# Nothing Is Stopping Ice Dams



## SLSTech (Jan 19, 2021)

Well I would start here - BS4D: Ice Dam’s, Icicles & Attic Condensation, Oh My… (thehtrc.com) but it sounds like they never did any air-sealing, just blew & went. Another item is others might not get them as they have so much heat loss it melts it all or they have little stoppers that go on the roof to help prevent it from sliding. Are you shaded & they aren't? Truly need to know location & what type of snow load you get as you will still get some no matter what you do


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## 3onthetree (Dec 7, 2018)

I didn't quite follow how the loft and garage is now, but basically you need an attic space that remains as close as possible to the outside temperature. You do that by insulating and air sealing the ceiling plane adequately. Then on metal roofs you install snow guards, of which there are a few versions.


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## Lee698 (Jan 23, 2021)

The metal roof has diverters. This is how the ice builds up to such great thickness.

I live in upstate NY, lake-effect, snow-belt capitol. 

The entire back of the house gets full sun----when we have it. This area is known for grey, cloudy skies. That said, ice and snow will still obviously melt given the right conditions.

The front of the house, no sun. 

The dams are equally bad, front and back, which I find odd since the front gets no sun. (Well...the ridge gets sun though. That might be enough for the front dams????)

It's unusual that we have gotten so little snow this year so far, so I'm surprised with the works that's been done that I'm seeing mini-dams with just a few inches of snow.

Thanks for the help, btw.


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## Chris616 (Dec 31, 2019)

You’re using the term “ice dam” to refer to something different than what I do, I think. You haven’t mentioned water leakage through the roof, which is the principal problem of what I consider to be an ice dam. Please review this page so that we can understand better the issue that you’re having. Is that the problem, or are you instead concerned about snow and ice sliding off the metal roof and the damage that can do to gutters, siding, people, etc.?

Chris


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## Bud9051 (Nov 11, 2015)

I've seen those "ice curls" and when they come down they can do some damage.
I have made a lot of improvements on my cape to prevent ice dams, almost there. But I have learned a lot and I'm a retired energy auditor so really a good understanding now.

The advice to insulate and air seal is good, but without air sealing the heat passes right through your blown in insulation.

Pictures would help so we can see what you see.

With front and back being very similar it implies the heat that is melting the snow is coming from the attic. A few pictures of what is up there will help.

Air leakage can often involve large and small leaks. With new insulation it can be difficult to access and seal the small ones. But large leaks are worth the effort. However your weatherization program SHOULD have done some air sealing. Contact them and ask, it was a must and they know it.

Those pictures will help.

Bud


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## de-nagorg (Feb 23, 2014)

I have a warning for all readers. 

A few years ago, a local lady was out in winter, knocking off those Ice Dams, on her home, with a push broom.

The thing dislodged, and covered her and she suffocated , before anyone found her.

So be very careful, when they form, and never get under them. 

As for your problem, you have heat loss into your attic somewhere, here the Weatherization people, use a pressure test, to see where that is, and seals up that area, to prevent any heat loss into the attic.


ED


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## Lee698 (Jan 23, 2021)

Okay...from the roof graphic supplied, the dammed water would be about where the diverters are. As snow melts/refreezes, ice builds, lather, rinse, repeat, until you have several inches of ice built up from the edge of the roof back to behind and/or just behind the diverters. This happens the entire length of the house, front and back, including garage.

Air sealing is something no one's mentioned, and I didn't know enough to ask. I'll see if I can get info from the state's program, but if they were supposed to do it and didn't, or thought they did a good enough job..... I'll also run that by my contractor.

Pictures would help but I don't have a way to do it.


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## Lee698 (Jan 23, 2021)

The weatherization program did a pressure test. Guess I should call and not only ask about air sealing but that test and why they didn't do this or that.

Those ice dams are truly a nightmare. They scare the hell out of me. 

Thanks, again.


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## Chris616 (Dec 31, 2019)

Hmm…it’s still unclear to me what the problem is that you’re trying to solve. Do you have any indication of leakage of water through the roof, suggesting that water is pooling behind a dam of ice on the roof?

If the problem that you’re trying to solve is snow/ice sliding off a metal roof, that requires a different solution to that involved in stopping the formation of ice dams. Our metal-roofed shop is completely unheated, so it isn’t internal building heat that causes the fairly gnarly curls to come off of it.

