the house. The entire gutter had ice damming.

I did a tear-off new roof this past summer. A few things I did that probably helped to reduce the problem of ice damming. First I added a ridge vent. It's only 8' long. Second I installed 2" X 16" x 4’ rigid foam panels between the roof rafters and then blew in cellulose under those, 14" thick. Third, I cut in soffit vents all around the perimeter.

This winter in my area of Ohio we have seen heavier snow and temps are about in the normal range. Right now, 16” on the ground and below freezing for the last 30 days. The last few days it been up to 30-34 degrees and by the weekend they say a high of 36. The snow on the roof is melting on the east side and some on the south. No ice buildup yet and I do hear it dripping in the downspouts. The roof is still covered with 8-10” of snow.

I doubt that I will get through the thaw/freeze/thaw cycle without some ice build-up but we shall see. I am positive the venting of the roof has helped. At least as I compare my home to my neighbors. It certainly did its job through the hot summer heat. And it made a huge difference in the temp of the rooms on the second floor for both seasons.


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## piste (Oct 7, 2009)

Shamus said:


> Good thread.
> 
> Second I installed 2" X 16" x 4’ rigid foam panels between the roof rafters and then blew in cellulose under those, 14" thick. Third, I cut in soffit vents all around the perimeter.
> .


So if I understand correctly....you put up these panels between the rafters in a way that created a gap between the panel and the roof and then blew the cellulose into that gap?? 

You are touching on a thought that I had...which is...Even though my attic floor is pretty well insulated and I have decent ventilation....I COULD put some insulation in the roof too...to keep any heat in the attic from dissipating to the roof alternatively letting it vent out through the venting. Being as I have a furnace in my attic there is no amount of floor insulation that will eliminate attic heat in winter. Now all that being said....insulating the roof in addition to the floor (of course without blocking the venting) is not only expensive but in a way pointless because....at SOME point the snow WILL melt. doing all of the above will just slow the process down and not sure what degree of a "Fix" it would be for the ice damming and icicle issue anyway.


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## Shamus (Apr 27, 2008)

piste said:


> So if I understand correctly....you put up these panels between the rafters in a way that created a gap between the panel and the roof and then blew the cellulose into that gap??


No, sorry I should have explained it better. I installed the W foam panels made specifically for creating an air space between the roof and insulation. You want to have air-flow, so no insulation. 

The purpose of these are to make sure you don't block the air-flow when you stuff/blow insulation in the attic.

I know, clear as mud. I'll find a photo in a minute.


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## handy man88 (Jan 23, 2007)

piste said:


> So if I understand correctly....you put up these panels between the rafters in a way that created a gap between the panel and the roof and then blew the cellulose into that gap??
> 
> You are touching on a thought that I had...which is...Even though my attic floor is pretty well insulated and I have decent ventilation....I COULD put some insulation in the roof too...to keep any heat in the attic from dissipating to the roof alternatively letting it vent out through the venting. Being as I have a furnace in my attic there is no amount of floor insulation that will eliminate attic heat in winter. Now all that being said....insulating the roof in addition to the floor (of course without blocking the venting) is not only expensive but in a way pointless because....at SOME point the snow WILL melt. doing all of the above will just slow the process down and not sure what degree of a "Fix" it would be for the ice damming and icicle issue anyway.


With your furnace in the attic, which is quite common, I spoke to a neighbor today who has extreme icicicle issues who said that she's resorted to keeping the thermostat @ 60F and not doing laundry during the night time.


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## MJW (Feb 7, 2006)

Wildie said:


> From what I have read in this discussion, ventilation is a waste of effort!
> We cannot stop heat loss into the attic, all we can do is minimize it! So, if eaves and soffits are problem, why not quit using them!


Venting is a must, especially attic spaces.

http://www.buildingscience.com/documents/insights/bsi-035-we-need-to-do-it-different-this-time


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## Wildie (Jul 23, 2008)

MJW said:


> Venting is a must, especially attic spaces.
> 
> http://www.buildingscience.com/documents/insights/bsi-035-we-need-to-do-it-different-this-time


You may have missed my post #24, where I included a link to a CMHA article!


http://www.cmhc-schl.gc.ca/en/co/mah...gemare_001.cfm

A quote from this article! "If you have properly sealed the attic you should not need more attic ventilation. Attic ventilation is overrated. In winter, the cold outside air cannot hold much humidity or carry moisture away from the attic. In summer, attic temperatures are more affected by the sun and shingle colour than by the amount of ventilation"

This article touts that leakage into the attic from the inside of the house is the culprit and our efforts to correct this is more relevant, over trying to vent it with cold air.
If the air cannot absorb the moisture, it will just condense against cold surfaces and cause problems.
Ventilation has been a 'sacred cow' and now the scientists at CMHA refute its value!
The roofers won't like this as it would mean a major loss of income to them!


