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The downpipes are open at both ends. Their purpose is to lead rainwater and snowmelt collected from the roof to the eaves channels down to the ground level and further into underground pipes leading the water away from the property in a controlled manner. Insulating them from the outside would do no good.

Ohh my mistake i just didn't got it first time. I was with the sanitation pipes and water pipes... It seems to be a problem... Don't you have an attachment to it from where it can be opened. pouring hot water from the opening of attachment will for sure help.

We have never had a problem with freezing water pipes or sewers. Yes, I could pour hot water to the eaves channels but there is simply too much ice for it to be worth it.