Chris


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## Lee698 (Jan 23, 2021)

The old roof leaked. I can only assume that the metal roof took care of that issue.

The other day I read something about chimney (and roof vent?) seals being a potential cause of heat loss (and I assume, therefore, leaks).


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## Bud9051 (Nov 11, 2015)

When talking about "leaks" I'm talking about air leakage between house and attic not water leaks through the roof. Did the weatherization company give you a report with details?

Bud


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## Lee698 (Jan 23, 2021)

Another poster was asking about water leaks. 

The weatherization work report reads: filter slot cover, vent bath fan, misc. air sealing, spray foam attic, hatch improvement.

As for the bath fan venting: weatherization folks said the bathroom wasn't vented in the first place, so they vented it, but when I gutted the bathroom last year, the plumbing company said it hadn't been vented to the outside, so they corrected it.


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## Bud9051 (Nov 11, 2015)

If the weatherization crew didn't vent it to the outside I seriously question their competence. I've known a few and talked with many and good ones do the job right.
Hoping for pictures.

Bud


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## Lee698 (Jan 23, 2021)

If I see my neighbor out today or tomorrow I'll ask him to take a pic.

Not saying you can't be young and do a good job, but experience counts for a lot. The weatherization company sent out two very young guys to do the actual work order.


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## MTN REMODEL LLC (Sep 11, 2010)

Some pictures would help....But

1) Is the dam build-up principally over/on your eaves.....the part of your roof that overhangs the structure....and how big are the eaves......(how far do they overhang) That generally is indicative of heat loss to an attic that melts the snow untill it gets to the colder eaves.

2) Both insulation and air sealing is important to prevent heat loss to the attic. Ceiling can lights can be a very significant source of heat loss to an attic.

Heat gain in the attic can also be a function of the sun heating the roofing, what color is your metal roof...is it standing seem....the sun heats exposed roofing with heat that rises in your attic, melting snow up high on your roof that subsequently freezes as it rolls down to cooler parts of your roof (eaves)

3) In the alternative if a warm attic is the issue, you have the alternative of cooling off the attic to basically outside temperatures. You state above:

"1) Installed attic baffles. Originally was going to install in every other joist but installed in every one. My understanding is that the baffles would direct the heat to the ridge. 2) Sealed off the original outside vent to prevent heat escaping to the garage."

3 ) The baffels are good, IF YOU HAVE A RIDGE VENT or alternative high vents to disipate that heat. Gable vents help also.....otherwise you are just heating the high part of your roof that just freezes as it runs down to the cooler and lower eave parts .

Certain climatic conditions (winds and orientation of the home to the sun and roof valley structures creating areas that melt more sloowly or faster) can be prone to the buildup....snow builds in a shaded sturcture or over a ridge that melts slower than snow above it allowing the runoff to freeeze before running off the entire roof structure. Metal roofs have a tendence to slough snow to lower part of the roof....just becaise it's slippery.

Let us see some pictures.

I would almost say to put some good snow stops on your eaves and live with it ONLY BECAUSE YOU SAY YOU HAVE EXTENSIVE EXPERIENCE WITH NO LEAKS. Guess I would be reluctant that a standing seem would not eventually leak though.

Good luck...


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## Lee698 (Jan 23, 2021)

A neighbor is going to get a pic today or tomorrow. The sun is out today and there's melting so the mini-dams may disappear.

Contractor told me there was a ridge vent. Don't know about gables.

There are diverters on the roof, but only over man doors. The dams go from edge of roof to behind/just behind diverters, maybe a couple feet total, and run the entire length of house front and back.

The metal roof color is sage/olive green.

Snow stops: Are they basically the diverters already on the roof?


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## 3onthetree (Dec 7, 2018)

Lee698 said:


> Snow stops: Are they basically the diverters already on the roof?


Diverters are straight metal pieces to direct water around your doors when there are no gutters:









The snow guards are little pieces screwed or epoxied onto the metal panel or the metal ribs (besides the rail type pictured another post) to hold the majority of snow/ice from sliding down:









Whether it's the sliding or the ice dam backup, the same heat escape causes both. What the normal sun will cause melting, and refreezing overnight, depends somewhat on the temperature swings and presence of sun. The heat escape, if worse enough, can cause it even if its cloudy or consistently cold that outside temp wouldn't cause melting.