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## BamBamm5144 (Oct 6, 2009)

Wildie - You must have skipped over post #25 where Grumpy told you that the CMHA article goes against every other reputable resource.

Your article states that if you have properly sealed the attic you dont need any more ventilation. Majority of homes dont have a properly sealed attic. Also, the article indicates that you still must have some sort of proper attic ventilation. I dont know how this will be a major loss of income for roofers when it is not even a big source of income in the first place.

Ventilation is a funny thing. It is not even the roofers responsibility but all too often we are the ones who have to address the problem and offer the appropriate solution. It is almost like the Heating *Ventilation* Air Conditioning guys just sort of want to get rid of the V and just be known as HAC.


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## longshanks (Jul 23, 2009)

I'm surprised by CMHC's claim that ventilation doesn't matter. The prevailing view in my area is that it's not something you should overlook. 

In response to Handy Man's question -- right now I have gable vents and a couple of those mushroom vents (not sure what the proper name for them is).

I've gone over the entire attic floor and done my best to seal all air leaks there, and based on observations thus far, I've managed to reduce a fair bit of heat loss, and the resulting ice dams. A building inspector looked at my house and said that the heat loss may be attributed to skylights, and the best way of dealing with it would be to stop air leaks (done), insulate the skylight tunnels (done), and then install a ridge vent to allow attic heat to escape. Despite all the insulating I've done, the attic temps are still warmer than outdoor temperatures, and I am still getting some ice buildup on the shingles.


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## Wildie (Jul 23, 2008)

BamBamm5144 said:


> Wildie - You must have skipped over post #25 where Grumpy told you that the CMHA article goes against every other reputable resource.
> 
> No, I did read it and the very point of my posts is to bring attention to the fact that we may be misinformed about the value of ventilation. Makes me wonder how reputable, the reputable sources are?
> 
> ...


 In my area, its the roofing and siding contractors that look after the attic ventilation. The HVAC guys don'y seem to like climbing ladders! :no:


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## BamBamm5144 (Oct 6, 2009)

Wildie - Who knows if any sources are truly credible on anything. I keep hearing about Global warming but we have been having record amount of snowfalls here in the states. Every few years there seems to be a new thing so I do agree with you there.

However, I have worked on many homes that were improperly ventilated and had ice damming problems. After correcting the problems, they no longer have the same problems as they used to. If your home was purchased in 1948, your roofer may have very well been right. My home is from 1979 and although it at least met or succeeded all minumum building standards at the time, it would be unacceptable if this same house was built now.

Did you have ice problems before the roof was redone? If so, did re-doing the roof and ventilation help to reduce or completely eliminate any ice problems?

One more point here. Shingle Manufacturers try do everything possible to not hold any liability if their product fails. One thing that voids any warranty is improper ventilation and each manufacturer has their guidelines to the appropriate amount.


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## Wildie (Jul 23, 2008)

BamBamm5144 said:


> Wildie - Who knows if any sources are truly credible on anything. I keep hearing about Global warming but we have been having record amount of snowfalls here in the states. Every few years there seems to be a new thing so I do agree with you there.
> 
> However, I have worked on many homes that were improperly ventilated and had ice damming problems. After correcting the problems, they no longer have the same problems as they used to. If your home was purchased in 1948, your roofer may have very well been right. My home is from 1979 and although it at least met or succeeded all minumum building standards at the time, it would be unacceptable if this same house was built now.
> 
> ...


 This global warming thing is a farce generated by those who hope to cash in the Energy Credit scam. ( another subject).
Where I live ,we have been having an easier winter, but this has been preceded by harsh winters for ten years.

I never have had any ice problems, although in conjunction with the new roof, I installed anothe R20 over the existing insulation. The total insulation must be approaching R40. I made an effort to seal off any infiltration into the attic also!

Roofing warranty's are questionable, under the best of circumstances. Roof's are not like something mechanical that fails completely! 
Roof's deteriorate over the course of time and any argument would be, if it failed sooner, rather than later.
I have never ever heard of anybody, ever making a warranty claim that was accepted.
You buy a 20 year roof and 10 years you have a problem. Who's going to go to bat for you! Where I live roofing contractors come and go with wind! So, you can't count him for help! 
It may be possible to hire somebody who has credentials that would make him a credible witness. But would it be worth the bother. 
A 20 year roof that cost $5000, that has failed after 10 years may be elligable $2500 in compensation. However, your expert counsel may cost you that much, so whats the point!
In my mind, I don't place much value in roofing waranty's.


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## MJW (Feb 7, 2006)

R38 is code with the IRC in ceilings, although any house without energy trusses will not get anywhere close to R38 on top of the walls in the attic. 

With the net anyone can find a "study" that proves their point. 

We used to seal crawl spaces, roofs, walls, etc.... in the past, didn't work. They used to seal and heat roofs in the 60's, it just didn't work. The new system with venting and insulating works.


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