February 2015: New England's getting a huge amount of snow and cold this winter, and the roof accumulations and resulting ice-dams have been quite impressive here and there. And when all this finally melts for real, it's going to be very very wet for a while. [Small images are linked to larger detailed ones] |
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Church building near Sudbury |
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Ice dams on a typical hip roof, mostly on the southern side |
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A small Cape with a big problem, as often happens to this house style. The mid-wall "rooflet" is probably a huge thermal bridge via its structural attachment, and may not be insulated at all |
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Interesting melt patterns on a store roof, showing obvious thermal bridging from interior structure. Similar to the problem that Joe Lstiburek had on his barn, or what happens when SIPs are joined together without scrupulous sealing details |
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The thickness of the ice-dam is inversely proportional to the height of the snow above it, as might be expected |
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Different methods of trying to deal with it: cutting drainage channels with ice-melt, either in a stocking "sausage" or by itself |
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Or going after it with good ol' brute force |
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| Commercial buildings try a variety of solutions: a bunch of guys with shovels, or just haul the snowblower up top and go nuts with it. And speaking of nuts, this video is about a few of the other fun things Bostonians have been, uh, throwing themselves into this winter | |
Meanwhile, back home ...
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No ice-dams here, but a large drift of accumulation which must represent a considerable amount of weight. Observed that the relentless cold has shrunk the siding enough to open a gap [pink box] that must not have been overlapped quite enough during construction |
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The previous shot enabled only by having a path shoveled well back into the yard, ending at a carefully carved measurement face in the undisturbed pack. 34 inches at the time, variable density from top to bottom, representing at least 6 inches of equivalent water. Melt is going to be, uh, interesting to say the least |
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The slightly disturbing discovery a little later: the roof rafters are actually bending just a little bit under the load, meaning that it might be prudent after all to excavate the basement bulkhead for access, get the ladder up there, and shovel off some of the excess weight |
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[Rough calculation: Boston's accumulation to date of 80 inches of fairly
fluffy stuff, at a 10:1 ratio snow to water, gives the equivalent of about
8 inches of water. At 62 pounds per cubic foot that's a theoretical
40+ PSF on the roof, at or over generally accepted maximum engineered
snow loads. Alternatively, 34 inches of packed stuff at maybe a 5:1
ratio, minus a little that might have blown off, is still 6+ inches of
water and thus gettin' up there.
In other words, time for a little topside adventure before this crap gets rained on] | |
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The impending melt is why it's important to keep the catch-basin grates by the street accessible and cleared, instead of being buried by plows. Because when the time comes, we're gonna *need* these |
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The paving around the new manholes is already cracking from the nonstop cold. It's only about six months old |
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Similarly, the asphalt patch at the end of the driveway has clearly shrunk in the deep-freeze and cracked away from the pavers and the rest of the street |
The one downside of heat pumps
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Ice accumulation around bottom of the heat pump condenser box, from all the defrost meltwater not being able to fully run out the drain holes before congealing up again. Helped right along by the endless succession of snowstorms, swirling even more ice into the coils. See this thread for related discussion |
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Manual defrost operation: tarp up the box and run the system in *cooling* mode for a while, using a little heat from inside the house and try to keep it in the unit to warm up the entire thing |
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After about 20 minutes of cooling-mode run, the inch or so of ice in the bottom can be !carefully! broken up and removed to expose the main drain hole again [green arrow] |
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Additional heat for thawing can come from any number of creative sources; a heat-gun or hair dryer would probably help too. [From the *second* go-round of this, with the fan removed completely for more working room] |
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Accumulated strata of successive defrost cycles are fairly easy to see in the extracted chunks |
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The right long-term answer: some heat tape strategically run around the bottom of the unit and *through* the drain hole. All of 42 watts [1 KWh/day] for far more peace of mind, and only really needed during the snowstorms |
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Cleared area maintained around the heat pump to encourage free airflow, shoveled as a "perfect carve" for a smooth deflection angle |
More local scenes
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| A neighbor wrestling with his monster ice dam. Most of the snow above it got pulled off, but this thing is stuck down hard and cantilevered way out over the edge. We couldn't figure out what's holding it up and why it hasn't fallen off and ripped the whole gutter down with it. That could happen anyway when the thaw comes | |
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Mysterious frozen dribble from the window weep-holes; may be condensation from the inside seeping down through the weatherstripping and transferring outward through the hollow bottom of the frame |
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Another gift from the plowman! The dirty brown stuff at the end is yet another dense plow ridge, and the street is completely hidden. Plenty more upper-body workout in store |
The Cape in Winter
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On my way to the Cape for a weekend, behind a dump-truck load of snow. It had just gotten onto the highway and on accelerating, began dropping lots of swirling "snow ghosts" on the road behind it |
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A very cold sunset over Woods Hole, where the harbor is all iced up -- a fairly rare occurrence, I'm told. One of the fellas who works there has shot an aerial video showing the extent of the ice-pack |
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A nearby boat channel, similarly choked with ice. On the way back
from touring the
Arisia Relaxacon hotel
in the grip of winter.
Also see this video for some of the dynamics of how ice is carried and piled up by waves and tides. The last half is the most interesting |
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| Buzzards Bay largely frozen over, where floes move around and push each other up at crazy angles. Looks like an Arctic landscape in miniature | |
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Melting a recovered lump of bay ice, to test how brackish it is relative to the water. This took over 12 hours to finish at normal room temperature around it |
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| There are little critters caught in the ice! Dead by now, of course, but the water must be teeming with these. On reasonably good authority, several barnacle larvae and a copepod or two, each about a millimeter long | |