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## Lee698 (Jan 23, 2021)

Wow, okay, so what I've heard called diverters are actually snow guards. I have those around the man doors rather than the diverters you pictured. Explains why they never diverted the rain and why you get wet. (I'll have to look for those on the neighbors metal roof once the snow melts. I don't ever remember seeing those.)

In my head, I'm thinking the diverters you pictured would still be a good vehicle for build-up. (Unless you mentioned that for another reason.)


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## Missouri Bound (Apr 9, 2011)

It takes a couple of things for ice dams to form.
When the attic temperature rises above the outside temperature snow on a roof will begin to melt.
This happens when the attic insulation isn't adequate and or the attic ventilation isn't adequate.
When this happens the ice forms over the soffit because it is cool but thaws behind the soffit.
The ice blocks the water from running off and it can penetrate the roof.
Depending on the type of metal roof you have this can be a serious problem, but usually it only affects shingled roofs (or tiled)
Your soffit needs to be vented with no insulation over the soffit.
Your attic insulation material needs to go over the exterior wall to the outside of that wall.
But if you have inadequate venting on the roof or the ridge the soffit ventilation cannot work.
How is your metal roof vented?
I personally know a couple of metal roof installer who NEVER put roof vents in because they say they are not needed.
Adequate, properly installed ceiling insulation is the best way to prevent ice dams from forming.


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## Lee698 (Jan 23, 2021)

House pics aren't close enough to see the mini-dams. (A lot melted today with the sun and higher temp, anyway.) If close up, you would still see ice formed between the vertical ridges.

New contractor said the soffits were all clear. 

The roof pic below is not my roof, but the ridge vent along the top is what mine looks like.


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## Dave Sal (Dec 20, 2012)

Even though someone installed baffles in the attic for the soffit vents, have you actually determined that there are working soffit vents in place? The reason I ask is that this past summer I was helping my parents replace their TV antenna coaxial cable in their attic, and I noticed that it was blazing hot up there in spite of them having adequate roof vents and a power attic vent. The soffits had venting every few feet, or so I thought. Closer inspection showed the perforated aluminum soffit vents were simply installed over plywood soffits. In about three places they actually took the time to cut the holes in the plywood for the vents. To a casual observer it looked like there was an appropriate amount of soffit venting when in fact there was almost none. The attic needs to "breathe" with cool air being sucked in by the soffit vents and replacing the hot air in the attic which flows out the roof vents. 
My own house, a tri-level, which I bought as new construction, had zero soffit venting when I bought it. I didn't know much about this stuff but a couple years later I ended up cutting 50 soffit vent holes (25 lower level and 25 upper level) in the plywood soffits and adding vents. I used to get icicles all the time and the snow would melt on the roof right away. Now, with about R60 insulation and adequate venting, my roof stays snow covered until the temps warm up outside or the sun melts it.


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## Lee698 (Jan 23, 2021)

A neighbor just told me yesterday that their soffit vents were as you described with your parents house. Neighbors construction was done the same time and identical in structure to mine. They had plywood with a few drilled holes. My new contractor said the soffits were clear, but I don't know if he checked more than one area. I'll give him a call.

The old contractor, who put the metal roof on...I don't know what he did or didn't do.

Thanks to all for your input. Learned a few things. Very appreciative of the help.


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## Bud9051 (Nov 11, 2015)

We are slowly getting there.
You said "They had plywood with a few drilled holes. " If vents are the round pop-in style that may be part of your problem. I'll expand. Pop-in vents (TBD) provide very little air flow, some as low as 19% NFA (net free area). A review of the needed ventilation area and a determination as to what you actually have is necessary. 

Do the baffles that were installed run from soffits all the way up to the ridge? They should only extend above the installed insulation.

Can you get a picture of that ridge vent from inside the attic?

Bud


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## Lee698 (Jan 23, 2021)

Contractor didn't take the baffles all the way to ridge. I'd guess the baffles went about as far as the 14" insulation; when I saw the baffles, I touched them to see what they were like since I'd never seen baffles, and can only estimate from memory their length. 

I can't get into attic to get an inside view of ridge (short of paying a handyman to take a picture). 

