Every ice dam problem is actually an insulation problem, the saying goes.
fwiw
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Every ice dam problem is actually an insulation problem, the saying goes.
fwiw
I would say design in a lot of cases
For me it’s always at the eve, where there is little to no insulation in the soffits. The rest of my attic is ceiling blown insulated style. Most of the melt comes from heat from vents, or sun and ambient temps that are just over zero (like what would happen at unfrozen ground level under the regular snowpack. Water runs down to the roof above the soffit and where it freezes. By removing the snow from that section of the eve the water has a chance to run off, or do a freeze and sublimate cycle that wouldn’t happen under the insulating roof snow.
At least that’s my story and I’m sticking to it. Seems to work so far, and while not Tahoe or Mammoth Lks snowpack, we often get snowpacks over a metre in our yard for extended periods, heavy years with 1.5m or a bit more.
We got 2.5’ at 2600’ in the Sierra foothills over 2days. Just above snow line. Rear locking diff on the land cruiser, 4lo, 2nd gear start and it was able to pack down a track in our several hundred-foot gravel driveway enough for our light awd Toyota Matrix to get out. Small skid steer loader and tractors owned by neighbors moved the snow on our private road. Older kid and I shoveled off our deck and paved areas. I finally shoveled to dirt a route to the covered wood piles. Currently cannot full extend by dominant arm at the elbow, which I think is a result of shoveling. Anybody know which muscle is doing that? Bicep, tricep, or something else?
I’ve seen a lot of peeps in the higher Sierra shoveling off their roofs because there’s a lot of water rolling in for the next 14 days. Friend with an older a-frame in bear valley can’t close any interior doors anymore and apparently there is not much to do or put the snow to relieve weight off their roof short of plowing the roads to their place (snowbound community) and bringing in a large excavator and dump truck, which is not realistic.
Yup, generally speaking it’s insufficient attic insulation. https://icedamremovalguys.com/what-c...-dam-can-form/Quote:
Originally Posted by ötzi
Heat tape is some sad ass shit. It’s like when a fat guy starts putting his belt above his gut.
I had the last few feet of shingles removed, and replaced with powder coat metal. Lots of newer homes or commercial bldgs in Tahoe and Mammoth have this. Tends to shed the snow naturally when sunny or temps increase. Sometimes if I’m traveling for a month I’ll come home to 8 ft drifts on the roof. But no ice dam issues.
Not 100% effective. Our neighbor has been in his house for 15 years, and his roof has metal edges. Never had ice dam issues before, but last week his ceiling in his bedroom collapsed.Quote:
Originally Posted by frorider
It seems the only way to fully eliminate ice damning without removing snow and ice from your roof 100% is to live underground. ;-) I suppose a flat roof designed to hold all of the potential snow in your area is an alternative, but will then in turn create other issues.
Cold roofs may work, but are reliant on simple roof designs and maintaining a reliable plenum for air flow from eave to a high point like ridge or shedded soffit over the insulated cavity to remove excess heat. A snow covered ridge vent, for instance, eliminates the air flow.
There are constantly changing variables from day to day, month to month, year to year, location to location, roof area to roof area, temperature to temperature, aspect to aspect, solar radiation to solar radiation, insulation to insulation, material to material, etc, etc. that come into play. Throw some rain, then freezing in the mix and it gets even more messed up.
Insulation resists thermal transfer. It does not eliminate it in conventional construction and certainly not in older structures or areas were there is very little insulation, like structural components at valleys or roof pitch transitions. Snow is also an insulator and also has mass. Where thermal equilibrium between the internal and external temperatures occurs is dependent on all kinds of variables.
Where water could freeze could be outside the roof or inside. It can happen on unheated porch roofs if the ambient temperature rises enough to melt snow on them from below.
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I know a guy who is a roofer and broke his back falling 10 feet. He drags himself around on crutches and still roofs without full mobility in his legs. He has people who work for him, but he still gets up on roofs and fastens shit down.Quote:
Originally Posted by Alpinord
What Alpinord says. Good design and execution handles 90% of it but the other 10% just happens. This is what I see at 8,000 feet in the Northern Mountains.
It shitty (generally older) construction, the heat from inside the home is transferred to the roof deck and melts the snow. Once the melt water gets outside the building envelope it freezes. This is usually on your eve and gable overhangs. It is usually worse on roofs that are not above attics (rafters and vaulted ceilings)
On new construction, it is usually shitty roof design. Around here the architects are under pressure from the client to deliver the pretty house. Some GCs really focus the conversation around "you don't want that" many don't. It this case it is usually were the roof pitch is exposed to the sun and then the melt water drains to a cold place like a valley or even a shady spot where one pitch shades another.
What seems to work is spray foam in the lid and 2 layers of Ice and Water Shield. This is expensive nerdy shit but it's the game we play.
