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Porch ceiling frost and ice

Jeremy Zheng
5 years ago

Happy New Year!

I have a frustrated frost issue on my porch ceiling. My house is completed on Oct, 2017.

See pic 2 , My main entry porch roof is big triangle shape, it has quite big cavity space inside like attic.

First time I discovered the issue was a couple month ago when winter started, I noticed on the warm day, the ceiling closing to Den window area dripping water. I reported to builder and they sprayed insulation foam at highlighted in yellow area (see pic 1) . Around Christmas time, -40 °C cold snap hitted Alberta and I noticed frost on the ceiling again (see pic 3), builder opened soffits and discovered that inside cavity, a lot of frost, and ice built up (pic 4). Today is very warm my whole porch ceiling dripping water like crazy.

My builder told me that need a vent on the roof to help warm air escape. I am trying to figure where the warm air coming from. From the construction time the photos I took I have noticed that a heating duct pipe when through (see pic 1 red line ), I measured the temperature (see pic3 in red circle area) last week is + 4 °C, at that time, surrounding air temperature is -14 °C. apparently there must be some heat loses and escaped into porch attic cavity. condensation water built up to make frost and ice in the night time, at warm day time, ice melted, water dripping down.

My question are:

If just heat escapes into porch cavity, why so much moisture. The heat loses from heating duct pipe will not carry any moisture, just radiate warm air emitted into porach cavity, it should not cause any ice or frost formation, where is moisture coming from.

Will adding ventilation vent on top of roof help solve frost issue?

Is any other possible issue cause this problem?

Pic 1

Pic 2

Pic 3

Pic 4

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