The weatherization people (the young guys) took pics to show me all the light coming into the attic from the outside, though I don't recall any specifically of the ridge. Didn't ask for them to forward the photos, either. Didn't think they'd ever come in handy.


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## Bud9051 (Nov 11, 2015)

Never too late to ask for those pictures it's just a few clicks if they still have them.
Can you confirm those round vents described? Maybe a picture?

Bud


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## Lee698 (Jan 23, 2021)

I'll see if those pics still exist....

As for the round vents/venting in soffits, I can only ask the contractor what was inside the soffits and how many areas he checked. I'll get on that tomorrow.


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## Lee698 (Jan 23, 2021)

The pics from the weatherization company are gone.

Talked to the contractor who said the ridge vent is open as are all the soffits. 

Thus far, everything seems to be the way it's supposed to be. Think I'll have to give into heating cables.


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## Dave Sal (Dec 20, 2012)

Don't take the contractors word for it. It should be relatively simple to take a flashlight and shine it up under the soffits and see if you see an actual hole into the attic. If it's like my parents house, you'll see solid plywood instead.


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## Lee698 (Jan 23, 2021)

I was thinking last night that I'd find something to poke up through the soffit holes, lol.


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## Bud9051 (Nov 11, 2015)

How many of those round vents do you see from the outside? Pictures? 
How many sq ft is your house, then I can calculate how much venting is needed?
Did you get a report from MASS SAVES?

As a note, I see a few homes up here in Maine who went with the heating cables, I should have grabbed some pictures. One had ice columns from the roof all the way to the ground at the bottom of every "V" formed by the cables.
Also, once you install those cables you can no longer rake the snow off or have someone do it for you. I see so many newer homes that have followed the rules and have a nice covering of snow without a single icicle. 

Don't give up yet.
Bud


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## Lee698 (Jan 23, 2021)

With the snow caps on the metal roof, you can't roof rake, anyway.

MASS SAVES? Think you mean the weatherization company? I'm in upstate/central NY and the company no longer has the pics. 

The house is 864 sq ft., about 50' long. As for the soffit vents (I assume that's what you mean by round vents): There are about 46 sections of soffit on each side; it alternates three "columns" of solid sections of soffit, then three sections of columns with holes.(Each column is about 4" making each section about 12") Math doesn't add up exactly. Each three-column section has 243 vent holes.

A lot of pics on the internet show all soffits on a house having vents, whereas mine is every other. I poked through a few holes with a bamboo skewer and the skewer went all the way through. I'll try to poke some other sections later. 

The pic below off the internet shows alternating soffit vents, though mine alternate three-column sections with no holes, then three-column sections with holes. (With so much work left to do on the house, I had to cut back on expenses when the husband died so the first thing to go was the cell phone.)

Why would ice build up in the V of heating cables, unless they weren't turned on? 

Used the live in Maine, mid-coast. Miss it. Was an analyst with a government contractor outboarding naval guided missiles. That was a lot easier than this ventilation stuff, lol. But I'm learning....


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## Lee698 (Jan 23, 2021)




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## Bud9051 (Nov 11, 2015)

Mass Saves, sorry my confusion different thread.
I also mistook your description of having round holes as being the pop-in style, yours are not. The vents pictured should be just fine with adequate net free area.

You asked "Why would ice build up in the V of heating cables, unless they weren't turned on?" Mother nature can be cruel and can deliver just the right temperatures where snow will melt for whatever reason and as it runs off it freezes.

As for them not having those pictures, that is just a less complicated way of saying they won't give them to you. They keep those records for many years in case there are complications where they need to prove what they did, like an insurance company trying to blame them for some resulting damage.

Additional question, I assume you have a basement? Is the ceiling finished or open beams where you can see the bottom of the floor above. If open you can look for some of the larger air bypass opening. The energy company would have done their air sealing from the attic but smoke test from the basement would tell you if air is still flowing upwards. More details if needed.

Bud


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## Lee698 (Jan 23, 2021)

We live around a swamp so most houses are on slabs, like mine.