So it appears all of you agree with the link I posted.
Here’s a more contractor-oriented link https://bct.eco.umass.edu/publicatio...ting-ice-dams/
Sealing out the warm air from getting into attic is key.
For decades my mom had a house at altitude in the CH alps. Hudge amounts of snow. Attics were cold AF. I don’t recall any houses in the village having any ice dam issues ever.
Yes you win the internet. It was a good summary by guys selling snow removal services but not the whole picture. A heat audit is not necessarily going to help everyone. But the line about removing snow can’t hurt and might help about everyone, except those who have nowhere else to put the snow.[emoji6]
Edit: regarding attics, you can power vent attics and for new construction provide a deeper ‘energy heel’ in the truss design to provide deeper insulation over the exterior walls while providing positive air flow from soffit vents. For older houses, the insulation gets compressed over the walls due to the heel depth of a 2x4 or a 2x6 with no air flow vs 14-16” or more. I’ll post some details later.
Parallel chord or scissor trusses can also be used vs TJI or dimensional lumber rafters to provide greater insulation and air flow over vaulted spaces. For heat in vaulted spaces, radiant floor (ideally with a mass) is more efficient than forced air because the heat source radiates warmth to you, vs heating the whole volume to feel comfortable, which in turn generates more heat at the ceilings.
EDIT 2: detail grab from library showing some typical roof conditions:
Attachment 450879
In my experience it's a combination of all the above factors with ventilation being more important than people realize. If we ever get stupid enough to build a place it's going to have a fucking single shed roof withstanding seam steel covering.
^^^^
IE no valleys. The Swiss & Bavarians figured it out a while ago. KISS!
As Foggy Goggles stated, the architects and designers are more pressured to do what they are told than what they know might work in suburban Phoenix, but not at 9,000 feet. I've had one client only over the years that insisted on 'NO VALLEYS ANYWHERE' and one let me fully loose to provide a very simple roof on a higher end home! The rest are Heinz 57 & complicated.
That's what we've got and made it through the winter with no icicle formation until ambient temps got enough above freezing to begin melting snow on our roof. The only thing I don't like is not having access to under the roof in case issues so show up.Quote:
Originally Posted by I Skied Bandini Mountain
We haven't had enough snow to worry about it this year but in years past we've had some issues in one small spot at the edge of an overhang which is directly above the back door (which is the main door we use) and the dryer vent. It's only a small spot but I think enough heat comes out of the house right there and gets under the overhang and melts shit just enough that a little water trickles down into the gutter, then freezes and backs shit up.
Even then it doesn't cause any problems until there's a warmer day and melt water wants to get in the gutter, can't because it's full of ice, so it overflows onto the landing right below and freezes there, which can be life threatening coming out the door if you're not paying attention.
I bought a little piece of heat tape for the spot but it's sitting on a shelf in the garage until next year. Salt and sand on the landing makes it manageable but gets tracked through the house and makes a mess.
Two a-frames at bear valley. These are not being used this winter. On a hillside. The one on the left is 3 stories. The bottom floor is a partial floor. I’m pretty sure they both have decks.
Attachment 450887
Any ice dams?Quote:
Originally Posted by bodywhomper
I don’t see any ice dams.
I have no realistic way to clear the upper roof. Local building code says house should have been designed for about 140# per square foot snow load, minimum, so just gonna have to hope it holds up. Guesstimating about 6-7' deep on the roof in the deepest parts - north facing valleys.
I pulled down some snow from the lower edges where I can reach from the ground, on the north side. The south, west, and east sides melted off a lot before the last 10 days of storms, so there's much less on those sides.
Warm storm in two days means rain at my elevation...
https://uploads.tapatalk-cdn.com/202...0f16a3c07e.jpg
I've posted a pic of this new construction house in my neighborhood before, but here it is again in all its poorly designed glory, with the right side roof terminating directly into the garage wall on the left. It's hard to see it now under all the snow. https://uploads.tapatalk-cdn.com/202...f55a685701.jpg
I was working on a place in the YC, a gigantic slopeside with ski in/out access. The access off the ski room was on the side pretty close to another gigantic 4th/5th/6th home, and both roofs shed off into that gap. That along with the lack of sun and hillside build just filled that area with about 12 feet of snow. In order to finish the siding in that area we had to do a bucket brigade with two excavators and a front end loader for snow removal.
I'd love to see what it looks like today. There's no way anybody can keep that clear by hand for the ski in/out access.
