I have a cape cod. The boiler is in the basement and vents to the outside about a foot above ground level. I get a considerable amount of snow melt and ice buildup in the attic section directly above the vent. I have recently been remodeling and I cut a hole to get into this section of the attic (about a 6'x12' area between 2 alcoves). My initial intent in here was to investigate and patch up cold spots on the wall as we had a breeze coming through a corner that borders this.
I found 3 things that could be causing my snow melt and ice buildup.
- Spots that are not well insulated, particularly switches, outlets, and a corner section.
- 2 Copper radiant heat pipes that go from one end of the attic to the junction box at the other end that were just sitting under the insulation, fully exposed every 16" over the studs.
- Steam…coming from the boiler, into the eave vents and into the attic. This is condensing on the roofing nails, then dripping onto the insulation.
I can solve the first 2 with various types of insulation. I could block the eave vents, which is a quick solution. I could extend the pipe out and up past the roof, which with the current ice issue, could just get knocked down, plus I'm not sure how it would look aesthetically. I could also move the pipe from one basement wall to another (likely best permanent solution).
My question is, is it safe or acceptable to block off that section of the eave vents? Is there a solution that allows water to drip out, but not allow steam to come in? If I covered the vents with blown insulation, it should block the steam and allow water to drip through it.
Best Answer
The problem is most likely hot exhaust coming from the vent entering the attic and melting snow on the roof, creating an ice dam and snow melt.
Since you have continuous soffit vents, blocking off any one section would not be the end of the world. You would want to block it with an air barrier material like plywood or foam insulation board, sealed at the edges with caulk or spray foam. Blown cellulose alone won't cut it, since it is air-permeable.
Relocating the vent could work too. Having it exit the house under a gable end rather than an eave would put the exhaust farther away from the roofline and out of the path of a soffit.