I had heard differnt schools of thought on vent stack blockages, one they add a extra outer tube kinda like a inside out augmentation tube, then ther is the suspending the pantyhose with a cup full of icemelt just inside the mouth of the vent, problem with this is it requires reloads and sucks if its a two story house, the better one I heard about was placeing a length of 3/4" copper tube down the vent pipe and slant the bottom end so air will rise up the tube and cutting off its top a couple inches below the mouth of the vent pipe, the copper is supposed to radiate heat from down below to help keep the top open.
My sewer line hasent iced for awhile (city line) my neighbors do take hot showers all the time from the water vapor that rises out the cleanout, I figure the hot water vapor freezes it turns to snow blocking off drainage in other sewer lines tapped into the city sewer line, I try to not use much hot water If I can, I wash most laundry with cold water, when showering I keep it short and business like when finished turn to cold water to clear the vapor or flush the toilet,
After the big power outage in Barter Island awhile back I looked into a electric free kerocene heater in case something happened that I had to keep the home warm for a week at -40 with no power.
It wasent easy to come up with, Wood heating isant a option, the area I live in is coastal and not much drift wood, the problem of make up air and sealing it all off when not in use, pluse the constant care pluse the wood I find is water logged and full of silt that plays hell on chainsaw's, so I settled on a Kero-sun radiant heater, Its a generator of Co gas but with some venting will keep the house warm.