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## hornetd (Oct 30, 2014)

Bud9051 said:


> We are slowly getting there.
> You said "They had plywood with a few drilled holes. " If vents are the round pop-in style that may be part of your problem. I'll expand. Pop-in vents (TBD) provide very little air flow, some as low as 19% NFA (net free area). A review of the needed ventilation area and a determination as to what you actually have is necessary.
> 
> Do the baffles that were installed run from soffits all the way up to the ridge? They should only extend above the installed insulation.
> ...


Bud 

Help me out here. I'm a retired electrician and the only roofing I have done is to my church's summer camp accessory buildings. The Camper cabins have metal roofs that were installed by real roofers. Those, of course, have no snow stops because we don't care if the snow slides down during the winter when no one is using the cabins. The cabin windows have snug fitting awning shutters that are closed in the off season. The windows down each side of the cabins are screened not glazed. The metal roofs on the camper housing cabins is to guard against falling limbs, customarily called widow makers by those who work in the forest in winter, penetrating the roof and injuring campers when the wind gets up. All of that means that I do not have experience with metal roofs over heated buildings. 

When you say, about the baffles, that "They should only extend above the installed insulation." can you tell me why that would be? I thought those went up to the ridge to chill the underside of the roof deck with the cold air coming in through the soffits so that it would not get heated by warm air from inside of the home. From what you are saying I must be wrong about that. What purpose do the baffles serve? Do they keep the insulation from going all the way up to the roof decking and thus blocking the flow of air from the roof vents? 

-- 
Tom Horne


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## Bud9051 (Nov 11, 2015)

With baffles run all the way to the ridge the warm air pools into the whole attic waiting to be pushed up by the colder incoming air, remember "hot air does not rise by itself".

With shorter baffles that incoming cooler air dumps into the attic and begins moving the warmer air up and out the high vents. You want the warmest air in the attic to be near the top where it can be exhausted.

It is not always possible to stop at the top of the insulation such as with a vaulted ceiling but those situations pay a penalty with reduced ventilation.

Also consider, if the vent space from soffit to ridge is filled with cold air you get zero air flow. Air flow depends upon the weight difference between warm and cold air so ironically we need warmer air as part of the ventilation process.

I can dig for more reasons but just the limited vent space is sufficient reason to not run the baffles all the way up. 

Bud


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## hornetd (Oct 30, 2014)

Bud9051 said:


> With baffles run all the way to the ridge the warm air pools into the whole attic waiting to be pushed up by the colder incoming air, remember "hot air does not rise by itself".
> 
> With shorter baffles that incoming cooler air dumps into the attic and begins moving the warmer air up and out the high vents. You want the warmest air in the attic to be near the top where it can be exhausted.
> 
> ...


I'm not trying to be a genuine PITA when I ask if the floor below the attic were properly sealed and insulated were would the warm air come from then? I was GUESSING that the baffles would take their heat from the metal roofing just above them as soon as it got warm enough to start melting the snow. The cold air coming in to replace the heated air rising out of the baffle channels would keep the lower end from melting and then refreezing wouldn't it. If the whole attic is cold there would be no melting to refreeze into ice dams. I'm only trying to follow how this particular system works. I'm retired out of 45 + years as an active volunteer firefighter and I have an associate of science in fire protection technology. I used to think that I had this thermal dynamics stuff down. Then along comes something like this to inject a good dose of humility into the mix. 

-- 
Tom Horne


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## Bud9051 (Nov 11, 2015)

Both sources of heat can play a role in forming ice dams, solar energy and attic heat.
As for the heat in the attic that can be due to air leakage from below and/or thermal conduction through the drywall. Air leakage from below is dominant if the insulation is minimal and it would take extreme efforts to get that leakage down to zero. Only homes that achieve those extreme results are air sealed as the home is being built and the total leakage is measured.

Baffles often limit the depth of the air space to around one inch where the experts suggest closer to 2 inches. The smaller gap with air films above and below limits the flow as does the length of that channel. But the baffles do not address thermal conduction through the rafters.

I'm not saying baffles running bottom to top isn't going to work, I just prefer to avoid the added effort and cost and to cool the entire attic.

Bud


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## APA (Jul 13, 2018)

I don't see any more ice damming than usual on metal roofs. I think some roof cleats would help. You have some air leaks going into your attic. You have a lovely small home. If I lived closer, I would come and crawl up in there and seal the leaks for you. This board sometimes gets too technical and goes way beyond what is practical for the average homeowner. Not everyone is a building scientist.


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