Best way to stop boiler steam from entering attic

Question

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.

1. Spots that are not well insulated, particularly switches, outlets, and a corner section.
2. 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.
3. 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.

Answer 1

There is only one right answer: build a chimney and vent it above the roof. If the aesthetics don't bother you, just extend the vent duct right to or above the roof line.

If you don't extend it beyond the roof line, you will continue to get the issues with the ice dams since the heated vapor will melt the snow above the exhaust point.

My house is built in the 70's and we have a chimney (no fireplace) which vents the exhaust from my gas water heater.

Answer 2

My old physics teacher would give you an 'A' for simply creating this question.

It is important to remember that whatever solution you choose must fix the problem, and not just move the problem to a different place - AKA: the Wack-A-Mole paradox.

I think the first step is to get an infrared thermometer,I chose this one,but pick your own vendor and price point

http://www.amazon.com/Etekcity-Lasergrip-Digital-Infrared-Thermometer/dp/B00DMI632G/

This will allow you to identify the source of the heat leaks, and locate the problem areas.

After you know what problem you are trying to fix, we can move forward from there.

Answer 3

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.

Answer 4

Can you explain how steam is getting into the attic, your item #3. You said that the boiler is in the basement and vents to the outside??? There should be no steam venting outside the home. My only thought is that there is a vent line coming out the top of the condensate tank (if you have a condensate tank). If this is the problem then you have other problems with the heating system that should be addressed. Can you investigate where the vent line comes from? As for item #2, do you know what the copper pipes are used for, and why are they in the attic? As for the attic problems I would consult insulation contractors and get their recommendations for insulation and attic venting. A wrong decision from you could add to the problem and become a costly mistake in later years.