What's the moisture content? 1 Cubic foot of water = 62 lbs (per water weight calculator)= ~ 17 % of 6' x 1 sq. ft. Take a 5 gallon bucket of snow, let it melt. Measure depth of water vs bucket height for percentage.Quote:
Originally Posted by El Chupacabra
WOW.Quote:
Originally Posted by El Chupacabra
The a-frame on the left likely has a dormer on the top floor which may have some ice dam issues. Those owners probably won’t know until summer.Quote:
Originally Posted by Alpinord
My buddy’s a-frame is just down the street. It also has a dormer on the third floor, which is where the interior door closing issue was first recognized over a month ago. He’s up there now trying to figure out how to move some weight off his roof and making some turns.
In California, these winter storms may result in a federal disaster declaration which may result in federal grant $$ to private property owners for home repairs.
IME another thing to look out for is flooding, maybe 5 yrs ago in oct we had snow followed by rain, it was bad enough to cave in a couple of roofs so people were shoveling roofs but also it totally saturated the watertable and caused a bunch of flooded basements
now i clear a swath directly in front of & behind the house
It varies so much that it'd be impossible to measure without getting up on the top roof and cutting a sample column. The very bottom of the snowpack is probably ice, then very very dense snow, then working its way up to light fluff on the very top.Quote:
Originally Posted by Alpinord
I'm in a snow drought area this season. No matter this discussion is hugely interesting.
Which makes me think of the latest infrared cameras you plug into Android (and i-) phones. They are great for seeing where hot and cold spots on a roof or anywhere else are, x10 better if you have access inside the eaves and crawl spaces.
I'm on my third one.
First one was about $450. One buddy asked can he borrow it? I said yes. After a few weeks I had to ask about it, he asked how much it cost and he said I'll just keep it here's your $450 + some more for the effort. I got a second one this time cost was about $325, someone else asked to borrow it, same thing he kept it and paid it off.
I'm now on my third one and this time the cost was $250. They can be as low as $199 up to $500.
Still amazing little devices that take any guess work out of insulating and air sealing.
My house is a good example of bad roof design. This is on the north side of the house and that door is the front door.
Attachment 450922
At least it looks like that steel sheds snow well. I have a Cor-ten steel roof and it doesn't seem to shed all that well, maybe my angle just isn't steep enough.Quote:
Originally Posted by adrenalated
Yeah, perfect for burying you as you are heading in/out.Quote:
Originally Posted by zion zig zag
Moisture content is gonna be pretty damn high if it rains n 2 days like he said. That shit's gonna be heavy.Quote:
Originally Posted by Alpinord
Rain could add: 5.2 lbs/sq. ft./in of depthQuote:
Originally Posted by ötzi
CA and western NV are gonna have some problems with the 2+ weeks(?) of forecasted warmer wet storms. Hope there’s no EQs in the Sierra over that time.
Forecast from NOAA this afternoon looks like rain/snow level will be above my house elevation for the entire storm from late Wed until Mon. Snow line as high as 8500', I live at about 5900'. Am hoping for some melt off from the rain and 40-45* temps, and not just saturating all the snow on the roof. I'm going to dig out the drains tomorrow to help encourage drainage away from the house. Most of the gutters are full of ice, so they're going to have to melt out before they can help transport water away.Quote:
Originally Posted by Alpinord
It would be fine if not for the intersecting roof line from that little bonus room to the looker's right of the door. It only sheds from that valley if I get the roof rake out and help it along.Quote:
Originally Posted by zion zig zag
Right?Quote:
Originally Posted by J. Barron DeJong
Nothing like some good ole fashion wanking for therapy and results. My shop has never had ice build up like this. It has always released on it's own. It's interesting that the entirety of the recycled metal roof is fully iced where the dormer isn't. Still trying to wrap my head around what chain of events caused this to happened. The weak layer is the one that released 10 days ago causing the avalanche ten miles away:
Attachment 450932
Attachment 450933
@adrenalated: If you took out those two windows in the bonus and put the front door there under a little gable roof with the ridge running back it would make a nice entrance
It would, but then the wife would lose her art room so that'd be a hard sell. She comes and goes through the garage anyway so she doesn't give a shit how treacherous the front door is.Quote:
Originally Posted by ötzi
My personal experience with rain on snow events at my 6000 ft level in the northern sierra is that on slopes surfaces the rain removes more weight than it adds. I'm thinking of a storm in the early 90's that dumped rain on 9 feet of fresh snow and produced enough runoff to raise Donner Lake over the road, carry decks and propane tanks down the Truckee R, and flood Reno. Of coure I'm sure it depends on the air and water temps, on the nature of the existing snow pack, etc. Here's hoping my past experience bears out, although not to the degree of flooding.
I have shoveled my 40 x 15 foot deck twice in the last week--3 feet of snow each time, to get the snow pack down to the deck rail. My secret weapon is a snow scoop--the kind you push with two hands. It's amazing how much snow you can move with that compared to a shovel, assuming you have someplace to push it to.
how good is art anyways? Might need a heart-to-heart talk with her over this.Quote:
Originally Posted by adrenalated