Vent Pipe Leak
We live in Kentucky and just experienced another ice storm. We consistently have ice dam roof leaks on our shallow slope roofs during these storms and this time I finally found the specific cause. With our roof vent pipe surrounded by about 1″ thick ice plus 4″ of snow, the warmth from the pipe melted the ice and snow around the vent pipe creating a ring of melt water trapped by the surrounding ice. This trapped water leaks through, runs down rafters and or the vent pipe and leaks into the house.
I have been trying to think of a vent pipe treatment that would prevent this in the future. Perhaps an insulating outer pipe with a hood ring. Suggestions? Available products?
Rocky Sky
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Interesting question. Do you have a vented attic? Ideally the vent would cool off on the way through the vented attic and be less hot as it exits the roof. Insulating it as the goes through the roof makes sense, but I've never seen that done or seen products for it.
Yes, It goes through a vented attic. Almost new asphalt shingle roof.
Yesterday I went up with hot water hose and made channel up from roof edge and around vent pipe. Leak slowed and then stopped. It is thawing today and it started leaking again. EEERRRGGGG!
Rockysky,
Shallow pitched roof with asphalt shingles?
I have a bit of an unusual idea for you to try:
I suspect the warm air is INSIDE that vent pipe, causing the exterior of the vent pipe to melt snow and ice in contact with it. Maybe you could sleeve the vent pipe with a slightly larger pipe to provide a 1/2" or so air gap all the way around. Let air flow from the attic through that vent channel and out. You'll need some kind of cap that allows for this air flow. The result will be cool air (hopefully :-) from the attic cooling and insultating the warmer vent pipe and hopefully preventing or limiting the ice melt problem you're seeing.
This is basically how B vent works for hot flue gasses, but in reverse. This MIGHT solve your problem, but I've never tried it myself so you'd be doing an expieriment here. If you try it, please report back with results!
Bill
Be sure to inspect the rubber boot from the roof collar to ensure that the ice didn't create any rips or tears in the boot. If it did, you can/could install a second boot taken from another roof collar and apply over the original without replacing the whole collar. Seal with some silicone, including a large bead that will make good contact with the second boot and then seal the second boot also. It will add a second layer of protection for any future ice problems.
my bet is that warm air is following the pipe upwards and hitting the bottom of the sheathing
Use a lead pipe boot. It does not rely on a rubber gasket