Ice dam forming, but only on half the array. Help needed

[Burningislove]

My panels are split 50-50 on two sections of roof, both facing the same direction, same roof pitch, same light exposure, and so forth. After the most recent snow storm, one half shed the snow as I'd expected and 2 days later after a nice sunny day the panels are 100% snow free and there is only minimal snow remaining downhill of them that is not causing any problem.

The other half, virtually nothing slid off the roof or panels, and there is a 18" high wall of built up snow & ice that will prevent any snow from sliding off. I'm not worried about the weight or roof support, my roof is very well built. However, I'm very worried about ice dams forming and serious water damage, and just annoyed that I've lost half my generating capacity. I've repeatedly read that I shouldnt try and remove the snow for fear of damaging the panels, yet after 6 days there is no way this blockage is coming down on its own for at least 2 more months.

Do I use a roof rake and pad it with something soft and try and chip away the edge, even if just enough to create a channel for melt water? Do I do the ole trick of filling panty hose w/ ice melt and seeing if I can melt a channel?

Attached is a few days old pic to illustrate. The panels on the left side are now 100% snow free, the ones on the right are more or less unchanged.

[Burningislove]

And yes, I did read Bruce's "Sun Hours" post before posting this and searched other threads, but didn't find much conclusive help that applied to my installation type.

[peakbagger]

Can we get more info on the structure?. By the looks of the windows and trim it looks like one side or the other is an addition? It there a dividing wall in the attic? It sure looks like side has more heat loss into the attic then the other and that is leading to one melting off quicker than the other. Is this new install this year or have you gone through a couple of winters and if they have been up for awhile, have you seen this before.? Do you own the system or is it a lease?. If its a lease you can complain that they installed a faulty design and they need to fix it, if you own it its lot hearder but if its new install you could call the installer and claim its bad design.

In the short term, its time to get the ladder out. I personally use a standard plastic ice rake to clean off my panels and have for quite a few years, others fear panel damage and advocate a rubber squeegee edge. I will let you make that call. You really shouldn't put salt on aluminum frames. The real problem is that the area under the panels is warmer than the lower edge of the roof where the meltwater from the panels drips and forms ice. If you chip into the ice at the lower edge and add rock salt you may be able to get some channels running. Unfortunately the normal approaches to prevent ice damming are probably going to make things worse. My panels are on a second floor roof but I can reach the lower section of panel and the 18 inch strip of roof and when snow builds up on the panel or at the base of the panel I rake the snow off. If you can make it though the winter, it may be time to consider pulling the shingles and putting in wide flashing at the base of the panel that runs back up the roof. Electric heating cables also work well. Most folks leave them on all the time when in reality they are only need for a few hours to get the water flowing. Of course that does bring up a point if the panels generation would cover the heating cables wattage?

It would be interesting to use a thermal camera on the two roofs to see if there is significant difference in roof temp.

[Burningislove]

Can we get more info on the structure?. By the looks of the windows and trim it looks like one side or the other is an addition? It there a dividing wall in the attic? It sure looks like side has more heat loss into the attic then the other and that is leading to one melting off quicker than the other. Is this new install this year or have you gone through a couple of winters and if they have been up for awhile, have you seen this before.? Do you own the system or is it a lease?. If its a lease you can complain that they installed a faulty design and they need to fix it, if you own it its lot hearder but if its new install you could call the installer and claim its bad design.

It would be interesting to use a thermal camera on the two roofs to see if there is significant difference in roof temp.

You've got a keen eye. Yes, the house in the left-side (no dam) is a newer addition in 2006 versus the original house (dam) built in 1986. Both sides have soffit vents and ridge vents. The addition (left) is a garage & hobby area with no heat, so I'd have expected less melting on that side and not more. There is some thermal crossover as the main house is heated with a woodstove and a connecting door in both downstairs and attic evens out the temp between the two sides. The attics should be close in heat as they are very well vented and well insulated. I've never had ice dam problems before on either section pre-solar installation.

This is the install's first winter and first appreciable snow, system went live in June 2015. I fully own the sytem, and plan on calling the installer tomorrow. The panels on the right side w/ the dam are further up the roof than the ones on the addition, two rows versus three. So I can likely get the first 12" or so of the snow dam clear with a roof rake and not risk hitting the panels, even without a ladder! (whew). I was not going to put any ice melt on the panels or near the frames, just the roof itself downhill of the panels.

Tomorrow is supposed to be very warm and rain, so will be a game changer

[DanKegel]

Or... maybe the heat is causing the ice dams? Is the vented attic in the original house in equilibrium with the outdoor temperature, or is it warmer? if it's warmer, maybe that's the problem. Google building science ice dam for some ideas.
e.g. http://buildingscience.com/documents...d-135-ice-dams

[Burningislove]

The original house attic is well vented, and should be close to the outdoor temp. As posted, I've never had an issue with ice dams before on either half of the house. Also, the flip side of the house (both constructions) faces East (panels face west) and gets the same amount of sunlight per day as the panel side. There are no snow/ice dams of any kind presently on either the original or addition side.

The only real difference between the two sections of house that have panels is that the left side (addition) has 3 rows of panels and the most downhill edge is much closer to the roof edge (about 12") than the side that is dammed up. The latter has 2 rows of panels, and has more clearance to both the bottom and peak of the roof. So my initial thought is that the side that didnt dam up is OK because snow sliding off those panels would have fallen off the edge of the roof given their proximity to the edge. The two-row side would have dumped onto the roof and has further to travel before falling off.

[peakbagger]

I think your speculation on the cause of the problem is correct. My roof panels that look to be similar pitch will sometimes let go in one shot and whomp it goes down to the ground. Other times it melts from the top down and forms a minor ice dam.on the asphalt shingles. If I get it with a rake it sometimes will slide down and start piling at the roof again or just as frequently it will let loose and come down with hard whump. The attached photo was obviously taken in the summer but as you can see I get some help with ice dams from the lower array. In the winter the lower array is cranked up to 60 degrees off vertical so they tend to reflect sun up under the soffits to warm up the overhang. I do get some ice build up on the strip of roofing but expect the lower array puts in enough heat to keep it from building up. I also don't have gutters. Many folks pull their gutters in winter as they are frequently a source for ice damming. I do have some deflector grilles at the base of the soffits that redirect flow off the roof so it doesn't form a trench at a drip line but they can cause icicles.

I have speculated that the approach may be to make removable ramp out of uhmw plastic preferably in black that spans from the lower lip of the lower panel to the edge of the roof. This would encourage the snow to keep sliding instead of getting caught on the roof. Water doesn't tend to freeze to UHMW readily especially if there is some slope. I would remove it in non snow season to allow unrestricted air flow under the panels and to cut down on UV cooking the UHMW.

In case someone wonders, even with the lower array tipped up, the snow generally slides off the roof and misses the lower edge of the lower array most of the time. The SHW panels tends to form a mound of snow at its base. I haven't seen any ice damming but its interesting to hear the circulator pump running with half the panel covered with snow. When I replaced the roof prior to putting up all the panels, I covered top to bottom with ice and water shield so ice damming isn't a leaking issue.

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[Legacy]

This may not help you this year but you should be able to find this at a store near you
for any future years. These seem to do the job if you cannot find any other problem in the roof
http://www.canadiantire.ca/en/pdp/ro...l#.VsJEz-CAfIU

This is in Canada but should be no problem to find in the U.S.